EVOLUTION -BIOLOGY CLASS 12
TAARIKA MOHAN EVOLUTION COMPLETE NCERT COVERED 1.Origin of life is considered as unique event in the history of universe. 2. Universe is almost 20 billion years old. 3.Big bang theory gave an idea of origin of universe. 4.Earth is almost 4.5 billion years old. 5.Early earth : Had no atmosphere Was covered with CO2,CH4,water vapor and NH3. Had reducing atmosphere. O2 combined with NH3 and CH4 to form water. 6.Life appeared- After 500 million years of formation of earth i.e., almost 4 billion years ago. 7.Theory of panspermia: Early Greek thinkers+Astronomers Units of life called SPORES were transferred to different planets. 8.Theory of spontaneous generation-Life came out of rotting and decaying matter like straw and mud. This was disproved by LOIS PASTEUR. PASTEUR'S EXPERIMENT: Life comes only from pre-existing life. Pre-sterilized flask+killed yest+NO AIR=No life Pre-sterilized flask+killed yest+AIR=Life. Did not answer how first life form came on earth. 9.CHEMICAL EVOLUTION: Giv...
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