Summary:
Given our oxygen rich environment, it is hard to believe that the Earth originally had an oxygen-free atmosphere. Over billions of years, the oxygen content built up to a level where it can support the vast numbers organisms that live on Earth. Still, scientists are struggling to reconstruct the rise of oxygen. Recently, Dr. Canfield and his colleagues published ground-breaking work on this subject. Because rocks have chemical fingerprints left behind by ancient Earth’s atmosphere, the team is able to discover what the composition of early Earth’s air. For example, iron and oxygen bond to form rust. The more molecules that form in the presence of oxygen, the more abundant oxygen was at that time. However, when looking at the oldest rocks on Earth, they found no oxygen formed molecules. Despite the sun’s rays creating oxygen by breaking it off other molecules, oxygen quickly disappears. This is due to its ability to easily bond with a wide range of molecules. However, on the rocks that are about three billion years old, there is evidence of oxygen in their molecules. This is due to increased amount of photosynthetic microbes, which created more oxygen and less carbon dioxide. Nevertheless, there was an increase in oxygen-dependent life, therefore, the oxygen levels decreased again. Finally, since the continents moved, forming more deserts, there was less life and more oxygen.
Relevance:
This relates to our second unit about matter and energy and touches upon the subject of ecology. Oxygen is one of the most abundant elements in the Earth’s crust and atmosphere. Therefore, to think that there was virtually no oxygen in ancient Earth is mind-boggling. Even the smallest amount of oxygen made by the sun’s rays breaking it off other molecules quickly become bonded. This is due to its six valence electrons. This leaves two bonding sites for other molecules, thus creating a diverse range of combinations. The result of these bond are the molecules that the team looks for in the ancient rocks. Ecology played an important role in the increase/decrease of oxygen. Because the continents moved to latitudes where deserts formed instead of life-sustaining biomes. Therefore, there was an increase in oxygen, due to the decrease in oxygen breathing organisms. Because of matter, energy, and ecology, we are able to breathe highly oxygenated air.
You state that as the population of oxygen dependent life increases, the levels of oxygen in the atmosphere decreases. Do you think that rapid human population growth could drastically effect the levels of oxygen in the atmosphere to an extent where we may not have enough to support ourselves?
ReplyDeleteEventually, but it is dependent upon the amount of photosynthetic vegetation is left. According to http://sciencefocus.com/qa/how-many-trees-are-needed-provide-enough-oxygen-one-person it takes about 7-8 trees worth of oxygen, and because there would be less forest, therefore more land to farm, there would be less trees. Overall, there will be such a low amount of oxygen that we could not support ourselves, but it will not occur for a long time
DeleteDid they find the photosynthetic microbes in the rocks? How do they know the photosynthetic microbes were there, and how did they figure out the microbes were photosynthetic?
ReplyDelete