Reptiles: Key characteristics
Amniotic egg: made reptiles fully independent from water
- Chorion: outer membrane below egg shell; allows gas exchange but keeps water in
- Amnion: encases developing embryo within fluid-filled cavity
- Yolk sac: provides food for embryo through blood vessels
- Allantois: encases cavity for waste products
- Fertilization must be internal
Dry skin: watertight, layers of scales that develop from epidermal cells with keratin (same protein as in finger nails, bird feathers, mammal hair)
Thoracic breathing: movement of rib cage