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How Fish Breathe
Evolution theory says that first of all life began in water. So millions of years before man cameon earth, fish were already breadthing in the water. Fish, are the first backboned animals that existed on the earth.
Gradually, fish developed into different kinds as the type of water and environment demanded. That is why, now it’s hard or almost impossible to find the most primitive fish of the oceans.
Fish have a long tail that it uses as a power engine and with the help of which it guides itself. All fish breathe through their gills except the “lungfish”. A fish takes water in its mouth, the water goes to the gills and flows out of the opening behind the gills. Gills take oxygen out of water as we breathe oxygen out of air and uses it to purify its blood. If the water becomes polluted, fish comes at the top of water level to takeout oxygen from the air. But it can’t do this frequently because its gills do not have the capacity for using oxygen in the air.
Although fish have an extraordinary sense of touch and taste, but they have a nervous system just like any other animal. The blood of fish is cold. Ficanalso smell and hear. They have ears, which are inside their head and therefore are called ‘internal ears’.
The colour of fish’s skin is also very important for their survival and protection from enemies. They are usually dark on the top and light underneath. If we see them from the ground they look dark-just like the ocean or river bed. But seen from the depth of waters, they look light in colour, just like water. With such a trait, they can swim around safely, to an extent, confusing their enemies whether it’s mere water of fish swimming in it!.
One thing more there are several types of fish, indicating the several ways in which they survive. Till now man has found 20,000 different kinds of fish.