Lecture 20 - Lecture 20 1) Amniotes are a monophyletic...

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Lecture 20 1) Amniotes are a monophyletic group – the amniotic egg only evolved once. a) Reptilia is paraphyletic if it doesn’t include birds – but birds have descended from dinosaur reptiles. b) Turtles are still in dispute over whether they are reptilia or not. 2) Evolution of the Mammal a) Endotherms vs. Ectotherms (Warm blooded vs. cold blooded) i) Ectotherms - Because ectotherms use environmental energy, it is relatively cheap and they do not need such a high caloric intake for energy. However, the downside is that this system relies on environmental conditions. This also makes them vulnerable to predation, etc. Their body temperature can fluctuate. ii) Endotherms - Use metabolic energy to maintain a constant body temperature. Disadvantage is that it is energetically expensive – This is why many endotherms have insulation to keep in heat. Advantage of a constant body temperature means they can maintain a high level of energetic performance despite environmental conditions. 3) Somewhere at the base of the tree (right after
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This note was uploaded on 02/09/2012 for the course BIOL 104 taught by Professor Smith during the Spring '09 term at Arkansas State.

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Lecture 20 - Lecture 20 1) Amniotes are a monophyletic...

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