1. Lecture Date ________ Chapter 47 –Animal Development

3. 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

5. 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

6. 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

8. 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

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