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Difficulty: HardCirculatory and Transport Systems in Animals

Match each cardiac anatomical structure and circulatory pattern with the corresponding vertebrate group that characteristically exhibits it.

  • Two-chambered heart (one atrium, one ventricle) operating a single circulatory circuitPisces (e.g., Tilapia)
  • Three-chambered heart (two atria, single unsegmented ventricle) operating incomplete double circulationAmphibia (e.g., Adult Toad)
  • Three-chambered heart with two atria and a ventricle partially divided by an incomplete muscular septumSquamate Reptiles (e.g., Agama Lizard)
  • Four-chambered heart with complete muscular division between left and right ventricles operating complete double circulationAves and Mammalia (e.g., Pigeon and Goat)

Answer

Two-chambered heart with single circulation matches Pisces; Three-chambered heart with unsegmented ventricle matches Amphibia; Three-chambered heart with incomplete septum matches Squamate Reptiles; Four-chambered heart with complete ventricular separation matches Aves and Mammalia.
Each vertebrate class exhibits specific anatomical heart structures reflecting evolutionary complexity: Pisces have a 2-chambered heart (single circulation), Amphibia have a 3-chambered heart with an unsegmented ventricle, non-crocodilian Reptiles possess an incomplete septum in the ventricle, and Aves/Mammalia possess a 4-chambered heart with complete separation of oxygenated and deoxygenated blood.

Step-by-Step Solution

1
Analyze the circulatory complexity of fishes (Pisces).
Fishes have a single circuit system powered by a simple 2-chambered heart (one atrium, one ventricle).
Deoxygenated blood flows from tissues to atrium, to ventricle, to gills for gas exchange, and directly to body tissues without returning to the heart first.
2
Analyze the cardiac structure of adult amphibians.
Amphibians transition to double circulation but possess a 3-chambered heart without ventricular division.
Two separate atria receive systemic and pulmocutaneous blood, but both discharge into a single common ventricle.
3
Examine the evolutionary variation in reptile hearts.
Non-crocodilian reptiles possess a partially divided ventricle via an incomplete septum.
This partial septum provides higher separation of pulmonary and systemic blood streams than amphibian hearts, though division remains incomplete.
4
Identify the high-efficiency circulatory system of birds and mammals.
Aves and Mammalia possess a fully 4-chambered heart with two separate ventricles.
Complete interventricular septum prevents any mixing of oxygenated blood destined for body tissues and deoxygenated blood heading to lungs, supporting endothermy.

Key Concept

Evolutionary comparative anatomy of vertebrate cardiac chambers and circulatory pathways.
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Topics

Circulatory and Transport Systems in Animals

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