What caused the amount of oxygen in the atmosphere to stabilize to the extent that it is today? a. oxygen was toxic to many of the organisms living at the time. b. carbon dioxide dissolved into the oceans, eventually forming carbonate rocks. c. carbon dioxide dissolved into the oceans and was eventually used in the formation of sea creatures' shells. d. the amount of oxygen consumed by respiratory organisms balanced the amount of oxygen produced by plants undergoing photosynthesis.

D. The amount of oxygen consumed by respiratory organisms balanced the amount of oxygen produced by plants undergoing photosynthesis.


There are a lot of created theories in which biologists engaged themselves to explain such phenomenon that occurred thousands of years ago, and experts say such study is hard to replicate, the start of prokaryote cells. Prokaryotes were said to be the first organisms that existed and were able to exhibit photosynthesis that produced oxygen that spread across the atmosphere. Hence, consider the Theory of Spontaneous formation of organic moleculeswhich suggests that the early earth had less to none oxygen. Thus, the atmosphere was abundant with the gases, CO2 and N2 with some other small amounts of H2, H2S, and CO. Hence, in Stanley Miller’s experiment when electrical sparks or “lightning” came in contact with these gases, the newly formed mixtures of CH4, NH3, and H2 were catalyzed. With these newly formed gases in interaction with H2O came the first synthesized some amino acids that compromised the earliest organic molecules which evolved to macromolecules, to be organelles of a cell. Which in the latter macromolecules are in today, maybe have been before the early nucleic acids (able to replicate) or proteins of these early cells. 

The correct answer is c.