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review final part II

review final part II - Chpt 13 When do we see rapid change...

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Chpt. 13 When do we see rapid change in evolution? Species introduced to a new area Alteration of environment Often related to multiple loci and many alleles Main goal of quantitative genetics (evolution of phenotypes)- how much of the variation is due to genetics and environment Variance- the average of the squared deviations of observations from the arithmetic mean of a sample. V p = V G + V E Phenotypic variance (V p ) Genetic variance (V G ) Subdivided into Addictive variation (V A ) - addictive affects of alleles are responsible for the degree of similarity between parents and offspring and therefore are the response to selection within populations. If the effects are additive the offspring trait should be the average of the parent’s trait. V A =2pqa 2 2pq=frequency of heterozygote ‘a’=deviation from the mean Measures the response to selection- change in mean character state of one generation as a result of selection in previous generation Dominance variation (V D ) Interaction variance (V I ) Interactions between genes and the environment Environmental variance (V E )
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Selection on quantitative structures- vestigial features in cave organisms. Why are features that no longer have function lost Mutations that cause degeneration of an unused character become fixed by genetic drift because variations in the character are selectively neutral Selection against an unused organ because it interferes with some important function or requires energy and materials that could better be used for other purposes Trait negatively correlated with another feature that increased due to selection Correlated selection- independent genetic variation in multiple traits. selection favors some combination of those traits. Environmental correlation- two features of individuals with the same genotype may vary together because both are effected by environmental factors Genetic correlation- genetic differences that affect both characters Linkage disequilibrium among the genes that independently affect each character
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