eliciamcnally to Hannah, Ian, Jono, Mark on 26 Jun 2013.
Hannah Brotherton answered on 26 Jun 2013:
This is just evolution. Fish have found a role in the ocean, where they are predators or they are prey, and there is a whole world down their that we don’t know about. By having fish, we have ecosystems down there which affects the oceans – how acidic they are and how much oxygen and air there is down there (yes there is oxygen in water 😛 ). We don’t need to be living underwater, because we wouldn’t contribute anymore than fish would. Fish have evolved to be perfect for the ocean, because the best of the best survived and adapted when things changed and their traits are now the best for living in the water – like gills and fins.
But why do we have flying fish????? I have no idea lol 😛 I didn’t think fish needed to fly
But evolution still happens now, so maybe one day if we have more mammals on land becoming extinct, something needs to take it place (because everything has a role on this earth). So maybe a fish will evolve to just peep out of the water see there’s a new job on the land and only those that could hold their breath or move across the land would eventually evolve to become land animals.
Mark Hodson answered on 26 Jun 2013:
it’s to do with how we breathe.
Our lungs would fill with water underwater and we wouldn’t get oxygen out of the wwater fast enough so we’d suffocate. Fish can’t live on land as their gills (their equivalent to lungs) collapse if they are not wet and then they don’t work properly.
Jono Bone answered on 26 Jun 2013:
Like us fish make energy by breathing oxygen and eating food. We also both need to get rid of carbon dioxide as a waste product. Lungs and gills are just different ways of swapping the good oxygen for the bad carbon dioxide. Lungs are specially designed for animals living on land, while gills are specially designed for animals living under water. Like Hannah said its evolution that has determined weather an animal evolved lungs.
Apparently flying fish fly do avoid predators like dolphins. They can’t breath out of the water though. Also amphibians (e.g. frogs, newts) can breathe both in and out of water!
Ian Wilson answered on 26 Jun 2013:
As the others have said, this is all down to the organs we use to breathe. We breathe through lungs, which are designed to take in air. Blood capillaries cover the inner surfaces of the lungs and the oxygen from the air diffuses into the blood. If we were to live underwater, we’d breathe in water, which would block our lungs and stop us from getting any oxygen. We’d drown and die 🙁
Unless we had diver’s suits on but I’m not sure that’s what you were getting at… 😛
On the other hand, fish breathe through gills. They drink in water and pass it through their gills. Inside the gills, the oxygen in the water diffuses into the blood. Fish can take up to 70% of the oxygen out of water!
The gills are kind of like our lungs but they’re designed to filter oxygen from water, whereas our lungs aren’t. It’s simply that we’ve evolved differently and so need to get our oxygen from different places.
Hope that helps,