Partial preview of the text
Download The human life and evolution and more Summaries Biology in PDF only on Docsity!
HAPTERT — 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 miverse originated about 20billion 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, CHs, COz& NH released from molten mass covered the surface, ~ The UV tays from the sum broke up water into Hy and Op. - Oxygen combined with NH3& CH, ta form water, CO; etc. - The ozone layer was formed. As il cooled, the water vapour fell as rain to form oceans. - Life appeared almost four billion years ago. Theories of origin of life 1. Theory of spontaneous generation (Abiogenesis): ltstates that, life came out of decaying and rotting matter like straw, mud etc. Louis Pasteur demonstrated that life comes only frompre-existing life and disproved this theory. He showed that in pre-sterilized flasks, life did not come from killed yeast. In another flask open to air, new living organisms arosc. 2. Biogenesis: Proposed-by Francisco Redi, Spallanzani &Louis Pasteur. It states that, life originates from | pre-existing life. 3. Cosmic theory (Theory of Panspermia); It states that,the units of life (spores) were transferred to different planets including earth. ‘4. Theory of special creation: It states that, living & non-living was created by some supernatural power (God). 3. Theory of chemical evolution: Proposed by Oparin & Haldane. It states that, the first form of life was originated is etc. from non-living inorganic & organic molecules such as CH., NHs, HO, sugars, proteins, nucleic acid ie. “Abiogenesis first, but biogenesis ever since”. — : STANLEY MILLER EXPERIMENT TO TEST CHEMICAL EVOLUTION OF LIFE , Harold Urey & Stanley Miller conducted an cxperiment toprove ‘ theory of chemical evolution. They created a condition similar tu that of primitive earth (i.¢. high temperature, volcanic storms, vevasuun reducing atmosphere containing CH4, NU, 1120, Th etc). Purp They made electric discharge in a closed flask containing : “ hy gate CH4, NHs, Ho and water vapour at 800° C. As a result, some amino acids are formed. >» Water out pom 2-4 Winter in In similar experiments, others observed formation of sugars, nitogen bases, pigment and Lats. First non-cellular form of life originated 3 billion ycars ago. Water droplets They were RNA, proteins, Polysaccharides etc. ‘Water contalatny, Botta ‘organise eauponnds Liquid water in way EVIDENCES FOR EVOLUTION 1. Paleontological evidences 86 EVOLUTION 
