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Adaptation Sheet.docx

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Biology 3466B
Yolanda Morbey

Adaptation Ch. 10 363-391 Adaptation a trait, or integrated suite of traits, that STEP 2: Tests several alternate hypotheses increases the fitness of its possessor and is said to be adaptive Phenotypic differences between species are called adaptations Phenotypic differences between populations within species are called local adaptions Objectives Experimental Design Distinguish these terms: adaptation, natural selection, evolution Defining a test and effective control group is critical All of the treatments must be handled exactly the Design studies to test for adaptation same Explain reaction norms & phenotypic plasticity Debate constraints on adaptation Can discriminate multiple hypotheses Minimize cofounding effects Randomization is a key technique for equalizing Consider When Studying Adaptations other, miscellaneous effects among groups Repetition on many individuals is essential Differences among populations or species are not always adaptive Not every trait of an organism, or every use of a traitbservational Studies by an organism is an adaptation Used when experiments are impractical or No every adaptation is perfect inappropriate Seeks to find circumstances in nature that resemble an experiment Methods to Test for Adaptation Comparative method o Between species or between populations The Comparative Method o With or without phylogenetic correction (among species; no phylogenetic correction) Selection experiments Tests of adaptive hypotheses The comparative method seeks to evaluate hypotheses by testing for patterns across species, such as correlations between traits and features of the environment Tests of Adaptive Hypotheses Eg. Testes Size in Bats A well designed experiment isolates and tests the effects that Large testes size is an adaptation for living in a large a single, well-defined factor has on the phenomenon in question social group The selection factor is the environment In an ideal experiment, the control and experimental groups The environment is used to infer as adaptation are treated identically except for exactly one factor Eg. Zonosemata Flies Phylogenetic Dependence STEP 1: Evolutionary Analysis; state question precisely When preparing a scatterplot for use as the basis of claims about What is the adaptive function of the wing markings and nature: wing-waving display in the Zonosemata fly? Want ALL data points to be independent of each other Each point therefore makes a separate statementAdaptation Phylogenetically independent contrasts PhylogenetiPhylogenetically independent contrasts A simple scatterplot may provide weak evidence (b) plot pairs of sister species that 2 traits evolved in tandem (when phylogenetically dependent) (end up with only 2 data points) 10/31/2011 Phylogenetic Independent Contrasts Look at question: when species diverge from a commonve ancestor, does the species that evolves larger/31/2011 independently away from their common (represented by the same colored lines) Phylogenetic dependence Phylogenetically independent contrasts 9 Left with scatter plot of points Each point = divergence of contrast between pairs of Phylogenetic dependence Phylogenetically independent contrasts sister species as they evolved Phylogenetically independent contrasts Phylogenetically independent contrasts extant species: M-Q ancestral species: R-U same coloured lines (4): sister species that 7 diverged from a common ancestor 8 QUEST extant species: M-Qerge from a common ancestor, does the species that evolves larger group size also evolve same coloured lines (4): sister species that larger testes? 7 diverged from a common ancestor 8 If contrast are correlated then can conclude that when a Phylogenetically independent contrasts How to usePhylogenetically independent contrastsdivergence between species evolves a larger group size that its sister species, it pairs of sister species 11
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