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Animal Development

Animal Development. Stages of Early Embryonic Development Cellular an Molecular Basis of Morphogenesis and Dfferentiation. Preformation vs Epigenesis. Preformation -suggested smaller organisms was found in the sex cell(s)

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Animal Development

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  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

  4. 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 Amniote Egg-Development

  5. 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

  6. 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

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