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Unformatted text preview: Lecture 9 EEB 13 5 February 2008 Dr. Hespenheide kinds of microevolutionary change : - affect kinds/frequencies of alleles- four: mutation, migration. natural selection, genetic drift 3. natural selection - review:- biologically, two different aspects to natural selection - genotypes vary in survival to reproductive age (but not longevity by itself ) reproduction - finding mates and having offspring - fitness is a measure of success in survival/reproduction property of genotypes, relative thus, adaptations are characteristics/traits that increase fitness fitness depends on particular environments environment actually has two roles in evolution popular view of environment: environment = ecology- recycling, backpacking, saving whales, planting trees 1. affects expression of genes : genotype phenotype environment- the same gene can produce different phenotypes in different environments - norm of reaction (Mayr, p. 129)- it is difficult to understand evolution in molecular terms because of the steps between the gene and a trait, each of which is affected by the environment: gene (DNA) mRNA enzyme process/structure trait- evolution is change in DNA, but natural selection acts on traits- additionally, gene expression is affected by genes at other loci- variability is due to both genetic and environmental variability total phenotypic = variability produced + genetic variability by environment variability- only genetic component of variability is subject to selection [concept of heritability = (genetic variability)/(total variability) -used by plant/animal breeders in improving traits of interest]- controversy: human intelligence (IQ) and social policy on education - is intelligence determined mostly by genes (nature) or environment...
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- Winter '08