Fish have gills:
- these are made up of thin layers of tissue.
- the layers are thin so thay there's only a short distance for gases to difuse across.
- gills are contained in a special gill cavity.
- water is pumped over the gills constantly.
Gills don't work in air, as without water they stick together.
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- Transport gases via tubes called tracheae or tracheal tubes.
- Air gets to the tracheae through spiracles, which open when the insect needs oxygen, and close when they don't.
- The tracheae have a moist lining, which the gases can diffuse though into the tissues.
- There is no blood supply, but air is constantly pumped though.
- The tracheae have a large surface area tand come into close contact with individual cells to make them very effective at gas exchange.
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Tadpoles and Frogs
Tadpoles: Have gills covering their bodies.
- Tadpoles undergo metamorphasis.
- exchange gases in both water and air.Adukt frogs can exchange gases in both water and air.
- gas exchange takes place through the skin, which is very moist, and has a rich blood supply to aud the diffusion.Most gas exchange takes place through the skin, which is very moist, and has a rich blood supply to aud the diffusion.
- simple pair of lungs for when it is on land.Frogs also have a very simple pair of lungs for when it is on land.
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