|
a generation-to-generation change in allele frequency. |
microevolution |
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The original source of all genetic variation is _____. |
mutation |
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According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool. |
sexual reproduction |
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does not change the frequency of alleles in the gene pool. |
sexual reproduction |
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The evolutionary effects of genetic drift are greatest when _____. |
the population size is small |
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What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population? |
founder effect |
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No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is |
reshuffling of alleles due to sexual reproduction |
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In evolutionary terms, an organism’s fitness is measured by its _____. |
contribution to the gene pool of the next generation |
|
Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____. |
directional selection |
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What is the only evolutionary mechanism that consistently leads to adaptive evolution? |
natural selection |
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_______ has a "sorting" effect, it consistently increases the frequency of alleles that improve the match between an organism and its environment. |
natural selection |
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How does diploidy help to preserve genetic variation? |
It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes. |
|
Natural selection tends to decrease |
genetic variation |
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Recessive alleles are shielded from natural selection in |
heterozygotes |
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does natural selection act on individuals or populations? |
individuals |
|
a change in allele frequencies in a population over generations |
microevolotion |
|
the mechanisms that cause allele frequencies to change |
natural selection, genetic drift, gene flow |
|
the transfer of alleles from one population to another |
gene flow |
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which of the three causes adaptive evolution |
natural selection |
|
how genetic variation is measured at the molecular level |
nucleotide variability |
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does nucleotide variability result in phenotypic variation? |
rarely |
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how do you measure gene variability |
the average % of loci that are heterozygous |
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What often reflects genetic variation |
phenotypic variation |
|
the product of inherited genotype and environmental influence |
phenotype |
|
natural selection can act on phenotypic variation that has a |
genetic component |
|
4 sources of genetic variation |
mutation, gene duplication, rapid reproduction, sexual reproduction |
|
ultimate source of genetic variation |
mutation |
|
only mutations in cells that produce _____ can be passed to offspring |
gametes |
|
one way that mutations can be helpful |
ones that alter protein production |
|
what equation can be used to test whether a population is evolving |
hardy weinberg equation |
|
the most important genetic variation for microevolution in populations |
allelic variation |
|
a localized group of individuals capable of interbreeding and producing fertile offspring |
population |
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consists of all the alleles for all loci in a population (the sum of all alleles in a population) |
gene pool |
|
the location of a gene on a chromosome |
loci |
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the relative quantity of a genotype for a gene in a population |
genotype frequency |
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the relative quantity of an allele for one gene in a population |
allele frequency |
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states that frequencies of alleles and genotypes in a population remain constant from generation to generation |
hardy weinberg principle |
|
allele frequencies will not change if |
gametes contribute to the next generation randomly |
|
what preserves genetic variation in a population |
mendelian inheritance |
|
the hardy weinberg principle describes a population that is |
not evolving |
|
describes the constant frequency of alleles in a not evolving population |
hardy weinberg equilibrium |
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describes how allele frequencies fluctuate unpredictably from one generation to the next |
genetic drift |
|
tends to reduce genetic variation through losses of alleles |
genetic drift |
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two examples of genetic drift |
founder effect and the bottleneck effect |
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genetic drift that occurs when a few individuals become isolated from a larger population |
founder effect |
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genetic drift that can result from a drastic decrease in population size due to a sudden environmental change |
bottleneck effect |
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two examples of gene flow |
movement of reproductive individuals, movement of gametes |
|
the ability of alleles to be passed on to another generation |
fitness |
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the only mechanism that consistently causes adaptive evolution |
natural selection |
|
an increase in the frequency of alleles that improve fitness |
adaptive evolution |
|
3 modes of natural selection |
directional selection, disruptive selection, stabilizing selection |
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natural selection that favors individuals at one end of the phenotypic range |
directional selection |
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natural selction that favors individuals at both extremes of the phenotypic range |
disruptive selection |
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favors intermediate variants and acts on extreme phenotypes |
stabilizing selection |
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natural selection for mating success |
sexual selection |
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marked differences between the sexes in secondary sexual characteristics |
sexual dimorphism |
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competition among individuals of one sex (usual males) for mates of the opposite sex |
intrasexual selection |
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occures when individuals of one sex (usually females) are choosy in selecting their mates |
intersexual selection |
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suggests that if a trait is related to male genetic quality of health, both the male trait and female preference for that trait should increase in frequency |
good genes hypothesis |
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genetic variation that does not give a selective advantage or disadvantage |
natural variation |
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heterozygotes can carry recessive alleles that are hidden from the effects of selection |
diploidy |
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occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population |
balancing selection |
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occurs when heterozygotes have a higher fitness than do both homozygotes |
heterozygote advantage |
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occurs when the fitness of a phenotype declines if it becomes to common in the population |
frequency dependent selection |
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