Natural Selection (Continued) - AP Biology
- Identify a process that can counteract natural selection by maintaining variation.
- Gene flow. Immigration introduces new alleles that may be selected against.
- What role does genetic variation play in natural selection?
- It provides the raw material for selection. Without variation, natural selection cannot act on populations.
- What is artificial selection?
- Selective breeding by humans to enhance desirable traits. Humans act as the selective pressure instead of nature.
- Identify the main driving force of natural selection.
- Environmental pressures. External factors that determine which organisms survive and reproduce.
- What is an adaptation?
- A heritable trait that increases fitness. Must be both inherited and beneficial for survival or reproduction.
- Which term describes changes in allele frequencies due to random sampling?
- Genetic drift. Random changes occur independently of natural selection pressures.
- What is directional selection?
- Selection that favors one extreme phenotype. Shifts population toward one end of the trait distribution.
- Which term describes the loss of genetic variation due to random events?
- Genetic drift. Random sampling effects strongest in small populations.
- What is coevolution?
- Reciprocal evolutionary changes in interacting species. Species evolve in response to each other's evolutionary changes.
- What is the significance of a selection coefficient?
- It measures the strength of selection against a genotype. Quantifies how much a genotype reduces reproductive success.
- What is sexual dimorphism?
- Distinct differences in size or appearance between sexes. Results from different selective pressures on males and females.
- Identify a source of genetic variation in a population.
- Recombination. Crossing over during meiosis creates new allele combinations.
- What is a selective pressure?
- An environmental factor that influences survival and reproduction. Determines which traits are advantageous or disadvantageous.
- Identify a factor that can lead to adaptive radiation.
- Ecological opportunities. New environments allow rapid diversification into multiple niches.
- What is a polymorphism?
- The occurrence of different forms among individuals of a population. Multiple alleles maintained in population by various selective pressures.
- Which term refers to a trait that arises due to common ancestry?
- Homologous trait. Shared evolutionary origin produces similar structures across species.
- What is a gene pool?
- The total collection of genes in a population. Contains all genetic material available for natural selection.
- Which phenomenon can result from random mating in large populations?
- Hardy-Weinberg equilibrium. Describes stable allele frequencies when evolution is not occurring.
- Identify a consequence of genetic drift.
- Reduced genetic diversity. Random events remove alleles regardless of their fitness value.
- Which term refers to the movement of alleles between populations?
- Gene flow. Migration transfers genetic material between populations.
- What is the role of recombination in evolution?
- Shuffles alleles, creating new combinations. Independent assortment and crossing over increase genetic diversity.
- Identify a factor that can lead to reproductive isolation.
- Geographic barriers. Physical separation prevents gene flow between populations.
- Which type of selection favors extreme phenotypes?
- Disruptive selection. Selects against intermediate values, increasing variation.
- Identify a mechanism that can lead to genetic drift.
- Bottleneck effect. Random reduction in population size that reduces genetic diversity.
- What is the definition of natural selection?
- The process by which organisms better adapted to their environment tend to survive and reproduce. Darwin's mechanism for evolution through environmental pressures.
- Which term describes a trait that no longer serves its original purpose?
- Vestigial trait. Remains due to evolutionary history despite loss of function.
- Identify the result of a population's adaptation to its environment over time.
- Increased fitness. Better-adapted populations have higher survival and reproductive rates.
- Which term describes the differential survival and reproduction of individuals?
- Differential fitness. Measures relative reproductive success among individuals in a population.
- How does sexual selection differ from natural selection?
- Sexual selection focuses on traits that improve mating success. Sexual selection specifically targets reproductive success over survival.
- Which type of selection favors intermediate phenotypes?
- Stabilizing selection. Reduces variation by selecting against extreme values.
- Identify a result of stabilizing selection.
- Reduction in phenotypic variation. Average phenotypes have highest fitness, reducing population variation.
- What is genetic hitchhiking?
- An allele's increase in frequency due to linkage with a favorable allele. Neutral allele increases due to proximity to beneficial allele.
- Which term describes selection that acts against both extreme phenotypes?
- Stabilizing selection. Maintains population around the average phenotype value.
- Which type of selection can lead to speciation?
- Disruptive selection. Can split populations into distinct groups with different traits.
- What is meant by 'fitness' in the context of natural selection?
- The ability to survive and reproduce. Measures an organism's reproductive success relative to others.
- Which factor can increase genetic variation within a population?
- Mutation. Creates new alleles that increase genetic diversity.
- Which type of selection favors one phenotype over others?
- Directional selection. Creates consistent change in one direction over time.
- What is the founder effect?
- Genetic drift occurring when a new population is established. Small founding population carries limited genetic diversity.
- What is a selective sweep?
- A process where a favorable allele increases in frequency. Strong selection rapidly increases beneficial allele frequency.