BIO 180 Lecture 15:02

feathers evolved from simple projections or scales

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Unformatted text preview: rs. - Feathers evolved from simple projections or scales. What Did They Do? Airfoil, insulation, camouflage, communication - Still unknown whether flight evolved “ground-up” or “trees-down”. Further Modifications For Flight - Skeleton: 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 - Cost: - 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 dominant, large...
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