1. Animal Development Stages of Early Embryonic Development
Cellular an Molecular Basis of
Morphogenesis and Dfferentiation

2. Preformation vs Epigenesis
Preformation-suggested smaller organisms was found in the sex cell(s)
Epigensis-Aristotle, embryo gradually emerged from a formless egg

3. The Stages of Early Embryological Development
Fertilization-actives the egg; fuses egg and sperm nuclei, acrosomal and cortical reactions, egg activation
Cleavage-partitions the zygote; morulablastula
Gastrulation-rearranges blastula into 3 layered embryo
Organogenesis-organs form, “larva” forms

7. Amniote Egg-Development
Avian Development (birds)
egg white-protein rich solution, provides additional nutrients
yolk-ovum containing large food reserve, blastula forms on top of the yolk, actually blastodisc floating on top of the yolk
Mammalian Development-
Inner cell mass-forms embryo, some membranes
Trophoblast-forms the placenta
Much smaller yolk reserve
Organogenestis forms neural tube, notochord, and somites

10. The Cellular and Molecular Basis of Morphogenesis and Differentiation
The changes in cell shape and the cell migrations during cleavage, gastrulation and organogenesis are morphological movements
Includes: cell extension, contraction and adhesion
Reorganization of the cytoskeletoncell shape changes
Cells move to form layers,
Partially guided by extracellular matrix

11. Cytoplasmic Determinants and Cell-Cell Inductions
Heterogeneous distribution of mRNA, proteins, etc. during cleavage different blastomeres receive different substances
Diffusible chemical signals from nearby and adjacent cells induces changes in gene expression