Biology Chapter 12 Flashcards

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Questions and Answers

What is gene flow?

Alleles move between populations.

What is an example of gene flow?

Migration.

What is genetic drift?

Allele frequencies in a population change as a random result of random events or chance.

What is an example of genetic drift?

A man steps on a group of beetles, randomly killing most of the green ones but leaving most of the brown ones alive. Signup and view all the answers

What is the founder effect?

A small group leaves the home population and establishes a new, isolated settlement; new group of alleles does not represent the frequency in the original population. Signup and view all the answers

What is an example of the founder effect?

Northern elephant seals have reduced genetic variation most likely due to being hunted. Signup and view all the answers

What is the bottleneck effect?

A sudden reduction in a population's genetic diversity due to a sudden decrease in a population. Signup and view all the answers

What is an example of the bottleneck effect?

The Afrikaner population of Dutch settlers in South Africa has an abnormally high count of Huntington's Disease. Signup and view all the answers

What is mutation?

Mutations are the raw material for evolution. Genes contribute to phenotypes. Natural selection acts on phenotypes. Signup and view all the answers

What is non-random mating?

Mating occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals. Signup and view all the answers

What is an example of non-random mating?

All mating on this planet is non-random mating. Signup and view all the answers

What is sexual dimorphism?

Any difference between the sexes of a species. Signup and view all the answers

What is an example of sexual dimorphism?

In some species, the male is larger than the female, and in others, such as some spiders, the female is larger than the male. Signup and view all the answers

What is sexual selection?

A differential change in the relative frequencies of genes due to differences between individuals in their ability to mate. Signup and view all the answers

What is an example of sexual selection?

Many plants have flowers that are pretty and brightly colored to attract pollinators. Signup and view all the answers

What is stabilizing selection?

Selection against extreme phenotypes. Signup and view all the answers

What is an example of stabilizing selection?

In humans, birth weight is an example of stabilizing selection. Signup and view all the answers

What is disruptive selection?

Selection against intermediate phenotypes. Signup and view all the answers

What is an example of disruptive selection?

London's peppered moths varied in color, with dark moths surviving better in polluted areas. Signup and view all the answers

What is directional selection?

Trait is moving in one direction. Signup and view all the answers

What is an example of directional selection?

Giraffes having long necks. Signup and view all the answers

What is the frequency of heterozygous?

pq Signup and view all the answers

What is the frequency of homozygous dominant?

p^2 Signup and view all the answers

What is the frequency of homozygous recessive?

q^2 Signup and view all the answers

Study Notes

Gene Flow

Refers to the movement of alleles between populations, often through migration.

Genetic Drift

Involves random changes in allele frequencies within a population, leading to shifts that are not due to natural selection.

Example of Genetic Drift

A scenario where a random event, such as a man stepping on beetles, disproportionately affects the survival of one color (e.g., green beetles), resulting in changed population dynamics.

Founder Effect

Occurs when a small group breaks away from a larger population to establish a new, isolated community, leading to a new allele frequency that may differ significantly from the original population.

Example of Founder Effect

Northern elephant seals exhibit reduced genetic variation after a severe population decline due to hunting, contrasting with the more genetically diverse Southern elephant seals.

Bottleneck Effect

Describes a drastic reduction in a population's genetic diversity resulting from a significant drop in population size.

Example of Bottleneck Effect

The Afrikaner population in South Africa shows a high incidence of Huntington's Disease due to the founder effect from its original settlers, who carried the gene at a higher frequency.

Mutation

Mutations serve as the raw material for evolution by altering genes that influence phenotypes, which are subject to natural selection.

Non-random Mating

Occurs when certain individuals have a higher likelihood of mating, leading to selected reproductive pairings rather than random selection.

Example of Non-random Mating

All mating behaviors globally exhibit non-random patterns, as individuals generally choose mates based on specific criteria rather than randomly pairing.

Sexual Dimorphism

Refers to any physical differences between male and female members of a species.

Example of Sexual Dimorphism

In many mammals, males are larger than females, whereas in some spiders, females are the larger sex.

Sexual Selection

Involves the differential reproduction that occurs when individuals vary in their success at finding mates due to certain traits.

Example of Sexual Selection

Brightly colored flowers attract more pollinators, leading to increased reproduction and retention of these color traits in the plant population.

Stabilizing Selection

A process that favors intermediate phenotypes and selects against extreme variations.

Example of Stabilizing Selection

In humans, optimal birth weight reflects stabilizing selection, as both very low and very high weights pose risks to infant and maternal health.

Disruptive Selection

Favors extreme phenotypes at both ends of the spectrum while selecting against intermediate traits.

Example of Disruptive Selection

London’s peppered moths show a color variation where dark moths thrive in industrial areas while light moths dominate in rural settings, highlighting the survival advantage based on environmental adaptation.

Directional Selection

Involves consistent selection for one extreme phenotype over time.

Example of Directional Selection

Long necks in giraffes are a classic illustration of directional selection, as height provides advantages in feeding.

Hardy-Weinberg Equations

Frequency of heterozygotes is calculated as pq.
Frequency of homozygous dominant individuals is represented by p².
Frequency of homozygous recessive individuals is calculated as q².

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Description

Test your knowledge on key concepts from Biology Chapter 12 with these flashcards. Learn about gene flow, genetic drift, and their real-world examples. Perfect for students looking to reinforce their understanding of population genetics.