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Difficulty: HardCirculatory and Transport Systems in Animals

During a physiological investigation of circulatory dynamics across different vertebrate groups, hydrostatic pressure was monitored as blood passed through the respiratory organs and systemic tissues. Which of the following organisms utilizes a cardiac structure that re-pressurizes oxygenated blood after it leaves the lungs, ensuring high-pressure delivery directly into the systemic aorta without mixing with deoxygenated blood?

  1. Domestic fowl (*Gallus gallus*)Answer
  2. B
    African toad (*Amietophrynus regularis*)
  3. C
    Tilapia fish (*Oreochromis niloticus*)
  4. D
    Agama lizard (*Agama agama*)

Answer

Domestic fowl (*Gallus gallus*) possesses a four-chambered heart that completely separates pulmonary and systemic circuits, allowing oxygenated blood from the lungs to be re-pressurized before entering systemic arterial circulation.
The correct answer identifies an avian species (*Gallus gallus*). Birds and mammals have evolved a four-chambered heart with two separate atria and two separate ventricles. This anatomical design completely separates the pulmonary and systemic circuits, allowing oxygenated blood returned from the lungs to be pumped by the thick left ventricle at high pressure directly into the systemic aorta to support high metabolic activity.

Step-by-Step Solution

1
Identify the key functional requirement described in the stem
The requirement is a heart structure supporting complete double circulation—re-pressurizing oxygenated blood returning from lungs before sending it to systemic tissues without mixing with deoxygenated blood.
Single circulation causes pressure to drop across gill capillaries, while incomplete double circulation leads to mixing in an undivided or partially divided ventricle.
2
Evaluate the cardiac anatomy of the listed vertebrate taxa
Tilapia (Pisces) has 2 chambers (single circulation); African toad (Amphibia) has 3 chambers; Agama lizard (Reptilia) has 3 chambers with an incomplete septum; Domestic fowl (Aves) has 4 fully separated chambers.
Complete division of both ventricles in birds and mammals prevents mixing and allows the left ventricle to generate high systemic pressure independently of the low-pressure pulmonary circuit.
3
Select the organism matching complete double circulation with high systemic arterial re-pressurization
Domestic fowl (*Gallus gallus*) is the correct organism.
As an avian species, it has a fully compartmentalized four-chambered heart.

Key Concept

Comparative Vertebrate Circulatory Anatomy and Double Circulation Hydrodynamics
Estimated Time:1m 15s
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Topics

Circulatory and Transport Systems in Animals

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