Outline-1, BIO 3220, Development


A. Gametes

1. Sperm

2. Egg

a. Microlecithal– Small amount of yolk, found in amphioxus and eutherians

b. Mesolecithal– Medium amount of yolk, found in lampreys, dipnoans, chondrosteans and amphibians

c. Macrolecithal –Large amount of yolk found in most fish, reptiles, birds, monotremes

d. Isolecithal –Even yolk distribution

e. Telolecithal –Uneven yolk distribution

1. Vegetal Pole –Yolk region

2. Animal Pole –High metabolic activity

f. Vitelline Membrane –Surrounds egg

g. Various additional layers around egg, depending on group: Jelly, Capsule, Shell, Albumin, Corona Radiata, Zona Pellucida

B. Oviparous Animals “Egg-Birth”, Lay eggs as in many fish, birds, many amphibians

C. Viviparous Animals “Live-Birth”, Most mammals, and tried by all groups but birds and agnathans

D. Ovoviviparous Animals “Egg-Live-Birth”, Hatched inside mother as in Squalus

E. Fertilization– Joining of gametes

1. Internal vs External

2. Zygote

F. Cleavage and Blastula

1. Microlecithal

a. Blastomeres

b. Blastocoel

c. Blastocyst in mammals

d. Inner cell mass

e.Trophoblast cells

2. Mesolecithal

3. Macrolecithal

a. Blastoderm

b. Blastocoel

G. Gastrulation

1. Germ layers form

2. Notochord forms

3. Bilateral symmetry

4. Microlecithal eggs

a. Involution

b. Blastopore

c. Archenteron

d. Ectoderm

e. Notochord

f. Mesoderm

g. Coelom

h. Endoderm

5. Mesolecithal eggs

a. Epiboly

b. Ectoderm

1. Nervous System

2. Sensory

3. Neural crest cells –form sensory ganglia, melanocytes, adrenal gland, contribute to branchiomeric muscles/skeleton

4. Epidermis of skin/Lining mouth & anus

c. Endoderm

Form lungs and digestive structures

d. Mesoderm

1. Chordomesoderm

2. Epimere = dorsal mesoderm; Somite

a. Dermatome –Forms dermis of back

b. Myotome –Forms skeletal muscles other than pharyngeal

c. Sclerotome –Forms vertebrae & dorsal ribs

3. Hypomere = Lateral plate mesoderm

a. Somatic –Contributes to bone of girdles & limbs, muscles of body wall

b. Splanchnic –Contributes to muscles of heart, blood vessels and other visceral structures

c. Coelom –Body cavity

d. Somatopleure –Muscles and CT of body wall

e. Splanchnopleure –Muscles and CT of gut tube

4. Mesomere = intermediate mesoderm

a. Kidney tubules

b. Associated ducts

6. Macrolecithal eggs

a. Delamination [Blastoderm forms 2 layers: Epiblast, Hypoblast] –Epiblast becomes ectoderm, hypoblast becomes endoderm.

b. Primitive streak –Forms mesoderm and gives rise to >>>

c. Notochord

d. Mesenchyme

e. Body stalk– Forms between body and yolk

7. Mammalian embryo

a. Blastoderm

b. Delamination– Gives rise to hypoblast & epiblast

c. Primitive streak

1. Notochord

2. Mesoderm

d. Mesenchyme

e. Coelom

H. Neurulation –Nervous System Formation

I. Organogenesis –Beginning of ALL major organs of the body

J. Extraembryonic Membranes

1. Fish

a. Body stalk

b. Yolk sac –Only membrane needed, because respiration & excretion is into the water

2. Amphibians –No placenta, hatch early to eat!

3. Amniotes {reptiles, birds, mammals}– Membranes protect from desiccation, allow for respiration & excretion

a. Yolk sac – splanchnopleure

b. Amnion – somatopleure

Amniotic fluid

c. Chorion – somatopleure

d. Allantois – sphlanchnopleure –Gas exchange & waste receptacle

e. Placenta – umbilical cord –Allows for better waste removal & nutrient uptake; varies significantly – is primarily a yolk sac in marsupials.