Ecology Exam II Notes

Ecology Exam II Notes - Ecology Exam II Notes Importance of...

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Ecology Exam II Notes Importance of Genetic Variation to Ecology What is genetic diversity and why is it important? o Genetic diversity affect all hierarchical levels in ecology Genetic diversity Individual Population Community Ecosystem o Genetic diversity: Variety of alleles and genotypes present in the group under study Individual Social group Population Species Genetic diversity measures: Allelic diversity- number of alleles per locus in a population Heterozygosity- individual w/ more than one allele at a given locus (remember in diploids one copy from mother and one copy from father) Homosygosity- individual w/ the same allele at a give locus Importance of genetic variation Short term o Avoid inbreeding depression Long term o Maintain evolutionary potential o Inbreeding: Production of offspring by individuals that are related by descent Inbreeding depression: Reduction of survival and reproduction in inbred offspring vs. non-inbred offspring Good evidence that inbreeding adversely affects captive and wild populations Causes of inbreeding depression: 1. Increased homozygosity o Deleterious recessives (e.g. cystic fibrosis) 2. Decreased heterozygosity o Heterozygote advantage (e.g. sickle cell anemia) Both cause inbreeding depression but deleterious recessives are probably the major cause o Evolutionary potential Competitors, predators, parasites (disease) climate change species must evolve continually or go extinct Red Queen Hypothesis “Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!” Evolutionary forces affecting genetic diversity o Evolution: Change in allele frequencies btw generations o Mutation (generates new diversity) Selection 3 conditions must be met for evolution by natural selection:
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o 1. Variation in a trait o 2. Variation must be genetically based and heritable Able to pass to offspring o 3. Variation must result in fitness differences among individuals Fitness – the average number of offspring produced by individuals of a given genotype Alleles w/ highest fitness are more likely to be passed on Adaptation o Result of natural selection o A behavioral, morphological, or physiological trait that improves an organism’s ability to survive and reproduce in a given environment o “The fit btw the traits of a species and it’s environment” Krebs Migration Drift Genetic drift: o Frequencies of alleles transmitted to the following generation are likely to differ from the parents (some alleles, esp. rare ones, do not get passed on by change) o Genetic drift always reduces genetic diversity o Bottlenecks and Founder Events: Population size decreases drastically or individuals colonize an island or new geographic area Genetic diversity is lost, esp. rare variation
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This note was uploaded on 10/06/2008 for the course BIOL 30403 taught by Professor Horner during the Spring '08 term at TCU.

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Ecology Exam II Notes - Ecology Exam II Notes Importance of...

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