The Big Bang Theory
Evolution of life on earth has not been a simple process. Before we talk about the origin of life on earth, we need to know about the origin of the earth which supports life on earth. There are different theories about the origin of earth and life. But, the strongest theory that exists is the big bang theory. This theory of evolution tries to explain how the earth came into being and how it evolved into this living condition that we are in today. It suggests how the universe formed from a massive explosion 20 billion years ago. Origin of the earth took place long after this explosion; somewhere around 4.5 billion years ago.
Evolution of Life
Once earth originated, it grew, and the living conditions like the climate, and atmosphere stabilized. Condensation of gases took place giving rise to modern-day galaxies. The early earth had no proper atmosphere. The atmosphere back then consisted of ammonia, methane, carbon dioxide and water vapor. The climate of the atmosphere was extremely high. The UV rays broke up the water molecules into hydrogen and oxygen molecules. Gradually the temperature came down and the water vapor condensed to form rain. The rains filled up all the depressions to form the water bodies. The ammonia and methane in the atmosphere also combine with oxygen and converted into carbon dioxide and other gases.
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