Fish live in the water and breathe by absorbing oxygen through their gills. Fish are cold-blooded animals, so their internal body temperature is influenced by the environment. Many fish have scales and use their fins to swim. Fish have a spine but do not have external ears or eyelids. Fish also have air bladders, which keep them afloat.Continue Reading
A fish's gills are special organs which contain thousands of small blood vessels called capillaries. The gills constantly filter oxygen out of water and into the fish's bloodstream. Gills are also useful for excreting waste from the fish's bloodstream. Some fish, such as sharks, have multiple gill openings.
Fish have sharp or smooth scales that protect the fish from injury. Fish create a mucous covering over the scales, which helps protect against infection by trapping bacteria and keeping it from entering the fish's body. This mucous also reduces friction, which helps the fish easily swim through the water.
According to the International Union for Conservation for Nature, about 800 species of fish live in the United States and there are 30,000 species worldwide. Scientists believe that thousands of fish species have not been identified. Fish are a more diverse species than any other group of vertebraes.Learn more about Fish
Fish have gills because these organs are used to extract oxygen from the surrounding water in which a fish lives. Gills are different from lungs because gills generally work unidirectionally: water moves in one direction across the gills in order for the organs to extract oxygen.Full Answer >
Fish gills act as the equivalent of a mammal's lungs by taking in oxygen and releasing carbon dioxide. Oxygen and carbon dioxide travel across small, thin-walled blood vessels in both lungs and gills. In terms of evolution, gills are significantly older than lungs.Full Answer >
By definition, fish are animals that live in water, have gills and lack limbs. They are also chordates, which means they have a backbone-like structure that provides support for the body and acts as an anchor for the major muscles.Full Answer >
Fish can drown in water if there is not enough oxygen in the water. Water can run out of oxygen if fish overpopulation uses up the oxygen. Fish require a consistent intake of oxygen to survive. Their gills absorb oxygen from water molecules as water passes through the gill membranes.Full Answer >