evolution and ties its origin to the history of the earth and the pn atmosphere. 

How did it happen and what evidence supports this idea?

In the beginning, the universe was an intensely hot point whegematter and energy were indistinguishable. About 15 billion year agb there was a Big Bang (huge explosion). The universe started expandige and the temperature dropped drastically. In time, about 4.6 billion yey ago our earth and other planets appeared as part of the solar system. Primitive atmosphere of the earth was rich in Hydrogen. Soon gases fra the very hot and liquid core of the earth added more elements to atmosphere. It is believed that the earth’s atmosphere at this stay consisted carbon monoxide, carbon dioxide, Hydrogen, Nitrogen, wat, - vapours and was exposed to intense radiation and electric spark., - hardly had any free oxygen. With the passage of time, the atmospher,temperature gradually dropped. This allowed condensation and hea, rains which caused formation of oceans. Thunder and lightning spare together with ultraviolet radiation caused reactions of the atmosphety gases. This led to formation of simple organic molecules. These molecuke came down with rain and accumulated in the oceans, lakes, rivers ah: the soil over a very long period of time. These molecules had enoufa chances to interact in this environment and produce amino acids a! proteins which are the building blocks of life. This sequence of chemi evolution was demonstrated in the middle of the 20th century by soi, clever laboratory experiments. Scientists were able to produce ami acids and simple sugars from a mixture of methane, ammonia, hydrog and water by exposing it to electric sparks. More recent experimedi using electric sparks in laboratory chambers have successfully produ not only amino acids and sugar but also the basic ingredients of fe! substances and DNA, all of which are the constituents of life. 

Life originated on earth more than 3.5 billion years ago. We do not know how life formed, although the evidence is consistent with the hypothesis that it evolved spontaneously from chemicals. There is considerable discussion among biologists about what the early stages of such an evolutionary process might have been like. 

What was the first life form like? The first life form, perhaps, W sphere of naked protein or RNA and was capable of making its cof (reproduction). At some stage, a membrane assembled around the sp giving nse to the first cell. There is now general agreement that this firs form respired anaerobically because the earth’s atmosphere lacked oxygen; it reproduced asexually. Our present day knowledge of — pacteria and how DNA makes its copies provide enough hints in ges 2 the above view. The first living organism may have been like