Natural Selection Quiz
Questions: 16 · 10 minutes
1. What is the ultimate source of genuinely new alleles in a population?
Natural selection
Mutation
Genetic recombination
Gene flow
2. Male birds with elaborate feathers attract more mates but may be easier for predators to spot. If the feathers spread because mating gains outweigh survival costs, which mechanism is operating?
Genetic drift
Sexual selection
Artificial selection
Stabilizing selection
3. After an environmental change, the average body size in a population increases. What additional evidence is most important before concluding that natural selection caused the shift?
Individuals became larger after receiving more food during development.
The environmental change occurred at the same time as the size increase.
The population contained individuals of several ages.
Body-size differences were heritable and linked to differences in reproductive success.
4. A drought leaves mostly large, hard seeds on an island. Birds with deeper beaks open these seeds more successfully and produce more offspring. Over generations, average beak depth increases. Which process best explains the change?
Stabilizing selection favoring intermediate beaks
Directional selection favoring deeper beaks
Genetic drift acting without fitness differences
Acclimation causing each bird's beak to deepen
5. Which combination is necessary for natural selection to produce evolutionary change in a trait?
Identical individuals, environmental stability, and random mating
Variation in the trait, heritability, and differences in reproductive success associated with the trait
Mutation in every generation, geographic isolation, and a small population
A population goal, acquired traits, and equal reproductive success
6. A bird population mainly encounters small soft seeds and large hard seeds. Birds with small or large beaks feed efficiently, while birds with medium beaks handle neither seed type well. What pattern is this most likely to produce?
Stabilizing selection favoring medium beaks
Directional selection toward one fixed beak size
Disruptive selection favoring both beak-size extremes
Genetic drift with no difference in feeding success
7. A mountain splits one bird population into two isolated populations living in different environments. Which finding would most strongly indicate that natural selection contributed to their divergence?
Heritable traits shifted in different directions, and each shift was associated with greater reproductive success in its local environment.
Birds became different sizes because one side temporarily had more food, but the differences were not inherited.
Neutral alleles changed randomly in both populations, with no relationship to survival or reproduction.
Both populations retained the same trait frequencies despite facing different conditions.
8. Which statement best defines natural selection?
A population changes because every mutation spreads at the same rate, regardless of its effects.
Organisms develop traits they need during life and pass those acquired changes directly to their offspring.
Individuals with certain heritable traits leave more surviving offspring, causing those traits to become more common over generations.
Species deliberately adjust their inherited features to remain suited to the environment.
9. An allele improves survival in a cold habitat but reduces survival in a hot habitat. What principle does this illustrate?
Any allele that aids survival will inevitably become fixed.
Beneficial alleles must be advantageous in every environment.
Natural selection gives organisms traits according to future needs.
The fitness effect of a trait depends on environmental context.
10. Researchers raise offspring from several plant families under the same controlled conditions. Which result would best support the heritability required for natural selection?
Height differences among offspring consistently correspond to differences among their biological parent families.
Every plant grows to the same height because its environment is controlled.
Plants given more fertilizer grow taller than genetically similar plants given less fertilizer.
Individual plants grow taller as they become older.
11. Two small, isolated populations occupy similar environments. An allele has no measurable effect on survival or reproduction, yet its frequency rises in one population and falls in the other. What is the best explanation?
Genetic drift
Stabilizing selection
Adaptive mutation
Directional selection
12. Rabbits grow thicker coats each winter and shed them in spring. The pattern occurs within individual lifetimes and does not involve a generational change in allele frequencies. What is this an example of?
Directional selection
Speciation
Genetic drift
Phenotypic plasticity or acclimation
13. In a mammal population, very low and very high birth weights are associated with lower survival than intermediate birth weights. If the pattern persists, what type of selection is expected?
Disruptive selection
Directional selection
Stabilizing selection
Sexual selection
14. A rare pesticide-resistance allele is present before a pesticide is used. After repeated spraying, the allele becomes common. What can be inferred most directly?
The pesticide created the same resistance allele in every exposed insect.
Individual insects changed their genes after recognizing the pesticide threat.
Resistance increased because random drift always favors rare alleles.
Under pesticide exposure, carriers of the allele left more surviving offspring on average.
15. In evolutionary biology, what does an organism's fitness describe most directly?
Its relative contribution of surviving offspring to future generations
Its ability to survive for the maximum possible lifespan
Its physical strength compared with other members of the population
Its level of genetic complexity compared with ancestral organisms
16. After an antibiotic is introduced, resistant bacteria become common in a bacterial population. Which explanation is most accurate?
The antibiotic teaches exposed bacteria how to resist it, and they pass on what they learned.
All bacteria mutate in the same useful direction because resistance is needed.
Resistant variants survive and reproduce more successfully during treatment than susceptible variants.
The antibiotic increases resistance equally in every bacterium, regardless of inherited variation.