Bio 102: City of Bones

Bio 102 Chapter 4

Class Chondrichthyes
Rhizoprionodon
Head – region that holds most of the sensory organs and the nervous system
Trunk – contains most of the internal/visceral organs
Tail -for locomotion
Teeth -for feeding
Gill slits – respiration
Fins – locomotion
a. Pectoral
b. Dorsal
c. Pelvic
d. Caudal
Claspers- used to channel semen into the females cloaca during mating
Ceratotrichia -supports the fins
Urogenital papilla -exit of gametes
Rostrum
Nostrils – respiration
Cloacal aperture -exit of waste material

Dasyatis
Head
Tail
Fins
a. Dorsal
b. Pelvic
c. Pectoral
Rostrum
Nostrils
Oronasal groove -connects the mouth to the nasal organs
Cloacal aperture
Trunk
Spines- structural support (?)
Claspers
Spiracle
Nasofrontal process – covers the oronasal groove
Gill slits

Class Actinopterygii
Teleosts
Head
Tail
Lateral line -used to detect movement and vibration in the surrounding water
Operculum – covers the gill opening
Gill arches -support the gills
gill rakers – used for filter-feeding
Fins
a. Pectoral
b. Dorsal
c. Pelvic
d. Caudal
d. Anal
Urogenital papilla
Trunk
Scales – for protection/covering
Nostrils
Gill openings
Gills
Branchiostegal membrane – covers the ventral portion of the branchial cavity/gill opening
Anal opening

Polyodon
Rostrum nostrils
Operculum
Tail

Lepisosteus
Ganoid scales
Nostrils
Snout- enhances olfaction
Tail

Amia
Cycloid scales
Operculum
Homocercal tail

Polypterus
Ganoid scales
Diphycercal tail

Acipenser
Ganoid scales
Heterocercal tail

Class Sarcopterygii
Protopterus
Cycloid scales
Diphycercal tail

Class Amphibia
Necturus
Head
Tail
Nostrils/External nares
External gills
Upper arm
forearm
wrist
hand
Thigh
Shank
Ankle
Foot
Trunk
Diphycercal tail fin
Gill slits
Gular fold – used to attract mates

Class Reptilia
Varanus/Draco
Head
Trunk
Horny scales
External nares
Gular fold
Clawed limbs
Femoral pores -releases pheromones [and keratin]
Neck
Tail
Head shield – for protection
External ears
Parietal eye – photoreception
Lateral fold
Anus
Preanal pores – releases pheromones (?)

Chelone
Head
Trunk
Tail
External nares
Eardrum
Plastron
Bony plates
Carapace
Neck
Shell
Horny shields
Horny beaks
Lateral bridges – connects the carapace and plastron

Class Aves
Head
Trunk
Contour Feathers
Flight
Remiges
Primaries
Secondaries
Tertiaries
Rectrices
Covert – help smooth airflow over the wings and tail; cover bases of other feathers
Filoplume
Wings
Neck
Uropygium – region where tail feathers grow
Uropygial gland -secretes oil used for preening; waterproofing; antibacterial function
Beak
Cere – houses the nostrils; aids in either respiration or olfaction
External nares
External ear
Digits
Clawed hind limbs
Horny scales
Cloacal aperture

Class Mammalia
Felis
Fur – for protection/covering
Facial Region – houses the external sensory organs
Lips – provide sensory information about food prior to its placement in the oral cavity
External nares
Thorax – houses the heart and lungs, among others
Teats – exit of secretions from the mammary gland
Perineum- protection and separation of the urogenital and anal regions
Whiskers/vibrissae – used for tactile sensation
Cranial region – contains the brain
Nose
External ear
abdomen – houses the intestines, stomach and other digestive organs, among others
Clawed limbs
Anus

Rousettus
Wing membrane
Phalanges
Spur – supports the wing membrane (?)
Metacarpals
Clawed thumbs/feet – for climbing/hanging
Large pinnae

Manis
Elongated head
Long tail
Imbricated (def: arranged so that they overlap like roof tiles) horny scales
Snout
Clawed feet
External ear

Bio 102 Structures List: Chapter 3

Structures: Chapter 3

Phylum Hemichordata
External Features:
Proboscis- used for burrowing
Collar- contains the dorsal and
ventral nerve cords Branchiogenital region- contains the
gonads and gill pores
genital ridge- bulge formed by the gonads
Hepatic region- contains the hepatic
Caeca (with digestive function)
Abdominal region- contains the
intestine and the anus

Subphylum Urochordata
External features:
Oral siphon- entrance of water
Atrial siphon- exit of water
Tunic/test- support and protection of
the body
Internal features:
Mantle- incloses the viscera
Pharynx- passageway of water and
food
Atrium- collecting chamber of water,
leading to the atrial siphon

Subphylum Cephalochordata
External features:
Oral hood- covers the mouth area
Vestibule- collecting chamber for
water
Cirri- chemoreception
Metapleural folds- encloses the gill
slits
Atriopore- exit of water
Caudal fin- for locomotion
Dorsal fin- for locomotion
Anus- exit of waste
Myotomes- for locomotion
Myosepta- separates mytomes;
origin and insertion of the muscles
constituting each myomere
Internal features:
Wheel organ- trap food particles in
mucus for later digestion; directs
food particles towards the mouth
Hatschek’s groove
Hatschek’s pit- releases mucus;
Velum- works as a filter
Velar tentacles- functions as
chemoreceptors
Pharynx- passage of water and food
Peripharyngeal band- connects the
epi- and hypobranchial grooves
Gill bars- separates the gill slits
Gill slits- function in filter feeding
Atrium- cavity that receives water
Notochord- axial support
Neural tube- functions as the CNS;
coordinates the activity of all parts of
the lancelet
Ocelli- photoreceptors
Brain vesicle- main section of the
CNS
Pigment spot- rudimentary eye
Cross-section
Epidermis- serves as
covering/protection; respiration
Dorsal fin ray- supports the dorsal
fin
Fin ray- supports the fins
Metapleural folds
Myotomes- for locomotion
Neural tube
Neurocoel- cavity in the neural tube
Notochord
Atrium
Pharynx
Gill bars/slits
Epibranchial groove- secretes mucus
Hypobranchial groove- secretes
mucus
Midgut caecum- secretes enzymes
for digestion
Gonads- for reproduction
Nephridia- for excretion

Superclass Agnatha
Class Cephalaspidomorphi
External features:
Dorsal fins
Caudal fin
Fin rays
Buccal funnel- passage of food and
water
Lip tentacles- sensory function;
reinforce suction
Horny teeth- promotes attachment to
host
Tongue- for feeding
Mouth- for feeding
Nasohypophyseal opening- functions
as nostril
Eyes- functions as true eyes
Gill slits- for respiration
Cloacal pit- shared exit of urine,
feces and gametes
Sagittal section:
Buccal cavity- passage of food and
water
Esophagus- leads to the intestine
Pharynx- respiration and feeding
Velum- serves as filter
Gill slits
Gill pouches- contains the gills
Gill lamellae- attachments to the
walls of the pouches
Notochord- axial support
Branchial basket- supports the gills
Neural canal- contains the CNS
Nasohypophyseal canal- passage
Olfactory sac- enables smell
Nasopharyngeal sac- facilitates
olfaction

Campbell: CHAPTER 47 Animal Development

CHAPTER 47
Animal Development

CONCEPTS ON DEVELOPMENT

1. PREFORMATION
• egg or sperm contains an embryo that is a preformed, miniature infant
• development is enlargement of the embryo
• embryo must contain all its descendants

2. EPIGENESIS
• Aristotle
• Form of an animal emerges gradually from a relatively formless egg

FACTORS AFFECTING DEVELOPMENT
1. genome of the zygote
2. organization of the cytoplasm of the egg cell
• mRNA, proteins, and other substances are heterogenously distributed throughout the unfertilized egg

DEVELOPMENT

1. CELL DIVISION
2. DIFFERENTIATION
3. MORPHOGENESIS
• the process by which an animal takes shape

DIFFERENTIATION
1. after fertilization produces a zygote, cell division partitions the cytoplasm in such a way that nuclei of diff embryonic cells are exposed to different cytoplasmic envts

2. expression of different genes in different cells

3. embryo develops

4. inherited traits emerge by mechanisms that selectively control gene expression

5. differentiation

FERTILIZATION

MAIN FUNCTION
1. combine haploid sets of chromosomes from two individuals into a single cell, the zygote
2. activates the egg
• contact of sperm with egg surface initiates metabolic reactions within the egg that trigger the onset of embryonic development

GAMETES
– highly specialized cell types

1. sperm
2. egg

MAJOR EFFECTS OF FUSION OF SPERM AND EGG MEMBRANES
1. acrosomal reaction
2. cortical reaction

THE ACROSOMAL REACTION
– a sperm cell is exposed to molecules from the slowly dissolving jelly coat that surrounds an egg
– acrosom discharges its contents by exocytosis
– releases hydrolytic enzymes that enable an elongating structure called acrosomal process to penetrate the jelly coat of the egg
– tip of acrosomal process is coated with a protein that adheres to specific receptor molecules on the vitelline layer
– “lock-and-key” recognition – ensures that eggs will only be fertilized by sperm of same species
– leads to
• the fusion of sperm and egg plasma membranes
• entry of one sperm nucleus into cytoplasm
– fusion of membranes causes ion channels to open in egg’s plasma membrane
– Na+ enter cell
– Change in membrane potential – membrane depolarization – fast block to polyspermy
– Other sperm cells are prevented from fusing with egg’s plasma membrane

THE CORTICAL REACTION
– Series of changes in the outer zone/cortex of egg cytoplasm
– Fusion of egg and sperm triggers a signal-transduction pathway
– egg’s ER releases Ca+ into cytosol
• start: site of sperm entry
• propagates in a wave across the fertilized egg
– second messengers are produced
• IP3
• DAG
– IP3
• opens ligand-gated Ca channels in ER
• Ca+ released triggers opening of other channels
– High concentration of Ca+ brings about a change in vesicles – cortical granules
– cortical granules
• lie under egg’s plasma membrane
• fuse with plasma membrane
• release contents into previtelline space
– enzymes from granules separate vitelline layer from plasma membrane
– mucopolysaccharides produce osmotic gradient
– water is drawn into previtelline space – swells
– swelling pushes vitelline layer away from plasma membrane
– other enzymes hardens vitelline layer
– vitelline layer becomes fertilization envelope – resists entry of additional sperm
– membrane potential returns to normal
– fast block to polyspermy no longer functions
– slow block to polyspermy
• fertilization envelope
• other changes in the egg’s surface

ACTIVATION OF THE EGG

Effects of Increase in Ca+2 Concentration
1. triggering of cortical reaction
2. incite metabolic changes within the cell

– unfertilized egg – slow metabolism
– fertilization
• rates of cellular respiration and
• protein synthesis increase
– DAG activates a membrane protein
– H+ is transported out of the cell
– Egg cytosol becomes slightly alkaline
– pH change seems to be indirectly responsible for metabolic processes of egg to fertilization
– NOTE: sperm cells do not contribute any materials required for activation
– Nucleus of sperm cell within the egg starts to swell
– Merging of the 2 nuclei
– DNA synthesis begins

FERTILIZATION IN MAMMALS
– Generally internal
– Secretions in mammalian female reproductive tract
• alter certain molecules on surface of sperm cells that have been deposited
• increase motility of the sperm
– Capacitation – enhancement of sperm function in female reproductive tract
– Secondary oocyte is cloaked by follicle cells
– Capacitated sperm cell must migrate through follicle cells and then through zona pellucida
– Zona pellucida
• ECM of egg
• Consists of 3 glycoproteins forming filaments that are cross-linked in 3D network
• ZP3
 one of the glycoproteins
 functions as sperm receptor
– binding of sperm head to receptor molecules induces acrosomal reaction
– protein-digesting enzymes + hydrolases from acrosome enables sperm to penetrate zona pellucida
– acrosomal reaction exposes a protein in the sperm that binds and fuses with egg membrane
– binding of sperm and egg
– depolarization of egg membrane – fast block to polyspermy
– cortical reaction
– enzymes from cortical granules catalyze alterations of zona pellucida – slow block to polyspermy
– microvilli (fingerlike extensions) of egg cell take sperm into egg
– basal body of flagellum divides and forms two centrosomes with centrioles in zygote
– NOTE: unfertilized mammalian eggs have no centrosomes of their own – centrosomes from sperm generate mitotic spindle for cell division
– Haploid nuclei do not fuse immediately
• envelopes of both nuclei disperse
• chromosomes from two gametes share a common spindle apparatus during first mitotic division
– diploid nuclei form in the two daughter cells

DEVELOPMENT OF EMBRYO

1. Cleavage
• creates a multicellular embryo
• blastula

2. Gastrulation
• produces a three-layered embryo
• gastrula

3. Organogenesis
• generates rudimentary organs from which adult structures grow

CLEAVAGE
– succession of rapid cell divisions that follow fertilization
– cells undergo S and M phases of cell cycles but skip G1 and G2 phases
– embryo does not enlarge during this period
– simply partitions the cytoplasm of the zygote into many blastomeres
• smaller cells
• each has its own nucleus

CLEAVAGE IN EGG CELLS WITH POLARITY
– different regions of cytoplasm present in original undivided egg cell end up in separate blastomeres  sets stage for devtl events because of diff in components
– most animals have both eggs and zygotes with definite polarity (except mammals)
• defined by heterogenous distribution of substances in the cytoplasm
• specific mRNA, proteins, yolk
– planes of division follow pattern relative to poles of zygote

Poles
1. Animal pole
• lowest yolk concentration
• site where polar bodies of oogenesis are budded from the cell
• for some animals, marks the point where anterior end of embryo will form

2. Vegetal pole

Yolk
– stored nutrients
– its distribution is a key factor in influencing pattern of cleavage
– most concentrated in the vegetal pole
– most plentiful and has its most pronounced effect on cleavage in eggs of
• birds
• reptiles
• many fishes
• insects

Frog
– animal and vegetal hemisphere have diff coloration due to heterogeneous distribution of cytoplasmic substances
– plasma membrane and associated yolk rotate toward point of sperm entry
– rotation exposes the gray crescent
–

1. Animal pole
• Melanin granules embedded in cortex of cytoplasm
• Deep gray hue

2. Vegetal hemisphere
• more yolk
• yellow

3. Gray crescent
• Light-gray region of cytoplasm
• Located near the equator of the egg on the side opposite the sperm entry
• Important early marker of the polarity of amphibian egg
• Corresponds to dorsal side of later embryo

– Yolk tends to impede cell division
– Cleavage occurs more rapidly in animal hemisphere
– Embryo: different-sized cells

PATTERN OF CLEAVAGE (FROG AND SEA URCHIN)
1. Meridional (Vertical)
2. Meridional
3. Equatorial

Deuterostomes
– share many features of early embryonic development

1. echinoderms
2. chordates
3. other animal phyla

Protostomes
1. mollusks
2. annelids
3. arthropods

CLEAVAGE
1. Morula
• solid ball of cells
• embryo – lobed surface

2. Formation of blastocoel
• fluid-filled cavity
• forms within the morula
• sea urchins – centrally located
• frogs – in animal hemisphere – due to unequal cell division

3. Blastula
• hollow ball

TYPES OF CLEAVAGE
1. meroblastic
• incomplete division of a yolk-rich egg
• division is restricted to a small disc of yolk-free cytoplasm

2. holoblastic
• complete division of eggs having little or moderate amount of yolk
• found in sea urchins and frogs

DROSOPHILA
– yolk-rich egg
– unique type of meroblastic cleavage
– zygote’s nucleus is situated within a mass of yolk
– cleavage begins with the nucleus undergoing mitotic divisions that are not accompanied by cytokinesis
– production of several hundred nuclei  migrate to outer edge of egg
– more mitosis
– plasma membrane forms around each nucleus,
– embryo
• considered a blastula
• single layer of cells surrounding a mass of yolk

GASTRULATION
– Morphogenetic process
– Rearrangement of cells of blastula

CHANGES THAT DRIVE SPATIAL ARRANGEMENT OF EMBRYO
1. changes in cell motility
2. changes in cell shape
3. changes in cellular adhesion to
• other cells
• molecules of ECM

RESULT OF GASTRULATION
– some of the cells at or near the surface of the blastula move to an interior location
– three cell layers are established

GASTRULA
– 3-layered embryo
– positioning of cell layers allows cells to interact with each other in new ways

EMBRYONIC GERM LAYERS
1. Ectoderm
• forms outer level of gastrula

a. nervous system
b. epidermis of skin
c. epidermal derivatives
 skin glands
 nails
d. epithelial lining of mouth and rectum
e. sense receptors in epidermis
f. cornea and lens of eye
g. adrenal medulla
h. tooth enamel
i. epithelium of pineal and pituitary gland

2. Mesoderm
• partly fills the space between ectoderm and endoderm

a. notochord
b. skeletal system
c. muscular system
d. circulatory system
e. lymphatic systems
f. excretory system
g. reproductive system (except germ cells which starts to differentiate during cleavage)
h. lining of body cavity
i. adrenal cortex
j. kidney
k. dermis of skin

3. Endoderm
• lines embryonic digestive tract

a. epithelial lining of digestive tract (except mouth and rectum)
b. epithelial lining of respiratory system
c. liver
d. pancreas
e. thyroid
f. pancreas
g. thyroid
h. parathyroids
i. thymus
j. lining of urethra
k. lining of urinary bladder
l. lining of reproductive system

GASTRULATION IN SEA URCHIN EMBRYO
– begins at the vegetal pole
– individual cells detach from the blastula wall and enter blastocoel as migratory cells (mesenchyme cells)
– remaining cells flatten slightly to form vegetal plate that invaginates
– buckled vegetal plate undergoes extensive rearrangement of cells
– shallow invagination becomes the archenteron
– formation of blastopore
• open end of archenteron
• eventually becomes the anus
– another opening forms at the other end of archenteron  mouth end of rudimentary digestive tube

Tripoblastic Body Plan
– 3-layered body plan
– characteristic of most animal phyla
– established very early in devt

GASTRULATION IN FROG EMBRYO
– wall of blastula is more than one cell thick in some species
– first sign – small crease on one side of blastula (invagination)
– invagination becomes dorsal side
– formation of dorsal lip of blastopore
• forms where the gray crescent was located in the zygote
– successive invaginations of grps of cells near the dorsal lip result in completion of circular blastopore
– cells on surface rolling over edge of dorsal lip into interior (involution)
– cells move away from blastopore along roof of blastocoel
– involution continues
– migrating internal cells becoming organized into layered mesoderm and endoderm
– archenteron forms within endoderm
– circular lip of blastopore encircles a yolk plug
• consisting of large, food-laden cells
• protruding cells will move inward as expansion of ectoderm causes blastopore to shrink

ORGANOGENESIS
– stage wherein the three germ layers develop into rudiments of organs

FIRST EVIDENCES OF ORGAN BUILDING
1. folds
2. splits
3. dense clustering/condensation of cells

FIRST RUDIMENTARY ORGANS TO DEVELOP
1. neural tube
• will become the CNS

2. notochord
• skeletal rod characteristic of all chordate embryos

ORGANOGENESIS IN FROG
– notochord is formed from dorsal mesoderm that condenses just above the archenteron
– neural tube originates as a plate of dorsal ectoderm just above the developing notochord
– neural plate folds inward
– neural plate becomes the neural tube
– notochord elongates and stretches the embryo along its anterior-posterior axis
– notochord will function as a chord around which mesodermal cells gather and form the vertebrae
– other condensations occur in strips of mesoderm lateral to notochord – somites
• arranged serially on both sides along the length of the notochord
• give rise to vertebrae of backbone
• form muscles associated with axial skeleton
– lateral to the somites – mesoderm splits into two layers that form the lining of coelom
– morphogenesis and cellular differentiation continue to refine the organs
– neural crest
• unique to vertebrate embryos
• a band of cells that develops along the border where the neural tube pinches off from the ectoderm
– cells of neural crest migrates to various parts of the embryo forming
• pigment cells of skin
• bones and muscles of skull
• teeth
• medulla of adrenal glands
• peripheral components of nervous system
 sensory ganglia
 sympathetic ganglia
– leads to larval stage – tadpole

ADAPTATIONS OF EMBRYOS
– all vertebrate embryos require an aqueous envt for devt
– fish and amphibians – egg is laid in sea/pond – needs no special water-filled enclosure
– terrestrial vertebrate animals – reproduction in dry envts

1. shelled egg
• reptiles
• birds
2. uterus
• placental mammals

AVIAN DEVELOPMENT

CLEAVAGE
– meroblastic cleavage
– production of blastodisc
• cap of cells
• rests on the undivided yolk
– blastomeres sort into upper and lower layers
a. epiblast
b. hypoblast
– cavity between the two layers

GASTRULATION
– involves cells moving from the surface of the embryo to an interior location
– some cells of the epiblast move toward midline of blastodisc – detach and move inward toward the yolk
– primitive streak
• groove
• produced by medial movement on surface and inward movement of cells at the blastodisc’s midline
• lengthens over the surface of blastodisc
• marks what will become the anterior-posterior axis
• functional equivalent of blastopore
– all the cells that will form the embryo come from the epiblast
– some of epiblast cells that pass through primitive streak move laterally into blastocoel  mesoderm
– other epiblast cells migrate through the streak and downward  pushes out the cells of the hypoblast  endoderm
– epiblast cells remaining on the surface – ectoderm
– hypoblast
• contributes no cells to the embryo
• seems to help direct the formation of primitive streak before onset of gastrulation
• required for normal devt
• later segregate from endoderm
• form portions of a sac surrounding the yolk and a stalk connecting the yolk mass to the embryo
– borders of embryonic disc fold downward and come together
– embryo is pinched into a 3-layered tube joined at the midbody to the yolk

ORGANOGENESIS: NEUROGENESIS
– neural tube formation, development of notochord and somites are the same as in the frog
– only part of each germ layer contributes to the embryo itself
– tissue layers outside the embryo proper develop into 4 extraembryonic membranes

EXTRAEMBRYONIC MEMBRANES
– support further development within the egg
– each is a sheet of cells that developed from epithelial sheets external to embryo proper

1. yolk sac
• expands over the surface of the yolk mass
• cells will digest yolk
• blood vessels that develop within the membrane will carry nutrients into the embryo

2. amnion
• formed from lateral folds of extraembryonic tissue extending on top of the embryo
• separated from chorion by extraembryonic extension of the coelom
• encloses the embryo in a fluid-filled amniotic sac
• protects the embryo from drying out
• cushions the embryo against mechanical shocks

3. chorion
• formed from lateral folds of extraembryonic tissue extending on top of the embryo
• cushions the embryo against mechanical shocks

4. allantois
• originates as outpocketing of hindgut
• sac that extends into extraembryonic coelom
• functions as disposal sac for uric acid
• allantois + chorion = respiratory organ for embryo
• blood vessels transport oxygen into the embryo

MAMMALIAN DEVELOPMENT
– fertilization takes place in the oviduct
– earliest stages of devt occur while the embryo completes its journey to the uterus

EGG OF PLACENTAL MAMMAL
– small – stores little food reserves
– does not exhibit polarity with respect to contents of cytoplasm
– cleavage is holoblastic

CLEAVAGE
– relatively slow
– blastomeres are equal in size
– cells of early embryo are loosely packed

Compaction
– important event during early mammalian development
– occurs at 8-cell stage
– cells tightly adhere to one another
– involves the production of new proteins on the surface of the cells  cadherins

Blastocyst
– ~100 cells around a central cavity
– protruding into the blastocyst cavity is the inner cell mass
• cluster of cells
• develops into embryo proper and some of extraembryonic membranes
– trophoblast
• outer epithelium surrounding the cavity
• will form fetal portion of placenta (+mesodermal tissue)
• placenta will form from proliferated trophoblast and region of endometrium it invades
– embryo reaches the uterus and implants in the endometrium
– trophoblast initiates implantation by secreting enzymes that enable the blastocyst to penetrate the endometrium
– trophoblast thickens (bathed in blood) and extends fingerlike projections into surrounding maternal tissue
– inner cell mass forms a flat disc with upper layer and lower layer of cells
a. epiblast  embryo, placenta (mesodermal cells)
b. hypoblast  yolk sac
– extraembryonic membranes begin to develop
– trophoblast
• gives rise to chorion
• continues to expand into the endometrium
– epiblast has begun to form the amnion surrounding a fluid-filled cavity

GASTRULATION
– follow a pattern similar to birds and reptiles
– occurs by inward movement of cells from epiblast through a primitive streak
– mesoderm and endoderm is formed
– 3-layered embryo surrounded by extraembryonic mesoderm
– 4 extraembryonic membranes formed are homologous to chicks

EXTRAEMBRYONIC MEMBRANES
1. Chorion
• develops from trophoblast
• surrounds the embryo and other extraembryonic membranes

2. Amnion
• begins as a dome above the proliferating epiblast
• will eventually enclose the embryo in a fluid-filled amniotic cavity

3. Yolk Sac
• below the developing embryo proper
• encloses another fluid-filled cavity – does not contain yolk
• site of early formation of blood cells which later migrate into embryo proper

4. Allantois
• develops as an outpocketing of embryo’s rudimentary gut
• incorporated into the umbilical cord – forms blood vessels
 transport oxygen and nutrients from placenta to embryo
 rid the embryo of CO2 and nitrogenous wastes

ORGANOGENESIS
– early stages  follow a pattern similar to birds and reptiles
– begins with the formation of neural tube, notochord, and somites
– end of first trimester – rudiments of all major organs have developed

CELLULAR AND MOLECULAR BASIS OF MORPHOGENESIS

MORPHOGENESIS
– only in animals does it involve movement of cells
– movement of parts of a cell can bring about the changes mentioned below
– involves specific changes in

1. cell shape
2. cell position
3. cell adhesion

– these changes are involved in cleavage, gastrulation, and organogenesis

CHANGE IN CELL SHAPE
– usually involve reorganization of cytoskeleton

Formation of Neural Plate
1. microtubules oriented parallel to dorsal-ventral axis help lengthen cells in that direction
2. dorsal end: parallel array of actin filaments oriented crosswise contract
• gives cells a wedge shape
• forces ectoderm layer to bend inward

CHANGE IN CELL POSITION
– movement of cells from one place to another is also driven by cytoskeleton
– cells crawl within the embryo by using cytoskeletal fibers to extend and retract cellular protrusions
– cellular protrusions are usually
a. lamellipodia – flat sheets
b. filopodia – spikes

Gastrulation
– invagination is initiated by wedging of cells on the surface of the blastula
– penetration of cells deeper into the embryo involves the extension of filopodia by cells at the leading edge of migrating tissue
– leading cells help move a sheet of cells from embryo’s surface into blastocoel  forms endo and mesoderm
– migration of neural crest cells  example of individual cell migration

Convergent Extension
– involves cell crawling
– cells of a tissue layer rearrange themselves in such a way that the sheet of cells becomes narrower (convergence) while it becomes longer (extension)
– important in early embryonic development
– examples
• Archenteron elongates in sea urchin
• Involution in frog gastrula

Role of Extracellular Matrix
– Mixture of secreted glycoproteins lying outside plasma membrane
– Known to help guide cells in many types of morphogenetic movements

1. Tracks
• directing migrating cells along particular routes
• fibronectins/glycoproteins – help cells move by providing anchorage for cell crawling

Example: Amphibian Gastrulation
• fibronectin fibers line the roof of blastocoel
• mesoderm moves into interior of embryo
• cells at the free edge of mesoderm migrate along these fibers

2. Inhibiting migration in certain directions
• depending on substances they secrete, nonmigratory cells situated along migration pathways may promote or inhibit movement of other cell
• as migrating cells move along paths, receptor proteins on surface pick up directional cues from immediate envt

CHANGE IN CELL ADHESION
– glycoproteins that attach migrating cells to an underlying ECM play a role in holding cells together when migrating cells reach their destination and tissues and organs take shape

Cell Adhesion Molecules (CAMs)
– contributing to cell migration and stable tissue structure
– glycoproteins located on surfaces of cells
– binds to CAMs of other cells
– vary either in amount or chemical identity
– differences help regulate morphogenetic movements and tissue-building

Cadherins
– an impt class to cell-to-cell adhesion molecules
– require presence of Ca+2 for proper function
– gene for each cadherin is expressed in specific locations at specific times during embryonic devt

DEVELOPMENTAL FATE OF CELLS

DEPENDS ON…
1. cytoplasmic determinants
2. cell-cell induction

Development requires timely differentiation of many kinds of cells in specific locations

2 PRINCIPLES UNDERLYING DIFFERENTATION

1. In animals (except mammals), the heterogeneous distribution of cytoplasmic determinants in the unfertilized egg leads to regional differences in the early embryo
• partitioning hetero cytoplasm  cleavage parcels out diff
 mRNA
 proteins
 molecules
• local differences in cytoplasmic composition help specify the body axes
• influence expression of genes that affect devtl fate of cells
• cytoplasmic determinants are responsible for initial diff between cells in embryos

2. In induction, interactions among embryonic cells themselves induce changes in gene expression
• these interactions eventually bring out differentiation of many specialized cell types making up a new animal
• may be mediated by
 diffusible chemical signals
 cell-surface interactions

FATE MAPPING
– reveals genealogies in chordate embryos
– general territorial diagrams of embryonic devt
– Vogt

2 Conclusions

1. in most animals, certain early founder cells generate specific tissues of older embryo

2. as development proceeds, cell’s developmental potential becomes restricted
developmental potential – range of structures it can give rise to

CYTOPLASMIC DETERMINANTS

Polarity and the Basic Body Plan

Body Plan of Bilaterally Symmetrical Animal
1. anterior-posterior axis
2. dorso-ventral axis
3. left and right sides

Establishing basic body plan
– first step in morphogenesis
– prerequisite to devt of tissues and organs

Mammals
– Polarity is not obvious until cleavage

Frogs
– Locations of melanin and yolk define animal and vegetal hemispheres
– Animal and vegetal hem determines anterior-posterior body axis
– Fertilization triggers formation of gray crescent
– Formation of dorso-ventral axis

Restriction of Cellular Potency
– Asymmetric distribution of cytoplasmic determinants in egg does not necessarily lead to differences among earliest blastomeres
– First cleavage may occur along an axis that produces two identical blastomeres – equal devtl potential
– 1st 2 blastomeres are similar – totipotent
– fate of embryonic cells can also be affected by zygote’s characteristic pattern of cleavage

in many species
– only zygote is totipotent
– 1st cleavage divides cytoplasmic determinants in such a way that each blastomere will give rise to only specific parts of the embryo

Mammalian embryo
– remains totipotent until they become arranged into trophoblast and inner cell mass of blastocyst
– early blastomeres – equal amts of cytoplasmic components
– up to 8-cell stage  blastomeres look alike and each can form a complete embryo if isolated

NOTE:
– progressive restriction of potency is a general feature of devt in all animals
– In general, the tissue specific fates in late gastrulae are fixed

INDUCTIVE SIGNALS
– Different developmental potentials  one cell can influence the development of another cells
– Effect of induction  switching on a set of genes that make the receiving cells differentiate into a specific tissue

The “Organizer” or Spermann and Mangold

Dorsal lip of blastopore
– early gastrula
– plays key role in embryonic devt
– initiates chain of inductions that results in formation of neural tube and other organs
– primary organizer of the embryo

Amphibian Bone Morphogenetic Protein 4 (BMP-4)
– family of related proteins with variety o devt roles
– active exclusively on ventral side of gastrula
– major function of organizer cells is to inactive this on dorsal side of embryo

Optic Lens
– ectoderm cells destined to become lenses receive inductive signals from ectodermal cells that will become the neural plate
– additional inductive signals come from endodermal and mesodermal cells
– inductive signals from optic cup and outgrowth of developing brain

Pattern Formation of the Vertebrate Limb
– development of an animal’s spatial organization
– arrangement of organs and tissues in their characteristic places in 3D space
– requires cells to receive and interpret envtl cues that vary from one location to another
– cues + 3 axes tell cells their location
– organizer regions function as signaling centers

Positional Information
– molecular cues that control pattern formation
– tells a cell where it is with respect to animal’s body axes and help to determine how the cell and its descendants respond to future molecular signals

Limb Buds
– bumps of tissue
– beginnings of vertebrate limbs
– consists of a core of mesodermal tissue covered by ectoderm

3 Axes (Ex. Chick Limb)
1. proximal-distal (shoulder-to-fingertip)
2. anterior-posterior (thumb-to-little finger)
3. dorsal-ventral (knuckle-to-palm)

Apical Ectodermal Ridge (AER)
– limb-bud organizer region
– thickened area of ectoderm at the tip of the bud
– required for outgrowth of limb along PD axis
– for patterning along this axis
– cells produce and secrete several proteins of the fibroblast growth factor (FGF)  growth signals that promotes limp bud outgrowth
– guide pattern formation along DV axis

Zone of Polarizing Activity (ZPA)
– limp-bud organizer region
– located where posterior side of the bud is attached to the body
– necessary for proper pattern formation along AP axis
– cells nearest this give rise to posterior structures
– secretes Sonic hedgehog  impt growth factor

Forelimb vs. Hindlimb
– cells receiving signals from AER and ZPA respond according to devtl histories
– earlier devtl patterns have set up patterns of gene expression distinguishing future forelimbs from future hindlimbs
– differences cause cells of fore- and hindlimb to respond differently to the same positional cues

Campbell: CHAPTER 46 Animal Reproduction

CHAPTER 46
Animal Reproduction

TYPES OF ANIMAL REPRODUCTION
1. ASEXUAL
• creation of new individuals whose genes all come from one parent without the fusion of egg and sperm
• in most cases, relies entirely on mitotic cell division

2. SEXUAL
• creation of offspring by the fusion of haploid gametes to form a zygote (2n)
• gametes are formed by meiosis
• increases genetic variability among offspring by generating unique combinations of genes inherited from two parents
• may enhance reproductive success of parents when pathogens/other envtl facts change relatively rapidly

Ovum
• female gamete
• unfertilized egg
• relatively large and nonmotile cell

Spermatozoon
• male gamete
• generally a small, motile cell

ASEXUAL REPRODUCTION
– enable animals to produce identical offspring rapidly
– most advantageous in stable, favorable envts  perpetuates successful genotypes precisely

TYPES OF ASEXUAL REPRODUCTION
1. fission
2. budding
3. gemmules
4. fragmentation

FISSION
– many invertebrates reproduce in this manner
– separation of a parent into two or more individuals of approximately equal size

BUDDING
– involves new individuals splitting off from existing ones
– cnidarians, tunicates

GEMMULES
– specialized group of cells that can grow into new individuals
– invertebrates
– ex. Sponges

FRAGMENTATION
– breaking of a body into several pieces
– some or all of the pieces may develop into adults
– must be accompanied by regeneration  regrowth of lost body parts
– occur in
• sponges
• cnidarians
• polychaete annelids
• tunicates

ADVANTAGES OF ASEXUAL REPRODUCTION
1. enables animals living in isolation to produce offspring without locating mates
2. ideal for rapid colonization of habitat  can create numerous offspring in a short amount of time

SEXUAL REPRODUCTION
– reproductive cycles and patterns vary extensively among animals
– periodic nature of reproduction allows animals to conserve resources and reproduce when
• more energy is available than is needed for maintenance
• environmental conditions favor the survival of offspring

FACTORS CONTROLLING REPRODUCTIVE CYCLE
1. hormones
2. environmental cues

NOTE: Animals may reproduce sexually or asexually exclusively but may shift between the two modes

PARTHOGENESIS
– a process in which the egg develops without being fertilized
– adults produced are often haploid
– has a role in social organization for certain species of bees, wasps, and ants
– some genera of fishes, amphibians, and lizards reproduce by parthogenesis that involves doubling of chromosomes after meiosis to create diploid zygotes

HERMAPHRODITISM
– sexual reproduction presents a problem for sessile or burrowing animals & parasites  difficulty encountering member of opposite sex
– each individual has both male and female reproductive systems
– some fertilize themselves but usually mate with another member of same species
– during mating, each animal serves as both male and female  donates and receives sperm

Sequential Hermaphroditism
– an individual reverses its sex during its lifetime

1. protogynous  female first
2. protandrous  male first

MECHANISMS OF SEXUAL REPRODUCTION

FERTILIZATION
– union of sperm and egg

1. external
• eggs are shed by the female and fertilized by the male in the environment

2. internal
• sperm are deposited in or near the female reproductive tract
• fertilization occurs within the reproductive tract
• requires cooperative behavior leading to copulation
• requires sophisticated reproductive systems
 copulatory organs  deliver sperm
 receptacles  for storage and transport to ripe eggs

COURTSHIP BEHAVIOR
– Mating behavior of amphibians and fishes (external fertilization)
– mutual trigger for the release of gametes
• probability of successful fertilization is increased
• choice of mates may be somewhat selective

FACTORS AFFECTING RELEASE OF GAMETES
1. environmental cues
2. chemical signals from another individual releasing gametes

PHEROMONES
– chemical signals released by one organism that influence the behavior of other individuals of the same species
– small, volatile, water-soluble
– active in minute amounts
– many function as mate attractants

INTERNAL VS. EXTERNAL FERTILIZATION
– all species produce more offspring than survive to reproduce

EXTERNAL FERTILIZATION
– produces enormous numbers of zygotes
– proportion that survive and develop is quite small

INTERNAL FERTILIZATION
– usually produces fewer zygotes
– higher probability of survival
• greater protection of embryos
 resistant eggshells
Birds, reptiles, monotremes–Ca and protein shells
Fish and amphibians – gelatinous coat
 devt of embryo within reproductive tract
• prenatal care of the young

COMPLEX REPRODUCTIVE SYSTEMS

REQUIREMENTS FOR SEXUAL REPRODUCTION
1. systems that produce gametes and
2. deliver them to gametes of opposite sex

LEAST COMPLEX REPRODUCTIVE SYSTEMS
– least complex systems don’t contain distinct gonads  organs that produce gametes
– polychaete worms (Annelida)
• separate sexes but no distinct gonads
• eggs and sperm develop from undifferentiated cells lining the coelom

PARTS OF COMPLEX REPRODUCTIVE SYSTEMS
1. gonads
2. accessory tubules and glands
• carry and protect gametes and developing embryos

FLATWORMS
Male
1. genital pore
2. seminal vesicle
3. sperm duct  vas deferens
4. testis
5. vas efferens

Female
1. genital pore
2. uterus
3. yolk gland
4. yolk duct
5. ovary
6. oviduct
7. seminal receptacle

INSECT REPRODUCTIVE ANATOMY
Male
1. testis
2. vas deferens
3. accessory gland
4. seminal vesicle
5. ejaculatory duct
6. penis

Female
1. oviduct
2. accessory gland
3. ovary
4. spermatheca
• a sac in which sperm may be stored for a year or more
5. vagina
• where fertilization occurs

BASIC PLAN OF VERTEBRATE REPRODUCTIVE SYSTEMS
– basically similar
– male reproductive systems differ mainly in copulatory organs
– many nonmammalian vertebrates do not have a well-developed penis and simply evert the cloaca to ejaculate
– there are impt variations

Cloaca
– common opening of digestive, excretory, and reproductive systems in many nonmammalian vertebrates
– most mammals lack a cloaca

Uterus
– vertebrates  partially or completely divided into 2 chambers
– humans and other mammals, birds, snakes
• few young at a time
• uterus is single structure

MAMMALIAN REPRODUCTION
– human reproduction involves intricate anatomy and complex behavior

REPRODUCTIVE ANATOMY OF HUMAN MALE

External Reproductive Organs
1. Scrotum
• fold of the body wall
• holds the testes  for mammals, production of normal sperm cannot occur at body temp
• temp = 2 below temp in abdominal cavity

2. Penis
• composed of 3 cylinders of spongy erectile tissue derived from modified veins and capillaries
• baculum
 rodents, raccoons, walruses, other mammals
 bone that is contained in, and helps stiffen the penis
• main shaft is covered by relatively thick skin

a. glans penis
 head
 thinner covering
 more sensitive to stimuation

b. prepuce
 covers glans penis
 may be removed by circumcision

Internal Reproductive Organs
1. Testes
• consists of highly coiled tubules surrounded by several layers of connective tissue
• develop high in the abdominal cavity and descend into the scrotum just before birth

a. seminiferous tubules
 the coiled tubes
 where sperm is formed

b. Leydig cells
 scattered between seminiferous tubules
 produce testosterone and other androgens

2. Accessory Glands
• secrete products essential for sperm movement

a. prostrate gland
 largest of the semen-secreting glands
 secretes its products directly into the urethra through several smaller ducts

Prostatic fluid
 thin and milky
 contains anticoagulant enzymes and citrate (sperm nutrient)

b. bulbourethral glands
 pair of small glands along the urethra, below the prostrate
 before ejaculation, they secrete a clear mucus that neutralizes acidic urine remaining in urethra
 fluid also carries some sperm released before ejaculation

3. Accessory Ducts
• carry sperm and glandular secretions

a. epididymis
 coiled tubules
 where sperm from seminiferous tubules passes
 sperm become more motile and gain ability to fertilize
b. vas deferens
 muscular
 during ejaculation, sperm are propelled from epididymis to vas deferens
 run from the scrotum around and behind the urinary bladder

c. ejaculatory duct
 formed by joining of vas deferens and seminal vescile
 opens into the urethra

d. urethra
 tube that drains both excretory and reproductive system
 runs through the penis
 opens to the outside at the tip of the penis

Semen
– once in the female reproductive tract, prostaglandins in semen
• thin the mucus at the opening of the uterus
• stimulate contractions of the uterine muscles  help move semen up the uterus
– slightly alkaline  neutralize acidic envt of vagina
• protect sperm
• increase sperm motility
– when first ejaculated, sperm coagulates  making it easier for uterine contractions to move it along
– anticoagulants liquefy the semen  sperm begin swimming through the reproductive tract

REPRODUCTIVE ANATOMY OF THE HUMAN FEMALE

External Reproductive Structures

1. Clitoris
• at the front edge of the vestibule
• consists of a short shaft supporting a rounded glans  covered by prepuce
• consists of erectile tissue

2. Labia
• surrounding clitoris and vaginal opening

Vestibule
• region wherein the vaginal and urethral opening are located
• bordered by the labia minora  pair of slender skin folds

Labia majora
• a pair of thick fatty ridges
• encloses and protects the labia minora and vestibule

Internal Reproductive Organs
1. Ovaries
• lie in the abdominal cavity
• each is enclosed in a tough protective capsule
• contains many follicles

follicle
• consists of one egg cell surrounded by one or more layers of follicle cells
 nourish
 protect the developing egg cell
• all the follicles a woman will ever have are formed before birth
• starting at puberty until menopause, one follicle matures and releases its egg cell during each menstrual cycle
• cells also produce estrogens  primary female sex hormones
• ovulation  egg is expelled from the follicle

corpus luteum
• remaining follicular tissue grows within the ovary to form this solid mass
• secretes additional estrogens and progesterone  maintains uterine lining during pregnancy
• disintegrates when egg is not fertilized
• new follicle matures during the next cycle

2. Oviduct (Fallopian Tubes)
• egg is released into the abdominal cavity near the opening of the oviduct
• has a funnel-like opening
• cilia on the inner epithelium lining the duct
 help collect the egg cell  draw fluid form body cavity into the duct
 convey egg cell down the duct to the uterus

3. Uterus
• womb
• thick, muscular organ that can expand during pregnancy to accommodate fetus

a. Endometrium
 inner lining of the uterus
 richly supplied with blood vessels

b. Cervix
 neck of the uterus
 opens into the vagina

4. Vagina
• thin-walled chamber that forms the birth canal through which the baby is born
• repository for sperm during copulation
• Hymen
 vascularized membrane
 partially covers the vaginal opening in humans

Bartholin’s Glands
• located near the vaginal opening
• secrete mucus into the vestibule  lubricates and facilitates intercourse

Mammary Glands
– present in both sexes
– function only in women
– not part of reproductive system
– within the glands, small sacs of epithelial tissue secrete milk
– drains into a series of ducts opening at the nipple
– fatty tissue forms main mass (for nonlactating mammal)
– low level of estrogen in males prevents the devt of secretory apparatus and fat deposits
• male breasts remain small
• nipples are not connected to the ducts

SPERMATOGENESIS
– production of mature sperm cells
– continuous and prolific process in adult male
– occurs in seminiferous tubules of testes
– the developing sperm cells move toward the lumen of tubule as they undergo meiosis and differentiation
– four cells that results from meiosis all develop into mature sperm cells

Spermatogonia
– stem cells that give rise to sperm
– located at the periphery of each seminiferous tubule

Sperm
1. head
• contains nucleus (n)
• tipped with acrosome
 special body
 contains enzymes that help sperm penetrate the egg

2. neck
• mitochondria
• provide ATP for movement of tail

3. tail/flagellum
• plasma membrane

OOGENESIS
– development of ova  mature, unfertilized egg cells
Oogonia
– stem cells that give rise to oocytes
– multiply and begin meiosis (up to P1) in growing embryo

Primary Oocytes
– cells that have stopped maturing at P1
– remain quiescent within small follicles until puberty
– reactivated by FSH
• periodically stimulates a follicle to grow
• induces its primary oocyte to complete meiosis I and start meiosis II

Secondary Oocytes
– growth is arrested at meiosis II
– released during ovulation
– does not continue meiosis II right away
– fertilization triggers completion of meiosis  oogenesis is completed

OOGENESIS vs. SPERMATOGENESIS

Oogenesis Spermatogenesis

During meiotic div of oogenesis, cytokinesis is unequal
• almost all cytoplasm is monopolized by the secondary oocyte  goes on to form the ovum
• polar bodies
 smaller products of meiosis
 degenerate

All four products of meiosis develop into mature sperm

At birth, every ovary contains all primary oocytes it will every have

Cells from which sperm develop continue to divide by mitosis throughout male’s life

Has long resting periods
Produces mature sperm from precursor cells in an uninterrupted sequence

HORMONE REGULATION OF REPRODUCTION: MALES
– hormones from anterior pituitary and hypothalamus control
• androgen secretion
• sperm production

ANDROGENS
– principal sex hormones
– most impt: testosterone
– steroid hormones produced by Leydig cells of the testes
– directly responsible for primary and secondary sex characteristics of the male
– stimulates protein synthesis
– potent determinants of behavior in mammals and other vertebrates

PRIMARY SEX CHARACTERISTICS
– associated with reproductive system

1. development of vas deferentia and other ducts
2. development of the external reproductive structures
3. sperm production

SECONDARY SEX CHARACTERISTICS
– not directly related to reproductive system

1. deepening of the voice
2. distribution of facial and pubic hair
3. muscle growth

HORMONE REGULATION OF REPRODUCTION: FEMALES
– pattern of hormone secretion and reproductive events regulated by hormones are cyclic
– females release only one or a few eggs during each cycle

TYPES OF CYCLES
1. Estrous
2. Menstrual

ESTROUS CYCLE
– Other mammals
– ovulation occurs at a time in the cycle wherein the endometrium has started to thick  prepares uterus for possible embryo implantation
– no pregnancy  endometrium is reabsorbed by uterus  no bleeding
– more pronounced behavioral changes
– stronger effects of season and climate on cycle

MENSTRUAL CYCLE
– man and other primates
– ovulation occurs at a time in the cycle wherein the endometrium has started to thick  prepares uterus for possible embryo implantation
– no pregnancy  endometrium is shed  menstruation

Estrus
• most mammals will only copulate during the period surrounding ovulation
• period of sexual activity
• the only time vaginal changes permit mating
• female’s body temp increases slightly

1. Menstrual Flow Phase
• Day 1 of cycle: first day of menstruation
• Menstrual bleeding occurs, persists for a few days

2. Proliferative Phase
• thin endometrium begins to regenerate after a week or two

3. Secretory Phase
• two weeks in duration
• endometrium continues to thicken
 more vascularized
 develops glands that secrete a fluid rich in glycogen

Ovarian Cycle
– parallel to menstrual cycle

1. Follicular Phase
• several follicles being to grow
• the developing egg cell in each follicle
 enlarges
 coat of follicle cell thickens
• only one continues to enlarge and mature while others disintegrate
• maturing follicle develops an internal fluid-filled cavity  grows large  forms bulge near surface of ovary
2. Ovulation
• end of follicular phase
• follicle and adjacent wall of ovary rupture
• secondary oocyte is released

3. Luteal Phase
• remaining follicular tissue develops into corpus luteum
• endocrine cells of corpus luteum secrete female hormones

HORMONES
– growth of follicle and ovulation are synchronized with preparation of uterine lining for possible implantation

1. GnRH
• hypothalamus

2. FSH
• gonadotropin
• anterior pituitary
• stimulates follicle growth

3. LH
• gonadotropin
• anterior pituitary

4. Estrogens
• ovaries
• responsible for coordinating ovarian and menstrual cycles
• responsible for secondary sex characteristics

Secondary Sex Characteristics of Females
a. deposition of fat in breasts and hips
b. increased water retention
c. affect calcium metabolism
d. stimulate breast development
e. mediate female sexual behavior

5. Progesterone
• ovaries
• steroid hormone

Ovarian Cycle
Follicular Phase
– Stimulation of GnRH
– Secretion of small amounts of FSH and LH
– Cells of immature ovarian follicles have receptors for FSH but not for LH
– Cells of growing follicles secrete estrogens
– There is a slow rise in amount of estrogens in this phase  inhibits secretion of pituitary hormones  low FSH and LH levels

Effects of High Estrogen Concentrations
1. stimulates secretion of gonadotropins by acting on hypothalamus  inc GnRH
2. increased sensitivity of LH-releasing mechanisms in the pituitary to the hypothalamic signal (GnRH)
NOTE: greater effect for LH

– follicles have receptors for LH and can respond to LH
– increase in LH concentration induces final maturation of follicle

Ovulation
– occurs a day after LH surge

Luteal Phase
– LH stimulates transformation of follicular tissue to corpus luteum
– Corpus luteum secretes estrogens and progesterone
– As levels of estrogen and progesterone rise, combination of these hormones exerts negative feedback  inhibit secretion of LH and FSH
– Corpus luteum disintegrates near the end of this phase
– Concentrations of estrogens and progesterone decline rapidly  hypothalamus and pituitary are liberated from inhibitory effect
– Pituitary secretes enough FSH to stimulate growth of new follicles in ovary
– New follicular phase is initiated

Coordination of Ovarian and Menstrual Cycle
– Estrogens
• secreted in increasing amts by growing follicles
• hormonal signal to uterus
• causes endometrium to thicken
– before ovulation, uterus is already being prepared for possible implantation of embryo
– after ovulation, estrogens and progesterone stimulate continued development and maintenance of endometrium
• enlargement of arteries
• growth of endometrial glands
– rapid drop of ovarian hormones  spasms of arteries in uterine lining  menstruation

1. follicular – proliferative phase
2. luteal – secretory phase

Menopause
– the cessation of ovulation and menstruation
– 46-54  ovaries lose their responsiveness to FSH and LH
– results from decline in production of estrogens

EMBRYONIC AND FETAL DEVELOPMENT IN EUTHERIAN MAMMALS

CONCEPTION
– fertilization of the egg by a sperm cell

PREGNANCY
– gestation
– condition of carrying one or more embryos in the uterus
– continues until the birth of the offspring
– humans  266 days/38 weeks/9 months
– duration correlates with body size and extent of devt of young at birth

HUMAN GESTATION

First Trimester
– time of most radical chance for both mother and baby
– fertilization occurs in the oviduct

Changes in the Zygote

1. Cleavage
• zygote begins dividing
• after 24 hours

2. Blastocyst
• one week after fertilization
• 1 week after fertilization
• a sphere of cells containing a flattened cavity

3. Implantation into the endometrium
• blastocyst becomes embedded in endometrium
• endometrium grows over blastocyst
• embryo obtains nutrients directly from the endometrium for first 2-4 weeks of devt

4. Differentiation of body structures

Placenta
• tissues grow out from developing embryo and mingle with embryo  form placenta
• contains embryonic and maternal blood vessels
• diffusion of material between maternal and embryonic circulation
 provides nutrients
 exchanges respiratory gases
 disposes of metabolic wastes for embryo

Organogenesis
• development of body organs
• 4th week  heart begins beating
• 8th week  structures of adult are present in rudimentary form
• embryo is called a fetus
• rapid organogenesis  embryo is most sensitive to threats (radiation and drugs) that may cause birth defects

Changes in the Mother

Embryonic Hormones
– secreted by embryo
– signals embryo’s presence
– controls mother’s reproductive system
– ex. Human chorionic gonadotropin

Human Chorionic Gonadotropin (HCG)
– acts like pituitary LH
– maintains secretion of progesterone and estrogens by corpus luteum through first trimester
– absence  decline in maternal LH due to inhibition of pituitary by progesterone  menstruation/spontaneous abortion
– high levels in urine  detected by pregnancy tests

Changes in Reproductive System Caused by Progesterone
1. increased mucus in cervix  protective plug
2. growth of maternal part of placenta
3. enlargement of uterus
4. cessation of ovulation and menstrual cycling  (–) feedback on hypothalamus and pituitary
5. breasts enlarge rapidly and are often quite tender

Second Trimester
– fetus grows to ~30cm and is very active
– mother feels movements
– hormone levels stabilize as HCG declines
– corpus luteum deteriorates
– placenta secretes its own progesterone  maintains the pregnancy
– pregnancy is obvious

Third Trimester
– rapid growth of the fetus
– fetal activity decreases  less space
– mother’s abdominal organs become compressed and displaced
• frequent urination
• digestive blockages
• strain in back muscles
– interplay of hormones (estrogens and oxytocin) and local regulators (prostaglandins) induces and regulates labor
• estrogens
 highest level during last weeks of pregnancy
 trigger formation of oxytocin receptors on the uterus
• oxytocin
 produced by fetus and mother’s posterior pituitary
 stimulates powerful contractions by smooth muscles of the uterus
 also stimulates placenta to release prostaglandins
• prostaglandins
 enhances contractions
– physical and emotional stresses associated with contractions stimulate release of more oxytocin and prostaglandins  (+) feedback system for stages of labor

Stages of Labor
– strong, rhythmic contractions of uterus

1. opening up and thinning of cervix
2. expulsion of baby
• umbilical cord is cut
3. delivery of placenta
–

BIRTH (PARTURITION)

LACTATION
– postnatal care unique to mammals
– decreasing levels of progesterone free anterior pituitary  allow prolactin secretion
– prolactin stimulates milk production
– starts after 2-3 days
– release of milk from mammary glands is controlled by oxytocin

REPRODUCTIVE IMMUNOLOGY

Trophoblast
– arising along with embryo from blastocyst
– brings about implantation by growing into the endometrium
– later develops into fetal part of placenta
– barrier separating embryo from maternal tissue
– carries paternal antigens

Hypothesis 1
– prevents an immune repsonse against the embryo by interfering mother’s T lymphocytes
– induces devt of suppressor T cells in the uterus
– suppressor cells act only after other WBCs have identified trophoblast as foreign tissue
– if immunological alarm is not intense enough  father’s cell surface antigens are too similar to mother’s  no suppressor cells arise  embryo is attached
– similarity between maternal and paternal antigens may account for multiple miscarriages

Hypothesis 2
– trophoblast secretes an enzyme that breaks down local supplies of tryptophan  amino acid necessary for T cell survival and function

BIOLOGY 12 Mamaril Notes

BIOLOGY 12
Mamaril Notes

Animal Reproduction and Development:

Features of living organisms:
– Metabolism
– Growth and development
– Biological organization
– Responsiveness to stimuli
o Homeostasis, irritability
– Reproduction
o To maintain species
o Different from the other currencies because it is done at certain stages in the life cycle

Increase in population = depletion of resources
– ↑ competition
– ↑ diseases
– ↑ pollution
– ↓ food
– ↓ water

Biodiversity crisis – many species are on the verge of becoming extinct
__________________________________

Figure 52.21 – Human population growth

Year Population
1650 0.5 billion
1850 1 billion
1930 2 billion
1975 4 billion
1987 5 billion
1999 6 billion (reached on October 12, 1999)

Figure 45.12
9000 BC – domestication of plants, animals (11k years ago)
5200 BC (est.) – agriculturally based urban societies
1600 AD – beginning of industrial, scientific revolutions

Projected population for 2050: 9 B or 11 B

Only our species has that kind of population growth!

Edward O. Wilson – naturalist
– Entomologist – studied ants
– Evolutionary and conservatory biologist
– The Future of Life
Population of the world
Continent Current Population Projected Population for 2025
Asia 3.7 billion 4.7 billion
Europe 727 million 717 million
Africa 818 million 1.3 billion
South America 525 million 700 million
North America 316 million 382 million
Oceania 30 million 40 million

Population of the Philippines

Year Population
2001 76.4 million
2002 80 million
2005 85.2 million
2008 88 million

– In 2002, the Philippines was the 14th most populous country among 243 countries
– 2.37% growth rate from 1995 – 2000
– 2001 – we are the only Catholic country in Asia but we have the biggest growth rate

2002 statistics
– Germany has a negative population growth
o Population: 81.947
– Vietnam has a positive population growth
o Population: 80.305
o 1.7%
– Brazil – 1.9
– Mexico – 1.3

Demography
– Population studies
– Age-structure “pyramids”

Fig 52.23 – Age Structures of 3 Nations
– Sweden – decreasing
– US – many were born after World War II
o Baby boom generation
o Has a steady growth
– Mexico – comparable to the Philippines or Afghanistan

Youth Bulge:
– Youth: 15 years old – 24 years old
– 1980’s: youth bulge occurred in Hong Kong, Taiwan, and Singapore
– Indonesia and Thailand’s youth bulge occurred in 2000s

– Philippines:
o Youth: 16 million (versus the 5 million in 1965)
o It will peak at 2025 if present trends continue
o 23.8% of youth are having premarital sex
 11% of them are having sex with the same sex
__________________________________

Diliman Sex Study
– 1/3 do it
o 126 respondents had sex
– Use of protection:
o 40% – sometimes
o 36% – always
o 24% – never
– Kinds of protections used:
o 88% condom
o 10% birth control pills
o 12% rhythm

Several thousand years ago, the population growth was slow, but it increased rapidly in the latter part

Population Models:
1. J-shaped
o Exponential
o Populations that are in ideal environments
o Unlimited resources, no competition, no diseases
 Resources: space, food, water, nutrients, light, humidity

Examples of species with a J shaped pop’n:
– Human population*
– Bacterial culture
o Artificial population
– Cyanobacterium (blue green algae)*
o Laguna de Bay has Microcystis aeruginosa
o Algal blooms can cause chronic damage to environment
 Causes depletion of dissolved oxygen, so env becomes hypotoxic (low O2)
• It may lead to death in some species (fish)
– Insect pests*
o Forests – budworm
o Locust infestations
 Can cause damage to crops
– Mammals*
o If hunting becomes illegal
o Elephants, deer
* populations in the wild

The population can’t increase indefinitely because there is no such thing as unlimited resources

2. Logistic Model
o S-shaped/Sigmoidal growth
o Carrying capacity (K)
 Maximum number of individuals that can be supported by the environment without hurting the environment
 Leads to a population crash
• They will only stay at K or a little lower

Figure 52.15 – Lab population
– Paramecium – K = 900
– Daphnia – K = 135
o Population crashed because it exceeded K
__________________________________

The human population increases rapidly in spite of:
1. Humans have low fecundity
– Fecundity – condition of the number of eggs that the species produces
– 400 oocytes produced in a woman’s reproductive life
o Average: 6 offspring
o Maximum: 12 dozen
o Women: least fecund
– In contrast to:
o Common toad – 7,000 eggs per spawning
o Herring (fish) – 50,000 EPS
o Sturgeon (fish) – 6,000,000 EPS
 In danger of becoming extinct because Europeans are hunting sturgeons to make caviar
• Caviar: $200 per kilo
 Pre-historic fish
 Russian males eat caviar with vodka
 The Russian population is declining because the husbands get too drunk to have sex
o Tapeworm – 6,000,000 eggs every year for 35 years
 Intestinal parasite
o Queen termite – 11,000,000 eggs/year for 15 years

2. Humans have one of the longest generation times:
– Generation time – time (units) from the time an organism is born/hatched until they are able to have their first offspring
– Generation time and body size are inversely proportional
– Escherichia coli – one of the deadliest and most famous
o for further breakdown of food in the large intestine
o also make certain vitamins (Vit K) that the human body cannot produce through their metabolism
o takes only 20 minutes for one to become two

Generation times of some species:
– Protozoans – more or less a day
– Arthropods – 1 week to a month
– Small mammals – months to five years
– Big mammals – 5 years to 10 years+

3. Humans engage in sex
– Our species is the only one that does things differently

In what ways are we weird?
a. Ovulation is concealed
– Vs ape relatives – advertised
o Brightly colored genitals and swollen lips

Fig 15.12b: Our relatives: chimpanzees, gorillas, orangutans
– 2 species of chimpanzee:
o Pan troglodytes – common chimp
o Pan paniscus – pygmy chimp
– Similarity between chimps and humans in DNA: 98.4%

– Jared Diamond – Why is Sex Fun? The Evolution of Human Sexuality
o The Third Chimpanzee
o Procreation  Recreation

b. We have sex even when the woman is not ready to be pregnant
– Menstruation
– Menopause
c. Copulation occurs in private
d. Women undergo menopause (end of fertility)
__________________________________

Modes of Reproduction:
– Asexual Reproduction
o Reproduction of an individual without gametes (eggs/sperm). (Hickman, 1995)
o Formation of an individual whose genes all come from one parent, without fusion of sperm and oocyte (egg)
o Asexuals – organisms that reproduce asexually
– Sexual reproduction
o Reproduction with gametes

Asexual Reproduction
– Almost always relies on mitotic cell division
Advantages:
o Animals in isolation need not find mates
o Numerous offspring formed in little time
 Ideal for colonizing a habitat rapidly
o Little energy expenditure
– Beneficial in stable, favorable habitats, perpetuates successful genotypes precisely
– Disadvantages:
o Does not promote genetic variability
o Offspring are clones
 Genetically identical copies of a single parent

Cloning is advantageous only so long as:
– The parents are highly adapted to the env
– The env stays stable and favorable

Mechanisms of Asexual Reproduction:
1. Fission
– Splitting
– Sea anemones, Planaria (flatworms)

2. Budding
– Parent produces a small copy at first
– Cnidarians (hydra, hydrozoans), Annelids (freshwater oligochaetes, polychaetes)
– Figure 33.6: The life cycle of the hydozoan Obelia
o Buds appear as branches
– Oligochaeta (Aolosoma hemprichii)
o Aquatic
o Buds appear at posterior end

3. Fragmentation, then regeneration
o Sponges, cnidarians, turnicates, echinoderms (especially sea stars)

4. Gemmulation (formation of gemmules)
– Unique to freshwater sponges (and a few marine sponges)
– Gemmule – tiny ball but can be seen
– Formed when the sponge senses that their spongeworld is becoming bad (unfavorable conditions)
– It’s the quickest way to save themselves
– Covering: spicules
o For protection

Parthenogenesis
– Development of the egg without fertilization
– Sexual reproduction
– In rotifers, cladocerans (Crustacea), aphids, honeybees, frogs, whiptail lizards, turkey
– Only when conditions are just right
– No mammals

1. Rotifers
– Mainly freshwater, free-living, pseudocoelomates

Groups of Rotifers:
a. Bdelloid rotifers (Philodina)
– Only have ovaries (paired)
– They form eggs that pass through the colaca and anus in order to be deposited in the water
– All of them are females
– They have been here for 40 million years

Mamaril’s QOTD!
“No sex for 40 days and 40 nights? I’ll go crazy!”

b. Monogonot rotifers (Brachionus)
– Amictic females, amictic eggs
o Amictic: no meiosis
– Every egg becomes a new being
– One ovary rotifer
– Diploid parthenogenesis (2N)
– Can do this process for as long as 40 generations, only if conditions are favorable
– Mictic females, mictic eggs, unfertilized mictic egg  male!
o Mictic: they make 2 kinds of eggs
 Unfertilized haploid egg that becomes the male
o The zygote produced will remain dormant until favorable conditions come. Then they will become female rotifers capable of parthenogenesis.

The male monogonot rotifer:
– Smaller than the female because it has very little life and no digestive system.
– It only has:
o Cilia
o Plenty sperm
o One mission: to fertilize eggs of the female
 Hypodermic impregnation:
• He pricks the female’s skin with his tiny penis
– Lives for only 2-3 days

Mamaril’s QOTD!
Mamaril:
“When there is trouble in paradise, who are you going to call?”
Class:
“…..”
Mamaril:
“Of course, the usual answer is Ghostbuster, but perhaps I am asking the wrong generation”

2. Cladocera (Crustaceans) – Daphnia
– Almost all are females
– Freshwater, found in temperate areas
– Most studied (guinea pig of freshwater organisms)
– Asexual eggs (parthenogenetic eggs) are produced during good times:
o Favorable conditions (spring)
o Brood pouch – 6 eggs
o Viviparous young (live birth)
 Come out like mother
– Sexual eggs (ephippium, ephippia) are produced during bad times:
o Fewer in number (3 eggs)
o Need to be fertilized
o Covered with chitin
o Dropped in the lake  dormant
o They hatch in favorable conditions (spring)

3. Desert whiptail lizards – Cnemidophorus uniparens
– Unisexual (all females)

Figure 46.3: Sexual behavior in parthenogenic lizards
– “He” uses his tongue to flick at female to see if she is ready
– “He” mounts “himself” on top of her and bites the skin of “her” neck
– “He” bends “his” body until cloacal apposition (“cloacal kiss”) is possible
o Doughnut position
o Nothing is transferred; it only stimulates the female to release more eggs
 Pseudocopulation
– The second time around, they will reverse roles
o Explanation: hormones!
– The eggs develop through parthenogenesis

Quick notes about the lizards:
– A lizard may still reproduce by parthenogenesis by herself
o They only go through pseudocopulation in order to release more eggs
– These lizards are doing it in this manner, yet their ancestors are bisexual (C. inornatus)

Sexual Reproduction
– Mode of reproduction of majority
– Formation of new individuals by fusion of haploid gametes to form a zygote
– Gametes arise by meiosis
o Female gamete (egg, ovum, oocyte)
 Large and stationary
o Male gamete (sperm, spermatozoon, sperm cells)
 Much smaller and motile
 Almost always has a flagellum (others are amoeboid)
 Numerous
– Advantage: promotes genetic variability
o Generates unique combinations of genes inherited from 2 parents
o Offspring have a variety of phenotypes
o Enhances the reproductive success of the parents when environmental conditions change rapidly and adversely
– Disadvantage: biologically expensive (bioenergetically costly/large energy outlay)

Why is sex expensive?
Full separation into male and female imposes biologically expensive demands
1. All kinds of structural and behavioral adaptations to get sperm to the egg
a. Behavioral terms
o Male and female reproductive cycles must be synchronous (gametes released at the same time)
o Complex hormonal control mechanisms and sensory receptors that detect such stimuli as longer days and other environmental cues (water, rain)
o Means by which males and females recognize each other; energy outlays needed for coming up with structural signals as bright feathers and for performing courtship routines
 The male is almost always the prettier of the two

Mamaril’s QOTD!
“Girls, no need! Wag na kayo magpaganda… no hope rin naman!”

b. Structural terms (fertilization is less complicated among aquatic animals)
i. External fertilization – large number of sperm and eggs
ii. Internal fertilization – all-land dwelling animals and some aquatic forms
 Fewer sperm are transferred

2. Another requirement: nourishment of fertilized egg and protection of embryo
a. Yolk – food for the embryo
i. No yolk
 Mammals, except for egg bearing ones
 Alecithal
 Sea urchin egg – after 40 hours of fertilization, it reaches the larval stage and it is able to feed itself
ii. Moderate yolk
 Mesolecithal
 Frog eggs
iii. Much yolk
 Telolecithal
 Bird eggs
b. Parental care
i. Oviparous – eggs released outside
ii. Ovoviviparous – eggs develop within (usually in the oviduct) and hatched life from the mother’s body
 Feeds on the yolk; the embryo has no connection to the mother’s tissue
 Various annelids, some fishes (sharks), few snakes (copperhead), lizards, some brachiopods, gastropods
iii. Viviparous – egg is nourished directly from maternal tissues
 Mammals

Sharks are oviparous, ovoviparous, and viviparous

Figure 6.2, Hickman
Whales
– The male has a penis that is 3 m long
o When the female is around, the penis takes a life of its own
o After sex, he pulls it out and puts it inside his body
 To avoid being damaged
 And for hydrodynamics
– Fertilization is internal
Figure 46.8: Insect Reproductive Anatomy
Male:
– Testis (where sperm is formed)  vas deferens  receives mat’l from seminal vesicle penis
– Note: the penis is any structure as long as it can convey the sperm to the female.

Female:
– Must be structurally adapted to receive sperm
– Ovary  oviduct (fertilization)  spermatheca  vagina

Bees can’t stay long mating because they need to avoid predators

– The male stores a lot of sperm in the spermatheca

How do animals find each other?
– Male – rounded posterior end
– Female – pointed posterior end

Pheromones – chemical compounds (metabolites)
– Chemical signatures of animals
– Airborne/waterborne
– Catch attention of the opposite sex

Ex. Lepidoptera (butterflies and moths)
– Female releases sex pheromones to the air.
– The male flies to the female

What might smell good for one animal might be toxic to others

Do humans have pheromones?
– Yes and No!
– Before: Our ancestors had pheromones because they had no chance to look good
– Now: modern humans do things that wash away sex pheromones
o Bath products, esp. feminine wash (douching)

Mamaril’s QOTD!
Mamaril
“Girls, what do you do every day? It’s personal.”
Girl
“Wash my…”
Mamaril, scandalized:
“Don’t make it too personal!”
Girl
“Feminine wash”

German Shepherd – 225,000 olfactory cells
Humans – 5,000 olfactory cells

Separate sexes:
– Dioecious = gonochoristic
United sexes:
– Monoecious = hermaphroditism
– They have difficulties finding suitable partners

Figure 46.6: Reproductive Anatomy of a Parasitic Flatworm
– Chinese liver fluke (Clonorchis sinesis)
o Oriental liver fluke
o Found in bile ducts
o Waits for another Oriental liver fluke and they exchange sperm
 As a rule, cross-fertilization must be practiced

Figure 19-18: Earthworm Reproduction
– External fertilization

Simultaneous hermaphroditism
Sequential hermaphroditism
– Marine gastropod: Slipper shell limpet (Crepidula fornicata)
o Larva of gastropods – veliger (free swimming)
– Gonads are not present at the same time
– Male before – intersex
– Protandry – male  female
o May return to being a male after
– Protogyny – female  male
o Ex. coral reef wrasse

What makes the veliger larvae always turn out into males?
– The female releases sex pheromones to the water
__________________________________

Figure 51.19: Courtship behavior in the three-spined stickleback
– Freshwater fish
– Male: the belly is red and shimmery

1. F appears
2. M swims zigzag to the F
3. M swims toward nest
4. F follows
5. M shows entrance to nest
6. F enters nest
7. M prods F’s tale with trembling movements
8. F spawns and leaves
9. M enters the nest and fertilizes the eggs
In the North Pacific Ocean, 7 species of the Pacific Salmon have been identified
– Oncorhynchus tshawytscha
– They only enter a certain river to reproduce
– They swim upstream (this is difficult and dangerous because of the predators, rapids, waterfalls, etc)
– Once in the head waters, the male builds the nest immediately
– The young go back downstream until they reach the Pacific Ocean. They will grow and live there until it’s time to breed again.
– After they breed, they stay in the head waters and die
– Head waters – cradle and grave

– Semelparity (semelparous) – Condition in which organisms take a long time before they breed;
o They breed only once, then they die
o Pacific Salmons are the only animals known to do this
o Other examples of plants: agave, bamboo (takes a century)
– Iteroparity (iteroparous) – repeated reproduction

Figure 29-26: Life cycle of a leopard frog
1. It takes 3 years to become sexually mature
o They do it at night, in water
o The males croak
o They only breed with the same species
 They are able to distinguish other species through the sound the male makes (“frog call”)
2. Male clasps female (amplexus), eggs are fertilized as they are shed
o Male is smaller, on top
 Inner digits are swollen
• To assist him in amplexus
3. Eggs – surrounded by jelly coats
o Can float, sticky (can attach to plants)
o Jelly coat – for insulation
4. Cleavage
5. Embryo nourished by yolk
o tail bud stage
6. Tadpole begins feeding on algae after he wiggles himself out of the jelly
o external gills
o Herbivore!
7. Skin fold grows over external gill, water exits through spiracle
8. Hindlimbs, then forelimbs emerge
9. The tail shortens by reabsorption, metamorphosis nearing completion

– Froglet – young of frog
o Becomes a carnivore/insectivore
– The leopard frog does not take care of its eggs

Maternal Care for Frogs:
Figure 29-4: Reproductive Strategies of Anurans
1. Pygmy marsupial frogs
o Flectonotus pygmaeus
o Live in trees, their only access to water is rain
o Females have a dorsal brood chamber where eggs develop
2. Surinam frogs
o Females have holes (concavities) on their backs
 Where eggs develop until they become froglets
3. Poison arrow frogs
o Tadpoles cling to the back of the male (paternal care)
o Phyllobates bicolor
4. Darwin’s frog
o Rhinoderma darwinii
o No access to water, so the inside of the male’s body is the only moist environment.
o The male keeps the eggs in his vocal pouch until they become froglets
__________________________________

Human Reproduction
Figure 46.8: Reproductive anatomy of human male
– Testis
– Epididymis
o Where sperm mature
o If stretched, it goes as long as 5 m
– Floats in luminal fluid up the vas deferens
o 74 days until it reaches the ejaculatory duct
– Ejaculatory duct
o receives secretions from:
 Bulbourethral glands
• Mucus-like substance – lubrication
 Seminal vesicles
• Fructose – energy source of sperm
• Prostaglandins – have no function while inside male
o Cause contractions of the uterus
 Prostate gland
• Alkaline – neutralize pH of the vagina (pH 3.8 – 4.2)
o Masturbation: sperm die immediately
– Urethra, if sexually active
Sperm can stay in the vagina for 72 hours/3 days

– Scrotum – outside the abdominal cavity
o Evolutionary reason:
 To help maintain the temperature suitable for sperm formation
 34 oC
o Sometimes, the testes don’t descend from inside the abdominal cavity
 Temperature inside the abdominal cavity: 38 oC
• Inhibitory for sperm formation
 Cryptorchidism
• Infertile man!
• He does not have the right number, nor the right kind of sperm
– Seminiferous tubules – where spermatogenesis occurs
o Leads to a network called the rete testis

Sperm + Secretions = SEMEN
Semen:
– Body fluid (just like tears and saliva)
– Colorless, tasteless, nutritious
o Rich in protein – 30% more than cow milk
o Low in calories – 1/9 of sugar and fat in cow milk

Mamaril’s QOTD!
“Class, I am not encouraging you to engage in activities that involve eating semen. I don’t want you running to your mothers saying, ‘Mommy! Mommy! Semen pala, according to our Bio 12 lecture, is yummy yummy!”

Stratified epithelial tissue
– Basement membrane
o Spermatogonia lie here
 When born, this is what males have
o Sexual maturity  1o spermatocytes
 Beginning of spermatogenesis
o 2o spermatocytes  meiosis II
o Stem cells: starting cells
o End: 4 haploid sperm

Non Spermatogenic Cells:
1. Sertoli Cells
– Nurse cells, sustentacular cells
– Provide nourishment to spermatids until they become sperm
– Believed to release inhibin (exerts negative feedback on anterior pituitary and hypothalamus)

Figure 27.9B: Structure of a Human Sperm Cell
– Sperm – result of spermatid losing its cytoplasm
o Head:
 Nucleus – most important part
 Acrosome – cap that contains minute amounts of digestive enzymes
• Used to gain entry to the egg cell – nuclear warhead
o Neck
 Mitochondrion – supplies energy
 Centriole
o Flagellum
 Have microtubules made of protein tubulin (similar to actin)
• Provides strength to sperm

2. Interstitial Cells
– Interstitial endocrinocytes, Leydig cells
– Found in interstices between adjacent seminiferous tubules
– Synthesize the male sex hormones
o Androgens – testosterone

Figure 4-8: A Comparison of Functional Groups of Female (estradiol) and Male (testosterone) sex hormones
– Male lion – symbol of male sex
o Testosterone : O, CH3, CH3, OH (mandatory fxnl groups)
o Gives all the male characteristics
 Mane – attractive to lioness
– Female lion
o Estradiol: HO, CH3, OH
– Lifestyle:
o The lion stays at home while the lioness hunts. The food is offered first to the lion and the leftovers are given to the cubs.

Figure 26.3: The Major Endocrine Glands in Humans
– Ovary – where sex hormones for females are made
– Adrenal cortex – other source of sex hormones

Estradiol and testosterone can be synthesized from cholesterol  Steroids!

All of us have testosterone and estradiol
The reproductive system takes orders from the hypothalamus
– Does its regulation via pituitary gland/hypophysis

Figure 26.4A: Location of the Hypothalamus and Pituitary
– Anterior pituitary gland (APG)
o Infundibulum – links APG to hypophysis
o Releases FSH and LH

Process:
– Nerve cells in hypothalamus release gonadotropin releasing hormones
– Stimulates APG to release FSH and LH
– Blood stream
– Target organs

Figure 46.14: Hormonal Control of the Testes
– Refer to book
– FSH – works through Sertoli cells to promote spermatogenesis
– LH – ICSH (Interstitial cell stimulating hormone)
o Works through Leydig cells
o Testosterone:
 Spermatogenesis
 1o and 2o sex characteristics

– Testosterone sends message to APG and hypothalamus to slow down to prevent overproduction of sperm and over secretion of testosterone.
_________________________________

Testes  ejaculatory duct (74 days)
Spermatogonium  sperm (65-75 days)
Sperm produced: 300 M daily

What is happening to sperm in men?
– 1996, Brit Med J
o Men born after 1970 had a sperm count 25% lower than those born before 1959
– 1995, Study of men in Paris, France
o 2.1% annual decline over the past 20 years
– 1992, Skakkebaek et al
o Covered 15,000 men from 21 countries combining results of 61 separate studies over the past 50 years: decline from about 113 M per mL in 1938 to 66 M in 1990 – a plunge of nearly 50%
– Decline of quality of sperm
– Increase of incidence of testicular cancer and undescended testes
What may be causing oligospermy?
– Stress, smoking, drug use
– Men having children later in life
– Increase in STDs
– Shift from boxer shorts (gives ventilation) to briefs
– Environmental pollutants such as DDT (insecticide that combats malaria and insect pests especially after WWII), some forms of dioxins (dirty dozen), PCBs (used in computers) and a number of synthetic substances – environmental estrogens or xenoestrogens (POPS)
o Concern: they bind with receptors that normally recognize estrogens and other natural hormones, fooling the body into thinking that they are natural estrogens
o For men: natural estrogens work in testes (rete testis)
 Reabsorb the components of luminal fluid: ions, proteins, water
 Make the sperm more concentrated

Lab tests: small amounts of industrial chemicals, delivered at a crucial stage of fetal development, can “feminize” a male embryo
– Smaller testicles, low sperm output, miniscule penis
– For extreme cases, some don’t have a penis at all

How many sperm must a man house to be considered fertile?
– 48 million mL, where > 63% are motile sperm
– Infertile man:
o < 13.5 million mL-1, where < 32% are motile sperm

Mamaril’s take home messages!
– Check the equipment (testes should have descended)
– He should have the right number of sperm

Mamaril’s QOTD!
“When I got married to my wife, we signed a contract stating that I will always have the last word, and my last words are always ‘yes, I’ll do it.”

Figure 27. 2C: Sideview of the female reproductive anatomy
– Ovaries – where part of oogenesis takes place
o Every 20 days a 2o oocyte is released and goes to the fallopian tube where it could be fertilized
o Lifespan of oocyte: 48 hours
o Release oocyte alternately
– Vagina
o Passage of baby during delivery
o Where sperm are deposited
o Where sperm die
o Passage of menstrual flow

What makes the vagina acidic?
– Bacterium: Lactobacillus acidophilus
o As they metabolize, they produce lactic acid
o Same bacterium used in yogurt

Why do we need an acidic vagina?
– Kills the pathogenic bacteria that enters the vagina
– Kills sperm

– The egg is held along the ciliated cells of the fallopian tube
– When no fertilization occurs, the endometrium is sloughed off
– Sometimes the blastula is implanted in the oviduct or abdominal cavity
o Ectopic pregnancy – must have embryo taken out by surgery

Figure 44.6a: The position of the female reproductive system relative to the pelvic girdle and urinary bladder
– The reproductive system is protected by the pelvic girdle

Figure 46.16: Formation of the zygote and early post-fertilization events
1. Fertilization
o Conception, act of conceiving
2. Cleavage
3. Blastocyst implants
o Start of pregnancy

Figure 27.4 B: Meiosis in Oogenesis
– Embryos: oogonia
– Birth: 1o oocyte, no oogonia anymore
o Arrested in prophase of meiosis I
o 400,000
– Sexual maturity/puberty: one 1o oocyte starts to develop (released)
– Ovulation: 2o oocyte (N) – 400 only
o Remain as such until there is sperm
– Menopause: no more ovulation

Differences between oogenesis and spermatogenesis:
– Both start with stem cells
– One 2o oocyte is produced
o For boys, two 2o spermatocytes are formed
– Only 1 egg is formed
– Males do it for life

Figure 46.11: Human Oogenesis
– Follicle cells – make estrogen and progesterone
– Ovary – can be considered an endocrine gland
– 14th day of menstruation – fully mature follicle – triggers the release of the 2o oocyte
o The follicle becomes the corpus luteum.
 Continues to release the same hormones, but produces larger quantities of progesterone and less quantities of estrogen
o Not pregnant: after 10 days, the corpus luteum shrivels until it sinks into the substance of the ovary
o Pregnant: the corpus luteum stays until the 1st trimester, then it shrinks

Female reproductive cycles in mammals:
Estrous cycle Menstrual cycle
Non-primate mammals and a few primates Mainly in women and few primates
Advertised ovulation

Estrus phase – only when mammals engage in sex. When the female is sexually receptive
“in heat” Concealed ovulation
Endometrium is not sloughed off Endometrium is shed (menstrual flow)

Figure 46.15: The reproductive cycle of the human female
– 28 days

Ovarian cycle:
– Primary follicle
– Growing follicle Follicular phase
– Graafian follicle
– Ovulation
– Corpus luteum Luteal
– Disintegrating corpus luteum phase
Hormones:
– Estrogen – high amounts before ovulation
o To prepare the uterus for possible implantation
o Builds endometrium and connective tissues
– Progesterone
o Brings about growth of blood vessels
 Increases after ovulation
o Brings about accumulation of glycogen and enzymes
– Follicle-stimulating hormone (FSH)
o Development of follicle (keeps oocyte)
o Present until LH peaks
o Low estrogen  prevent other follicles from developing
– Luteinizing hormone (LH)
o High LH + high estrogen = ovulation
o Functions:
 Triggers ovulation
 Brings about change from residual follicle to corpus luteum
 Drives corpus luteum to stay for a while for progesterone

When should a woman have sex?
– Days 13-17
__________________________________

See table 27.7: STDS common in the US
– Trichomoniasis

Fact of life #4589439:
Without contraception 85 pregnancies would occur

How would the woman know that she is ovulating?
– Ovulation predictor test kits

How do men have sex?
– Erectile tissue – virtually empty spaces
o Corpora cavernosa
o A cascade of chemical events trigger erection
– Process of erection:
o Arousal 
o Parasympathetic nerves 
o release L-arginine 
o Enzyme 1 
o Nitric Oxide (NO) 
o Guanylate cyclase 
o cGMP (cyclic guanosine monophosphate
 relaxes and dilates blood vessels in the penis. Blood remains here longer

– Process of ejaculation
o 400 M sperm in 3.5 mL
– Enzyme 2 – breaks down nitric oxide

Erectile dysfunction
– Failure to release semen
– Solution: Viagra (1998)
o Has Sildenafil citrate
o Works by preventing enzyme 2
o Pfizer (earns 1 B a year because of this!)

Difficulties of a sperm’s life:
1. Sperm have to survive the journey to the urethra
o Subject to intense shearing forces
o Travel 5 m/s
o Have a flagellum that keeps them intact
2. Acidic vagina
3. Cervical mucus
o Prostaglandins
4. Hostile environment of the uterus
o Sperm capacitation:
 Gives a bath of glucose to sperm
 Proteins
o WBC see sperm as foreign bodies
o There are only a few hundred thousand sperm left at this point
5. Fallopian tube
o only 200 at this point

Mamaril’s take home message!
– Getting pregnant is not that simple

Fact of life #82947329:
30% of pregnancies end up in spontaneous abortion/miscarriage

Life lessons from Professor Mamaril:
How to Make Babies
Problems:
– Man infertile; oligospermy; sperm not motile enough
– Female infertile; failure to ovulate; blockage in oviducts
– Sexually transmissible diseases – often produce scar tissue that blocks the oviducs
– Antibodies produced in uterus immobilize sperm

Solutions: reproductive technology
1. Hormone therapy – to increase production of sperm or oocyte
2. Surgery – correct disorders like blocked oviducts
3. Cryoperservation – sperm banks; oocyte storage
o Stored in liquid nitrogen
4. Assisted reproductive technology (ART)
a. In vitro fertilization (IVF)
 Culture dish; up to 8 cells
 Taken from gonads
 When in the 8 cell stage, the secondary oocyte is brought to the oviduct
b. Zygote intrafallopian transfer (ZIFT)
 Zygote placed in oviduct
c. Gamete intrafallopian transfer (GIFT)
 Oocyte and sperm are placed in the oviduct
d. Surrogate motherhood
 Has ethical and legal problems

November 13, 2004
– Frances Harris (Georgia, USA)
o 5 children, pregnant with twins
o 59 y/o, menopausal
o Had tubal ligation
o Divorced from Raymond

January 18, 2005
– Romania
o World’s oldest mom – 66 y/o
o Triplets, but only 1 survived

Mamaril’s QOTD:
Mamaril:
“Why shouldn’t old women have babies?”
Migs:
“Because they won’t be able to take care of the kids”
Mamaril:
“That’s the serious answer. I’m not looking for the serious answer. The less serious answer is: the women might forget where they left their babies.”

Cloning 101: How to make your own clone
1. Remove nucleus from the egg cell
o Secondary oocyte, haploid
2. Add the nucleus from a somate cell from adult donor
3. Grow in culture to produce an early embryo (Blastocyst)
4. Blastula implanted in another female

Roslin Institute (Edinburgh, Scotland)
– Dr. Ian Wilmot
– Successful cloning – July 1996
o Announcement: Feb 1997
– Dolly
o Named after Dolly Parton because the nucleus brought in there was from the mammary glands
o 3 ewes involved
 Source of secondary oocyte
 Source of nucleus
 Surrogate mother
o Died February 2003. Got a viral infection and lung disease.
o 6 y/o

Figure 43.4: Overview of the stages of animal development
1. Gamete formation
2. Fertilization
3. Cleavage
4. Gastrulation
*** Neurolation – development of the nervous system
o First organ system to develop because it regulates everything else
5. Organogenesis
6. Growth, tissue specialization

External fertilization of sea urchins:
– They release gametes to water

How do these sperm and eggs find each other?
Problems:
1. Water movements
a. Waves
b. Current
c. Tide
2. Big sea
3. Simultaneous spawning

Solution:
– Oocytes have chemotactic factors
o Dispersed and picked up by the sperm
o Species-specific
o Lock and key principle

Animal Kingdom
Phylum Protozoa
Class 1: Mastigophora
o Move and fed by means of flagellum
Class 2: Sporoza
o Spore-formers
Class 3: Sarcodina
o By pseudopodia
Class 4: Ciliophora

Plant Kingdom
Bacteria
Algae
Fungi
Bryophytes
Tracheophytes

Sarcomastigophora – super class, combination of sarcodina and mastigophora because they are super similar

Protozoa – phylum of single-celled animals (before)

– Botany wanted Mastigophora and Algae (flagellated and photosynthetic)

3 Kingdom Scheme:
– Protozoa  Kingdom Protista
o Included algae at that time
o Monera:
 Bacteria
 1 group of algae
o Fungi had its own kingdom
o What was left: bryophytes, tracheophytes

Figure 28.3 Semantics and Phylogeny of Eukaryotes
– Ernst Haeckel

a. Five Kingdom System
Monera Protista Plantae Fungi Animalia

b. Eight Kingdom System
Bacteria Archaea
Archaezoa Protista (Protozoa) Chromista Plantae Fungi Animalia

c. Three Domain System
o Domain Bacteria
o Domain Archaea
o Domain Eukarya

PROTISTS
– 1674 – Antoni Van Leeuwenhoek
– 37,000-38,000 species (+44,000 fossil species) of protozoan protists
– Even a low-power microscope can reveal a great variety of organisms in a drop of pond water
– Protist – informal name of the kingdom of mostly 1-cell eukaryotes
– Advances in eukaryotic systematic have caused the classification of protists to change significantly
– Protists constitute a polyphyletic group, and Protista is no longer valid as a kingdom

Figure 26.2: Kingdom Protista Problem
– Choanoflagellates – protists but related to animals
– Fungi are closer to animals

Structural and Functional Diversity in Protists
– Protists exhibit more structural and functional diversity than any other group of eukaryotes
– Single-celled protists can be very complex, and all biological forms are carried by organelles in each individual cell
– The most nutritionally diverse of all eukaryotes
o Photoautotrophs – chloroplasts
o Heterotrophs – absorb organic molecules or ingest larger food particles
o Mixotrophs – combine photosynthesis and heterotrophic nutrition
o Can be exclusively photosynthetic, but under certain conditions, this is impossible so they resort to heterotrophy. They can switch back to photosynthesis after.
– Can reproduce asexually/sexually or by sexual processes of meiosis and syngamy

Endosymbiosis in Eukaryotic Evolution
– Endosymbiosis – process in which certain unicellular organisms engulf other cells, which become endosymbiotic and ultimately organelles in the host cell
– There is now considerable evidence that much protist diversity has its origins in endosymbiosis
o We are all descendants of bacteria
– Mitochondria evolved by endosymbiosis if an aerobic prokaryote
– Plastids evolved by endosymbiosis by means of a photosynthetic cyanobacterium
o Gave rise to red algae and green algae
– Green algae underwent secondary endosymbiosis
o They were ingested in the food vacuole of heterotrophic eukaryotes and became endosymbiotic themselves
 Ex. Chlorarachniophytes

The Five Supergroups of Eukaryotes
– No longer thought that amitochondriates are the oldest lineage of eukaryotes
– Our understanding of the relationships among protist groups continues to change rapidly
– One hypothesis divides all eukaryotes into 5 supergroups:
o Excarta, Chromalveolata, Archaeplastids, Rhizaria, Unikonta

1. Excavata
– characterized by its exoskeleton

a. Diplomonads
o Have modified mitochondria called mitosomes
o Derive energy anaerobically through glycolysis
o Have two equal sized nuclei and many flagella

Giardia intestinalis
– May be in the intestine of humans, and in wild and domestic animals
– Millions of cysts pass in the feces
– Wilderness streams or lakes are contaminated with cysts
– Cysts are durable; they may last for 2-3 months
– Cysts can be taken by drinking contaminated water

b. Parabasalids
o Have reduced mitochondria called hydrogenosomes that generate some energy anaerobically
o Trichomonas vaginalis – greatest infection

Trichomonas vaginalis
– Largest (7-32 micrometers long) of trichomonads present in humans
– Inhibits vagina primarily; associated w lowered acidity
– Treatment: suppositories, douche with dilute vinegar, powders containing boric acid or acid creams or jellies, antibiotics
– Males: invades prostate
– STD

c. Euglenozoans
o diverse clade that includes predatory heterotrophs, photosynthetic autotrophs

i. Kinetoplastids
 Single mitochondrion with an organized mass of DNA – kinetoplast
 Trypanosoma – causes sleeping sickness in humans

Trypanosoma congolense
– Disc-shaped DNA containing organelle within a large mitochondrion
– 3 subspecies:
o Trypanosoma brucei
o Trypanosoma gambiense
o Trypanosoma rhodesiense
– Trypanosomiasis
– Vector: tse-tse fly Glossina (insecta: Diptera)

ii. Euglenids
 1 or 2 flagella that emerge from a pocket at one end of the cell
 Some species can be both autotrophic and heterotrophic
 Parts:
• Light detector
• Eyespot
• Short flagellum
• Long flagellum

Budo – free living and does not harm anyone

2. Chromalveolates
o Alveolates
o Stramenopiles

a. Dinoflagellates
o Freshwater
o Cells that are reinforced by cellulose plates
o Mixotrophic or heterotrophic
o Dinoflagellate blooms – “red tide”

Rodney Barker
– All the Waters Turned into Blood
o About dinoflagellates

Pyrodinium bahamense var compressum
– First discovered in the Red Sea
– Causes red tides in the Philippines
Pyrodinium bahamense var bahamense
– Never been reported as toxic

Pfiesteria piscicida
– In North Atlantic Ocean
– 24 stages in life cycle:
o Cyst – bottom  breakout into flagellates
o Flagellated stages suck out juices of menhader and oily fishes, amoeboid stages feast of the dead fish
– Called “the cell from hell”
Ceratium hirundinella, Notiluca
– Bioluminescent
Zooxanthellae
– Endosymbionts in hard corals in gastrodermis of hermatypic corals

b. Apicomplexans
o Parasites of animals and can cause serious human diseases
o One end – apex – contains a complex set of organelles specialized for penetrating a host
o Have a non-photosynthetic plastid, the apicoplast
o Complex life cycles
o Not motile

Plasmodium
– Causes malaria
– Number 1 parasite killer
– Requires both mosquitos and humans to complete its life cycle
– Approximately 2 million (1%) die each year from malaria
– 200 million – 300 million victims of malaria
– Efforts are ongoing to develop vaccines that target this pathogen

– Vector: mosquito Anopheles (Diptera), female
– No. of species of mosquitoes: 3000-3500
o Anopheles: 100
o Those that transmit malaria: < 2 dozen

Species and periodicities of episodes of chills and fevers:
– Plasmodium vivax
o Tertian/benign malaria, every 48 hours
– Plasmodium falciparum
o Subetertian, malignant tertian malaria, every 40 – 48 hours
o Most virulent

– Schizogony – asexual reproduction of Plasmodium
– Plasmodium falciparum Erythrocyte Membrane Protein (PfEMP1) – mediates adhesion to host cells
– See life cycle of Plasmodium, Figure 28.10 (Campbell)
– Merozite

Peritrophic membrane of the gut:
– SM1 gene
– PLA 2 gene
– Both multiple effector genes.
– From another mosquito. These are inserted to the genome of the other mosquito to prevent ookinete from becoming oocyot
– Single chain antibody
– Genetically modified Anopheles

Difficulties in controlling malaria:
The vector mosquito Anopheles:
– Persistence of breeding places
– Different susceptibilities of Anopheles individuals to insecticides
The human host:
– Exposure to the mosquito
Parasite:
– Alters surface chemistry of RBC so that RBC sticks to the tissue lining of the blood vessel
– Intracellular
– Different species of Plasmodium
– Different stages of Plasmodium

c. Ciliates
– Micronuclei – function during conjugation, a sexual process that produces genetic variation
– Conjugation – separate from reproduction (binary fission)
– Macronuclei – control the everyday functions of the cell, such as feeding, waste removal, and maintaining water balance

3. Rhizarians
– Have threadlike pseudopodia

a. Forams/foraminiferans
o Tests – porous multichambered shells that hardened with calcium carbonate.

b. Radiolarians
o Delicate, symmetrical skeletons made of silica

4. Unikonta

a. Amoebozoans
o Amoebas that have lobe- or tube-shaped pseudopodia

i. Entamoebas
 Parasites
 Infect all classes of vertebrates as well as some invertebrates

Entamoeba gingivalis
– Stays inside the mouth
o Feeds on bacteria
– Acquired through oral contact
Entamoeba histolytica
– Number 3 parasite killer
– Causes amoebic dysentery
– Spread via contaminated drinking water, food, or eating utensils
– 100,000 deaths worldwide per year
Iodamoeba buetschii
– May cause intestinal ulceration in humans

Life cycle of Naegleria fowleri
– Causes primary amoebic meningoencephalitis (PAM)
– Found in hot springs (they enjoy high temperatures)

__________________________________

INVERTEBRATES
– Spirobranchus giganteus – “Christmas tree worm”
o the main part is wrapped in a calcareous tube
o pink – tentacles )radioles)
 for gas exchange and capturing food

Charles Darwin
– Talked about:
o How different species have come about
o Diversity and unity
o 1,300,000 species of animals
– 12 Feb 1809 – birthday
– 24 Nov 1959 – wrote a book
o 150th anniversary of the publication of his book “The Origin of Species”
 Editor: James D. Watson
– 27 Dec 1831 – the HMS left Plymouth and went on a five year trip and he was on board

Mamaril’s QOTD!
“True love has no happy ending because true love has no end.”

Main three species infecting humans:
Schistosoma japonicum
Schistosoma mansoni
Schistosoma haematobium
Radix guadras

Campbell: Chapter 22(Descent with Modification: A Darwinian View of Life)

Chapter 22: Descent with Modification: A Darwinian View of Life

A. The Historical Context for Evolutionary Theory
• Introduction
 Biology came of age on November 24, 1859, the day Charles Darwin published On the Origin of Species by Means of Natural Selection.
 Focus on the great diversity of organisms – origins, relationships, similarities and differences, their geographic distribution, and their adaptations to surrounding environments
 Darwin made two points:
1. species today descended from ancestral species
2. mechanism for evolution termed natural selection.
 Populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring that other individuals.
 Result is evolutionary adaptation: a prevalence of inherited characteristics that enhance organism’s survival and reproduction in specific environments.
 Genetic composition of the population had changed over time. (evolution)
• Western culture resisted evolutionary views of life
• The Scale of Nature and Natural Theology
1. Plato and Aristotle held opinions that opposed any concept of evolution.
 Species permanent, perfect and do not evolve
2. Judeo-Christian culture
 Species were individually designed and nonevolving
• Carolus Linnaeus
 Specialized in taxonomy: branch of biology concerned with naming and classifying the diverse forms of life.
 Binomial system of classification: genus – species
• Cuvier, fossils and catastrophism
 Study of fossils also layed the groundword for Darwin’s ideas.
1. Fossils
 relics or impressions of organisms from the past preserved in rock. Shows that a succession of organisms has populated earth throughout time
• Paleontology
 Study of fossils
 Developed by Georges Cuvier
 Cuvier found out that extinction had been a common occurrence in the history of life. Advocated catastrophism.
• Theories of geologic gradualism helped clear the path for evolutionary biologists
 James Hutton: possibility to explain landforms by looking at the current mechanisms operating at the world
 Hutton and Gradualism
1. Gradualism
 Profound changes is the cumulative product of slow but continuous process
 Charles Lyle and Uniformitarianism
1. Uniformitarianism
 Geologic processes have not changed throughout the Earth’s history.
 Led Darwin to believe two things
1. Earth must be very old
2. slow and subtle processes persisting over a long period of time can add up to substantial changed
• Lamarck placed fossils in an evolutionary context
 Erasmus Darwin: Life evolved as environments changed
 Jean Baptiste Lamarck
1. Use and disuse
 Useful part stronger and bigger, not useful part deteriorated
2. inheritance of acquired characteristics
 modifications can be passed to offspring
B. The Darwinian Revolution
• Charlers Darwin
 Born in Shrewsbury, W. England
 University of Edinburgh to study medicine
 Christ College in Cambridge University to become a clergy
 Under Rev. John Henslow
 Capt. Robert FitzRoy
• Field research helped Darwin frame his view of life: The Voyage of the Beagle
 HMS Beagle in Dec. 1831
 Mission of the voyage was to chart poorly known stretches of the South American coastline
 Endemic species in the Galapagos island
 Collected finches from Galapagos, although similar seemed to be of different species
 Read Lyell’s Principles of Geology, led him to believe
1. earth very old,
2. constantly changing
3. life on earth has also evolved
• Darwin’s focus on Adaptation
 New species arise from gradual accumulation of adaptations to a different environment
 Finches and their beaks which are adapted to specific foods in their environments
 Was already a famous naturalist, visits from Lyell, Henslow
 1858, Darwin received a letter from Alfred Wallace a British naturalist working in the East Indies with a manuscript of natural selection similar to Darwin’s
 July 1 1858, presented Wallace paper with excerpts from Darwin to the London Linnaean Society
 A year later, Darwin finished the Origin of Species
 Biological diversity is a product of evolution
• The Origin of Species developed two main points: the occurrence of evolution and natural selection as its mechanism
1. Descent with Modification
 All organisms related through descent from some unknown ancestor from the remote past
 Descendants spilled over and adapted to the various environments
 Asian and African elephant
 Most branches of evolution are dead ends, 99% of all species that have ever lived are extinct
 Linnaeus helped Darwin by his idea of “groups subordinate to groups”
 Linnaean scheme reflected the brainching history of the tree of life, organisms at different taxonomic levels related through descent from common ancestors
2. Natural selection and adaptation
 Ernst Mayr dissected the logic of Darwin’s theory of natural selection
 E. Mayr, The Growth of Biological Thought: Diversity, Evolution, and Inheritance. (Cambridge, MA: Harvard University Press, 1982)
 Observations (1-3):
a. All species had a great potential fertility that population size will increase exponentially if all that were born reproduced successfully (completed one life cycle)
b. Populations tend to be stable in size except for seasonal fluctuations
c. Environmental resources are limited
 Inferences (1)
a. Production of more offspring for survival, only a fraction of offspring survives each generation
 Observations (4-5):
a. Individuals in a population vary, no two are the same
b. Much of the variation is heritable
 Inference (2-3):
a. Survival is not random, depends in part on the hereditary constitution of the individuals
b. Unequal ability to survive and reproduce will lead to gradual change in population, favorable characteristics accumulating over the generations
 Summary of Darwin’s ideas:
a. Natural selection is differential success in reproduction
b. Natural selection occurs through an interaction between environment and the variability inherent among individual organisms
c. Product of natural selection is the adaptation of populations of organisms to their environment
 Elaborations
a. Idea of overpopulation
 After reading Thomas Mathus’ essay on human population (1798)
 Much of human suffering – disease, famine, wars – was the consequence of the potential for the human population to increase faster than the food supplies and other resources
b. Increasing frequency of favored traits in a population is evolution
 Artificial selection of Darwin, selective breeding
 Darwin incorporated gradualism into evolutionary theory: minute changes operating in varying contexts over vast spans of time could account for the entire diversity of life.
 Summarize two main features of the Darwinian view of life:
1. diverse forms of life have arisen by discent with modification from ancestral species
2. the mechanism of modification has been natural selection working over enormous tracts of time.
• Some subtleties of Natural Selection
1. Importance of populations in evolution
 A group of interbreeding individuals belonging to a particular species and sharing a common geographic area
 Smallest unit that can evolve, individuals do not evolve
 Evolution measured only in changes in a population over a succession of generations.
2. natural selection can only amplify or diminish only heritable variations
 no evidence that characteristics acquired during a lifetime can be inherited
3. specifics of natural selection are situational
 environmental factors vary from place to place from time to time.
• Examples of natural selection provide evidence for evolution
1. natural selection in action: the evolution of insecticide-resistant insects
 insects that survive the first wave of insecticide attack have genes that enable them to resist the chemical attack
 offspring inherit genes for pesticide resistance
 insecticide does not create resistance individuals but selects for resistant insects that are already present in the population
2. the evolution of drug-resistant HIV
 3TC
• Other evidence of evolution pervades biology
1. Homology
 Novel features are altered versions of ancestral features
 Similarity in characteristics resulting from common ancestry is known as homology
a. Anatomical Homologies
 Forelimbs of all mammals
 Taking on different functions in each species, the basic structures were modified
 Comparative anatomy (comparison of body structures between species) confirms that evolution is a remodeling process
b. Vestigial organs
 Structures of little importance to the organism
 Remnants of structures important to ancestors
c. Embryological Homologies
 Pharyngeal pouches in all vertebrate embryos
d. Molecular homologies
 All species of life use the same basic genetic machinery of DNA and RNA, genetic code is essentially universal
e. Homologies and the Tree of Life
 Homologies mirror the taxonomic hierarchy of the tree of life.
2. Biogeography
 Geographic distribution of species suggested evolution to Darwin
 Species more related to other species living in the same areas, than similar species on a different area
a. Sugar glider and flying squirrel : converget evolution
 Endemic: found no where else in the world
a. Fruit flies Drosophila in Hawaii
3. The Fossil Record
 Prokaryotes precede all eukaryotes
 Fishes then amphibians, then reptiles then mammals and birds
 Evolutionary transitions leave signs in the fossil record
 Darwinian view of life supported by evolutionary patterns of homology that match patters in space (biogeography) and time (fossil record)
• What is theoretical about the Darwinian view of life?
 Darwin gave biology a sound scientific basis
 “There is grandeur in this view of life.
 Basilosaurus ancient what linking past and present.

Chapter 23: The Evolution of Populations
A. Introduction
 Evolution on the smallest scale or microevolution, can be defined as a change in the allele frequencies of a population.
 Liguus fascitus marine snail
B. Population Genetics
• Darwin not gain acceptance that natural selection be the mechanism for evolution
• The modern evolutionary synthesis integrated Darwinian selection and Mendelian Inheritance
 Quantitative characters are influenced by multiple genetic loci
 An important turning point for evolutionary theory is the birth of population genetics
1. Population Genetics
 Emphasis on the extensive genetic variation within populations and the importance of quantitative characters
 Darwinism and Mendelism reconciled; genetic basis of variation and natural selection worked out.
1. Modern Synthesis
 A comprehensive theory of evolution in the 1940s.
 Integrates paleontology, taxonomy, biogeography, population genetics
 Theodosius Dobzhansky and Sewall Wright, Ernst Mayr, George Gaylord Simpson, G. Ledyard Stebbins
 Emphasis on the importance of populations as the units of evolution, central role of natural selection as the mechanism for evolution, the idea of gradualism.
• A populations’ gene pool is defined by its allele frequencies
1. Population
 A localized group of individuals belonging to the same species
2. Species
 A groups of populations whose individuals have the potential to interbreed and produce fertile offspring in nature.
3. Gene pool
 The total aggregate of genes in a population at one time
 Consists of all alleles at all gene loci in all individuals of the population
• The Hardy-Weinberg theorem describes a nonevolving population
 Gene pool for a nonevolving population
 Theorem states that the frequencies of alleles and genotyps in a population’s gene pool remain constant over the generations unless acted upon by agents other than Mendelian segregation and recombination of alleles.
 * check notes on this
C. Causes of Microevolution
• Microevolution is a generation-to-generation change in a population’s allele frequencies
 if frequencies of alleles or genotypes deviate from values predicted by the Hardy Weinberg equation, it is because the population is evolving
 new definition of evolution
1. Evolution
 Is a generation-to-generation change in the a population’s frequencies of alleles.
 Referred to as microevolution due to its small scale
2. Microevolution
 Occurring even if the frequencies of alleles are changing for only a single genetic locus.
• The two main causes of microevolution are genetic drift and natural selection
 Natural selection always has a positive effect, only on that adapts populations to its environment
1. Genetic Drift
 Smaller the sample the greater the chance of deviation from an idealized result (sampling error)
 A change in population’s allele frequencies due to chance is called genetic drift.
a. The bottleneck effect
 Genetic drift due to a drastic reduction in population size
 Reduces overall genetic variability in a population, some alleles are likely to be lost from the gene pool
b. The founder effect
 Genetic drift likely whenever few individuals from a larger population colonize an isolated island or lake, or some other new habitat
 The smaller the sample size, the less representative of the population they left
 Genetic drift in a new colony is known as founder effect
 Probably accounts for high frequency of certain inherited disorders in humans
2. Natural Selection
 Differential success in reproduction
 Results to disproportion
 Only one to adapt the population to its environment
 Maintains and accumulates favorable genotypes in a population
3. Gene Flow
 Genetic exchange due to the migration of fertile individuals or gametes between populations
 Tends to reduce difference between populations
4. Mutation
 A change in an organism’s DNA
 Alters the gene poopl of a population by substituting one allele for another
D. Genetic Variation, the substrate for natural selection
• Genetic variation occurs within and between populations
 Occurs in all sexually reproducing individuals
 Not all variations are heritable
 Only the genetic component of variation can have evolutionary consequences as a result of natural selection because it is the only component that transcends generations
• Variations within populations
 Both quantitative and discrete characters contribute to variation within a population
 Quantitative variation usually indicates polygenic inheritance
 Discrete characters are an either-or basis, determined by a single gene locus
• Polymorphism
 When two or more distinct morphs are each represented in high frequencies to be readily noticeable
 Occurs only with discrete characters
• Measuring genetic variation
 Measure both at the level of whole genes (gene diversity) and at the molecular level of DNA (nucleotide diversity)
• Variations Between Populations
1. geographic variation
 differences in gene pools between populations or subgroups of populations
2. cline
 graded change in some trait along a geographic axis
E. Mutation and sexual recombination gamete genetic variation
 Two random processes that create variation in the gene pool o f a population
• Mutation
 new alleles originate only by mutation
 Only mutations that occur in cell lines that produce gametes can be passed along to offspring
 A mutation that alters a protein is often harmful than beneficial
• Sexual recombination
 Genetic differences from the unique recombinations of existing alleles each individual receives from the gene pool
F. Diploidy and balanced polymorphism preserve variation
• Diploidy
 Recessive alleles in heterozygotes
 The rarer the recessive allele the greater the degreeof protection from natural selection
• Balanced polymorphism
 Ability of natural selection to maintain stable frequencies of two or more phenotypic forms in a population
1. Heterozygote advantage
2. frequency dependent selection
 survival and production of one morph declines when it becomes too common in the population
• Neutral Variation
 No selective advantage
G. A Closer Look at Natural Selection as the Mechanism of Adaptive Evolution
• Evolutionary fitness is the relative contribution an individual makes to the gene pool of the next generation
1. Darwinian fitness
 Is the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals
2. relative fitness
 the contribution of a genotype to the next generation compared to the contribution of alternative genotypes for the same locus
 survival alone does not guarantee reproductive success
 relative fitness is zero for a sterile plant even if it outlives others
• The effect of selection on a varying characteristic can be directional, diversifying or stabilizing
 Natural selection can affect the frequency of a heritable traits in a population is three different ways:
1. Directional selection
 Common during environmental change and migration
 Peter and Rosemary Grant – finches in the Galapagos
2. Diversifying selection
 Occurs when environmental conditions are varied in a way that favors individuals on both extremes of a phenotypic range over intermediate phenotypes
3. Stabilizing selection
 Act against extreme phenotypes and favors that more common intermediate variants
• Natural selection maintains sexual reproduction
 The advantage of sex is that the process of meiosis and fertilization generate the genetic variation upon which natural selection can act as the agent of adaptation
• Sexual selection may lead to pronounced secondary difference between sexes
1. Sexual dimorphism
 Distinction in appearance
2. Intrasexual selection
 Direct competition among individuals of the same sex for mates of the opposite sex
3. Intersexual selection
 Also called the mate choice; individual’s of one sex are choosy in selective their mates from individuals of the other sex.
H. Natural Selection cannot fashion perfect organisms
• Four reasons why natural selection cannot produce perfection
1. evolution is limited by historical constraints
 do not create from scratch
2. adaptations are often compromises
3. not all evolution is adaptive
 affected by chance
4. Selection can only edit existing variations
 new alleles do not arise on demand
 natural selection operates on a “better than basis”

Chapter 24: The Origin of Species
A. Introduction
• Macroevolution
 The origin of new taxonomic groups
• Speciation
 The origin of new species
 The key process because any genus, family, or higher taxon originates with a new species that is novel enough to be the inaugural member of the higher taxon.
 2 patterns of speciation:
1. Anagenesis
 Phyletic evolution,
 The accumulation of changes associatied with the transformation of one species into another
2. Cladogenesis
 Branching evolution
 The budding of one or more new species from a parent species that continues to exist.
 Only one to promote biological diversity by increasing the number of species.
B. What is a species?
• Species
 Comparing morphology, differences in body functions, biochemistry, behavior and genetic make-up.
• The biological species concept emphasizes reproductive isolation
 Ernst Mayr, 1942 : biological species concept
1. Biological species concept
 Defines a species as a population or group of populations whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot produce viable, fertile offspring with members of other species.
 United by being reproductively compatible
 Reproductive isolation with each species isolated by factors that prevent interbreeding, blocking genetic mixing with other species.
 Emphasis on separateness of different species due to reproductive barriers
• Prezygotic and postzygotic barriers isolate gene pools of biological species
1. Prezygotic barriers
a. Prezygotic barriers
 Impede mating between species or hinder the fertilization of ova if members of different species attempt to mate
b. Habitat isolation
 Two species that live in different habitats within the same ara may encounter each other rarely.
 Thamnophis garter snakes
c. Behavioral isolation
 Elaborate courtship rituals of particular species
d. Temporal isolation
 Two species that breed during different times of the day, different seasons, or different years cannot mix their gametes
e. Mechanical isolation
 Anatomically incompatible
 Male and female copulatory organs may not fit together
f. Gametic isolation
 Even if gametes of different species meet, they rarely fuse together to form a zygote
2. Postzygotic barriers
a. Postzygotic barriers
 Prevent the hybrid zygote from developing into a viable fertile adult
b. Reduce hybrid viability
 Genetic incompatibility between the two species may abourt development of the hybrid at some embryonic stage.
 Rana
c. Reduced Hybrid Fertility
 Hybrids are completely or largely sterile
 Prevents gene flow
 Mules: cross between horse and donkey
d. Hybrid breakdown
 First generation hybrids are viable and fertile, but second generation mate, their offspring are feeble and sterile
• The biological species concept has some major limitations
 Does not work as a criterion for distinguishing species in nature.
 No utility for life-forms that are asexual
• Biologists have proposed several alternative concepts of species
1. Ecological species concept
 Defines species in terms of its ecological niche, the set of environmental resources a species use
 Accommodates asexual species
2. pluralistic species concept
 the factors that are most important for the cohesion of individuals as a species vary
 non is useful in actually identifying various species in nature, hence taxonomists depend mainly on morphological characteristics
1. Morphological species concept
 Does not explain why species exist
 Characterizes each species in terms of a unique set of structural features
2. genealogical species concept
 defines a species as a set of organisms with a unique genetic history
 define species in terms of unique genetic markers
C. Modes of Speciation
 Two main modes based on how gene flow among populations is initially interrupted
1. Allopatric speciation
 Speciation takes place in populations with geographically separate ranges
 Separation in space
2. sympatric speciation
 speciation takes place in geographically overlapping populations
• Allopatric speciation: Geographic barriers can lead to the origin of species
 Conditions for allopatric speciation
1. can occur if individuals colonize a new geographically remote area and become isolated from the parent population
2. likelihood increases when population is small and isolated
3. if cannot interbreed when come into contact, speciation has occurred
• Ring species: allopatric speciation in progress?
 Ensatina eschscholtzii north American salamander
• Adaptive Radiation on Island Chains
 Evolution of many diversely adapted species from a common ancestor
• How do reproductive barriers evolve?
 Two things to consider
1. geographic isolation does not qualify as reproductive isolation in the biological sense
2. speciation is not due to some drive to erect reproductive barriers around a population.
• Example of evolution of Prezygotic barrier
 Dianne Dodd of Yale University
 Reproductive barriers evolve in allopatric populations as the result of the population’s adaptive divergence in different environments
 Experimented with fruit flies, Drosophila pseudoobscura exhibite mate choice
• Example of evolution of postzygotic barrier
 Robert Vickery of the University of Utah
 Interbreeding of monkey flower Mimulus glabratus
 Proportion of fertile offspring decreased upon mating species from more distant populations
 Exhibited hybrid breakdown
• Summary of allopatric speciation
 New species forms while geographically isolated from its ancestor
D. Sympatric speciation: A new species can originate in the geographic midst of the parent species
• Polyploid speciation in Plants
 Polyploidy: cell division that results in an extra set of chromosome, a mutant condition
 Autopolyploid: an individual that has more than 2 chromosomes sets all derived from a single species.
 Allopolyploid: contribution of two different species to a polyploidy hybrid
• Sympatric speciation in Animals
1. Lake Victoria in East Africa
 home to 200 species of closely related fish belonging to the cichlid family.
a. Pundamililia pundamilia vs Pundamilia nyererei (rigid mating preferences of females)
 can result when some subset of the population become reproductively isolated because of a switch to a habitat, food source, or other resource notused by the parent population (wasps)
• Summary of sympatric speciation
 Requires the emergence of some type of reproductive barrier that isolates the gene pool of a subset of a population without geographic separation from the parent population
E. Punctuated equilibrium model has stimulated research on the tempo speciation
• Punctuated equilibrium
 Incorporates ideas about the tempo of speciation in their explanations of what we see in the fossil record
 Species diverge in spurts of relatively rapid change instead of slowly and gradually
F. From Speciation to Macroevolution
• Microevolution
 A change over the generations in a population’s allele frequencies, mainly by genetic drift and natural selection
• Speciation
 Occurs when a population’s genetic divergence from its ancestral population results in reproductive isolation
• Macroevolution
 Cumulative change during millions of speciation over vast tracts of time
 Level of change evident over the time scale of the fossil record
• Most evolutionary novelties are modified versions of older structures
 Complex structures evolved in increments from much simpler versions that had the same basic function
1. Exaptation
 Structures that evolves in one context but become co-opted for another function
a. Honeycomb bones of birds
• “Evo-devo” genes that control development play a major role in evolution
1. Evo-devo
 the interface between evolutionary biology and the study of how organisms develop
 how slight genetic divergences can become magnified into major morphological difference between species
2. allometric growth
 proportioning that helps give a body its specific form
3. heterochrony
 evolution of morphology that arises by a modification in allometric growth
 evolutionary change in the rate or timing of developmental events
a. salamander feet
4. paedomorphosis
 retention of juvenile structures in an ancestral species
 macroevolution can also occur from changes in genes that control the placement and spatial organization of body parts
1. homeotic genes
a. Hox genes
 Provide positional information in an embryo
• An evolutionary trend does not mean that evolution is goal oriented
 Horse descended from smaller ancestor Hyracotherium modern horses are larger genus Equus
1. species selection
 analogous to the production of a trend within a population by natural selection

Chapter 25: Phylogeny and Systematics
A. Introduction
• Phylogeny
 The evolutionary history of a species or group of related species
• Systematics
 The study of biological diversity in an evolutionary context
B. Fossil record and geologic time
• Fossil record
 Ordered array in which fossils appear within layers of sedimentary rocks that make the passing of geologic time
• Sedimentary rocks are the richest source of fossil
• Paleontologists use a variety of methods to date fossils
 Fossils are reliable only if we can determine their ages
1. Relative Dating
a. Index fossils
 Similar fossils belonging to same strata
 Shells of sea animals
b. Geologic time scale
 Consistent sequence of historical periods
 Geologic time scale grouped into 4 eras:
a. Precambrian
b. Paleozoic
c. Mesozoic “age of reptiles”
 dinosaurs
d. Cenozoic
 Each era represents a distinct age in the history of earth and its life
 Boundaries between the eras correspond to times of mass extinctions when many forms of life disappeared and were replaced by diversification of the survivors
 Eras divided more into epochs
 Geologic eras not equal in duration.
2. Absolute dating
 Age is given in years
a. Radiometric dating
 The measurement of certain radioactive isotopes in fossils or rocks is the method used to determine the age of rocks and fossils on the scale of absolute time
 Carbon 14
b. Half-life
 Each radioactive isotope has fixed rate of decay
 The number of years it takes for 50% of the original sample to decay is unaffected by temperature, pressure etc
 Carbon 14 has a half life of 5,730 years
 Uranium-238 half life of 4.5 billion years
• The fossil record is a substantial but incomplete chronicle of evolutionary history
 A substantial fraction of species that have lived probably left no fossils, most fossils that are formed have been destroyed, and only a fraction of the existing fossils have been discovered
• Phylogeny has a biogeographic basis in continental drift
 Formation of Pangaea
 Pangaea broke up during the Mesozoic era
 Continental drift
1. explains much about the current distribution of organisms
• The history of life is punctuated by mass extinctions
 Mass extinctions followed by diversification of certain taxonomic groups that escaped extinction
 A species may become extinct when:
1. habitat destroyed or changed
2. evolutionary change in one species has and impact on other species, making other susceptible to extinction
 extinction is inevitable in a changing world
 most distinct mas extinction
1. Permian mass extinction
 250 million years ago
 defines the boundary between Paleozoic and Mesozoic eras
 claimed 90% of the species of marine animals
 time continents merged to form the Pangaea
 massive volcanism
 oxygen deficits in oceans
2. Cretaceous mass extinction
 65 million years ago
 boundary between Mesozoic and Cenozoic eras
 doomed more than half the marine species and exterminated many families of terrestrial plants and animals including dinosaurs
 volcanic eruptions contributed to cooling
 but what is favored is the impact hypothesis
a. impact hypothesis
 collision of an asteroid or large comet with earth.
 Cloud blocked sunlight disturbed climate
 Has two parts: collision occurred and event caused the cretaceous mass extinctions
 Chicxulub crater
 Impact caused the earth to darken for years and reduction of photosynthesis lasted long enough for food chains to collapse
 Caused a firestorm

Chapter 50: An introduction to ecology and the biosphere

A. The Scope of Ecology
• Ecology
 The scientific study of interactions between organisms and their environments.
• Abiotic components
 Non-living chemical and physical factors such as temperature, light, waters and nutrients.
• Biotic components
 Living. All the organisms that are part of the individual’s environment.
• Charles Darwin
 Laid the groundwork for ecology.
 Events that occur in the framework of ecological time translate into effects over the longer scale of evolutionary time.
• Organismal ecology
 Is concerned with the morphological, physiological and behavioral ways in which individual organisms meet the challenges posed by their biotic and abiotic environements.
• Population
 Is a group of individuals of the same species living in a particular geographic area.
• Population ecology
 Concentrates mailing on factors that affect how many individuals of a particular species live in an area.
• Community
 Consists of all organisms of all the species that inhabit a particular area
• Community ecology
 Deals with the whole array of interacting species in a community.
 Focus on the ways in which interactions such as predation, competition, and disease affect community structure and organization.
• Ecosystem
 Consists of all the abiotic factors in addition to the entire community of species that exist in a certain area.
• Ecosystem ecology
 Emphasis on energy flow and cycling of chemicals among the various biotic and abiotic components.
• Landscape ecology
 Deals with arrays of ecosystems and how they are arranges in a geographic region.
• Landscape / seascape
 Consists of several different ecosystems linked by exchanges of energy, materials and organisms.
 Focuses on the ways in which interactions among populations, communities and ecosystems are affected by the combination of different ecosystems.
• Biosphere
 Is the global ecosystem.

B. Ecology provides a scientific context for evaluating environmental issues
• Rachel Carson’s Silent Spring (1962)
 Pesticide use and its effect on nontarget organisms causing population decline.
• Precautionary principle
 An ounce of protection is worth a pound of cure.

C. Factors affecting the distribution of organisms
 Distribution of animals associated with patterns of continental drift that followed the break-up of Pangaea
• Biogeography
 Is the study of the past and the present distribution of individual species.
• Flowchart of factors limiting geographic distribution
1. Dispersal
 Is a critical process for understanding both geographic isolation in evolution and the broad patters of current geographic distributions
a. Species transplants
 Able to determine success only after one life cycle is complete.
 2 possible outcomes:
 transplant successful: distribution limited because the area is inaccessible, time has been too short to reach the area, failure of species to recognize the area as a suitable living space
 transplant unsuccessful: distribution limited either by other species or by physical and chemical factors.
2. Behavior
 Habitat selection
3. Biotic factors (other species)
 Predators, parasitism, competition, disease
4. Abiotic factors
a. Chemical factors: water oxygen, salinity, pH, soil nutrients, etc.
b. Physical factors: temperature, light, soil structure, fire, moisture, etc.
D. Problems with Introduced Species
• African Honeybee
 Example of unpredicted and undesirable consequences.
 Apis mellifera scutellata
 Very aggressive subspecies of honeybee brought to Brazil in 1956 to produce more honey than the standard Italian honeybee (Apis mellifera ligustica)
 Escaped by accident and been spreading throughout the Americas.
 Since aggressive may drive out established colonies of Italian honeybees and threaten the honey industry.
• Zebra Mussel
 1988, Dreissena polymorpha native to the freshwater Caspian Sea of Asia.
 Discovered in Lake St. Clarie near Detroit.
 1985, a ship carried larvae of the mussel in its ballast water from a freshwater port in Europe to the Great Lakes, where it was emptied.
 A pest. Reproduces rapidly and forms dense clusters several layers thick on hard surfaces.
 Efficient suspension feeders, alter the native communities of organisms in the process.
 Depress populations of zooplankton
 Crowd out native mollusk species by colonizing all hard surfaces, including the shells of freshwater clams.
 May result to extinction of native species
• The Tens Rule
 A rough generalization for the success of introduced species which makes the statistical prediction that an average of one out of ten introduced species become established and one out of ten established species become common enough to become pests.
E. Behavior and habitat selection contribute to the distribution of organisms
 Distribution of species may be limited by the behavior of individuals in selecting habitat.
 Insects have a very sterotypes oviposition (egg-depositing) behavior, restrict their local distribution to certain host plants. ex. European corn borer.
 Anopheline mosquitoes are important carriers of disease.
 Evolution does not produce perfect organisms for every suitable habitat.
 Not all evolved behaviors remains adaptive due to human intervention and environmental changes.
• Biotic factors affect the distribution of organisms
 Negative interactions with other species, predation, competition and disease.
 Absence of other species in which the transplanted species depends on.
1. sea urchins and kelp (predation)
 where sea urchins that graze on kelp are common, kelp cannot be established.
 Local distribution of kelp limited by sea urchins.
F. Abiotic factors affect the distribution of organisms
1. Temperature
 Effect on biological processes and the inability of most organisms to regulate body temperature precisely.
2. Water
 Essential to life, water balance
3. Sunlight
 Provides energy that drives nearly all ecosystems
 Meter of water selectively absorbs 45% of the red light and about 2% if the blue light passing through it.
4. Wind
 Wind-chill factor
5. Rock and soil
 Physical structure, pH and mineral composition of rocks and soil limit the distribution of plants and animals that feed upon them.
G. Water and Temperature are the major climatic factors determining the distribution of organisms
 Four abiotic factors – temperature, water, light and wind – are the major components of climate.
• Climate
 The prevailing weather condition at a locality.
• Climate and Biomes
1. Biomes
 Are major types of ecosystems that occupy broad geographic regions.
 Temperature and rainfall
• Global climate patterns
 Earth’s global climate patterns are largely determined by the input of solar energy and the planet’s movement in space.
 Earth tilted 23.5 degrees relative to its plane of orbit
 More sunlight on the areas near the equator, the tropics and experience least seasonal variation.
• Local and Seasonal Effects on Climate
 Proximity to water
 Mountains effect on solar radiation, rainfall and local temperature.
• Microclimate
 Climate variation at a fine scale
 Trees in forests, moderate climate below
• Long term climate change
 Climatic warming (global warming) will have profound effects on the biosphere
 American beech (Fagus grandifolia)
H. Aquatic and terrestrial biomes
• Aquatic biomes occupy the largest part of the biosphere
 Distinguish between freshwater biomes and marine biomes on the basis of physical and chemical differences.
 Marine (3% salt concentration) freshwater (less than 1%)
• Vertical stratification of aquatic biomes
 Light absorbed by water and microorganisms in it, intensity decreases with depth
1. Photic zone
 Where there is sufficient light
2. Aphotic zone
 Little light penetrates
3. Thermocline
 A narrow stratum of rapid temperature change; separates a more uniformly warm upper layer from a more uniformly cold deeper waters.
4. Benthic zone
 The bottom of all aquatic biomes, the substrate.
 Made up of sand and organic and inorganic sediments (ooze)
 Occupied by communities of organism called benthos which have a major source of food called detritus.
• Freshwater biomes
 2 general categories:
1. standing bodies of water (lakes and ponds)
2. moving bodies of water (rivers and streams)
 in most lakes organisms are distributed depending on the distance from the shore.
1. Littoral zone
 Rooted and floating aquatic plants flourish; shallow well lit waters close to shore.
2. limnetic zone
 well lit waters farther from the shore, occupied by a variety of phytoplankton consisting of algae and cyanobacteria
3. Profundal zone
 Where remains of organisms in limnetic zone sink into; aphotic.
 Lakes often classified according to their production of organic matter.
1. Oligotrophic
 Deep and nutrient poor with sparse and unproductive phytoplankton in limnetic zone.
2. Eutrophic
 Shallower, high nutrient content, phytoplankton are very productive and waters are often murky.
3. Mesotrophic
 Moderate amount of nutrients and phytoplankton productivity.
 Cultural eutrophication
 at headwaters of streams, the water is often cold and clear, little sediment, few mineral content
 nutrient content of flowing water biomes is largely determined by the terrain and vegetation through which water flows.
• Wetlands
 An area covered with water that supports aquatic plants
 Favor growth of specially adapted plants called hydrophytes, which can grow in water or in soil that is periodically anaerobic due to the presence of water.
 Different types of wetlands, ranging from marshes to swamps to bogs.
 Among the richest of biomes
 Provide water storage basins that reduce the intensity of flooding, improve water quality by filtering pollutants
• Estuaries
 Area where a freshwater stream or river merges with the ocean.
 Often bordered by extensive coastal wetlands called mudflats and salt marshes.
 One of the most biologically productive biomes
 Breeding ground for many marine organisms.
• Zonation in marine communities
 Marine communities are distributed according to depth of water, degree of light penetration, distance from shore, and open water versus bottom.
 Intertidal zone: zone where land meets water, beyond it is the neritic zone, the shallow region over the continental shelves.
 Oceanic zone: past continental shelves, very great depths.
 Pelagic zone: open water of any depth, bottom is the seafloor or the benthic zone.
• Intertidal zones
 Is alternately submerged and exposed by the twice-daily cycle of tides.
 Affected much by humans and pollution
• Coral reefs
 In warm tropical waters in the neritic zone
 Currents and waves constantly renew nutrient supplies to the reefs and sunlight penetrates to the ocean floor, allowing photosynthesis.
 Dominated by the structure of the coral itself.
 Dinoflagellate algae live on their tissues; such affect corals rate of calcium carbonate deposition. Reef formation depends on this symbiotic relationship.
 Susceptible to pollution.
 High water temperatures cause corals to “bleach” – to expel their symbiotic dinoflagellates and die.
 Global warming could destroy coral reefs.
 Crown of thorns sea star
• The oceanic pelagic biome
 Far from shore, constantly mixed by ocean currents.
 Nutrient concentrations generally lower than in coastal areas
• Benthos
 Nutrients reach bottom through “raining down” in the form of detritus
 Neritic benthic communities are extremely productive. Composition of species varies with distance from the shore, water depth, and composition of the bottom.
1. Abyssal zone
 very deep benthic communities, organisms are adapted to continuous cold, high water pressure and near or total absence of light, and low nutrient concentrations.
2. deep-sea hydrothermal vents
 midoceanic ridges.
 Dark hot, oxygen deficient environment, chemoautotrophic prokaryotes.
I. The geographic distribution of terrestrial biomes is based mainly on regional variations in climate
 Latitudinal patterns of climate over the earth’s surface, there are latitudinal patterns of biome distribution.
 Terrestrial biomes often named for major physical or climatic features and for their predominant vegetation.
 Also characterized by microorganisms, fungi, and animals adapted to that particular environment.
 Vertical stratification in forest: canopy, low-tree stratum, shrub, ground layer of herbaceous plants, the forest floor (litter layer) and finally the root layer.
 Arctic tundra, has a permanently frozen stratum called permafrost.
 Vertical stratification of a biome’s vegetation provides different habitats for animals.
1. ecotone
 area of intergradation of one terrestrial biome to another.
 Biomes are dynamic and natural disturbance rather than stability tends to be the rule.
• Tropical forest
 Pronounced vertical stratification, little light
 Many of the trees are covered with epiphytes (plants that grow on other plants instead of soil)
 Rainfall is the prime determinant of the vegetation growing in the area.
• Savanna
 Large herbivores (giraffe) and their predators
 Grasses and scattered trees are the dominant plants
 Fire an important abiotic component
 Regular seasons of water drought
• Desert
 Sparse rainfall (less than 30 cm per year) main determinant
 Water conservation adaptations by both plants and animals
• Chaparral
 Dense, spiny evergreen shrubs dominant vegetation
 Bush fires
• Temperate grassland
 Key to persistence of grasslands is seasonal drought, occasional fires and grazing by large mammals, all of which prevent establishment of woody shrubs and trees.
 Prairie
• Temperate deciduous forest
 Dense stands of deciduous trees where there is sufficient moisture to support these trees.
 More open than rain forests, has distinct vertical layers
 Drop leaves during winter and animals undergo hibernation and bird migrate to warmer climates
• Coniferous forest / taiga
 Dominated by conifers
 Temperate rain forests
 Warm moist air from the Pacific supports these unique communities
 Receive heavy snowfall during winter
• Tundra
 Permafrost (permanently frozen subsoil) bitterly cold temperatures and high winds are responsible for the absence of trees and other tall plants
 Receives very little annual rainfall, water cannot penetrate the permafrost and accumulates in pools on the shallow topsoil.
J. The spatial scale of distributions
• Different factors may determine the distribution of a species on different scales
• Most species have small geographic ranges

Chapter 52: Population Ecology
A. Introduction
• Population ecology
 Concerned with measuring changes in population size and composition and with identifying the ecological causes of these flunctuations
B. Characteristics of populations
• Population
 A group of individuals of a single species that simultaneously occupy the same general area
 Rely on the same resources
 Are influenced by similar environmental factors
 High likelihood of breeding with and interacting with one another
• Two important characteristics of any population are density and the spacing of individuals
1. population size
 no of individuals it includes
 two important characteristics of any population is its density and its dispersion
1. Population density
 Number of individuals per unit area or volume
2. dispersion
 pattern of spacing among individuals within the geographic boundaries of the population
• Patterns of dispersion
 Not all areas provide equally suitable habitat giving rise to patchiness
 Forms of dispersion
1. clumped
 most common
 individuals aggregated in patches
 also associated with mating behavior
a. “safety in numbers”
2. uniform
 evenly spaced
 may result from direct interactions between individuals in a population
 not as common
3. random
 unpredictable dispersion
 occurs in the absence of strong attractions or repulsions among individuals of a population
 position of each individual is independent of others
C. The logistic model of population growth incorporates the concept of carrying capacity
 Populations subsist in a finite amount of available resources
 Ultimately there is no limit to the number of individuals that can occupy a habitat
• Carrying capacity
 Maximum population size that a particular environment can support at a particular time with no degradation of habitat.
 Not fixed, varies over space and time with the abundance of limiting resources
 Energy limitation is one of the most significant determinants of carrying capacity
 Crowding and resource limitation can have a profound effect on the population growth rate
1. if organisms cannot obtain sufficient resources to reproduce, birth rate will decline
2. if cannot find enough energy to maintain themselves, per capita death rate increases
D. The logistic population growth model and life histories
 Life history traits that natural selection favors may vary with population density and environmental conditions
• K-selection
 Selection for life history traits that are sensitive to population density
 Density-dependent selection
 Tends to maximize population size
 Operates in populations living at densities near the limit imposed by their resources
• r-selection
 selection for life histories that maximize reproductive success in uncrowded environments c
 density independent selection
 tends to maximize r, the rate of increase
 occurs in variable environements in which population densities flunctuate well below carrying capacity
E. Population Limiting Factors
• Terms:
1. Density dependent
 Death rate rises as population density rises
 Birth rate falls with rising density
 Example of negative feedback
2. Density independent
 Birth rate or death rate does not change with population density
 No feedback to slow down population growth
• Negative feedback prevents unlimited population growth
 Resource limitation is crowded populations can stop population growth by reducing reproduction
 Increasing population density intensifies intraspecific competition for declining nutrients, resulting in lower birth rate
 Territoriality: the defense of a well bound physical space may set a limit on density
 Population density also influences the health and thus the survival of organisms
 Predation may also be an important cause of density dependent mortality
 Accumulation of toxic waste is another component that can contribute to density-dependent regulation of population size
 Impact of disease

Chapter 53: Community Ecology
A. What is a community?
• Community
 Is any assemblage of populations in an area or habitat
• Species richness
 The number of species that they can contain
• Relative abundance
 Differ in kinds of species
B. Interspecific interactions and community structure
• Interspecific interactions
 Relationships between species of a community
• Populations may be linked by competition, predation mutualism and commensalisms
1. Competition
 Interspecific competition for resources can occur when the resources are in short supply
 Competition for two species that need the same resource
 Result may be a reduction in density of one or both species, or the elimination of one or both.
a. The competitive exclusion principle
 G. F. Gause (Russian ecologist) 1934
 Paramecium Aurelia and paramecium caudatum
 Even a slight advantage will eventually lead to local elimination of the inferior competitor
b. The ecological niche
 The sum total of a species use of the biotic and abiotic resources in its environment
 Two species cannot coexist in a community if their niches are identical
2. Predation
 Includes herbivory and parasitism
3. Mutualism
 Mutual symbiosis
 An interspecific interaction that benefits both species
 Requires coevolution of adaptations in both participating species
4. Commensalism
 And interaction between species that benefits only one of the species involved in the interaction.
C. Trophic structure is a key factor in community dynamics
• Trophic structure
 The dynamics and structure of a community depend to a large extent on the feeding relationships between organisms
• Food chain
 Transfer of food energy from its source in plants (primary producers) through herbivores (primary consumers) to carnivores (secondary and tertiary consumers) and eventually to decomposers
 Charles Elton: food chains are not isolated, hooked together into food webs
• Food webs
 What transforms food chains into food webs?
1. a species may weave into the web at more than one trophic level
• What limits the length of a food chain?
 Two hypotheses as to why food chains are relatively short
1. energetic hypothesis
 length is limited by inefficiency of energy transfer along the chain
2. dynamic stability hypothesis
 long food chains are less stable than short chains.
 Fluctuations at lower trophic levels are magnified at higher levels potentially causing extinction of top predators
D. Dominant species and keystone species exert strong control on community structure
• Dominant species
 Are species in the community that have the highest abundance or highest biomass.
 Exert powerful control over the occurrence and distribution of other species.
a. American chestnut
E. Ecological succession is the sequence of community changes after disturbance
• Ecological succession
 Transition in species composition over ecological time
• Primary succession
 If it begins in a virtually lifeless area where soil has not yet formed
• Secondary succession
 Occurs when an existing community has been cleared by some disturbance that leaves the soil intact

Chapter 54: Ecosystems
A. Introduction
• Ecosystem
 Consists of all the organisms living in a community as wells as all the abiotic factors with which they interact.
 Involves two processes
1. energy flow
2. energy cycling
B. The ecosystem approach to ecology
 Trophic levels bases on main source of nutrition and energy
• Trophic relationships determine the routes of energy flow and chemical cycling in an ecosystem
1. primary producers
 trophic level that support all others
 autotrophs
2. heterotrophs
 organisms above the trophic level of the primary producers
 directly or indirectly depend on the photosynthetic output of primary producers
3. primary consumers
 herbivores that eat primary producers
4. secondary consumers
 carnivores that eat herbivores
5. tertiary consumers
 carnivores that eat other carnivores
6. Detritivores or decomposers
 Consumers that get their energy from detritus, the nonliving organic material.
 Play a central role in material cycling
• Decomposition connects all trophic levels
 Organic material that makes up the living organisms in an ecosystem gets recycled
C. The efficiency of energy transfer between trophic levels is usually less than 20%
• Trophic efficiency
 is the percentage of production transferred from one trophic level to the next.
 80-95% of the energy available at one trophic level never transfers to the next
• Pyramids of production
 Represents the multiplicative loss of energy from a food chain
 Trophic levels are stacked in blocks with primary producers forming the foundation
 Size of each block is proportional to the production of each trophic level
• Pyramids of biomass
 Represents one ecological consequence of low trophic efficiencies
 Each tier represents the standing crop (the total dry weight of all organisms) in a trophic level
 Most pyramids narrow because energy transfers in trophic levels are so inefficient
1. turnover time
 have small standing crop biomass compared to their production
a. phytoplankton
• Pyramids of numbers
 Multiplicative loss of energy from food chains severely limits the overall biomass of top-level carnivores that any ecosystem can support
 Pyramid numbers: the size of each block is proportional to the number of individual organisms present in each trophic level
D. Herbivores consume a small percentage of vegetation: the green world hypothesis
• Green world hypothesis
 Herbivores consume relatively little biomass because they are held in check by a variety of factors including predation, parasites and disease
1. plants have defenses against herbivores
2. nutrients, not energy supply, usually limit herbivores
3. abiotic factors limit herbivores
4. intraspecific competition can limit herbivore numbers
5. interspecific interactions check herbivore densities
E. The cycling of chemical elements in ecosystems
 Chemical elements are available only in limited amounts
 Biochemical cycles: because nutrient circuits involve both biotic and abiotic components of ecosystems
• Biological and geologic processes move nutrients between organix and inorganic compartments
 Two general categories of biochemical cycles
• A general model of chemical cycling
 Nutrients accumulate in four reservoirs which have two characteristics:
1. whether it contains organic or inorganic materials
2. whether or not materials are directly available for use by organisms
 compartments or organic materials:
1. living organisms and detritus
2. fossilized deposits
 coal, oil, peat
 nutrients not assimilated directly
 inorganic compartments:
1. available for use by organisms
 matter (elements and compounds)
2. not available
 tied up in rocks become available only after erosion and weathering
 water cycle not fit in so well, more of a physical process than a chemical one.
• The Nitrogen Cycle
 80% nitrogen, most in nitrogen gas form which is unavailable to plants
 enters ecosystem via two pathways:
1. atmospheric deposition
 NH4+ and NO3- two forms of nitrogen available to plants are added to soil by being dissolved in rain
2. nitrogen fixation
 convert N2 to mineral that can be used to synthesize nitrogenous organic compounds such as amino acids.
 Rhizobium at root nodules of legumes
 Cyanobacteria
 Returned to atmosphere through atmospheric deposition
a. Nitrification
 Oxidation of ammonium to nitrite and then to nitrate
b. Denitrification
c. Ammonification
 Decomposition of organic nitrogen back to ammonium
• *ack tamad na, check diagrams na lang
F. Human activities may be causing climate change by increasing carbon dioxide concentration in the atmosphere
• Greenhouse effect
• Global warming

Chapter 55: Conservation
A. Introduction
 Conservation biology is a goal-orriented science that seeks to counter the biodiversity crisis, the current rapid decrease in the Earth’s great variety of life
B. The biodiversity crisis
 Extinction is a natural phenomenon that has been occurring almost since life first evolved
 High rate of species extinction caused by an escalating rate of ecosystem degradation by a single species – Homo sapiens
• The three levels of biodiversity are genetic diversity, species diversity and ecosystem diversity
1. Lost of genetic diversity
 First level of biodiversity is genetic variation
 Genetic variation between and within populations
 Detrimental effects to other species and to humans
2. Loss of species diversity
 Second level of biodiversity is a variety of species in an ecosystem or throughout the entire biosphere what we call species richness
a. Endangered species
 One that is in danger of extinction throughout all or a significant portion of its range
b. Threatened species
 Those that are likely to become endangered in the foreseeable future throughout all or a significant potion of their range.
 Concerns of conservations biologists regarding species loss
a. International Union for Conservation of Nature and Natural Resources, 13% of the 9040 known bird species in the world are threatened. 1,183 species
b. Center for Plant Conservation 20,000 known plant species in the US, 200 have become extinct, 730 are endangered
c. 20% of freshwater fishes in the world have become extinct or are endangered.
 One of the largest extinction events was the loss of 200 of 300 species of cichlids in Lake Victoria, East Indies, have been lost due to the introduction of the exotic predator the Nile perch.
d. 123 freshwater vertebrate and invertebrate species have become extinct in N.America, hundreds are threatened.
e. Harvard biologist, Edward O. Wilson and the Hundred Heartbeat Club, where species that belong are those that have a number of 100 individuals
f. Half of all plant and animal species will be gone by the end of this century
 Global extinction: loss for all its locales
3. Loss of Ecosystem Diversity
 Variety of the biosphere’s ecosystems is the third level of biological diversity
 Each ecosystem have an important impact on the biosphere
• Biodiversity at all three levels is vital to human welfare
 E.O. Wilson: biophilia (our sense of connection to nature and other forms of life)
• Benefits of species diversity and genetic diversity
 Biodiversity is a crucial natural resource
 Loss of species means the loss of genes
• Ecosystem services
 Benefits that individual species provide to humans are often substantial
 Humans are dependent on ecosystems and on interactions with other species
 We are also at risk
1. Ecosystem services
 Encompass all the processes through which natural ecosystems and the species they contain help sustain human life on Earth.
a. Purification of air and water
b. Reduction of the severity of droughts and floods
c. Generation and preservation of fertile soils
d. Detoxification and decomposition of wastes
e. Pollination of crops and natural vegetation
f. Dispersal of seeds
g. Nutrient cycling
h. Control many agricultural pests by natural enemies
i. Protection of coastal shores from erosion
j. Protection from ultraviolent rays
k. Moderation of weather extremes
l. Provision of aesthetic beauty
 Human life would cease without these services
C. The four major threats to biodiversity are habitat destruction, introduced species, overexploitation and food chain disruptions
• Habitat Destruction
 Habitat fragmentation leads to species loss
1. Habitat reduction and fragmentation in the Wisconsin forest
• Introduced species
 Contributed to about 40% of extinctions
1. Introduced species
 Are those that humans move from the species native locations to a new geographic regions
 Some cases intentional
a. European red foxes
 Introduced to Australia
b. Nile perch to Lake Victoria
 Accidentally
a. Brown tree snake
 12 species of birds and 6 lizard species have become extinct in Guam
 introduced species that gain a foothold usually disrupt their adopted community often preying on native species or outcompeting native species for resources
 good intentions
a. Kudzu (from Japan)
 to prevent soil erosion
 took over vast expanses of Southern landscape
b. purple loosestrife
 claiming 200,000 wetlands per year
 crowding out native plants and the animals that feed on the native flora
c. European starling
 120 european starlings in Central Park in 1890
 population increased to 100 million in less than a century, displacing many of the native songbird species in the US and Canada
d. fire ants
 eliminated 2/3 of native species of ants in Texas
e. Argentine ant
 Decimating populations of native ants in California
f. Caurlerpa
 California lagoon
 Displacing many of the algae there
 50,000 introduced species in the United States alone with the cost to the economy of over $130 billion in damage and control efforts not including the priceless loss of native species
• Overexploitation
 Humans harvesting of wild plants or animals at rates exceeding the ability of populations of those species to rebound
 Overhunting and overfishing of animals
 Elephants, whales, rhinoceroses
a. Great auk (Pinguinis impernnis)
 Islands in Atlantic Ocean
 Extinct because of demand for feathers, meat and eggs
b. Decline of African elephant
 Take 10-11 years to reach sexual maturity
 Fertile female has a single calf every 3 – 9 years
 6% growth rate per year
 illegal hunting for ivory is the major cause, poaching
c. North American Blue Fin Tuna
 Sushi and sashimi
 $100 per pound
 reduced to 20% of its natural size in 1980
• Disruption of food chains
 Extinction of one species can doom its predators
 Host-specific parasites can become instinct if their host become extinct
1. Forest eagle of New Zealand extinct upon the extinction of Moas, flightless birds.
2. black footed ferret on the Great Plains of N. America parralled decline of its main prey, prairie dogs.
D. Conservation at the population and species levels
 Two main approaches:
1. small-population approach
2. declining-population approach
• According to the small population approach, a population’s small size can draw it into an extinction vortex
 A species is designated as endangered when its populations are very small
 This approach studies the processes that can cause very small populations to finally become extinct
1. Extinction vortex
 A downward spiral unique to small populations
 A small population is prone to positive feedback loops of inbreeding and genetic drift that draw the population down the vortex toward smaller population size until no individuals exist
 Key factor is the loss of genetic variation on which a population depends for adaptive evolution
a. Lousewort Pedicularis
 low genetic variability
 low genetic variability does not necessarily lead to permanently small populations
• How small is too small for a population?
 Depends on type of organism
1. Minimum viable population size
 Minimum population size where rare species will be able to sustain their numbers and survive
2. Population viability analysis
 Objective of analysis is to be able to make a reasonable prediction of a population’s chances for survival over a particular time
3. Effective population size
 Based on breeding potential of the population
• The declining population approach is a proactive conservation strategy for detecting, diagnosing and halting population declines
 Focus on threatened and endangered populations even if they are far greater than minimum viable size
 Emphasis on environmental factors that cause a population to decline
1. Steps in the Diagnosis and treatment of declining populations
a. Confirm that the species is presently in decline or that it was formerly more widely distributed or more abundant
b. Study the species’ natural history to determine its environmental requirements
c. Determine all the possible causes of the decline
d. List the predictions of each hypothesis for the decline
e. Test the most likely hypothesis first
f. Apply the results of this diagnosis to the management of threatened species
* other parts wag na! hehe…

Campbell: CHAPTER 50 (An Introduction to Ecology and the Biosphere)

CHAPTER 50
An Introduction to Ecology and the Biosphere

Organisms
• open systems
• interact continuously with their environments

Ecology
• The scientific study of interactions between organisms and their environments — determines
– distribution
– abundance of organisms

Environment

1) Abiotic Components — nonliving
– chemical >>> nutrients, water, salinity, pH, oxygen
– physical factors >>> temperature, light, soil structure, fire, moisture

2) Biotic Components — living

Ecology and Evolution

Ecological Time —— minutes, months, years
Evolutionary Time —- decades, centuries, millenia

ECOLOGICAL RESEARCH

1) Organismal ecology
2) Population ecology
3) Community ecology
4) Ecosystem ecology
5) Landscape ecology

Organismal Ecology
• morphological, physical, and behavioral ways in which individual organisms meet the challenges posed by their biotic and abiotic environments
• geographic distribution of organisms is often limited by the abiotic conditions they can tolerate

Population Ecology
• Population — a group of individuals of the same species living in a particular geographic area
• concentrates on factors that affect how many individuals of a particular species live in an area

Community Ecology
• Community
– consists of all the organisms of all the species that inhabit a particular area
– assemblage of populations of many different species
• deals with whole array of interacting species in a community

Ecosystem Ecology
• Ecosystem
– consists of all the abiotic factors and entire community of species that exist in a certain area
– an ecosystem may contain different communities
• emphasis on energy flow and the cycling of chemicals among the various abiotic and biotic components

Landscape Ecology
• deals with array of ecosystems and how they are arranged in a geographic region
• landscape or seascape — consists of several different ecosystems linked by exchanges of energy, materials, and organisms

Biosphere
• global ecosystem
• sum of all the planet’s ecosystems

FACTORS AFFECTING THE DISTRIBUTION OF ORGANISMS

Biogeography
• study of past and present distribution of individual species

Factors Limiting Geographic Distribution
1) Dispersal
2) Behavior
3) Biotic Factors
4) Abiotic Factors

Species Dispersal
• critical process for understanding geographic isolation and broad patterns of current geographic distributions
• one way to determine if dispersal is a key factor limiting distribution is by observing the results when humans transplant species

Two Outcomes
1) Transplant successful
2) Transplant unsuccessful

Transplant Successful
• distribution limited because the area is inaccessible
• time has been too short to reach the area
• species fails to recognize area as suitable living space
• potential range of species is larger than its actual range

Transplant Unsuccessful
• distribution is limited either by other species or
– parasites, predators, competitors, pathogens
– transplant area could lack required positive effects of interdependent species
• abiotic factors

Introduced Species
1) Accidental
2) Intentional/Planned

African Honeybee (Apis mellifera scutellata)
• aggressive subspecies
• brought to Brazil
• to breed a variety that would produce more honey than the standard Italian honeybee
• escaped by accident
• drove out existing colonies of Italian honeybees
• reached the U.S.

Zebra Mussel (Dreissena polymorpha)
• fingernail-sized mollusk native to Caspian Sea (Asia)
• discovered in Detroit
• a ship carried larvae of zebral mussel in its ballast water
• became a pest
• reproduced rapidly and formed dense clusters several layers thick on hard surfaces
• clogged water intakes, electrical power systems, and other industrial facilities in the Great Lakes
• efficient suspension feeders — make the water clearer
• alters native communities
• fed on phytoplanktons — depressed popln of zooplanktons
• clearer water >>> more sunlight >>> increased growth of rooted aquatic plants in shallow waters
• crowd out native mollusk species

The Tens Rule
• not all introduced species are successful
• 1 out of 10 introduced species become established
• 1 out of 10 established species become common enough to become pests

Behavior and Habitat Selection
• habitat selection is applicable to plants and animals
• evolution does not produce perfect organisms for every suitable habitat
• not all behavior that has evolved remains adaptive, particularly in ecosystems modified by humans
• envtl conditions may change such that formerly adaptive behaviors are now maladaptive
• even with suitable genetic variation, natural selection may not be able to operate quickly enough to adjust habitat selection behavior to some abrupt envtl change

Biotic Factors
• negative interactions with other species
– predation
– competition
– disease
• absence of other species upon which the transplanted species depends

Abiotic Factors
• patterns of geographic distribution mirror regional differences in
– temperature
– rainfall
– salinity
– light
• envt varies in both space and time
• although two regions of the Earth may experience different conditions at any given time, daily and annual fluctuations of abiotic factors sometimes blur or accentuate the distinctions between those regions

Temperature
• effect on biological processes
• most organisms are not able to regulate body temp precisely
• few organisms can maintain active metabolism at extreme temps
• internal temp of an organism is affected by heat exchange with its envt

Water
• freshwater and marine organisms live submerged — problem: water balance
• terrestrial organisms — problem: constant hreat of dessication

Sunlight
• provides energy that drives nearly all ecosystems
• impt for devt and behavior of organisms that are sensitive to photoperiod
– relative lengths of day and night
– more reliable indicator for cuing seasonal events

Wind
• amplifies the effects of envtl temp
• increase heat loss due to evaporation and convection
• contributes to water loss
• can have an effect on plant morphology

Rocks and Soil
• physical structure
• pH
• mineral composition

AQUATIC BIOMES
• occupy largest part of biosphere in terms of area
• light is absorbed by water and microorganisms so light intensity decreases rapidly with depth

Vertical Stratification of Aquatic Biomes

Light Stratification
1) Photic —– where there is sufficient light for photosynthesis
2) Aphotic — where little light penetrates

Temperature Stratification
• whatever depth sunlight penetrates — warm
• thermocline — narrow stratum of rapid temp change
• deeper waters remain cold

Benthic Zone
• bottom of all aquatic biomes
• substrate
• made up of sand, organic and inorganic sediments
• occupied by benthos — collective name for communities of organisms inhabiting this zone
• detritus — source of food, dead organic matter

Marine Biomes
• ave salt concentrations = 3%
• evap of seawater provides most of planet’s rainfall
• ocean temps have major effect on world climate and wind patterns
• marine algae and photosynthetic bacteria supply substantial amount of O2

Freshwater Biomes
• salt concentration = 1% or less

1) standing bodies of water
– lakes
– ponds

2) moving bodies of water
– rivers
– streams

Lakes

1) littoral zone
– where rooted and floating aquatic plants flourish
– shallow, well-lit waters close to the shore

2) limnetic zone
– well-lit, open surface waters farther from the shore
– occupied by a variety of phytoplankton — algae & cyanobacteria
– zooplankton graze on phytoplankton

3) profundal (aphotic zone)
– most small organisms are short-lived and their remains sink to this zone
– microbes use oxygen for respiration as they compose detritus

Types of Lakes
• according to production of organic matter

1) Oligotrophic
2) Eutrophic
3) Mesotrophic

Oligotrophic Lakes
• deep and nutrient-poor
• phytoplankton in limnetic zone are relatively sparse and not productive
• oxygen-rich water
• usually supports diverse poplns of fish and invertebrates
• small surface area relative to depth

Eutrophic Lakes
• usually shallower
• nutrient content of water is very high
• phytoplankton are very productive
• waters are often murky
• larger surface area relative to depth
• high organic content >>> high decomposition rates >>> low oxygen

Mesotrophic Lakes
• moderate amount of nutrients and phytoplankton productivity

Cultural Eutrophication
• runoff from surrounding land brings additional sediments and nutrients to oligotrophic lake
– human activity speeds up this process
– excess amounts of N, P >> affects growth of algae and phytoplankton
• popln explosion of algae
• production of much detritus
• eventual depletion of oxygen supply
• water is now unusable
• lake’s aesthetic value decreased

Moving Bodies of Water
• move in one direction
• headwaters
– cod and clear
– carries little sediment
– few mineral nutrients
• channel is usually narrow with swift current passing over substrate
• downstream
– water is more turbid
– tributaries have joined to form a river
– more sediment
• nutrient content is largely determined by terrain and vegetation through which water flows

CHAPTER 52
Population Ecology

• populations are relatively stable over time
• no popln can grown indefinitely

DEFINITION OF A POPULATION
• group of individuals of a single species that simultaneously occupy the same general area
• rely on the same resources
• influenced by similar environmental factors
• high likelihood of breeding and interacting with one another
• characteristics are shaped by interactions between individuals and their envts

DENSITY
• number of individuals per unit area or volume
• differences in density is due to
– patchiness of envt — not all areas provide equally suitable habitat
– patterns of spacing

DISPERSION
• pattern of spacing among individuals within the geographic boundaries of the population

1) Clumped
2) Random
3) Uniform

Clumped
• most common
• individuals aggregate in patches
• clumped in sites where envtal factors favor germination and growth

Random
• unpredictable dispersion
• occurs in the absence of strong attractions or repulsions among individuals of a population
• position of each individual is independent of other individuals

Uniform
• evenly spaced
• may result from direct interactions between individuals in popln
• plants: may be due to shading and competition
• animals: territorial behavior and aggressive social interactions

POPULATION GROWTH

Logistic Model: Carrying Capacity
• as any popln grows larger, its increased density may influence the ability of individuals to harvest sufficient resources for
– maintenance
– growth
– reproduction
• poplns subsist on finite amount of available resources
• as popln increases, share of each individual decreases
• there is a limit to the number of individuals that can be occupy a habitat

Carrying Capacity
• max popln size that a particular envt can support at a particular time with no degradation of the habitat
• not fixed — varies over space and time with the abundance of the limiting resources
• energy limitation is one of the most significant determinants of carrying capacity
• shelters, refuges from predators, soil nutrients, water, suitable nesting and roosting sites can also be limiting

Logistic Model: Life Histories
• predicts diff growth rates for low- and high-density poplns, relative to carrying capacity of envt

High Densities
• each individual has few resources available >>> little or no popln growth
• selection favors adaptations that enable organisms to survive and reproduce with little resources
• competitive ability and maximum efficiency of resource utilization should be favored in poplns that are near or at their carrying capacity

Low Densities
• abundant resources >>> popln can grow rapidly
• empty envt should promote adaptations that promote rapid reproduction
• increased fecundity and earlier maturity would be selected for

K-selection
• selection for life history traits that are sensitive to popln density
• density-dependent selection
• tends to maximize popln size
• operates in poplns living at a density near the carrying capacity

r-selection
• selection for life history traits that maximize reproductive success in uncrowded envts
• density-independent selection
• tends to maximize rate of increase
• occurs in variable environments in which popln densities fluctuate below carrying capacity or in open habitats where individuals are likely to face little competition

CHAPTER 53
Community Ecology

COMMUNITY
• assemblage of poplns in an area or habitat
• has a set of properties defined by its species composition and a structure determined by interactions between species
• differ in species richness — no of species they contain

COEVOLUTION
• Reciprocal evolutionary adaptations of two interacting species
• a change in one species acts as a selective force on another species, in which counteradaptation in turn acts as a selective force on the first species

TROPHIC STRUCTURE
• Feeding relationships between organisms
• transfer of food energy from its source in plants and other photosynthetic organisms to herbivores to carnivores and to decomposers — food chain
• food chains are hooked together into food webs

Food Chains into Food Webs
1) a given species may weave into the web at more than one trophic level
2) most consumers are nonexclusive

What Limits the Length of a Food Chain
1) energetic hypothesis
2) dynamic stability hypothesis

Energetic Hypothesis
• length of food chain is limited by inefficiency of energy transfer along the chain
• only 10% of energy stored in organic matter of any trophic level is converted to organic matter at the next trophic level

Dynamic Stability Hypothesis
• long chains are less stable than short chains
• fluctuations at lower trophic levels are magnified at higher levels causing extinction of top predators

DOMINANT SPECIES
• species in a community that have the highest abundance or highest biomass
• most competitive in exploiting limited resources
• greater success in avoiding predators

ECOLOGICAL SUCCESSION
• transition in species composition over ecological time

1) primary
2) secondary

Primary Succession
• begins with virtually lifeless area where soil has not yet formed
• autotrophic bacteria — life forms that are initially present
• lichens and mosses are commonly the first macroscopic autotrophs
• soil develops gradually
– rocks weather
– accumulation of decomposed remains
• once soil is present, lichens and mosses are overgrown by other plants
– grasses
– shrubs
– trees from nearby areas
• eventually, an area may be colonized by plants that will be the prevalent form of vegetation

Secondary Succession
• occurs where an existing community has been cleared by some disturbance that leaves the soil intact
• often the area begins to return to its original state
• earliest plants to recolonize such areas are often herbaceous species
• if area is not burned or heavily grazed, woody shrubs may replace most of herbaceous species
• forest trees may replace most of the shrubs

Three Key Processes
1) early arrivals may facilitate/contribute to appearance of later species
2) early species may inhibit establishment of later species
3) early species may be completely independent of the later species so that they tolerate the later species

CHAPTER 54
Ecosystems

Primary Producers
• trophic level that ultimately supports all others
• autotrophs
• use light to synthesize organic cpds

Heterotrophs
• organisms in trophic levels above the primary producers
• directly or indirectly depend on photosynthetic output of primary producers

Primary Consumers
• herbivores

Secondary Consumers
• carnivores

Tertiary Consumers

Detritivores
• decomposers
• consumers that get their energy from detritus — nonliving organic material

ECOLOGICAL PYRAMIDS

Pyramids of Production
• represents multiplicative loss of energy from a food chain

Pyramids of Biomass
• each tier represents standing crop in a trophic level
• most biomass pyramids narrow sharply from primary producers at the base to top-level carnivores

Pyramids of Numbers
• multiplicative loss of energy from food chains severely limits overally biomass of top-level carnivores that any ecosystem can support
• top-level predators tend to be large animals
• the limited biomass at the top of the pyramid is concentrated in a relatively small number of individuals
• populations of top predators are typically small >>> may be widely spaced >>> more susceptible to extinction

GREEN WORLD HYPOTHESIS
• explains why numbers of herbivores don’t grow uncontrollably
• herbivores consume little plant biomass because they are held in check by a variety of factors

1) plants have defenses against herbivores
2) nutrients, not energy supply, usually limit herbivores
3) abiotic factors limit herbivores
4) intraspecific competition can limit herbivore numbers
5) interspecific competition can limit herbivore densities

NUTRIENT CYCLES

See 54.15

Nitrogen Cycle
• atmospheric nitrogen is gaseous — N2 >>> cannot be used by plants
• 2 pathways
1) atmospheric deposition
2) nitrogen fixation

Atmospheric Deposition
• accounts for 5-10% usable nitrogen that enters ecosystems
• NH4+ and NO3- are added to the soil by being dissolved in the rain/settling as part of particles >>> form that is usable for plants

Nitrogen Fixation
• only certain prokaryotes can convert N2 into usable forms
• Nitrogen-fixers
– soil bacteria
– Rhizobium
– cyanobacteria
• NH3 is released >>> to be used by other organisms
• most soils are slightly acidic so NH3 + H+ = NH4+
• NH3 is a gas >>> pH of soil = 7 >>> NH3 escapes to atmosphere >>> forms NH4+
• NH4+ concentrations in rainfall are correlated with soil pH
• plants can use ammonium directly but NH4+ is used by anaerobic bacteria >>> NO2- >>> NO3- (nitrification)
• NO3- released can be reassimilated by plants
• ammonification — decomposition of organic nitrogen back to ammonium

Phosphorus Cycle
• organisms require phosphorus as a major constituent of
– nucleic acids
– phospholipids
– ATP
– mineral constituent of bones and teeth
• does not cinlude movement through the atmosphere — no significant P-containing gases
• P occurs only in one biologically impt inorganic form — PO4-3
• weathering of rocks adds phosphate to soil
• producers incorporate phosphate into organic molecules
• transferred to consumers in inorganic form
• excreted by consumers as phosphate
• humus and soil particles bind phosphate so that recycling of P tends to be quite localized in ecosystem

CHAPTER 55
Conservation Biology

• scientists have formally named 1.5 M species of organisms
• human activities are altering
– trophic structures
– energy flow
– chemical cycling
– natural disturbance
• amount of human altered land surface is approaching 50%
• we use over half of all accessible surface fresh water
• globally, the rate of species loss may be 1,000 times higher than at any time in the past 100K years

LEVELS OF BIODIVERSITY

1) genetic diversity
2) species diversity
3) ecosystem diversity

Loss of Genetic Diversity
• individual variation within a popln
• genetic variation between poplns associated with adaptations to local conditions
• if one popln becomes extinct, a species has lost some of the genetic diversity that makes adaptation possible
• detrimental to adaptive prospects of species

Loss of Species Diversity
• variety of species in an ecosystem or throughout the entire biosphere
• endangered species — one that is in danger of extinction throughout all or a significant portion of its range
• threatened species — those that are likely to become endangered in the foreseeable future throughout all or a significant portion of their range

Examples
• 1,183 / 9,040 (30%) of known bird species are threatened with extinction
• 50% drop in popln densities of migratory songbirds in the last 40 years
• 200 / 20,000 known plant species in the US are extinct
• 730 / 20,000 are endangered or threatened
• 20% of known freshwater fishes in the word have either become extinct or are seriously threatened
– cichlids in Lake Victoria, East Africa: 200 / 300 have been lost
• 123 freshwter vertebrate and invertebrate species have become extinct in N America since 1900
• 4% of known freshwater species will become extinct each decade
• E. O Wilson — Hundred Heartbeat Club — less than 100 individuals of a species remaining
– Philippine Eagle
– Chinese river dolphin
– Java rhinoceros
• over half of all plant and animal species will be gone by the end of this century

Types of Extinctions
1) Local
2) Global

Loss of Ecosystem Diversity
• within each ecosystem, the biological community has a network of interactions among poplns of diff species
• each ecosystem can have impact on whole biosphere
• an ecosystem has characteristic patterns of energy flow and chemical cycling

Campbell: Chapter 38 (Plant Reproduction and Biotechnology)

Chapter 38
Plant Reproduction and Biotechnology

ALTERNATION OF GENERATIONS
– Gametophyte (N) and sporophyte (2N) take turns producing each other
– Sporophyte is dominant generation
– Over the course of evolution, gametophytes became reduced in size and dependent upon their sporophyte parents

1. sporophyte undergoes meiosis
2. 4 spores (N) are produced
3. mitosis of spores
4. gametophyte (N) – multicellular male and female plants
5. mitosis and cellular differentiation
6. gametophytes develop and produce gametes
• sperm
• egg
7. fertilization
8. zygote (2N)
9. zygote divides by mitosis
10. formation of new sporophytes

SEXUAL REPRODUCTION IN ANGIOSPERMS
– sporophyte develops a flower
• reproductive structure of angiosperms
• unique to angiosperms
– male and female gametophytes develop within anthers and ovaries respectively, of a sporophyte flower
– pollination
• by wind or animals
• brings a male gametophyte to a female gametophyte
– fertilization takes place within the ovary
– devt of seed
• occurs within the ovary
• contains sporophyte embryos
– ovary becomes a fruit

Structures unique to angiosperms
1. flower
2. fruit

FLOWER
– specialized shoots bearing the reproductive organs of sporophyte
– varies in size, shape, and color
– typically composed of 4 whorls of floral organs
• highly modified leaves
• separated by short internodes
– are determinate shoots  cease growing once flower and fruit are formed
– attached to the stem by receptacle

FLORAL ORGANS

1. Sepals
• nonreproductive organs
• enclose and protect the floral bud before it opens
• green and leaflike in appearance

2. Petals
• nonreproductive organs
• brightly colored
• advertise the flower to pollinators

3. Stamen
• male reproductive organ

a. filament
 stalk
b. anther
 terminal structure
 contains pollen sacs – where pollen is produced

4. Carpel (Pistil)
• female reproductive organ
• flowers may have multiple carpels
• for some species, several carpels are fused into a single structure – ovary with two or more chambers, each containing ovule(s)

a. style
 slender neck
 stigma
 found at the tip
 sticky structure
 landing platform for pollen
b. ovary
 located at the base of the carpel
 ovule(s)
 contain a single sporangium
 form within chambers of ovary

Sporangia
– found in stamens and carpels
– where spores and gametophytes develop

Pollen Grains
– develops into the male gametophyte
– form within pollen sacs of anthers

Embryo Sacs
– female gametophytes
– egg-producing structures
– form within ovules in ovaries

TYPES OF FLOWERS

Based on Floral Organs
1. Complete
• have all 4 organs
2. Incomplete
• lacking one or more floral organs
• ex. most grasses (no petals)

Based on Sexuality of Flower
1. Bisexual (Perfect)
• has both stamens and pistils
• an incomplete flower that lacks sepals or petals may also be bisexual
2. Unisexual (Imperfect)
• missing either stamens or carpels
• called staminate or carpellate

Types of Plants (Sexuality)
1. Monoecious
• staminate and carpellate flowers are located on same plant
2. Dioecious
• staminate flowers and carpellate flowers on separate plants
• ex. date palms

FORMATION OF MALE AND FEMALE GAMETOPHYTES

MICROSPOROGENESIS
– development of male gametophyte
– occurs within the anthers

1. Microsporocytes (2N)
• within sporangia in pollen sacs
2. Meiosis
3. 4 microspores (N)
4. Mitosis
5. 2 cells (for each microspore)
a. generative cell
 eventually produce sperm
b. tube cell
 encloses generative cell
 will produce pollen tube
6. encapsulation of 2-celled structure
• thick, resistant wall
7. pollen grain
• 2-celled structure + wall
• an immature male gametophyte
8. generative cell divides by mitosis
9. result: 2 sperm cells (from each generative cell)
• sperm cell = male gamete
• germinated pollen grain = mature male gametophyte
• in most species, this occurs after pollen tube begins to form

MEGASPOROGENESIS

1. Megasporocyte (2N)
• one cell in the sporangium in the ovule
• grows
2. Meiosis
3. 4 Megaspores (N)
4. only one megaspore survives (for most angiosperms)
5. megaspore continues to grow
6. nucleus of megaspore divides by mitosis 3x  1 cell with 8 (N) nuclei
7. membranes partition this mass into embryo sac – multicellular female gametophyte
a. 1 egg cell
 female gamete
 located at one end of the embryo sac
b. 2 synergids
 flank the egg cell
 function in guidance and attraction of pollen tube
c. 3 antipodal cells
 opposite end of embryo sac
 unknown function
d. 2 polar nuclei
 not partitioned into separate cells
 share cytoplasm of large central cell of embryo sac
8. ovule = embryo sac + surrounding integuments (protective layers of sporophytic tissue)

POLLINATION
– occurs when pollen released from anthers lands on a stigma

TYPES OF POLLINATING AGENTS
1. Wind
• to compensate for randomness, wind-pollinated plants release enormous quantities of pollen grains
2. Animals
• transfer pollen directly between flowers

STEPS
1. pollen grain lands on receptive stigma
2. pollen grain absorbs moisture and germinates
3. each pollen grain produces a pollen tube  essential for sperm delivery
4. pollen tube grows down into the ovary via the style
5. generative cell mitotically divides to form 2 sperm
6. pollen tube enters ovary
7. pollen tube probes through micropyle – gap in ovule integuments
8. pollen tube discharges sperm into embryo sac
9. fertilization

MECHANISMS THAT PREVENT SELF-FERTILIZATION
– contributes to genetic variation by ensuring that sperm and eggs come from diff plarents
– dioecious plants cannot self-fertilize – unisexual

For bisexual flowers
1. stamens and carpels mature at different times

2. stamens and carpels are arranged in such a wa that it is unlikely that an animal pollinator could transfer pollen from anthers to stigma of same flower

3. self-incompatibility
• most common strategy
• ability of plant to reject its own pollen and pollen of closely related individuals
• biochemical block prevents pollen form completing devt
• analogous to immune response of humans – based on ability to distinguish self from nonself
• recognition of self pollen is based on S-genes – genes for self-incompatibility
• if pollen grain and stigma have same alleles at S-locus, then pollen grain fails to complete formation

a. gametophytic self-incompatibility
 block occurs in pollen grain
 bean, tobacco, rose
b. sporophytic self-incompatibility
 block response by cells in stigma
 mustard family

NOTE: many agriculturally impt plants are self-compatible

DOUBLE FERTILIZATION
– one sperm fertilizes egg = zygote
– other sperm combines with 2 polar nuclei – (3N) nucleus in large central cell of embryo sac
– large cell will give rise to endosperm
• food storing tissue of seed
• double fertilization ensures that endosperm will only develop in ovules where egg has been fertilized

Similarity to Fertilization in Animals
1. increase in cytoplasmic Ca+2 levels of the egg after gamete fusion
2. establishment of block to polyspermy

DEVELOPMENT OF THE SEED
– ovule develops into seed
– ovary develops into fruit enclosing the seed
– embryo develops from zygote – seed stockpiles proteins, oils, and starch
• nutrients are initially stored in endosperm
• cotyledons assume to storage function later on

ENDOSPERM DEVELOPMENT
– NOTE: endosperm devt usually precedes embryo devt
– After double fert – 3N nucleus of ovule’s central cell divides
– Mutinucleate cell with milky consistency
– Endosperm – liquid mass
– Multinucleate cell becomes multicellular when membrane forms between nuclei
– “naked” cells produce cell walls
– endosperm becomes solid
– ex. coconut milk – liquid endosperm
coconut meat – solid endosperm
– endosperm is rich in nutrients
– most monocots and some dicots – endosperm contains nutrients that can be used by the seedling after germination
– many dicots – food reserves of endosperm are completely transferred to cotyledons

EMBRYO DEVELOPMENT
– first mitotic division of zygote – transverse
a. Basal cell
 continues to divide transversely
 produces the suspensor
 thread of cells
 anchors embryo to parent plant and in some, the endosperm
 functions in transfer of nutrients to the embryo from the parent and endosperm
b. Terminal cell
 divides several times
 forms spherical proembryo attached to suspensor
– cotyledons begin to form as bumps on proembryo
– embryo elongates
– meristems on two ends of the embryo – sustains primary growth indefinitely after seed germinates
– 3 primary meristems are present in the embryo
a. protoderm  dermal
b. ground meristem  ground
c. procambium  vascular tissues

2 Features of Plant Form
– established during embryo devt

1. root-shoot axis – meristems at opposite ends
2. radial pattern of 3 primary meristems set to give rise to 3 tissue systems

STRUCTURE OF MATURE SEED
– last stages of maturation – seed dehydrates
– embryo stops growing until seed germinates
– embryo and food supply are enclosed by seed coat
• protection
• from integuments of ovule

Dicot Seed
1. hypocotyl
• embryonic axis below the point where cotyledons are attached
• terminates in radicle
2. epicotyl
• embryonic axis above cotyledons
• tip: plumule – shoot tip + pair of miniature leaves
3. cotyledons
4. endosperm
• Castor bean
• Contains food supply

Monocot Seed
1. Scutellum
• specialized cotyledon
• thin
• large surface area pressed against endosperm
• absorbs nutrients from endosperm
2. sheaths
a. coleoptile
 covers the young shoot
b. coleorhiza
 covers the young root
3. endosperm

DEVELOPMENT OF FRUIT
– simultaneous with seed devt
– pollination triggers hormonal changes that cause the ovary to begin its transformation
– wall of ovary becomes the pericarp
– other parts of flower are shed
– in some angiosperms, floral parts contribute to fruit
– ripens at about the same time that its seeds are completing their devt

Ripening of Dry Fruit
– aging of fruit tissues
– aging allows fruit to open and release the seeds

Ripening of Fleshy Fruit
– controlled by complex interaction of homrmones
– pulp becomes softer as a result of enzymes digesting cell walls
– color change
– fruit becomes sweeter – organic acids/starch molecules are converted to sugar

Function of the Fruit
1. protects the enclosed seeds
2. aids in seed dispersal

SUMMARY
– formation of gametes
– dispersal of pollen grains
– pollination – pollen lands on stigma
– pollen grain produces pollen tube
– formation of 2 sperm cells
– pollen tube discharges sperm into ovule
– double fertilization
– zygote gives rise to embryo
– ovule that contains the embryo develops into a seed
– entire ovary develops into a fruit – may contain one or more seeds, depending on the species
– seeds are dispersed
– if seeds are deposited in sufficiently moist soil, they germinate

EVOLUTIONARY ADAPTATIONS FOR SEED SURVIVAL

Seed Dormancy
– phase of extremely low metabolic rate and suspension of growth and devt
– conditions to break dormancy vary
– increases the chance that germination will occur at a time and place most advantageous for growth

Seed to Seedling
(see Campbell)

ASEXUAL REPRODUCTION

1. Fragmentation
• separation of parent plant into parts that reform the whole plant

2. Apomixis
• produce seeds without flowers being fertilized
• diploid cell in ovule give rise to embryo  ovules mature into seeds

3. Grafting
• makes it possible to combine the best qualities of different species or varieties into a single plant
• usually done when plant is young
• stock – plant that provides the root
• scion – grafted plant part
• quality of fruit is determined by genes of scion

4. Cloning

Advantages of Sexual Reproduction
1. genetic variation
2. seed
• can disperse to new locations
• can wait to grow until envtl conditions improve

Advantages of Asexual Reproduction
1. a plant well-suited to an envt can make many copies of itself
2. offspring are not as frail as seedlings

Campbell: Chapter 31 (Fungi)

Chapter 31
Fungi

KINGDOM FUNGI
– eukaryotes
– multicellular
– differ from other eukaryotes in terms of
• mode of nutrition
• structural organization
• growth
• reproduction

MODE OF NUTRITION: ABSORPTIVE NUTRITION
– enables fungi to live as decomposers and symbionts
– small organic molecules are absorbed from surrounding medium
– digestion of food outside body
• exoenzymes – hydrolytic enzymes secreted into the food
– associated with ecological roles as
• decomposers (saprobes)
• parasites
• mutualistic symbionts

Structural Organization
– adaptations for absorptive nutrition
• extensive surface area
• rapid growth
– yeasts are only unicellular fungi
– vegetative bodies
• nutritionally active
• usually hidden
• diffusely organized around and within tissues of food sources

1. Hyphae
• tiny filaments
• composed of tubular walls surrounding plasma membranes and cytoplasm
• fungus concentrates its energy and resources on adding hyphal length (overall absorptive surface area) rather than girth

Mycelium
 interwoven mat formed by hyphae
 feeding network of fungus
 may be huge
 may be subterranean
 provides the extensive surface area for absorption
 nonmotile

Haustoria
 modified hyphae
 nutrient-absorbing tips that penetrate tissues of host

a. septate
 hyphae divided into cells by cross-walls
 septa generally have pores large enough to allow flow of organelles from cell to cell
b. coenocytic
 aseptate
 hyphae are not divided by cross-walls
 hyphae consists of a continuous cytoplamsic mass with many nuclei
 results from repeated division of nuclei without cytokinesis

2. Chitinous cell wall
3. Reproductive structures

MODE OF REPRODUCTION
– reproduce by releasing asexual or sexual spores
– spores
• function in dispersal
• account for geographic distribution of species

Generalized Life Cycle of Fungi
– nuclei of fungal hyphae and spores of most species are haploid except for transient 2N stages that form during sexual life cycles

Asexual
1. Mycelium
2. Spore-producing structures
3. Spores
4. Germination
5. Mycelium

Sexual
1. Mycelium
2. Plasmogamy
• fusion of cytoplasm when mycelia come together
3. Heterokaryotic stage
• genetically heterogenous mycelia
• fusion of two hyphae that have genetically different nuclei
4. Karyogamy
• fusion of nuclei
5. Zygote
6. Meiosis
7. Spore-producing structures
8. Spores
9. Germination
10. Mycelium

DIVERSITY OF FUNGI
1. Division Zygomycota (Bread Molds)
2. Division Ascomycota (Sac Fungi)
3. Division Basidiomycota (Mushrooms)

DIVISION ZYGOMYCOTA (BREAD MOLDS)
– mostly terrestrial
– form resistant structures during sexual reproduction
– coenocytic hyphae – septa are found only where reproductive cells are formed
– mycorrhizae
– ex. Rhizopus

SEXUAL REPRODUCTION
1. Neighboring mycelia of opposite mating types [(+) & (–)]
• identical in appearance
• differ in chemical markers
2. Formation of gametangia
• hyphal extensions
• walled off around several haploid nuclei by septum
3. gametangia undergo plasmogamy
4. heterokaryotic zygosporangium
• resistant structure
• represents the zygote stage but it does not have diploid nucleus
• multinucleate structure
• metabolically inactive
5. develops rough, thick-walled coating
6. karyogamy
7. meiosis
8. zygosporangium germinates into sporangium
9. sporangium disperses spores
10a. spores germinate and grow into new mycelia

ASEXUAL REPRODUCTION
10b. dispersal and germination of spores
11. new mycelium
12. sporangia
• bulbous
• develops at tip of hyphae
13. production of new spores

DIVISION ASCOMYCOTA (SAC FUNGI)
– marine, freshwater, terrestrial habitats
– range in size and complexity
– include plant pathogens
– half of ascomycete species live with alga – lichens
– some form mycorrhizae with plants
– distinguishing feature: production of spores in sac-like asci
– bear their sexual stages in macroscopic fruiting bodies – ascocarps

SEXUAL REPRODUCTION
1. haploid mycelia of opposite mating types become intertwined and form ascogonium (F) and antheridium (M)
2. formation of cytoplasmic bridge
3. plasmogamy
• ascogonium receives nuclei form antheridium
• produces heterokaryotic bulge called ascogonium
4. ascogonium
• coenocytic
• extends hyphae into dikaryotic cells
• cells at the tips of dikaryotic hyphae develop into asci
5. ascocarp from dikaryotic hyphae
6. tips of ascocarp’s dikaryotic hyphae are partitioned into asci
7. karyogamy within asci
8. 2N nucleus divides by meiosis
9. 4 N nuclei
10. each N nuclei divides by mitosis (4×2)
11. 8 nuclei in ascus
12. ascospores
13. dispersal of ascospores
14. germination of ascospore
15. new mycelia

ASEXUAL REPRODUCTION
16. Ascogonium
17. Conidiophores
• produces conidia – naked spores
• specializaed hyphae
18. Disperal of conidia – wind
19. Germination
20. New mycelium

Zygomycota Ascomycota
Asexual Spore Inside sporangia Conidiophores
With wall Naked
Heterokaryotic More extensive

DIVISION BASIDIOMYCOTA (CLUB FUNGI)
– mushrooms, shelf fungi, puffballs, and rusts
– basidium
• transient diploid stage
• clublike shape
– impt decomposers
– mycorrhiza, plant parasites
– best at decomposing lignin
LIFE CYCLE OF BASIDIOMYCOTA
1. haploid mycelia of opposite mating types
2. plasmogamy
3. dikaryotic mycelium – long-lived
4. transformation of dikaryotic mycelium to basidiocarps (fruiting bodies)
5. cytoplasmic streaming  swelling of hyphae
6. surfaces of basidiocarp’s gills are lined with basidia
• (dikaryotic cells)
• sources of sexual spores
7. karyogamy
8. meisosi
9. each basidium grows four appendages
10. one haploid nucleus enters each appendage and develops into basidispore
11. spore dispersal
12. germination
13. short-lived haploid mycelia

Asexual reproduction is less common

SUMMARY

Division Key Feature
Zygomycota Resistant zygosporangium as sexual stage
Ascomycota Sexual spores borne internally in asci
Basidiomycota Sexual spores borne externally on basidia

MOLDS
– rapidly growing, asexually reproducing fungus
– mycelia grow as saprobes or parasites
– Rhizopus

DEUTEROMYCETES
– Imperfect fungi
– No known sexual stages
– Reproduce asexually by producing spores

YEASTS
– Unicellular fungi
– Inhabit liquid or moist habitats
– Asexual reproduction
• simple cell division
• pinching of small bud cells off a parent cell

LICHENS
– often mistaken for mosses or other simple plants
– grows on rocks, rotting logs, trees, and roofs
– symbiotic association of millions of photosynthetic microorganisms held in a mesh of fungal hyphae
– absorb most of needed minerals from dust or rain
– asexual reproduction as symbiotic units also occurs
• fragmentation
• formation of soredia – small clusters of hyphae with embedded algae
– impt pioneers on newly cleared rock and soil surfaces
– may do not stand up very well to air pollution
– able to live in envts where neither fungi nor algae could live alone

1. fungus
• mostly ascomycete, some basidiomycetes
• gives lichen its overall shape and structure
• tissues formed by hyphae account for most of lichens mass
• provides suitable envt for growth
• fungal pigments help shade algae from intense sunlight
• reproduce sexually

2. photosynthetic partners
• cyanobacteria or chlorophyta
• occupies inner layer
• provides food (and nitrogen for cyano)
• reproduce independently of fungi by cell division

MYCORRHIZAE
– mutualistic association of plant roots and fungi
– increases absorptive area of roots

FUNGUS-LIKE PROTISTS

CHYTRIDIOMYCOTA
– mainly aquatic
– may be saprobes or parasites
– has a flagellated stage
– absorptive mode of nutrition
– chitinous cell walls
– coenocytic hyphae
– some may be unicellular