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Learning objective

Explain counter-current gas exchange in fish gills.

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Topic

Exchange substances official content

Subtopic

Gas exchange

Aqa A Level BiologyOrganisms exchange substances with their environment

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Quick explanation

Explain counter-current gas exchange in fish gills

  • This point belongs to Exchange substances official content, especially Gas exchange.
  • You need to be able to explain counter-current gas exchange in fish gills.
  • The key ideas to know are gill and gas exchange.
  • Use the linked flashcards and practice questions to check recall, then practise applying the idea in an exam-style answer.

Key concepts

gillgas exchange

Why it matters

This objective helps connect Gas exchange to exam-style questions, flashcards, and revision notes for Exchange substances official content.

Quick student answer

What is the primary advantage of counter-current gas exchange in fish gills?

Direct answer

It allows for higher oxygen concentration in the blood.

Key terms

  • Diffusion: The passive movement of molecules from an area of higher concentration to an area of lower concentration.
  • Concentration gradient: A difference in the concentration of a substance across a space, which drives diffusion.

Common trap

Confusing counter-current with concurrent exchange: Remember that in counter-current exchange, the flow of water and blood is opposite, which maintains a gradient for gas exchange.

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