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Reptile Derivatives Birds and mammals. Archaeopteryx = “first” bird.

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Presentation on theme: "Reptile Derivatives Birds and mammals. Archaeopteryx = “first” bird."— Presentation transcript:

1 Reptile Derivatives Birds and mammals

2 Archaeopteryx = “first” bird

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

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7 Shy feathers; insulation

8 Why fly?: to glide from tree to tree or to chase insects?

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12 Synapsids = mammal like reptiles

13 Pelycosaurs = Dimetrodon

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

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16 Therapsids

17 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

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

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21 Mammals; monotremes, platypus and echidna Lay eggs.

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

23 Marsupials and Placentals – Parallelism And no eggs

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

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

26 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

27 Marsupial pouch with ‘baby’

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

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