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The sequence of the one-way gaseous exchange mechanism in a fish is?

The sequence of the one-way gaseous exchange mechanism in a fish is?
Take Free Practice Test On 2026 JAMB UTME, Post UTME, WAEC SSCE, GCE, NECO SSCE
  • A Mouth --> operculum -> gills
  • B Mouth -> gills > operculum
  • C Operculum > gills -> mouth
  • D Gills -> operculum --> mouth
Correct Answer: Option B
Explanation:
Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills.

In some fish, capillary blood flows in the opposite direction to the water, causing counter-current exchange. The gills push the oxygen-poor water out through openings in the sides(opercula) of the pharynx.

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