For photosynthetic organisms to evolve and become more abundant than chemosynthetic organisms, what variable must have changed i
n the environment of ancient earth? carbon dioxide must have become more abundant. nitrogen must have become more abundant in the atmosphere. oxygen must have become more abundant. endosymbiosis needed to occur between a smaller prokaryote and a larger prokaryote.
The evolution of organisms are based on the resources available in order for it to be capable of growth still. In the given choices above, the substance or chemical that changed over time is the supply of carbon dioxide which is an essential substance for photosynthesis. Thus, the answer the first choice.
