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18 Cards in this Set
- Front
- Back
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Natural selection acts on a) ANSWER but only b)ANSWER evolve.
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a.individuals b.populations |
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What does the Hardy-Weinberg principle describe?
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It describes a hypothetical population that is not evolving, i.e., a population in which allele frequencies remain unchanged over time.
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Genetic drift includes all of the fallowing except: a) Leads to adaptations
b) Natural disasters c) Is a random process d) Unlikely to increase fitness |
a |
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Founder's effect and Bottleneck effect are components of A) gene flow or B) gene drift
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b |
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Negative results from gene flow can include:___________ and ___________.
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homogenization of a population, reduce effects of localized adaptations
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Alleles are used to express:
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Alleles are a variant form of a gene, used to represent the genotype and phenotype of organisms. Combinations of alleles express an idividuals genotype and influence the individuals phenotype (physical appreance of genotype).
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The process of natural selection depends on
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genetic variation.
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A mechanism of evolution whereby alleles move between populations as a result of migration is called______.
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Gene flow
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Define Sexual selection.
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Some animals have traits that may seem disadvantageous, such as large manes in lions or gaudy feathers in peacocks, however, as a result of these adaptations, the animals are seen as more attractive to potential mates and this increases their chances of reproduction.
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The rise in frequency of antibiotic resistance due to the overuse of antibiotics is an example of ________ .
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directional selection
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Discuss the significance of genetic drift in very small populations.
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Genetic drift is the process by which allele frequencies fluctuate in a population due to chance alone. It does not lead to adaptation, and is unlikely to increase fitness. In very small populations there are fewer alleles, thus each allele plays a larger role within the population. Furthermore, due to the smaller number of alleles, genetic drift is able to act more quickly and with greater consequences on small populations, and thus its effects may supersede natural selection pressures. Fluctuations within only a few generations can easily lead to alleles becoming lost entirely (0%) or becoming fixed (100%). This lack of genetic variation due to genetic drift in a small population can leave the population maladapted to its environment.
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3 broad modes by which alleles change over time |
stabilizing selection disruptive selection directional selection |
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stabilizing selection
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natural selection selects against the extreme phenotype of a particular trait and instead selects for individuals with median phentotypes |
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disruptive selection
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selects for the two extremes of a trait rather than the median phenotype. they tend to increase in variatin in a population..lead to rise of two species from a single |
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directional selection
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the median variation for a trait moves toward one of the extreme. Strong in changing environments |
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What is the basis of evolution?
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Changes in allele frequencies, alleles control the traits of an organism, such as corn. The diversity of corn kernels arise from a variety of alleles of the gene for kernel color.
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What is Gene flow important for?
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Alleles moving between populations
increasing genetic variation Decreases effects of genetic drift can lead to homogenization across populations Can swamp out the effects of localized natural selection and adaption |
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