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Difficulty: MediumVertebrates: Poikilothermic Classes (Pisces, Amphibia, Reptilia)

A biological comparison is made among three poikilothermic vertebrates: a bony fish (tilapia), an amphibian (toad), and a reptile (snake). Which of the following statements correctly describes the cardiac structure and circulatory pattern of these organisms?

  1. The tilapia possesses a two-chambered heart with single circulation, whereas both the toad and snake possess a three-chambered heart with double circulation.Answer
  2. B
    The tilapia and toad both possess a two-chambered heart with single circulation, while the snake possesses a three-chambered heart.
  3. C
    The tilapia has a three-chambered heart, while the toad and snake both possess a four-chambered heart with complete separation of oxygenated and deoxygenated blood.
  4. D
    The tilapia has a two-chambered heart with single circulation, while the toad possesses a four-chambered heart with double circulation.

Answer

The tilapia possesses a two-chambered heart with single circulation, whereas both the toad and snake possess a three-chambered heart with double circulation.
The statement specifying that tilapia has a two-chambered heart with single circulation while both toad and snake possess a three-chambered heart with double circulation is scientifically accurate. Pisces have a single atrium and single ventricle pumping deoxygenated blood to the gills. Amphibians and non-crocodilian reptiles have two atria and one ventricle, allowing blood to pass through the heart twice per circuit.

Step-by-Step Solution

1
Analyze the circulatory system of Class Pisces (bony fish / tilapia)
Bony fishes have a two-chambered heart (1 atrium, 1 ventricle) through which deoxygenated blood flows once per complete circuit (single circulation).
Blood flows from heart to gills for oxygenation and directly to body tissues before returning to the heart.
2
Analyze the circulatory system of Class Amphibia (toad) and Class Reptilia (snake)
Both adult amphibians and non-crocodilian reptiles possess a three-chambered heart (2 atria, 1 ventricle) operating a double circulatory route.
Blood passes through the heart twice per complete circuit (pulmocutaneous/pulmonary circuit and systemic circuit).
3
Synthesize and match the correct comparative statement
Tilapia (2 chambers, single circulation); Toad and Snake (3 chambers, double circulation).
Accurately represents comparative cardiac evolution across poikilothermic vertebrate classes.

Key Concept

Comparative cardiac anatomy and circulatory pathways in poikilothermic vertebrates (Pisces, Amphibia, Reptilia)
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Topics

Vertebrates: Poikilothermic Classes (Pisces, Amphibia, Reptilia)

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