Chapter 16 - Evolution Flashcards
(21 cards)
What is a gene pool?
The total collection of genes in a population at any one time.
A gene pool includes all the alleles for every gene present in a given population.
What does relative frequency refer to?
The proportion of a particular allele among all alleles for that gene in a population.
It is often expressed as a percentage.
What is a single-gene trait?
A trait controlled by a single gene.
Examples include traits like flower color in pea plants.
What is a polygenic trait?
A trait controlled by two or more genes.
Examples include human height and skin color.
Define directional selection.
A type of natural selection that favors one extreme phenotype over others.
This can lead to a shift in the population’s phenotype distribution.
What is stabilizing selection?
A type of natural selection that favors intermediate variants and acts against extreme phenotypes.
It reduces variation and maintains the status quo for a particular trait.
Define disruptive selection.
A type of natural selection that favors extreme phenotypes over intermediate phenotypes.
This can lead to speciation as populations diverge.
What is genetic drift?
A random change in allele frequencies in a population, often having a more significant effect in small populations.
It can lead to the loss of genetic diversity.
What is the founder effect?
A type of genetic drift that occurs when a few individuals start a new population.
The new population may have a different allele frequency than the original population.
What does the Hardy-Weinberg principle state?
The allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences.
It serves as a null hypothesis for studying evolutionary change.
What is genetic equilibrium?
A state in which allele frequencies in a population remain constant over time.
This occurs under the conditions outlined by the Hardy-Weinberg principle.
Define speciation.
The process by which new species arise.
It often occurs due to reproductive isolation and genetic divergence.
What is reproductive isolation?
A mechanism that prevents species from mating and producing fertile offspring.
It can be prezygotic or postzygotic.
What is behavioral isolation?
A form of reproductive isolation where two populations have different mating behaviors.
This can involve differences in courtship rituals.
What does geographic isolation mean?
A form of reproductive isolation due to physical barriers that separate populations.
Examples include mountains, rivers, or distance.
What is temporal isolation?
A form of reproductive isolation where two populations breed at different times.
This can involve differences in mating seasons or times of day.
Define divergent evolution.
The process by which two or more related species become less similar over time.
This often occurs when populations adapt to different environments.
What is convergent evolution?
The process by which unrelated species evolve similar traits due to similar environments or pressures.
An example includes the wings of bats and birds.
What does gene flow refer to?
The transfer of alleles or genes from one population to another.
It can occur through migration and can increase genetic diversity.
What are mutations?
Changes in the DNA sequence that can lead to new traits.
Mutations can be beneficial, harmful, or neutral in effect.
What is a niche?
The role or function of an organism or species within an ecosystem.
It includes how it gets its energy and nutrients, where it lives, and its interactions with other organisms.
