Respiratory Systems
Gaseous Exchange Systems
Gaseous exchange is the delivery of oxygen from the lungs to the bloodstream, and the elimination of of carbon dioxide from the bloodstream to the lungs.
Here is a diagram of a human's gaseous exchange system.
Now how a fish breathes in and out is different to how we breathe. Humans breathe through their mouth or nose, whereas fish breathe through gills. This diagram shows how gaseous exchange occurs in a fish.
Venn Diagram of the Similarities and Differences
Here are some differences and similarities between a fish and a human's respiratory system:
Why do fish have respiratory systems which are so different to humans?
The answer is simple, we have different habitats. Fish live under water and collect oxygen from the water. Humans live on land and we get oxygen from the air in the atmosphere. Humans can go underwater but we have to hold our breath. We can only hold our breathe for a certain period of time, unlike fish, they live under water and they breathe in it. We have to adjust our breathing system to go underwater but fish cannot, they do not have the ability to hold their breathe on land. So that gives you the answer that gills of fish can only be used underwater. Other animals can do both, they can breathe under water and breathe on land. So they can live on both dry and wet habitats.
How is the way that gases are exchanged in fish similar to that of the human respiratory system?
It has a minor similarity because the breathing system is so different to each other. The only similarity is that both fish and humans breathe in oxygen from their mouth, humans can also breathe through their nose.