11.3 other mechanisms of evolution teks 7d, 7f key concept a population shares a common gene pool

11.3 Other Mechanisms of Evolution TEKS 7D, 7F

KEY CONCEPT A population shares a common gene pool.

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.

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

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

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

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

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

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

11.3 Other Mechanisms of Evolution TEKS 7D, 7F

KEY CONCEPT Natural selection is not the only mechanism through which populations evolve.

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

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

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

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.

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.

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

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.

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