Respuesta :
Answer:
Oparin and Haldane proposed that first life form originated from non-living molecules like proteins or RNA. Some scientists believed in the RNA world i.e. RNA as first macro molecules during evolution.
Explanation:
Oparin and Hadane suggested that the first form of life could have come from pre-existing non-living molecule such as protein or RNA. So formation of life form was preceded by chemical evolution represented as follows:
Free atoms -> simple inorganic molecules -> first simple organic molecules -> simple organic compounds -> complex organic compounds (like RNA, DNA, proteins) -> first life form
Two important protobionts (precursors of life) are coacervates and microspheres. Coacervates are mixture of proteins and polysaccharides. Microspheres are mixture of artificial organic compounds mxed with cool water.
RNA world: Since RNA can act as enzyme to assemble new RNA molecules on an RNA template, some scientists thought that coacervates may not be the precursor of life forms but RNA molecules were the first macro molecules and the initial steps on the evolutionary line for formation of more complex molecules.
The first living organism originated among organic molecules and in reducing atmosphere. Since there was no free oxygen in the atmosphere they were anaerobic and the organic molecules was the food source, thus they were heterotrophs. When the organic molecules exhausted autotrophs evolved from hetertrophs. These organism prepared their own organic molecules either by chemosynthesis or photosynthesis.
