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EVOLUTION

Biology

Evolution of life can be defined as the gradual changes in the genetic material and appearance of living organisms.

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Evolutionary biology is the study of history of life forms on earth.

Evolution of life can be defined as the gradual changes in the genetic material and appearance of living organisms.

 

Origin of life - Origin of the universe

  • The universe is very old almost 20 billion years old comprise of huge clusters of galaxies.

  • Galaxies contain stars and the clouds of gases and dust.

  • The origin of universe is explained by the Big Bang Theory. According to this theory, a huge explosion occurred, the universe expanded, temperature came down and hydrogen and helium were formed later. The galaxies were then formed due to condensation of gases under gravitation.

 

Origin of earth

  • In the solar system of the Milky Way galaxy, earth was supposed to have been formed about 4.5 billion years back.

  • Initially, the earth surface was covered with water vapour, methane (CH4), carbon dioxide (CO2) and ammonia (NH3).

  • The UV rays of the sun broke water into hydrogen and oxygen.

  • Hydrogen escaped and oxygen combined with NH3 and CH4 to form water, CO2 and other gases, also forming the ozone layer.

  • Cooling of water vapour led to rain which filled the depressions on earth's surface, forming water bodies like oceans.