Gas Exchange in Animals.

Fish

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.

Insects

• 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.

Tadpoles and Frogs

Tadpoles: Have gills covering their bodies.

Frogs:

• 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.