Describe how the evolution of photosynthesis changed the atmospheric and oceanic compositions. Provide one example of evidence that proves this event took place.
The evolution of photosynthesis played a significant role in changing the atmospheric and oceanic compositions of Earth. Before the evolution of photosynthesis, Earth's atmosphere was primarily made up of carbon dioxide and nitrogen, with only trace amounts of oxygen. However, as photosynthetic organisms such as cyanobacteria and algae evolved and began to use sunlight to convert carbon dioxide into oxygen and organic compounds, this process gradually increased the levels of oxygen in the atmosphere.
This rise in atmospheric oxygen had a profound impact on the composition of the oceans as well. As oxygen levels increased in the atmosphere, oxygen also began to dissolve into the oceans. This led to the oxidation of minerals in rocks and the formation of iron oxide deposits on the ocean floor. Over time, these processes gradually changed the chemistry of the oceans, leading to the formation of new minerals and impacting the diversity of marine life.
One example of evidence that proves the evolution of photosynthesis changed the atmospheric and oceanic compositions is the presence of banded iron formations in rocks dating back to the Precambrian era. These formations consist of alternating layers of iron-rich and silica-rich minerals, and are thought to have been formed as a result of the oxidation of iron in an oxygen-rich environment. The presence of these formations provides strong evidence that the evolution of photosynthesis led to increases in atmospheric oxygen levels, which in turn changed the chemistry of the oceans.