Examkin

Question

Difficulty: HardEvidence for Evolution: Comparative Biochemistry and Biogeography

Species of lungfish are restricted to isolated freshwater habitats in South America, Africa, and Australia. Comparative biochemical analysis demonstrates that their hemoglobin amino acid sequences share high homology with one another, but show marked divergence from the hemoglobin of marine teleosts inhabiting surrounding oceans. Which evolutionary concept best accounts for both their continental distribution and biochemical similarity?

  1. Vicariance following the breakup of Gondwana, preserving high molecular homology inherited from a common ancestral lineageAnswer
  2. B
    Convergent biochemical evolution driven by independent adaptation to similar freshwater conditions across isolated continents
  3. C
    Inheritance of acquired physiological traits in hemoglobin structure developed during individual responses to seasonal drought
  4. D
    Recent adaptive radiation occurring after transoceanic salt-water dispersal between the separated landmasses

Answer

Vicariance following the breakup of Gondwana, preserving high molecular homology inherited from a common ancestral lineage
The correct response recognizes that the presence of related freshwater species on South America, Africa, and Australia is a classic example of vicariance resulting from the fragmentation of Gondwana. High amino acid sequence identity in hemoglobin demonstrates homologous relationship derived from a shared ancestral gene pool prior to continental separation.

Step-by-Step Solution

1
Analyze the biogeographical distribution pattern
Lungfish exist only in South America, Africa, and Australia, landmasses that were once joined as part of the southern supercontinent Gondwana.
Disjunct distributions of strictly freshwater organisms across oceans indicate ancient vicariance caused by plate tectonics rather than recent long-distance dispersal.
2
Evaluate the comparative biochemical evidence
High amino acid sequence homology in hemoglobin among lungfish species indicates a close genetic relationship and a relatively recent common ancestor prior to lineage splitting.
Proteins like hemoglobin serve as molecular clocks; greater sequence similarity reflects smaller evolutionary distances between taxa.
3
Synthesize biogeographical and biochemical data
The combined evidence confirms that ancestral lungfish inhabited Gondwana before continental breakup, leading to geographic isolation (vicariance) while retaining inherited molecular similarities.
Only vicariance combined with shared ancestry explains both the restricted continental distribution and the high biochemical similarity.

Key Concept

Biogeographical Vicariance and Comparative Molecular Homology
Estimated Time:1m 30s
Rate this question

Topics

Evidence for Evolution: Comparative Biochemistry and Biogeography

More questions from this topic