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7. EVOLUTION, , Evolution is an orderly change from one form, to another., , Evolutionary Biology is the study of, evolutionary history of life forms., , ORIGIN OF LIFE, , - Big Bang Theory states that universe, originated about 20 billion years ago by a, singular huge explosion., , - The earth was formed about 4.5 billion years, ago., , - There was no atmosphere on early earth., Water vapour, CHy, COz & NH3 released from, , molten mass covered the surface., - The UV rays from the sun broke up water, into H) and Oy»., , - Oxygen combined with NH3 & CH, to form, water, CO, etc., , - The ozone layer was formed. As it cooled, the, water vapour fell as rain to form oceans., - Life appeared almost four billion years ago.
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s 2. - =, , , , THEORIES OF ORIGIN OF LIFE, , , , 1., , 2., , Theory of spontaneous’ generation, (Abiogenesis): It states that, life came out of, decaying and rotting matter like straw, mud, etc., , Louis Pasteur disproved this theory. He, demonstrated that life comes only from preexisting life., , He showed that life did not come from killed, yeast in a closed pre-sterilized flask. But in, an opened flask, life (microbes) appeared., , Biogenesis: Proposed by Francisco Redi,, Spallanzani & Louis Pasteur. It states that,, life originates from pre-existing life. But it, does not explain origin of first life., , Cosmic theory (Theory of Panspermia): It, states that, the units of life (spores) were, transferred to different planets including, earth., , Theory of special creation: It states that,, living things were created by some, supernatural power (God)., , Theory of chemical evolution: Proposed, by Oparin & Haldane. It states that, the first, form of life was originated from non-living, inorganic & organic molecules such as CHy,, , NHg, H20, sugars, proteins, nucleic acids etc., , i.e. “Abiogenesis first, but biogenesis ever, since”.
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Urey-Miller experiment, , , , , , , , , To vacuum, pump, , > Water oul, Condenser, <-- Water in, , Water droplets, , -———-Water containing, organic compounds, , Liquid water in trap
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- Harold Urey & _ Stanley’ Miller, experimentally proved theory of chemical, evolution. They created a condition like that, of primitive earth (i.e. high temperature,, volcanic storms, reducing atmosphere with, CHy, NH3, H20, Ho etc)., , - They made electric discharge in a closed flask, containing CH4, NH3, Hz and water vapour at, , 800° Cc. As a result, some amino acids are, formed., , - In similar experiments, others observed, formation of sugars, nitrogen bases, pigment, and fats., , First non-cellular forms of life originated 3, billion years ago. They were self-replicating, metabolic capsule containing RNA, proteins,, Polysaccharides etc.
