Chapter 47

Animal Development

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

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

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

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

Amniote embryos

Extraembryonic membranes: •yolk sac (support; circulatory function) •amnion (fluid-filled sac; protection)

•chorion (placenta formation)

•allantois (nitrogenous waste)