Mechanisms of Evolution Practice Questions
19 free Mechanisms of Evolution practice questions for the Zoology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which mechanism of evolution is entirely random and typically has a more significant impact on small populations?
- A Natural selection
- B Gene flow
- C Artificial selection
- D Genetic drift
Correct answer: Genetic drift
Genetic drift refers to random fluctuations in allele frequencies due to chance events. In small populations, these chance events can lead to the total loss of an allele much more easily than in large populations.
The movement of alleles between populations through the migration of breeding individuals is known as:
- A Genetic drift
- B Mutation
- C Stabilizing selection
- D Gene flow
Correct answer: Gene flow
Gene flow occurs when individuals move into or out of a population, bringing new alleles or changing the frequency of existing ones. This process tends to reduce genetic differences between the involved populations.
Which type of natural selection favors individuals at both extremes of a phenotypic range over intermediate phenotypes?
- A Stabilizing selection
- B Directional selection
- C Disruptive selection
- D Sexual selection
Correct answer: Disruptive selection
Disruptive (or diversifying) selection occurs when environmental conditions favor extreme traits. Over time, this can lead to the population splitting into two distinct groups, potentially leading to speciation.
A sudden reduction in population size due to a natural disaster, leaving behind a small surviving group with a different genetic makeup, is called:
- A The founder effect
- B Adaptive radiation
- C Balanced polymorphism
- D The bottleneck effect
Correct answer: The bottleneck effect
The bottleneck effect is a form of genetic drift where a large population is drastically reduced. The genetic diversity of the survivors may not represent the original population, leading to a loss of variation.
In the context of natural selection, what does 'biological fitness' primarily measure?
- A An individual's raw physical strength, running speed, and endurance
- B The overall longevity and total lifespan of the individual
- C The ability to survive and produce fertile, viable offspring
- D The total number of random mutations present in its genome
Correct answer: The ability to survive and produce fertile, viable offspring
Fitness is defined by reproductive success. An organism is considered fit if its traits allow it to survive long enough to pass its genes to the next generation relative to others in the population.
Industrial melanism in peppered moths, where dark-colored moths became more common during the Industrial Revolution, is an example of:
- A Directional selection
- B Stabilizing selection
- C Disruptive selection
- D Genetic drift
Correct answer: Directional selection
Directional selection occurs when an extreme phenotype is favored over others, causing the allele frequency to shift in one direction. In this case, soot-covered trees favored darker moths for better camouflage.
Which of the following is an example of the 'founder effect'?
- A A few birds blown off course that colonize a new, isolated island
- B A severe forest fire wiping out most of a deer population
- C Pollen from one cornfield accidentally blowing into a neighboring field
- D Antibiotic resistance developing within an existing bacterial colony
Correct answer: A few birds blown off course that colonize a new, isolated island
The founder effect occurs when a small group of individuals establishes a new population. The limited genetic variation of these 'founders' determines the genetic structure of the future population.
Stabilizing selection is most likely to occur in which type of environment?
- A A stable environment where the organism is already well-adapted
- B A rapidly changing environment with new predators and competitors
- C An environment offering two very distinct types of food sources
- D A newly formed, still-cooling volcanic island ecosystem
Correct answer: A stable environment where the organism is already well-adapted
Stabilizing selection acts against extreme phenotypes and favors intermediate versions. It helps maintain the status quo in a population that is already well-suited to its current environment.
What is the primary evolutionary consequence of constant gene flow between two populations?
- A An increase in the rate of speciation between the two populations
- B A significant increase in the overall genetic divergence seen over time
- C A steady decrease in genetic variation found within each population
- D A gradual decrease in genetic differences between the two populations
Correct answer: A gradual decrease in genetic differences between the two populations
Gene flow acts as a homogenizing force. By exchanging alleles, the two populations become more genetically similar, which can prevent them from evolving into separate species.
Sexual selection, such as the elaborate tail of a male peacock, is a specific form of:
- A Natural selection
- B Genetic drift
- C Mutation pressure
- D Gene flow
Correct answer: Natural selection
Sexual selection is a type of natural selection where individuals with certain inherited traits are more likely than others to obtain mates. It often results in sexual dimorphism.
The Hardy-Weinberg equilibrium describes a population that is:
- A A population that is evolving rapidly under intense selective pressure
- B A population currently in an active state of genetic drift
- C A population that is not evolving, with constant allele frequencies
- D A population undergoing intense and sustained natural selection
Correct answer: A population that is not evolving, with constant allele frequencies
Hardy-Weinberg equilibrium is a null model where allele frequencies stay the same from generation to generation. It only occurs if five conditions are met: no mutation, no gene flow, large population, random mating, and no natural selection.
Which of the following best describes 'mutation' as a mechanism of evolution?
- A It is the ultimate source of new genetic variation
- B It is the main force that changes allele frequencies in large populations
- C It always results in beneficial traits
- D It occurs only in response to environmental needs
Correct answer: It is the ultimate source of new genetic variation
While selection and drift sort existing variation, mutation is the only process that creates entirely new alleles. Without mutation, evolution would eventually stop because there would be no new traits to select for.
The 'Heterozygote Advantage' (e.g., Sickle Cell Trait) is a mechanism that maintains genetic variation through:
- A Directional selection
- B Balancing selection
- C Genetic drift
- D The founder effect
Correct answer: Balancing selection
Balancing selection occurs when natural selection maintains two or more phenotypes in a population. In areas with malaria, the sickle cell allele is maintained because heterozygotes are protected from malaria without having the full disease.
Which condition would most likely lead to genetic drift having a massive effect on a population?
- A Extremely large population size
- B Non-random mating
- C A very small population size
- D Frequent migration between populations
Correct answer: A very small population size
Genetic drift is inversely proportional to population size. In very small populations, the random loss of even one or two individuals can significantly alter the gene pool overnight.
Frequency-dependent selection occurs when the fitness of a phenotype depends on:
- A How common it is in the population
- B The mutation rate of the gene
- C The size of the individual
- D The distance migrated by the individual
Correct answer: How common it is in the population
In frequency-dependent selection, the fitness of a trait changes based on its prevalence. For example, if a predator learns to recognize the most common color of prey, the rarer color becomes more 'fit' until it becomes common itself.
What is 'Artificial Selection'?
- A Selection that occurs only in controlled laboratory settings
- B Selection driven by environmental changes such as global warming
- C Human-driven selection for desired traits in plants or animals
- D Selection that leads to non-functional vestigial organs
Correct answer: Human-driven selection for desired traits in plants or animals
Artificial selection (selective breeding) is the process by which humans choose specific individuals with desirable traits to reproduce. Examples include modern dog breeds and agricultural crops like corn.
Gene flow can act as a constraint on natural selection by:
- A Increasing the mutation rate within the population
- B Removing all dominant alleles from the gene pool
- C Introducing alleles poorly suited to the local environment
- D Forcing all individuals in the population to become homozygous
Correct answer: Introducing alleles poorly suited to the local environment
Migration can bring in alleles that evolved in a different environment. If these 'maladapted' alleles arrive faster than natural selection can remove them, they can prevent a population from becoming perfectly adapted to its local habitat.
The three-spine stickleback fish losing its pelvic spines in freshwater lakes while keeping them in the ocean is an example of:
- A Neutral evolution unrelated to selection
- B Genetic drift acting independently of environment
- C Natural selection favoring local adaptation
- D The founder effect from population isolation
Correct answer: Natural selection favoring local adaptation
This is a classic example of natural selection. In the ocean, spines protect against large predators, but in freshwater, spines are a disadvantage due to different predators (like dragonfly larvae) that can grab them, leading to the loss of the trait.
Which of the following does NOT change allele frequencies in a population?
- A Natural selection
- B Random mating
- C Genetic drift
- D Gene flow
Correct answer: Random mating
Random mating (panmixia) shuffles alleles into different combinations (genotypes) but does not, by itself, change the overall frequency of the alleles in the gene pool. The other three choices are the primary drivers of evolutionary change.