PPT On MICROBIAL EVOLUTION, SYSTEMATIC AND TAXONOMY
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1. MICROBIAL EVOLUTION, SYSTEMATICS AND TAXONOMY
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.
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