Variations in Populations - AP Biology
- What is a polymorphism?
- The presence of two or more variants in a population. Maintained by balancing selection or neutral evolution.
- Which concept describes the survival advantage of certain traits?
- Adaptation. Traits that increase fitness become more common over time.
- Which type of selection favors intermediate phenotypes?
- Stabilizing selection. Reduces variation by eliminating extreme phenotypes.
- Identify a source of genetic variation.
- Mutation. Creates new alleles through DNA sequence changes.
- Which term refers to the genetic makeup of an organism?
- Genotype. Determines which proteins are produced by an organism.
- What does it mean for a population to be in Hardy-Weinberg equilibrium?
- Allele frequencies do not change across generations. Indicates no net evolutionary change is occurring.
- Identify an example of a non-random mating pattern.
- Assortative mating. Individuals mate based on similar traits or characteristics.
- Identify an example of a selective pressure.
- Predators. Environmental factors that affect survival and reproduction.
- Define the Hardy-Weinberg principle.
- Allele and genotype frequencies remain constant in a population at equilibrium. Assumes no evolution is occurring in the population.
- Define phenotype.
- Observable characteristics of an organism. Results from interaction between genotype and environment.
- What role does genetic variation play in a population's adaptability?
- It provides material for natural selection to act upon. Higher variation enables response to environmental challenges.
- Identify one consequence of genetic drift.
- Loss of genetic diversity. Random changes reduce total genetic variation over time.
- What is the bottleneck effect?
- Reduction in genetic diversity due to a dramatic population decrease. Survivors carry only a subset of original genetic diversity.
- Define adaptive radiation.
- The rapid evolution of diversely adapted species from a common ancestor. Often occurs when new habitats become available.
- Which mechanism of evolution involves differential survival and reproduction?
- Natural selection. Individuals with beneficial traits produce more offspring.
- Identify a mechanism that can lead to speciation.
- Reproductive isolation. Prevents gene flow between diverging populations.
- What is a cline?
- A gradual change in a trait across a geographic range. Results from adaptation to varying environmental conditions.
- What is genetic recombination?
- The exchange of genetic material between different organisms. Produces new allele combinations in offspring.
- Identify an example of a prezygotic barrier.
- Temporal isolation. Breeding occurs at different times, preventing mating.
- What is directional selection?
- Selection that favors one extreme phenotype. Shifts population mean toward the favored extreme.
- Identify a condition necessary for Hardy-Weinberg equilibrium.
- No mutation. Also requires large population and random mating.
- What is an allele?
- A variant form of a gene. Different versions arise through mutation and recombination.
- Which type of selection favors extreme phenotypes?
- Disruptive selection. Eliminates intermediate phenotypes, increasing variation.
- What process increases genetic variation during meiosis?
- Crossing over. Exchanges chromosome segments between homologs during prophase I.
- What is the main effect of gene flow on populations?
- It reduces genetic differences between populations. Homogenizes allele frequencies across connected populations.
- Define genetic hitchhiking.
- An allele rises in frequency because it is linked to a beneficial allele. Occurs due to linkage disequilibrium between loci.
- What is meant by 'fitness' in an evolutionary context?
- Ability to survive and reproduce in a given environment. Measured by relative reproductive success compared to others.
- Define punctuated equilibrium.
- Rapid evolutionary change followed by periods of stability. Explains patterns seen in fossil records.
- Identify a factor that can cause allele frequencies to change.
- Natural selection. Drift, gene flow, and mutation also cause changes.
- What is a genetic locus?
- The specific location of a gene on a chromosome. Each locus can have multiple allelic variants.
- What is a postzygotic barrier?
- A mechanism that reduces the viability or reproductive capacity of hybrids. Acts after fertilization to reduce hybrid success.
- Which term describes the movement of alleles between populations?
- Gene flow. Migration introduces new alleles and reduces genetic differences.
- What is genetic variation?
- Differences in DNA sequences among individuals in a population. This diversity enables adaptation to environmental changes.
- What is allele frequency?
- Proportion of an allele in a population's gene pool. Changes over time through evolutionary forces.
- What role does mutation play in evolution?
- It introduces new genetic variations. Without mutations, populations lack raw material for evolution.
- What is the founder effect?
- Loss of genetic variation when a new population is established. Colonizers represent limited genetic sample of source population.
- Identify a factor that can lead to genetic drift.
- Small population size. Fewer individuals mean greater random sampling effects.
- Which type of natural selection can lead to speciation?
- Disruptive selection. Creates reproductively isolated subpopulations.
- What is a genetic bottleneck?
- A sharp reduction in the size of a population. Results in loss of rare alleles through random sampling.
- Define genetic drift.
- Random changes in allele frequencies in a population. Stronger in small populations due to sampling effects.