Bio Lectures

Bio Lectures - Bio Lecture 5 Gene pool concept...

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Bio Lecture 5 1/14/09 Gene pool concept Hardy-Weinberg princple assuming random mating Patterns of natural selecton -Heterozygote advantage -directional selection Stabilizing Selection-Reduces amount of variation so it gets more common to one type (scrunch together) Disruptive Selection- extreme phenotypes are favored and increase fitness. Middle type isn’t good Genetic Drift- any change in allele frequency in a population due to chance (sampling error) Random with respect to fitness. Not adaptive. Small populations are very susceptible to genetic drift. It can occur by any event that involves sampling error. Bottleneck- sudden decrease in population size (disease, nature, etc) Survivors then have smaller gene pool. Founder effect- if founding group is small the allele frequency differ from source populations (islands) Gene flow- movement of alleles from one population to another occurs when individuals leave a population, join another, and breed Mutation restores genetic diversity by introducing new alleles. ULTIMATE SOURCE OF ALL GENETIC INNOVATION. -random with respect to fitness -most mutation result in deleterious alleles-alleles that lower fitness, since its random Bio Lecture 6 Inbreeding increases the frequency of homozygotes and reduces the frequency of hetero in each generation +Doesn’t cause evolution doesn’t change allele frequency in population as a whole. Changes genotype frequencies but not allele frequency Inbreeding increases homozygosity (frequency of homozygote genes)
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Speiciation is the point where 2 lineages become independent in an evolutionaru sense (branch off) Genetic isolation or reduction in gene flow is key process in speciation Usually speciation creates two or more distinct species from a single ancestral group 3 aproaches to identifying species the biological species concept- considers populations to be evolutionary independent if they are reproductively isolated from eachother, they don’t inbreed. Absence of gene flow prezygotic isolation occurs when individuals of diff species are prevented from mating postzygotic is when individuals from diff populations do mate but the baby(zygote) has a lower fitness catorgorize gene flow as prezygotic and postzygotic the morphospecies concept- identify evolutionarily independent lineages by diff size shape or other features. Absence of gene flow phylogenetic species concept is based on the reconstructing the evolutionary history of populations. Species is defined as smallest monophyletic group on a tree that compares populations. On such a tree each tip is a phylogenetic species. clade or monophyletic group is subspecies are populations that live in distinct regions but aren’t distinct enough to be called a species Bio Lecture Chap 28 Definition of life - self sustained chemical system capable of undergoing natural selection. How it began- scientific/non-scientific
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This note was uploaded on 08/30/2011 for the course BIO 94 taught by Professor Staff during the Winter '09 term at UC Irvine.

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Bio Lectures - Bio Lecture 5 Gene pool concept...

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