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Difficulty: EasyEvolutionary Trends in Plants and Animal Systems

In the evolutionary progression of vertebrate circulatory systems, which group of organisms represents the first transition to a three-chambered heart consisting of two atria and a single ventricle?

  1. AmphibiansAnswer
  2. B
    Fishes
  3. C
    Birds
  4. D
    Reptiles

Answer

Amphibians are the first vertebrate group in evolutionary history to develop a three-chambered heart.
Amphibians represent the evolutionary transition from aquatic to semi-terrestrial existence. To support lung respiration alongside skin respiration, they evolved a second atrium, producing a three-chambered heart with two atria and one ventricle.

Step-by-Step Solution

1
Identify the primitive vertebrate heart condition
Fishes represent the earliest vertebrate circulatory arrangement with a two-chambered heart (one atrium, one ventricle).
Single circulation in aquatic environments requires only two heart chambers.
2
Trace the transition to terrestrial life and double circulation
Amphibians evolved lungs and a second atrium to receive oxygenated blood, forming a three-chambered heart (two atria, one ventricle).
The addition of a second atrium separates pulmonary and systemic venous return, making amphibians the first group with a three-chambered heart.

Key Concept

Evolutionary progression of vertebrate heart chambers from two chambers (fishes) to three chambers (amphibians).
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Topics

Evolutionary Trends in Plants and Animal Systems

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