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Difficulty: Very hardEvolutionary Trends and Adaptive Features in Organisms

During the evolutionary transition of vertebrates from aquatic to terrestrial environments, structural modifications in the circulatory system occurred to increase metabolic efficiency. Which of the following statements accurately describes the evolutionary trend in heart chamber structure and its physiological impact across vertebrate groups?

  1. Aves possess a four-chambered heart with complete separation of pulmonary and systemic circulations, preventing the mixing of oxygenated and deoxygenated blood.Answer
  2. B
    Amphibia possess a two-chambered heart with a single atrium and one ventricle, allowing single-circuit circulation.
  3. C
    Non-avian reptiles possess a completely divided four-chambered heart that prevents any ventricular mixing during resting states.
  4. D
    Pisces possess a three-chambered heart comprising two atria and one ventricle that drives blood directly through pulmonary capillaries.

Answer

Aves possess a four-chambered heart with complete separation of pulmonary and systemic circulations, preventing the mixing of oxygenated and deoxygenated blood.
Birds (Aves) and mammals represent the culmination of vertebrate circulatory evolution, featuring a complete inter-ventricular septum that divides the heart into four distinct chambers (two atria and two ventricles). This anatomical adaptation completely isolates oxygenated blood returning from the lungs from deoxygenated blood returning from body tissues, maximizing respiratory gas delivery to satisfy high endothermic metabolic demands.

Step-by-Step Solution

1
Analyze evolutionary progression of heart structure across vertebrate classes.
Pisces have 2 chambers (1 atrium, 1 ventricle); Amphibia and non-crocodilian Reptilia have 3 chambers (2 atria, 1 ventricle, with partial inter-ventricular septum in reptiles); Aves and Mammalia have 4 chambers (2 atria, 2 ventricles).
Tracking structural adaptations from simple single-circuit to double-circuit systems clarifies evolutionary trends.
2
Evaluate the functional consequences of double circulation in Aves and Mammalia.
Complete division by the inter-ventricular septum prevents mixing of oxygenated and deoxygenated blood, allowing high systemic blood pressure and efficient oxygen delivery required for endothermy.
Connecting anatomical structure to physiological performance identifies the correct adaptive outcome.

Key Concept

Vertebrate Heart Chamber Evolution and Circulatory Efficiency
Estimated Time:1m 15s
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Topics

Evolutionary Trends and Adaptive Features in Organisms

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