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BIO130H1 (434)
Lecture 3

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Spencer Barret

Lecture 3: Physical Challenges of environment for animals, emphasis on tradeoffs and alternatives: Why weasels are small predative, short furred, very long and thin in cold environment. However it lives in the north even though it can’t curl up into a sphere, only cold flat disk. They need to be thin to attack pocket gophers. Fitness gains of being a good hunter offsets fitness cost of expensive metabolism. Phenotypes of all organisms have tradeoffs (being good at x may mean being bad at y). Kangaroo rat conserves water in hot, dry environments by having erect posture, are bipedal meaning less heat gain from ground (hop like kangaroos). They have very efficient kidneys. They’re nocturnal, spend hot daytime underground. They hide seeds underground that can recapture water vapor lost from exhalation. Don’t need free water. Just eat seeds. Can break down fat molecules and make water. When physiological stress is too high (evasions): 1) Enter dormant stage like seeds, cysts, eggs, pupae, torpor with minimal metabolism 2) Hibernate or estivate (takes place in too hot/dry seasons) and store fat. 3) Enter nest
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