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Ecology Lec 7 (evolution & ecology) summary.docx

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Biology 2483A
Hugh Henry

Ecology Lec 7- Evolution & Ecology - Human impact- Trophy hunting- large permits to prevent ($100000), pay big; hunt big, avg size of males & horns decreased - Elephants poached for ivory = less elephants with tusks Evolution- genetic change overtime; descent with modification - As pop’n accumulates difference, it forms another species (with same characteristics, some diff) Mutation- very rare, given time, drives evolution because forms new alleles Recombination- produces different genotypes (offspring diff combo’s) Mechanisms of Evo’n 1. Natural selection- heritable traits survive, reproduce more successfully, increase in freq. - ONLY mechanism that consistenly causes adaptive evolution - Directional sel.: one phenotypic extreme favoured - Stabilizing sel.: intermediate phenotype favoured (not any extreme) - Disruptive sel.: both extremes favoured, (not intermediate) 2. Genetic drift- chance event determines what alleles passed on (not necess. good ones). - has bigger impact on smaller pop’ns 4 effects: 1. Fixation- some disappear, one fixates (100% freq.) 2. Genetic variation reduced- some alleles lost- BAD- can’t respond to enviro changs 3. Freq. of bad alleles increases- esp. if only mildly deleterious- BAD- bad survival 4. Differences between pop’s increase 3. Gene flow- alleles move between pop’n (individuals or gametes) 2 effects: 1. Populations become more similar 2. New alleles introduced in a population e.g. Resistance genes- freq will increase rapidly in populations exposed to insecticides (using insecticide = strong selection pressure for R genes) Adaptive evolution- ONLY by natural sel. (adaptation=feature that ↑survival/repro) - Beak length adapts to fruit size- 35 yrs - Antibiotic resistance- very fast Small gen. time + strong selective force = FAST EVO’N - Insecticide resistance Clines- patterns of change in a characteristic over a geographic region - e.g. Adh allele freq. decreases as latitude increases, less effective in colder temp Change in cline- Australia hotter, allele freq. increased Gene flow- can limit adaptation to local conditions - e
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