Question

Difficulty: MediumDarwin's Theory of Natural Selection

A population of desert pocket mice primarily displays light coat coloration. Following a volcanic eruption, dark basalt rock is exposed in their habitat, creating a new environment. Arrange the following steps describing the evolutionary adaptation of dark fur in this population according to Charles Darwin's theory of natural selection in their correct sequence, from first to last.

  1. 1Random genetic mutations introduce heritable variation in fur color, resulting in a small number of dark-furred mice.
  2. 2Dark basalt rock creates an environmental change where light-furred mice are easily spotted by visual predators.
  3. 3Dark-furred mice survive predation more frequently and pass their dark-fur alleles to a greater number of offspring.
  4. 4The proportion of dark-furred individuals increases across successive generations, adapting the population to the dark substrate.

Answer

The correct sequence of events is: (1) Random genetic variation introduces dark fur traits -> (2) Volcanic basalt rock establishes selective pressure from visual predators -> (3) Dark-furred mice experience higher survival and reproduction rates -> (4) The frequency of dark-furred mice increases in the population over generations.
Darwin's theory of natural selection follows a strict logical sequence: heritable variation arises randomly first, an environmental change creates selective pressure, individuals with advantageous variation experience differential survival and reproduction, and finally, the population undergoes evolutionary change as the advantageous trait becomes predominant.

Step-by-Step Solution

1
Identify the initial source of variation
Random mutations produce pre-existing variation (dark fur) within the light-furred population.
Natural selection can only act upon traits that already exist in a population's gene pool.
2
Identify the selective pressure
The exposure of dark basalt rock creates selective pressure via visual predation by owls and hawks.
Selective pressures determine which pre-existing variations offer a survival advantage.
3
Determine differential reproduction
Dark mice are camouflaged and thus survive predation at higher rates, producing more offspring.
Individuals with favorable adaptations contribute more offspring to the next generation.
4
Evaluate long-term population change
The frequency of the dark fur phenotype increases in the population across generations.
Evolution by natural selection is a change in allele frequencies within a population over time.

Key Concept

Logical progression of Darwinian natural selection (Variation -> Selective Pressure -> Differential Survival/Reproduction -> Population Adaptation)
Estimated Time:1m 30s
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