1. Animal Development
Chapter 47 ~ Animal Development

2. Embryonic development/fertilization
Preformation~ until 18th century; miniature infant in sperm or egg
At fertilization/conception:
Acrosomal reaction~ hydrolytic enzyme action on egg jelly coat….
Fast block to polyspermy~ membrane depolarization prevents multiple fertilizations….
Cortical reaction~ release of calcium causes hardening of egg outer layer and creates a...
Slow block to polyspermy and...
Egg activation~ increases metabolic activity; protein synthesis

3. The Fertilized Egg & Cleavage
Blastomeres~ resultant cells of cleavage/mitosis
Yolk~ nutrients stored in the egg
Vegetal pole~ side of egg with high yolk concentration
Animal pole ~ side of egg with low yolk concentration
Morula~solid ball of cells
Blastocoel~fluid-filled cavity in morula
Blastula~hollow ball stage of development

4. Cleavage

5. Gastrulation Gastrula~ 2 layered, cup-shaped embryonic stage
3 Embryonic germ layers:
Ectoderm~ outer layer; epidermis; nervous system, etc.
Endoderm~ inner layer; digestive tract and associated organs; respiratory, etc.
Mesoderm~skeletal; muscular; excretory, etc.
Invagination~ gastrula buckling process to create the...
Archenteron~ primitive gut
Blastopore~ open end of archenteron

6. Organogenesis: organ formation
Blastodisc~ cap of cells on top of yolk
Primitive streak~ invagination of blastodisc
Neural tube~ beginning of spinal cord
Somites~ vertebrae and skeletal muscles
Neural crest~ bones and muscles of skull

7. Amniote embryos
Extraembryonic membranes: •yolk sac (support; circulatory function) •amnion (fluid-filled sac; protection) •chorion (placenta formation) •allantois (nitrogenous waste)