Master AP Bio Unit 6 Practice Test

Evolution is defined as the change in allele frequencies within a population over generations. This fundamental concept encompasses all mechanisms that can alter genetic composition over time.

An adaptation is a heritable trait that improves an organism's ability to survive and reproduce in its specific environment. Such traits become more common in the population through the process of natural selection.

Fossils that show transitional forms provide direct evidence of evolutionary change over time by demonstrating intermediate states between ancestral and modern species. This fossil record documents the gradual changes that occur in lineages.

Mutation introduces new alleles into a gene pool, thereby increasing genetic variation. In contrast, processes like genetic drift and bottlenecks typically reduce variation by random loss of alleles.

One of the primary assumptions of Hardy-Weinberg equilibrium is that mating in the population must be random. This condition helps ensure that allele frequencies remain constant in the absence of other evolutionary forces.

Genetic drift leads to random fluctuations in allele frequencies, and these effects are much more pronounced in small populations. In small groups, chance events can significantly alter the genetic makeup over time.

A population bottleneck occurs when a dramatic reduction in population size results in the loss of genetic variation. The surviving population's gene pool is much smaller, which can reduce overall genetic diversity.

Allopatric speciation occurs when a geographic barrier divides a population, isolating groups from one another. Over time, this isolation allows each group to accumulate genetic differences leading to the formation of new species.

A fitness trade-off occurs when an increase in fitness related to one trait is accompanied by a decrease in fitness in another aspect. This balance ensures that no single trait is optimized at the expense of overall survival or reproduction.

Genetic drift is the random fluctuation of allele frequencies, particularly in small populations, which can cause deviations from the expected Hardy-Weinberg ratios. This process is driven by chance rather than selective pressures.

Heterozygote advantage occurs when individuals with two different alleles at a locus have a higher fitness than those with two identical alleles. This phenomenon can help maintain multiple alleles in a population.

Muller's ratchet describes the process by which small asexual populations accumulate harmful mutations over time. Without recombination, these deleterious mutations cannot be effectively purged, potentially leading to a decline in fitness.

Mutation is the source of new genetic variation, providing the raw material upon which natural selection and other evolutionary forces can act. Without mutations, evolutionary processes would lack the diversity needed for adaptation.

Sexual selection favors traits that enhance an organism's ability to attract and secure mates, even if those traits may reduce survival in other ways. Therefore, features that compromise survival can still evolve if they significantly boost reproductive success.

Molecular sequence comparisons can reveal conserved regions of DNA or proteins that indicate shared ancestry. When sequences are highly similar, it suggests that the species diverged relatively recently from a common ancestor.

Balanced polymorphism occurs when multiple alleles are preserved in a population because different environmental conditions favor different alleles. This dynamic equilibrium supports genetic diversity over time, even under rapid environmental change.

The founder effect occurs when a few individuals establish a new population, usually resulting in reduced genetic diversity. Over time, the limited gene pool can lead to increased inbreeding and a higher impact of genetic drift.

Frequency-dependent selection means that the fitness of a phenotype depends on its frequency relative to other phenotypes in the population, often favoring rare alleles. In contrast, directional selection consistently favors one extreme phenotype, shifting allele frequencies in a uniform direction.

A monophyletic group, or clade, consists of an ancestor and all of its descendants, indicating a single, unique evolutionary branch. Recognizing clades is crucial for understanding evolutionary relationships and the lineage-specific traits that arise from common ancestry.