Exchange in Fish and Insects

Exchange in Fish and Insects

Monday 1st March 2021

Exchange Surfaces

You will already have looked at exchange surfaces, and how they are specially adapted to carry out their functions.

Today we will be looking at how fish are adapted to absorb oxygen from the sea.

Open Ended

There are three factors that determine how effective a surface is at exchanging materials. One being a rich network of capillaries (in humans). What are two others?

Bony Fish

Fish have a small SA:Vol and so require a specialised system in order to get the oxygen they need.

Fish have gills to help them absorb O₂ from water which are highly specialised. Each fish has 5 pairs of gills covered by a plate.

Each gill has 2 rows of gill filaments (called lamellae).

These filaments are thin and highly folded.

Bony Fish

Water flow is maintained by the up/down movement of the operculum.

As the mouth opens, the operculum rises and water moves in due to differences in pressure.

The mouth then closes, the operculum drops and water is pushed through the gills.

Bony Fish - Counter Current Flow

The movement of water flows in opposite direction to blood flow.

This maintains a concentration gradient for diffusion along the entire length of the gill lamellae.

This is called counter current flow.

Open Ended

Name one way that fish are specialised for obtaining oxygen absorbed in water.

Insects

Youtube video

Multiple Choice

Where does oxygen enter a bony insects body?

• Spiracles

• Lungs

• Trachea

• Bronchi

Open Ended

Explain how bony insects obtain oxygen from the environment.