While the oceans provided the most conducive atmosphere for the occurrence of life, the dry lands offered further opportunities for growth and development. In the process of evolution, the movement of animals from the oceans to land was an important milestone.
In the earliest stages of life on earth, organisms lived only in the sea. Single-celled organisms gradually developed into multi-celled organisms. The first forms of plant life were algae, lichens and mosses. These plants provided food for the early forms of animal life in the sea.
In the course of time, in fact, millions of years, new forms of plant life developed. These new plants were more complex. They had some new features such as roots, stems and leaves, which made it possible for them to survive on land as well. Giant horse-tail plants and tree ferns started growing on land, mostly in wet, swampy areas on land.
When there was food available on land as well, animal life gradually began to evolve in order to survive on land. The availability of food was an important factor in the movement of animals to land. The first animals to move to land were probably worms and other soft-bodied invertebrates. They were followed by certain fishes that developed limbs to crawl and lungs for breathing. Reptiles that could live on both land and water came next. Such animals, as you know, are called amphibians.
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