Describe the conditions that led to the creation of autotrophic cells. What affect did autotrophs have on the environmental conditions under which life first arose?
The earliest biological cells were heterotrophs that fed on organic compounds much as pre biological cells had done. These early cells probably made use of ATP as their energy source since adenine and, hence, ATP formed readily under the abiotic conditions of the early earth. As the supply of organic nutrients, such as ATP, declined and competition between organism increased, selection favored the organisms that were superior at obtaining or processing food or that could produce the needed nutrients from raw materials via enzymatic activity. Yet, if life had remained purely heterotrophic all nutrients, including ATP, would have been eventually used up because the organisms' metabolism released into the atmosphere, a gas from which the abiotic synthesis of organic nutrients was much more difficult than it had been from methane. The evolution of autotrophs' photosynthetic pathways which used the energy in sunlight to at first directly synthesize ATP and later to synthesize carbohydrates from and water meant that life did not go extinct as more and more of the free nutrients were used up. From this point, all life on earth depended on the photosynthetic activity of autotrophs as the base of the food chain. The released by photosynthesis ended the conditions under which abiotic synthesis of organic
