summary of the three (3) current competing theories of the origin of life on Earth: It arrived from an extraterrestrial source; it originated as a heterotroph; it originated as an autotroph. Scientists to this day do not know how life came about on Earth. Yet, they continue to study many kinds of evidence and continue their research. At present there are three competing theories one how life on Earth came about. Life arrived here from an extraterrestrial source. Swedish scientist Svante Arrhenius popularized the idea of panspermia in the early nineties; the concept that life arose outside the Earth and that living things were transported to Earth to seed the planet with life. According to this passage, his theory does not explain
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According to the idea of many scientists, the first living things on the Earth were heterotrophs, which lived off organic molecules in the ocean. Evidence suggested that compounds were present in the oceans. However, because they existed before evidence of oxygen in the atmosphere, they would have been anaerobic organisms. Therefore, they could not have obtained the maximum amount of energy from the organic molecules in their environment. Due to a population increase caused by reproduction, this could have caused them to consume the supply of organic matter faster than it was being produced. Some of these heterotrophs were suspected of containing a mutated form of nucleic acid, which allowed tem to convert unusable material into a usable compound. Also, it was believe that with such mutation these organisms could have survived, where as those without it would have perished because the compound they used for food would have been insufficient. Given these mutations it was suggested that biochemical reactions could have taken place, making them able to use chemical reactions to convert raw chemicals into usable organic compounds thus adding to their metabolic process and an evolution of metabolic pathways.
It originated as an autotroph. The heterotroph hypothesis was the prevailing theory for the origin of living things for many years, until discoveries caused scientists to think otherwise. According to them the first organism was an autotroph