- frequencies or genotype frequencies in a population over time. - Genetic equilibrium in populations: the Hardy-Weinberg theorem. - Microevolution is deviation from Hardy- Weinberg equilibrium. - Genetic variation must exist for natural selection to occur. - Explain what terms in the Hardy- Weinberg equation give:. - allele frequencies (dominant allele, recessive allele, etc.). - Microevolution is a change in allele frequencies or genotype frequencies in a population over time. - population – a localized group of individuals capable of interbreeding and producing fertile offspring, and that are more or less isolated from other such groups. - allele frequency – proportion of a specific allele in a population. - note that the sum of all allele frequencies is 1.0 (sum rule of probability). - What is the frequency in the population of:. - The Hardy-Weinberg Theorem. - the Hardy-Weinberg theorem describes the. - frequencies of genotypes in a population based on the frequency of occurrence of alleles in the. - the frequency of occurrence of the A-allele in the population. - the frequency of occurrence of the a-allele in the population. - p 2 = frequency of homozygous dominant genotypes. - 2 pq = frequency of heterozygous genotypes. - q 2 = frequency of homozygous recessive genotypes. - Hardy-Weinberg Equilibrium. - if the Hardy-Weinberg theorem can be used to accurately predict genotype frequencies from allele frequencies for a population. - the population is in Hardy-Weinberg equilibrium or genetic equilibrium. - Describe the assumptions of the Hardy- Weinberg equilibrium model.. - large population size (due to statistical constraints, to minimize genetic drift). - no natural selection. - Microevolution is a deviation from Hardy-Weinberg equilibrium. - small population size: genetic drift. - natural selection. - consequences of small population size: genetic drift. - If only two individuals were picked they almost certainly won’t reflect the allele frequency in the larger population (in many cases, they can’t even possibly do so).. - As the selected sample gets larger it becomes more likely that the sample reflects the allele frequency in the larger population.. - Mating to produce the next generation is effectively sampling the population. - frequencies of the population.. - frequencies of populations because of small population size. - genetic drift tends to decrease genetic variation within a population. - genetic drift tends to increase genetic variation between populations. - consequences of small population size:. - genetic drift. - created by dramatic reduction in the population size. - them (gene flow), usually resulting in changes in allele frequencies. - gene flow tends to decrease genetic variation between populations. - mutations increase variation in the gene pool of a species. - even at the risk of harmful effects, mutations are necessary to increase variation in the. - population so that natural selection can produce organisms more suited to their environment. - if individuals do not mate at random, then Hardy-Weinberg equilibrium is not. - inbreeding does not change allele frequencies, but increases the frequency of homozygous genotypes. - phenotypes – really is an aspect of natural selection. - natural selection changes allele frequencies in a way that leads to adaptation to the environment. - populations undergoing natural selection are evolving, with alleles that contribute to better fitness increasing in frequency over. - natural selection only operates based on the current environment – as conditions change, different alleles will be selected for. - sexual selection (mate choices based on inherited characteristics) is an aspect of natural selection. - Explain three main types of natural selection.. - there are three types of natural selection. - stabilizing selection – occurs in populations well adapted to their. - directional selection – permits species to adapt to environmental change by favoring selection of one extreme over the other. - disruptive selection – when more than one extreme phenotype is favored over intermediate phenotypes. - example – pocket mice in the Tularosa Basin of New Mexico. - melanism: natural selection in black and white. - the ultimate source of genetic variation is mutations. - genetic variation can be. - environment than the heterozygote, the homozygous genotype will be more likely to be fixed in the population. - homozygous genotypes, variation tends to increase in the population. - there are cases where the frequency of a given genotype affects the degree to which it is or isn't selected in the population. - much of the genetic variation in a. - environments change some previously neutral variation may be acted on by natural selection
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