Probably the first living things when the earth cooled down were soft jelly- like substance. They were without any shell or bones, and lived in the sea. We have no fossil remains of those because they had no bones and so we have to guess ore or less. There are many jellies –like things like these in the sea even today. They are round but their shape is continually changing as they have no bone or shell. The spot in the center, it is called the nucleus which is a kind of heart. These animals, or whatever they are, have a curious way of diving and becoming two. They start getting thinner at one place and go on doing so still they break off into two jellies– like things. Both of these are just like the original one. You will see that the nucleus or the heart also divides and each part gets a bit of it. In this way, these animals go on diving and increasing
The first living things on this earth of ours must have been something of this very kind. What a simple from of life it was! There was nothing better or higher on the whole earth then. The real animals had not come as yet and man was to come million of years later.
These jelly-like things were followed by worms and shellfish and crabs. Then fishes came. We know a lot about these as they had bony parts or shells. When they died, their shells were left in the mud on the sea –floor. They were covered up by fresh mud and sand. A time passed, the mud became hard because of the pressure of sand and mud on top of it. It got so hard that it became a rock. In this way rocks were formed at the bottom of the sea. An earthquake or something else brought out the rock from under the sea and it became dry land. Then this dry land washed away by rain and rivers, and the shells which had been hidden in it for ages and ages came out. After studying them we can find out what kind of things lived on our earth before man came.
We have seen that the first living things on our earth had home in the sea. They could live only in water they came out and dried up, they died at once as the jellyfish dies today if it is left on the beach and dries up. But those jellyfishes and other sea animals which had tougher skins could stay a little longer on dry land. They did not dry up soon. So gradually the soft jellyfishes became fewer and fewer as they could not face dry land easily. Those with harder coverings became more and more in number.
Animals which changes and fit in with their surroundings have a better chance of living. So they go on increasing in numbers while the other does not. It shows how the simple animals slowly developed into higher kind of animals. Then in millions of years they developed into man. Ewe cannot see such changes going on around us as they are very slow and our lives are so short. But nature goes on working and making things more and more perfect. In never stops or takes rest.