Lecture 35 - BIOL104-04 Principles of Biology I Lecture 35...

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Unformatted text preview: BIOL104-04 Principles of Biology I November 29, 2010 Lecture # 35 Ch 54 Animal Development (54.1 - 54.4) Stages of development • Fertilization • Cleavage • Gastrulation • Organogenesis Fertilization • External – Aquatic animals • Internal – Terrestrial animals – Provides a non-dessicating environment Fertilization • Sperm penetration & membrane fusion • Egg activation • Fusion of nuclei The egg has a protective coat • Frog & Sea Urchin – Jelly layer – Vitelline envelope • Mammalian egg – Zona pellucida – Granulosa cells Sperm penetration • Leads to egg activation • Blocking of additional fertilization events – Egg releases cortical granules • Removes sperm receptors from egg • Release hyalin – Hyalin attracts waters – Forms the fertilization envelope – Prevents polyploidy • Incompatible with animal development Egg Activation • Sperm & egg membranes fuse • Dramatic increase in the levels of free intracellular Ca ++ • Starts at point of sperm entry and flows across the egg • Ca ++ acts as 2nd messenger to initiate changes in protein activity Fusion of cell nuclei restores...
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Lecture 35 - BIOL104-04 Principles of Biology I Lecture 35...

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