Theory of Chemical/Biochemical evolution/Modern theory of the origin of life/Operin-Haldane theory of the origin of life/ Materialistic Theory or Physico-chemical (Part -3)
F) Formation of colloids, co-acervates (protobionts or pre cells) or origin of primitive cell: The complex organic compounds of primordial soup in ocean aggregated together forming colloidal mass which was surrounded or bounded by water layer was called coacervates. They can grow by absorbing nutrients. Oparin called these aggregates as coacervates while Sidney fox called them Protenoids or Microspheres. The nucleic acid controlled the activities of coacervate and the fats formed a layer around it and showed a great affinity to water. This structure is called Eobiont. Some of the proteins within coacervates acted as enzymes and began metabolic activities.
G) Origin of the first cell (Prokaryote): Coacervates may produce the first cell-like structure. The first cell-like structure with the power of division is called Eobiont or Pre-cell. Oparin considered that the coacervates with nucleoprotein gave rise to primitive cells or Eobionts. Oparin also called it as protobiont. The eobiont absorbed food materials from the surrounding. In this way, the first prokaryotic, unicellular, heterotrophs, anaerobic organisms (present-day bacteria) evolved. It was similar to coccoid bacteria. This was a significant step in the transformation of pre cells into cells.
H) Origin of Heterotrophs and Autotrophs: The first cell or primitive cells were marine and heterotrophic in nature. The growth and multiplication of these cells caused depletion of food and an increase in CO2 due to fermentation. Later on, some of the eobionts became able to make food by using chemical energy. So they became chemoautotroph.
CO2+H2S → C6H12O6 + H2O + S
Some other eobionts developed chlorophyll molecules, which trapped solar energy to manufacture food from CO2 and H2O. They became photoautotrophs.
CO2+H2S → C2 H12O6 + H2O + O2
In this way, photosynthetic organisms were originated on the earth. This event helped to transform heterotrophs into autotrophs. Due to the release of oxygen as a byproduct of photosynthesis, the primitive reducing atmosphere was slowly and gradually converted into the oxidizing atmosphere. On other hand, the heterotrophs modified and different types of animals evolved. They started to consume autotrophs and used O2 to break down food material to release energy.
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