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Reptile Derivatives

Reptile Derivatives. Birds and mammals. Archaeopteryx = “first” bird. Reptilian features teeth, tail, pelvis – no sternum skull features Avian (bird) features feathers, longer front limbs. Shy feathers; insulation. Why fly?: to glide from tree to tree

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Reptile Derivatives

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  1. Reptile Derivatives Birds and mammals

  2. Archaeopteryx = “first” bird

  3. Reptilian features teeth, tail, pelvis – no sternum skull features Avian (bird) features feathers, longer front limbs.

  4. Shy feathers; insulation

  5. Why fly?: to glide from tree to tree or to chase insects?

  6. Synapsids = mammal like reptiles

  7. Pelycosaurs = Dimetrodon

  8. Function of “sail” Camoflage? Swimming? Thermoregulation Note: nasty carnivore

  9. Therapsids

  10. How to make a Mammal • Develop for carnivory = active • Hair – warm bloodedness • Limbs; under body, toes of equal length • Teeth; regionalization, multi roots, cutting • Lower jaw – one bone • Not there – change in reproduction

  11. A definition of mammal = three bones in middle ear, one bone in lower jaw

  12. Mammals; monotremes, platypus and echidna Lay eggs.

  13. Echidna – egg in pouch, Hatches in 9 days – young in pouch for 12 weeks. Gets milk.

  14. Marsupials and Placentals – Parallelism And no eggs

  15. Marsupial and placental reproduction; clevage total and equal - blastula forms with inner cell mass

  16. Inner cell mass forms layers of cells inside blastula Embryo implants into uterine wall

  17. On plate inside embryo – primitive streak forms Get chorion, amnion, allantois and yolk sac Placenta = chorion plus yolk sac in marsupials Placenta = chorion plus allantois in placentals

  18. Marsupial pouch with ‘baby’

  19. opossum young on nipple. Marsupiaols not primitive, but different Designed for an unpredictable environment – can dump kid to save mother.

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