How do bony fish create water flow over their gills during ventilation?

By changing the volume of the buccal cavity through lowering and raising the floor of the mouth, which draws water in and forces it over the gills.

What is the operculum in bony fish?

A bony flap covering the gills that opens and closes to assist the unidirectional flow of water over the gills.

What are gill filaments?

The primary projections from the gill arch in bony fish that provide structural support for the gill lamellae.

Define countercurrent flow in fish gills.

A system where blood flows through the gill lamellae in the opposite direction to the flow of water over the gills.

Why is countercurrent flow more efficient than parallel flow for gas exchange in fish gills?

Countercurrent flow maintains a concentration gradient along the entire length of the gill lamella, allowing continuous diffusion of oxygen into the blood and achieving higher oxygen extraction than parallel flow would permit.

OCR A-Level Biology H420

Cell Structure

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Exchange Surfaces

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Exchange Surfaces

Gas exchange in fish and insects

4 things to know
Components 01 and 03

Overview

The operculum, gill filaments and lamellae and why countercurrent flow is efficient, together with the spiracles and tracheal system of an insect.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Process

Explain gas exchange in fish gills.

Key term

What are spiracles in insects?

Key term

What are gill lamellae and what is their function?

Process

How does the insect tracheal system respond to increased metabolic activity?

Questions from this subtopic

Each one with the model answer underneath.

1
How do bony fish create water flow over their gills during ventilation?
Model answer
By changing the volume of the buccal cavity through lowering and raising the floor of the mouth, which draws water in and forces it over the gills.
2
What is the operculum in bony fish?
Model answer
A bony flap covering the gills that opens and closes to assist the unidirectional flow of water over the gills.
3
What are gill filaments?
Model answer
The primary projections from the gill arch in bony fish that provide structural support for the gill lamellae.
4
What are gill lamellae and what is their function?
Model answer
Gill lamellae (gill plates) are thin, plate-like secondary projections from the gill filaments where gas exchange occurs.
5
Define countercurrent flow in fish gills.
Model answer
A system where blood flows through the gill lamellae in the opposite direction to the flow of water over the gills.
6
Why is countercurrent flow more efficient than parallel flow for gas exchange in fish gills?
Model answer
Countercurrent flow maintains a concentration gradient along the entire length of the gill lamella, allowing continuous diffusion of oxygen into the blood and achieving higher oxygen extraction than parallel flow would permit.

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