BIS 2B Lectures 13-16.2010.Study Questions

BIS 2B Lectures 13-16.2010.Study Questions - BIS 2B SPRING...

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BIS 2B SPRING 2010 LECTURES 13-15 _____________________________________________________________________________________ POPULATION GENETICS & NATURAL SELECTION _____________________________________________________________________________________ I. T OWARD A G ENETIC D EFINITION OF E VOLUTION 1. Darwin’s dilemma resolved: blending inheritance, selection, & transmission genetics (Mendel, meiosis, & sex). a) The loss of variation by … 1) blending inheritance. 2) selection. b) The generation of variation by … 1) mutation (new cards added to the deck). 2) sexual reproduction (the deck gets reshuffled each generation). 2. Transmission genetics (rules governing transmission of gene from parent offspring). 3. Population genetics (rules governing changes in gene frequencies in populations) 4. Microevolution (evolutionary Δ w/in a breeding unit or species) versus Macroevolution (evolutionary Δ at and above the species level). 5. Phenotypic versus genetic definitions of microevolution: the importance of heritable/genetic (rather than just phenotypic) changes. a) Why we care about genetic changes 1) Dominance 2) Epistasis 3) Environmental effects: norm of reaction b) But remember, NATURAL SELECTION USUALLY ACTS ON PHENOTYPES, NOT GENOTYPES 6. A GENETIC DEFINITION OF EVOLUTION : A CHANGE OVER TIME IN THE PROPORTIONS OF INDIVIDUAL ORGANISMS DIFFERING GENETICALLY IN ONE OR MORE TRAITS . Such changes transpire by… the origin and subsequent alteration of the frequencies of alleles or genotypes from generation to generation within populations [ MICROEVOLUTION ]; the alteration of the proportions of genetically differentiated populations of a species; or by changes in the numbers of species with different characteristics [ MACROEVOLUTION ]. II. M ENDELIAN G ENETICS TO P OPULATION G ENETICS 1. Individuals, populations, & species. a) Individual organisms do NOT evolve: their genetic composition cannot change (Lamarck was wrong, remember?). 1) Individuals have genotypes, but offspring never have the same genotypes as their parents (unless they are cloned). The parental genotype is destroyed when an organism dies. Offspring usually get their genes from two separate parents b) Population : all the diploid individuals that actually interbreed ( i.e ., exchange genes) 1) Comparisons of relative reproductive success/fitness: fruit flies vs . humans.
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BIS 2B, Spring 2010 Page 2 c) Species (biological species concept) : a group of actually, or potentially (they could if they had access to each other), interbreeding organisms that is reproductively isolated from other such groups. 2. The gene pool : all the copies of alleles in a population. a) An example using M&Ms b) The literal view: imagine that all individuals in a population spawn their haploid gametes into a swimming pool gene pool. c) Haploid gametes in the gene pool pair up two-at-a time to form diploid zygotes . c) Allelic frequencies : the fraction/proportion of gametes in the gene pool that carry a particular allele at a given locus.
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