2DEVELOPED BY :Dr. SAROJ JAINMs.CHANDRABOLI GHORAI
3LEARNING OBJECTIVESAfter viewing this presentation, the student will be able to:Visualize history of origin of lifeDescribe various steps of origin of lifeUnderstand molecular level of organization of cells i.e. how atoms constitute living cellsCorrelate the phases of chemosynthetic theory with the biosynthetic processes occurring in living cellsDefine chemosynthesis and coacervates
4CHEMOSYNTHETIC THEORY Scientists believe that life might have originated on earth from non-living matter through a series of chemical reactions.It all happened 3600 m.years ago in water.This theory was strongly supported by research conducted by Stanley Miller.
5STAGES OF CHEMOSYNTHESIS Formation of simple organic compounds.Formation of major organic macromolecules.Formation of cell-like aggregates called coacervates.Coacervates become more organized with use nucleic acids.Beginning of evolutionary development.Appearance of autotrophic bacteria.
6CONDITIONS ON PRIMITIVE EARTH Atmosphere contained methane,ammonia, hydrogen gas and water vapors but NO FREE OXYGEN.Earth was volcanically active .Oceans were a ‘primordial soup’ of ammonia, phosphate,nitrogen and carbon.Earth was exposed to UV light and radiations.There was torrential rains for many years..
10FORMATION O F COMPLEX ORGANIC MOLECULES Peptide Fragment
11DNACOACERVATESRNAAIn the warm primordial ocean, aggregates of amino acids, proteins, and other hydrocarbons came together into a form called *coacervates*. Amino acids will spontaneously form coacervates in the same way that beads of vinegar in oil come together.
12Coacervates superficially resemble cells Lipid and protein membraneSelectively permeableAble to absorb compounds from the environmentChemical reactions may take place inside“Reproduce” by splitting when they get large
13First living cellsPhotoautotrophsCyanobacteriaArchaebacteria
14MILLER--UREY EXPERIMENT 1n 1953, a University of Chicago graduate student named Stanley Miller working in Harold Urey's lab flipped a switch sending electric current through a chamber containing a combination of methane, ammonia, hydrogen and water. The experiment yielded organic compounds including amino acids, the building blocks of life, and catapulted a field of study known as exobiology into the headlines. Since that time a new understanding of the workings of RNA and DNA, have increased the scope of the subject. Moreover, the discovery of prebiotic conditions on other planets and the announcement of a bacterial fossil originating on Mars has brought new attention to the study of life's originsMILLER--UREYEXPERIMENT
15CAN YOU ANSWER THESE: When and where did life originate on earth? Define ‘coacervates’?Why is chemo synthetic origin of life not possible today?What is a ‘peptide bond’?How do dietary amino acids get transformed into proteins?
16Acknowledgements NCERT Text book-XI MS ENCARTA Special thanks to Mr. V.K.Sodhi,Senior Lecturer,SCERT