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- Feathers evolved from simple projections
What Did They Do?
Airfoil, insulation, camouﬂage, communication - Still unknown whether flight evolved “ground-up” or
“trees-down”. Further Modifications For Flight
1. Bones thin-walled, hollow - strengthened by struts;
many fused. they lighten the load and use less energy when they are lighter.
2. Elongated keel on sternum for flight muscles.
3. Bill instead of heavy teeth.
- Superior circulatory, respiratory systems
* Endothermy (warm blooded)
- Generate own body heat from oxidation of food.
- Benefits: - can be active in cold
- high metabolism; sustained activity
- huge amount of food.
- Evolved independently in ray-finned fish (3 times) &
mammals. The Amniotic Egg
- Amphibians tied to water due to permeable skin and eggs.
- Early reptiles evolved amniotic egg and dry, water-tight
scaly skin superior ability to conserve water.
- Led to radiation of reptiles; quickly replaced amphibians as
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