Lecture 06-las-evol_adapt

Lecture 06-las-evol_adapt - Evolution & Adaptation...

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Updated 25 January 2009 LAS
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Buddy questions Scenario: For your independent project your group is interested in how changes in precipitation may affect species composition and you grow plants under different levels of water availability. Species A and B are both from a site with high water availability and the water availability in your ‘high’ treatment is similar to that of their native site. You find that species A has similar survival rates in both high and low water treatments while the survival of species B decreases in the low water treatment. A group member states that your results demonstrate that Species A has higher fitness than species B. Why is it not appropriate to use ‘fitness’ in this statement?
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Katydid in Costa Rica Starting with an example – Evolving to better avoid predation Mantid in Malaysia Mantid in Africa
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Evolution by natural selection = adaptation 1) Variation in traits 2) Differential reproduction Brown beetles live and reproduce more 3) Heredity Brown beetles have brown beetles 4) http://evolution.berkeley.edu/evosite/evo101/IIIENaturalSelection.shtm (green and brown beetles are the same species)
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(Reminder: other mechanisms of evolution) Genetic drift founder effects bottlenecks Mutation Migratio n Natural selection evolution = the change in a populations gene pool
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Fitness If the phenotypes have similar reproduction rates per surviving individual, and the brown phenotype has higher survival, then the brown phenotype is more fit. What if the green phenotype (for some reason) on average produces more offspring per individual – then which phenotype is more fit?
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Fitness is relative Fitness depends on the environment Fitness = the production of descendents over an individuals life time How might the fitness of each phenotype change if the ground becomes green? Consider – The brown phenotype has 10% survival. Is it fit? The green phenotype has 1% survival.
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ural selection – not random but also doesn’t have a Why not even better traits? - Lack of genetic variability -Trade-offs
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An individual itself does not benefit from evolution It is the gene pool that benefits from evolution
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Modes of selection
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Disruptive selection Hatched marks indicate reproductive maturity. Gross, M.R. 1985. Disruptive selection for alternative life histories in salmon. Nature 313: 47-48. Genny Anderdson
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Directional selection Disa nivea and the fly pollinator in South Africa The beauty of deceit B. Anderson, S.D. Johnson, C. Carbutt. 2005. American Journal of Botany 92:1342-1349.
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Some other examples of adaptation through natural selection . . . . . .
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Evolutionary arms race Brodie, E.D. et al. . 2005. Parallel arms races between garter snakes and newts involving tetrodotoxin as the phenotypic interface of coevolution. Chem. Ecol. 31 (2): 343-356.
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Lecture 06-las-evol_adapt - Evolution & Adaptation...

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