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Difficulty: MediumAdaptive Radiation and Mechanisms of Speciation

Following the mass extinction event at the end of the Cretaceous period, ancestral mammals underwent rapid diversification into diverse ecological roles, giving rise to burrowing, aquatic, flying, and terrestrial forms. Which of the following evolutionary processes best accounts for this rapid diversification into varied ecological niches?

  1. Adaptive radiation driven by the availability of unoccupied ecological nichesAnswer
  2. B
    Convergent evolution resulting in homologous structures across unrelated mammalian lineages
  3. C
    Inheritance of acquired traits resulting from mammals actively adapting to new habitats during their lifetime
  4. D
    Discontinuous variation caused by non-heritable environmental modifications in distinct ancestral groups

Answer

Adaptive radiation driven by the availability of unoccupied ecological niches
The correct answer highlights adaptive radiation, which occurs when a single ancestral species rapidly evolves into a variety of forms adapted to specific ecological niches, especially after mass extinctions free up ecological space.

Step-by-Step Solution

1
Identify the key evolutionary pattern described in the stem
A single ancestral mammalian lineage rapidly diverged into multiple specialized forms (flying, aquatic, burrowing) following a mass extinction event.
Mass extinctions clear ecological niches, creating opportunities for adaptive radiation.
2
Match the biological observation with the corresponding evolutionary mechanism
Diversification from one common ancestor into distinct morphological forms suited for different ecological niches defines adaptive radiation.
Natural selection acts on variations in the ancestral population as subgroups adapt to different ecological roles.

Key Concept

Adaptive Radiation and Mechanisms of Speciation
Estimated Time:1m 0s
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Adaptive Radiation and Mechanisms of Speciation

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