The branch of science that deals with living world is known as biology

The branch of science that deals with living world is known as biology. The animal biology, which deals with the science of animals, is termed as zoology, while plant biology is studied under the heading botany.

The study of ancient plants and animals together is grouped under the heading Palaeontology, which is an important branch of geology. For the systematic study of ancient plants and animals the branch paleontology is divided into palaeobotany that deals with the study of plant fossils, and palaeozoology, which is devoted to the study of remains of ancient animals.

A number of hypotheses have been proposed for the origin of the earth. It is postulated that at the start of the event, a huge mass of hot gases accumulated in the outer space, which gradually concentrated and solidified to give rise to the present solar family, with sun at the center, encircled by all the planets including our mother earth.

In due course of time, as the geological clock advanced, the earth from its hot gaseous state become a solid structure through a hot liquid phase and slowly cooled down to a stage when the temperature become congenial for the atmosphere to be separated into different layers along with the formation and accumulation of water.

As the environment became amiable for the sustenance of life on the earth, the living world (both plant and animal) initially originated in the small and large water bodies and gradually spread over and migrated to land and air space available on this earth.

A statistical account indicates that there are more than 350,000 types of plants and a little above 1,120,000 types of animals presently live on the surface of the earth, though quite a good number of them have perished forever during the past geological periods.

As we brood over, questions come to our mind as to how the living world originated? Whether all the types were created at one go? And when and how they come to live on this earth? To answer these questions, scientists through ages are engaged in the search for the truth.

According to the available scientific information, the living world originated long after the creation of the earth and only after the environment became congenial for them to live, some two to three thousand million years ago. At the beginning, the living bodies were very simple, primitive and unicellular in nature.

Gradually they differentiated into plants and animals and became more and more complicated and adapted to different ways of living. The number of different species gradually increased until they reached the enormous diversity of today.