Natural Selection

Darwin observed many finch species on the Galapagos Islands. To explain these observations, he

proposed that each species evolved from the same common ancestor, which was a finch species

that migrated to the islands from the mainland. What additional evidence did Darwin use to support

his explanation?

• The finch populations were very numerous, and different species often bred with one another.

• The finch species lived in different habitats on different islands, which isolated them from one another.

• The finch species were distributed evenly among all of the islands, but did not interbreed.

• The beaks of the finches were identical, allowing them to eat the same foods on any of the islands.

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A population of rabbits grows rapidly from one year to the next. Then one year, a disease strikes approximately one fourth of the adult rabbits. The disease remains with the population in the years that follow.

As explained by Darwin’s theory, which of these conditions allows the rabbit population to evolve by natural selection?

• The disease affects adult and juvenile rabbits equally.

• The disease reduces the ability of the rabbits to reproduce.

• Some rabbits are resistant to the disease, and they pass the resistance to their offspring.

• No rabbits are resistant to the disease, and all die when the disease strikes them.

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Which of the following is a situation that could cause evolutionary change that is NOT due to natural selection?

• A volcano erupts and kills many individuals in a population.

• A mutation produces sea stars that are less visible to predators.

• An insecticide is sprayed in a community to combat mosquitoes.

• Cattle are treated with antibiotics to prevent the spread of infections.

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The graphs below show the changes in crab color at one beach.

Which of the following is most likely to have caused the change in the distribution?

• A new predator arrived that preferred dark-tan crabs.

• A new predator arrived that preferred light-tan crabs.

• A change in beach color made medium-tan crabs the least visible to predators.

• A change in beach color made medium-tan crabs the most visible to predators.

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A population that is isolated in a remote environment is still able to experience genetic variation. How could genetic variation that contributes to evolution occur in such a population?

• A mutation in a liver cell produces liver cancer.

• Lateral gene transfer occurs that produces an organism that is less resistant to drought.

• A mutation in an egg cell causes a change in DNA that produces an organism that is more sensitive to sunlight.

• A mistake in DNA replication before meiosis produces an organism that is better able to outrun predators.

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The figure shows how natural selection of a single-trait gene affects lizard survival.

Which of the following most likely causes the changes in allele distribution?

• The allele for light gray coloration disappears from the population. This may be because light gray lizards are more visible to predators and therefore they might be less likely to survive and reproduce.

• The allele for black coloration decreases fitness and becomes less common. This may be because black coloration keeps the lizards cool during hot summer temperatures.

• Medium gray coloration in lizards appears to be a neutral mutant allele that allows the lizards to hide better from predators. This leads to increases in phenotype and allele frequency of gray coloration.

• Because black and medium gray lizards are less visible to predators, these alleles are neutral to natural selection and therefore will not disappear from the population of lizards.

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Grass plants in a population range in height from 6 cm to 25 cm. The short plants receive little sunlight, and the tall plants are eaten by grazing animals. Which statement best describes the effect of natural selection on the grasses?

• Because average height grass plants are favored, stabilizing natural selection is occurring.

• Because average height grass plants are favored, disruptive natural selection is occurring.

• Because tall grass plants are favored by the animals that eat grass, directional selection is occurring.

• Because short and tall grass plants are favored, normal natural selection is occurring.

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Scientists use several concepts to explain patterns of evolutionary change. Which evidence would be most useful for identifying a pattern of punctuated equilibrium in an evolutionary lineage?

• Similar bone structures among mammal species alive today

• An identical genetic code in use among all species alive today

• Fossil sequences that show gradual changes over long spans of geologic time

• Fossil sequences that show rapid changes over brief spans of geologic time

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Which of the following best illustrates natural selection?

• An organism with favorable genetic variations will tend to survive and breed successfully.

• A population monopolizes all of the resources in its habitat, forcing other species to migrate.

• A community whose members work together utilizing all existing resources and migratory routes.

• The largest organisms in a species receive the only breeding opportunities.

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Which of the following is NOT part of the that mechanisms of natural selection?

• Organisms produce more offspring than can survive.

• Disease and natural disaster will limit population growth.

• Species today descended with modifications from ancestral species.

• Organisms with advantages will survive and reproduce.

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