Ch. 47—Animal Development
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Transcript of Ch. 47—Animal Development
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Ch. 47—Animal Development
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Fertilization
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Fertilization
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Fertilization
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Fertilization
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Once fertilization is complete
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Animal Development
• Cleavage—rapid mitotic cell division into smaller cells—blastomeres
• Solid ball of cells—morula• Blastula produced when a
cavity called blastocoel forms
• Gastrulation—rearrangement of cells into 3 germ layers
blastomeres
Morula (solid ball of cells)
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Blastocyst• Blastula stage of
mammalian embryos• Trophoblast layer
enclosing the blastocoel– Chorion (outer
embryonic layer)
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Blastocyst develops into gastrula
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Gastrulation• Cells rearrange and fold inward at the blastopore to form a gastrula with three-germ layers:– Ectoderm (skin, nails, teeth)– Mesoderm (skeletal, muscular, excretory, circulatory, reproductive
systems; blood, bone, and muscle)– Endoderm (epithelial lining of digestive, respiratory, excretory
tracts; liver, pancreas)
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Organogenesis• Development of 3 germ
layers into the beginnings of organs– Notochord—stiff dorsal
skeletal rod (from mesoderm)– Neural plate—will become
brain and spinal cord (from ectoderm)
– Somites—blocks of mesoderm arranged along notochord; sign of segmentation
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Amniotes• Amnion—fluid filled cavity; protects embryo• Allantois—disposal sac• Chorion—exchange gases• Yolk sac—provides nutrients
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Eutherian mammals