PPT On MICROBIAL EVOLUTION, SYSTEMATIC AND TAXONOMY
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2. The Origin and Evolution of Life Life originated more than 3.8 billion years ago All of the compounds necessary for life could have formed spontaneously under conditions that existed on the early Earth The history of life spans five intervals of geologic time
3. Conditions on the Early Earth
4.5 billion years ago “Cloud” began to condense 4 billion years ago Crust and mantle formed Primitive atmosphere H2, N2, CO, CO2 , probably no O2 Hot temperatures
4. STROMOLITES
Stromatolites (3.5 bill. Yr) Rocks with distinctive layer structure Look identical to living mats of microbes Layers of microbes and sediment Top layer uses photosynthesis Lower layers use top layer’s byproducts
5. Early Evolution and Rise of O2
First organisms had simple metabolism Atmosphere was O2 free, must have been anaerobic Probably chemoheterotrophs Obtained nutrients from organic material Obtained nutrients from inorganic material Modern archaea appear to be close to the root of the tree of life Obtaining energy from chemical reactions involving hydrogen, sulfur and iron compounds (all abundant on early Earth)
6. Early Evolution
Natural selection probably resulted in rapid diversification Modern DNA has enzymes that reduce the rate of mutations RNA is not so lucky, more likely to have copying errors Higher mutation rate in early evolution than now
7. Photosynthesis
Most important new metabolic process evolved gradually Organisms that lived close to ocean surface probably developed means of absorbing sunlight (UV in particular) Once absorbed, developed method of turning it into energy Modern organisms of purple sulfur bacteria and green sulfur bacteria much like early photosynthetic microbes, use H2S instead of H2O for photosynthesis
8. For more Please Refer Our PPT. Thanks.
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Presentation Transcript:
1. MICROBIAL EVOLUTION, SYSTEMATICS AND TAXONOMY2. The Origin and Evolution of Life Life originated more than 3.8 billion years ago All of the compounds necessary for life could have formed spontaneously under conditions that existed on the early Earth The history of life spans five intervals of geologic time
3. Conditions on the Early Earth
4.5 billion years ago “Cloud” began to condense 4 billion years ago Crust and mantle formed Primitive atmosphere H2, N2, CO, CO2 , probably no O2 Hot temperatures
4. STROMOLITES
Stromatolites (3.5 bill. Yr) Rocks with distinctive layer structure Look identical to living mats of microbes Layers of microbes and sediment Top layer uses photosynthesis Lower layers use top layer’s byproducts
5. Early Evolution and Rise of O2
First organisms had simple metabolism Atmosphere was O2 free, must have been anaerobic Probably chemoheterotrophs Obtained nutrients from organic material Obtained nutrients from inorganic material Modern archaea appear to be close to the root of the tree of life Obtaining energy from chemical reactions involving hydrogen, sulfur and iron compounds (all abundant on early Earth)
6. Early Evolution
Natural selection probably resulted in rapid diversification Modern DNA has enzymes that reduce the rate of mutations RNA is not so lucky, more likely to have copying errors Higher mutation rate in early evolution than now
7. Photosynthesis
Most important new metabolic process evolved gradually Organisms that lived close to ocean surface probably developed means of absorbing sunlight (UV in particular) Once absorbed, developed method of turning it into energy Modern organisms of purple sulfur bacteria and green sulfur bacteria much like early photosynthetic microbes, use H2S instead of H2O for photosynthesis
8. For more Please Refer Our PPT. Thanks.
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