11.3 other mechanisms of evolution teks 7d, 7f key concept a population shares a common gene pool
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
KEY CONCEPT A population shares a common gene pool.
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic variation in a population is beneficial because it increases the chance that some individuals will survive.
• Genetic variation leads to phenotypic variation.
• Phenotypic variation is necessary for natural selection.
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic variation in a population is beneficial because it increases the chance that some individuals will survive.
• Allele = version of a trait• Ex: Trait in our population: eye color
Alleles would be brown, blue, green
Ex: Trait for frogs skin color
– Alleles: green and brown
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic variation in a population is beneficial because it increases the chance that some individuals will survive.
• Genetic variation is stored in a population’s gene pool.–made up of all alleles in a population
–allele combinations form when organisms have offspring
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
• Genetic variation is measured by allele frequencies.
– measures how common an allele is in a population– can be calculated for each allele in gene pool
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic variation comes from several sources.
• Mutation is a random change in the DNA of a gene.
– can form new allele– can be passed on to offspring if in reproductive cells
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic variation comes from several sources.
• Recombination forms new combinations of alleles.
– usually occurs during meiosis
– parents’ alleles arranged in new ways in gametes
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic variation comes from several sources.
• Hybridization is the crossing of two different species.
–occurs when individuals can’t find mate of own species
–topic of current scientific research
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
KEY CONCEPT Natural selection is not the only mechanism through which populations evolve.
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Gene flow is the movement of alleles between populations.
• Gene flow occurs when individuals join new populations and reproduce.
• (Ex: spores/seeds are spread to new areas)
bald eagle migration
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Gene flow is the movement of alleles between populations.
• Lots of gene flow results in similar neighboring populations
bald eagle migration
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Gene flow is the movement of alleles between populations.
• Limited gene flow results in an increased chance that two populations will evolve into different species.
bald eagle migration
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic drift is a change in allele frequencies due to chance.
• Genetic drift causes a loss of genetic diversity.
• Some alleles increase in frequency, others may become eliminated from the population
• It is most common in small populations.
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic drift is a change in allele frequencies due to chance.
• A population bottleneck can lead to genetic drift.
– It is an event that drastically reduces population size.
– The bottleneck effect isgenetic drift that occursafter a bottleneck event.
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
Genetic drift is a change in allele frequencies due to chance.
• A population bottleneck can lead to genetic drift.
• Northern Elephant Seals
– Hunted almost to extinction
– ~20 survived
– Genetic Variation drastically reduced when compared to Southern Elephant Seals
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
• The founding of a small population can lead to genetic drift.
– The Founder Effect occurs when a few individuals start a new population (colonize a new area).
– The founder effect is genetic drift that occurs after start of new population.
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11.3 Other Mechanisms of Evolution TEKS 7D, 7F
• Genetic drift has negative effects on a population.
–Population loses genetic variation, and becomes less likely to have some individuals that can adapt
–harmful alleles can become more common due to chance