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Difficulty: MediumVertebrates: Homoiothermic Classes (Aves and Mammalia)

A biologist dissects a homoiothermic vertebrate and identifies a muscular transverse partition that completely separates the thoracic cavity containing the heart and lungs from the abdominal cavity containing the digestive organs. Which class of homoiothermic vertebrates possesses this specific anatomical feature to assist in pulmonary ventilation?

  1. MammaliaAnswer
  2. B
    Aves
  3. C
    Reptilia
  4. D
    Amphibia

Answer

Mammalia is the correct class because mammals uniquely possess a muscular diaphragm separating the thoracic cavity from the abdominal cavity, which contracts to facilitate breathing.
Mammalia is the only vertebrate class possessing a muscular diaphragm that forms a complete partition between the thoracic and abdominal cavities. Contraction of the diaphragm increases thoracic cavity volume, lowering pressure to pull air into the lungs.

Step-by-Step Solution

1
Identify the homoiothermic (warm-blooded) vertebrate classes.
The two homoiothermic vertebrate classes are Aves (birds) and Mammalia (mammals). Reptilia and Amphibia are poikilothermic.
Eliminates non-homoiothermic classes based on the thermal regulation constraint in the stem.
2
Analyze the anatomical feature described in the stem.
A muscular transverse partition separating thoracic and abdominal cavities is a muscular diaphragm.
Determines the specific physiological structure described.
3
Compare respiratory anatomy between Aves and Mammalia.
Mammals possess a muscular diaphragm, whereas birds lack a diaphragm and rely on air sacs and sternal depression for lung ventilation.
Confirms Mammalia as the correct target class.

Key Concept

Anatomical distinctions between homoiothermic classes (Aves vs Mammalia)
Estimated Time:1m 0s
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Topics

Vertebrates: Homoiothermic Classes (Aves and Mammalia)

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