Meaning of Evolution - Practice Questions & MCQ

• To understand the changes in flora and fauna that have occurred over millions of years on earth, we must have an understanding of the context of the origin of life, i.e., the evolution of the earth, of stars and indeed of the universe itself. 
• Evolutionary Biology is the study of the history of life forms on earth.
• The origin of life is considered a unique event in the history of the universe.
• The universe is very old – almost 20 billion years old. Huge clusters of galaxies comprise the universe. 
• Galaxies contain stars and clouds of gas and dust. Considering the size of the universe, the earth is indeed a speck. 

Ancient Theories of Origin of Life:

• Theory of special creation: According to this theory, life was created by a supernatural power.
• Theory of spontaneous generation or abiogenesis: According to this theory, life came out of decaying and rotting matter like straw, mud, etc.
  • Evidence against this theory:  Louis Pasteur by careful experimentation demonstrated that life comes only from pre-existing life. He showed that in pre-sterilized flasks, life did not come from killed yeast while in another flask open to the air, new living organisms arose from ‘killed yeast’. 
• Theory of panspermia: According to this theory, units of life called spores were transferred to different planets including earth.
• Theory of chemical evolution or Modern Theory: This was proposed by Oparin and Haldane that the first form of life could have come from pre-existing non-living organic molecules (e.g. RNA, protein, etc.) and that formation of life was preceded by chemical evolution, i.e., the formation of diverse organic molecules from inorganic constituents.