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My_Ch47_lecture(2009050122180284) - Chapter 47 Animal...

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Chapter 47: Animal Development Purpose—to understand the stages of animal embryonic development What you MUST know in Ch 47: Fertilization Cleavage stages Gastrulation Extra-embryonic membranes Neurulation Fate maps Spemann and organizer Read Cliff’s for a concise review. Note (for the AP test, not our unit test), none of the topics is underlined...but Cliff’s does take 5 pages to review it . Cliff’s points out that the AP test focuses on gametogenesis (covered in Ch 46) and embryonic development, not on puberty or aging. Fertilization includes: 1. Recognition —sperm secretes a protein that recognizes receptor molecules on the glycoprotein vitelline layer (= zona pellucida in humans) plasma membrane of the egg 2. Penetration —sperm and egg plasma membranes fuse, and sperm nucleus enters the egg 3. Formation of fertilization membrane by the vitelline layer prevents extra sperm from entering the fertilized egg 4. Completion of meiosis II in the secondary oocyte produces an egg and a polar body 5. Fusion of nuclei & DNA replication —egg and sperm nuclei fuse, forming a zygote , with 46 chromosomes in
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humans. Each chromosome replicates, forming identical chromatids. Cleavage of the zygote : Consists of a series of cell divisions without cell growth (no increase of cytoplasm) Resulting cells = blastomeres Early cleavage stages have: o Embryo polarity Egg has upper animal pole and lower vegetal pole —the latter contains more food = yolk o Early cleavages are polar , dividing the egg from N to S pole (like orange sections); other cleavages are equatorial , parallel to the equator o In deuterostomes (echinoderms & chordates), early cleavages are radial , forming cells from the animal and vegetal poles that are aligned vertically, AND Cleavages are indeterminate , in that individual blastomeres have the potential to form a complete embryo independently o In protostomes (annelids, mollusks, arthropods), early cleavages are spiral , forming cells from the animal and vegetal poles that are aligned at an angle
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My_Ch47_lecture(2009050122180284) - Chapter 47 Animal...

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