Question

Difficulty: HardAdaptive Radiation and Mechanisms of Speciation

An ancestral fruit-eating mammal colonized an isolated archipelago containing varied, unexploited ecological niches. Over generations, descendant populations evolved distinct morphological structures adapted for burrowing, swimming, and nectar-feeding, yet all retained identical underlying skeletal limb configurations. Which evolutionary phenomenon best accounts for this rapid diversification, and what anatomical evidence confirms their descent from a shared ancestor?

  1. Adaptive radiation, evidenced by homologous structuresAnswer
  2. B
    Convergent evolution, evidenced by analogous structures
  3. C
    Lamarckian evolution, evidenced by inherited somatic modifications
  4. D
    Protective mimicry, evidenced by cryptic coloration adaptations

Answer

Adaptive radiation, evidenced by homologous structures
The correct response identifies adaptive radiation as the process where a single ancestral population rapidly diversifies to fill open ecological niches. The shared anatomical framework across different specialized limbs provides clear evidence of homology derived from a common ancestor.

Step-by-Step Solution

1
Analyze the ecological context of lineage diversification.
A single ancestral species colonizing an isolated region with multiple open ecological niches undergoes rapid speciation, which defines adaptive radiation.
Unexploited resources eliminate competition and drive natural selection toward specialization in distinct niches.
2
Evaluate the anatomical relationship among the modified limbs.
Structures modified for different functions (burrowing, swimming, nectar-feeding) that share a common underlying skeletal plan are homologous structures.
Homology reflects shared evolutionary origin despite morphological adaptation to different ecological roles.

Key Concept

Adaptive Radiation and Homology in Speciation
Estimated Time:2m 0s
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