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Difficulty: MediumEvolution and Adaptation

A population of rock pocket mice with inherited variation in fur color lives in a desert region where a past volcanic eruption created patches of dark basalt rock. Over many generations, the proportion of dark-furred mice inhabiting the dark rock areas increases significantly compared to the surrounding sandy desert. Which of the following best explains this evolutionary change?

  1. A
    Individual light-colored mice intentionally changed their fur pigmentation during their lifetime to camouflage against the dark rock.
  2. B
    The dark fur allele became genetically dominant over the light fur allele because the dark trait was needed for survival.
  3. Dark-furred mice had better camouflage from visual predators on the dark rock, surviving at higher rates and passing the dark fur trait to offspring.Answer
  4. D
    Constant exposure to hot volcanic rock stimulated the skin cells of adult mice to mutate and produce darker pigments directly.

Answer

Dark-furred mice had better camouflage from visual predators on the dark rock, surviving at higher rates and passing the dark fur trait to offspring.
Natural selection operates when inherited variations provide a survival advantage in a specific habitat. On dark basalt rock, dark-furred mice are less visible to predators, allowing them to survive longer and produce more offspring with the dark-fur trait. Over successive generations, this differential reproduction increases the frequency of dark-furred individuals in that population.

Step-by-Step Solution

1
Identify the mechanism of evolutionary change described in the scenario.
The scenario describes natural selection acting on pre-existing genetic variation in fur color within a changing environment.
Natural selection requires inherited phenotypic variation, selective environmental pressure, and differential reproductive success.
2
Evaluate how the dark substrate provides an adaptive advantage.
Dark fur provides camouflage against dark rock, reducing predation risk from visual hunters like owls and hawks.
Organisms with favorable adaptations are more likely to survive, reproduce, and transmit their beneficial alleles to the next generation.
3
Differentiate between population-level evolution and individual trait acquisition.
Populations evolve over generations as allele frequencies shift; individual organisms do not change their genetic makeup in response to environmental demands.
Traits acquired during an individual's lifetime do not alter heritable germline DNA.

Key Concept

Natural selection acts on existing genetic variation, leading to differential survival and reproductive success that shifts population traits over generations.
Estimated Time:1m 0s
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Topics

Evolution and Adaptation

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