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Animal gametogenesis and embryology (chapters 25, 32, 47) What is an animal?

Animal gametogenesis and embryology (chapters 25, 32, 47) What is an animal? multicellular, heterotrophic, ingest food no cell walls; organisms held together by extracellular matrix; intracellular junctions nervous and muscle tissues are unique distinctive stages of development

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Animal gametogenesis and embryology (chapters 25, 32, 47) What is an animal?

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  1. Animal gametogenesis and embryology (chapters 25, 32, 47) What is an animal? multicellular, heterotrophic, ingest food no cell walls; organisms held together by extracellular matrix; intracellular junctions nervous and muscle tissues are unique distinctive stages of development body development regulated by Hox genes

  2. What is a Hox gene? Contains a “homeobox” that enables it to bind to DNA as a transcription factor (3 -helices) Remainder of the protein helps determine which gene it regulates Some of these gene products help regulate body part development (homeotic genes) So far, homeotic genes have been found only in animals

  3. Model animals: Drosophila, nematodes

  4. Animals were traditionally classified based on anatomy (body plans) and embryology New approaches may modify old dichotomies: I. parazoa vs metazoa (eumetazoa) presence or absence of true tissues II. radial vs bilateral symmetry cephalization germ layers- radiata have two, bilaterals three

  5. Germ layers seen during gastrulation ectoderm- skin, nervous system endoderm- (archenteron)- digestive system, liver, lungs mesoderm- muscles, other internal organs

  6. III. Body cavity (of bilaterials) acoelomate (flatworms) pseudocoelomate (rotifers and roundworms) coelomates- body cavity completely lined by mesoderm tissue Purpose of body cavity? hydrostatic skeleton in invertebrates growth, development and positioning of internal organs

  7. Protostomes vs deuterostomes

  8. Stages of animal development fertilization cleavage gastrulation (formation of germ layers) organogenesis

  9. Cleavage distributes cytoplasm of zygote into many smaller cells Cells in most animals have polarity vegetal pole (yolk) animal pole (very little yolk) yolk is especially prominent in eggs of birds, reptiles, many fishes and insects affects cleavage- incomplete (meroblastic) vs complete (trophoblastic)

  10. Sea urchin gastrulation

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