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Ch 33 animal development

Ch 33 animal development . AP Biology Lecture . Cleavage . Rapid series of cell division. Embryo becomes a ball of even smaller cells Blastocoel - fluid filled cavity that forms Cell now referred to as a blastula. Individual cells called blastomeres . . Complete Cleavage . Little yolk

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Ch 33 animal development

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  1. Ch 33 animal development AP Biology Lecture

  2. Cleavage • Rapid series of cell division. Embryo becomes a ball of even smaller cells • Blastocoel- fluid filled cavity that forms • Cell now referred to as a blastula. • Individual cells called blastomeres.

  3. Complete Cleavage • Little yolk (stored nutrients) • All blastomeres equal size

  4. Incomplete Cleavage • Lot of yolk • Embryo forms as a disc of cells, blastodisc, on top of the yolk mass

  5. Mammal Cleavage • During 4th division, cells separate into two groups • Inner cell mass • Becomes embryo • Pluripotent • Surrounding outer cell • Trophoblast, an encompassing sac • Secretes the fluid to make the blastocoel • Becomes support structure to attach embryo to uterine wall

  6. Gastrulation • Blastula altered into embryo with multiple tissue layers and distinct body axes *body plan and first organs* • The germ layers form • Endoderm – innermost, from blastomeres inside the embryo Produces lining of digestive and respiratory tract

  7. Ectoderm – outermost, from cells outside the embryo • Produces nervous system and epidermal layer of skin • Mesoderm – middle layer, cells in between endoderm and ectoderm • Produces heart, blood vessels, muscles and bones

  8. http://bcs.whfreeman.com/thelifewire/content/chp20/2002001.htmlhttp://bcs.whfreeman.com/thelifewire/content/chp20/2002001.html

  9. Placental mammals • Inner cell mass splits • Upper layer- epiblast • Cells from endoderm and mesoderm • Eventually embryo • Lower layer- hypoblast • Eventually placenta

  10. Organogenesis • Development to form major organs and organ systems • Neurulation – formation of the nervous system • Neural plate- groove between folds eventually forms a hollow cylinder, neural tube, an overlaying layer of epidermal ectoderm • Some cells do not form into the neural plate but form neural crest which becomes the connection between the brain/spinal cord and rest of the body

  11. Segmentation during neurulation called somites • Found around the notochord • Produce cells that become • Vertebrae • Ribs • Muscle of trunk • Muscle of limbs • Lower layer of skin

  12. Amniotes • Extraembryonic membrane around the embryo • Nutrition • Gas exchange • Waste removal

  13. Mammals entire trophoblast embeds into the uterine wall • Hypoblast form chorion, membrane that limits water loss and aids in gas exchange • Chorion and maternal tissue form the placenta • Epiblast produces amnion, fluid filled amniotic cavity around the embryo

  14. http://lcmrschooldistrict.com/roth/PowerPoint_Lectures/chapter42/videos_animations/cleavage_implant.htmlhttp://lcmrschooldistrict.com/roth/PowerPoint_Lectures/chapter42/videos_animations/cleavage_implant.html

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