Lecture15 - Lecture 15 Adaption III Comparative Tests and...

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Lecture 15: Adaption III Comparative Tests and Limits on Adaptation Readings: Chapter 10.4: The Comparative Method Chapter 10.6: Trade-offs and Constraints Wednesday, Feb.19 th 1 Midway thro ug h the  e xam  Alan  pulls  o ut a big g e r brain
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Midterm Distribution 2 Total points for exam 34 instead of 35. Average: 64% Range 34-100%
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Learning Objectives 1. Describe the conditions under which comparative analysis would be used instead of observation or experimental tests. 2. Explain why species do not represent independent data points in comparative studies and how the method of phylogenetically independent contrasts corrects for this problem. 3. Explain how trade-offs can limit adaptation in response to selection. 4. Identify and differentiate between the four categories of constraint on adaptation identified in lecture and provide an example for each. 3
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Why don’t we always do experiments? COMPARATIVE TESTS can be used to investigate adaptation 4
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Comparative tests Comparative tests are useful when: We are interested in studying the evolution of form and function across taxa Experimental tests are too difficult The variation within a species is too small to test with observational data There is variation among species that can be observed & measured A good phylogeny is available (this gives us an accurate description of relationships among species) 5
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Comparative tests 6 Bats in the Suborder Megachiroptera roost in groups Group size varies among species from a few individuals to 1000’s Females are often polyandrous (mate with multiple males) Females can store sperm for up to 200 days Testes size has been observed to vary considerably among species
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Comparative tests Observation : Testes size varies among species of bats Hypothesis : 7
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Comparative tests Under what conditions would you expect to see more sperm competition and thus more selective pressure for the evolution of large testes?
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  • Spring '11
  • DAVIDSON
  • Evolution, Phylogenetics, asexuality, comparative tests, female flower size

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