Scientists have been thinking about the origin of nature. There are different theories about the origin of the Earth. Among these the commonly acceptable theory explains that a part of the Sun or a similar star got detached as a result of the attraction of another star. The planets including the Earth and then satellites have been created from the detached part of the sun.
According to this theory at the beginning the Earth was in a hot, gaseous state Subsequently the Earth gradually cooled and condensed to form the Earth as it is now. The core of the Earth is still in an extremely hot liquid and gaseous state. Nature of the Earth at the primary stage was not at all suitable for inhabitation of life. Gradually it became favourable for the existence of living forms. Now a question may arise in your mind as to how life originates in nature. Did plants and animals exist in nature from the very beginning?
There are different theories regarding the origin of life on the Earth. In the beginning of this chapter we have described an old concept of the origin of life But the theory presented by Oparin, a Russian scientist, about the origin of life is still accepted.
According to the theory of Oparin nature was quite hot when life was created Different gases such as ammonia (NH3), hydrogen (H2), methane (CH4) hydrogen cyanine (HCN) etc. were present in the atmosphere. During that period there was heavy rainfall and thunderstorm. Under such environmental condition amino acids were formed by the interaction of various gases and these amino acids are considered by scientists to be the first molecule of life The first cell or life came into being through incorporation of amino acids. It is also believed that life was created first in the primitive aquatic environment.