In your own words, describe how the evolution of photosynthetic organisms changed the compositions of the atmosphere and oceans.
Provide at least one example of evidence that proves this took place.
(2 points)
The evolution of photosynthetic organisms played a crucial role in changing the compositions of the atmosphere and oceans over time. Early photosynthetic organisms, such as cyanobacteria, started to produce oxygen through photosynthesis. This oxygenation of the atmosphere led to the Great Oxidation Event, which occurred around 2.4 billion years ago. This event significantly increased the levels of oxygen in the atmosphere, making it more suitable for aerobic organisms to thrive.
One piece of evidence that proves this evolution took place is the presence of banded iron formations (BIFs) in sedimentary rock layers. BIFs are rock formations that contain alternating layers of iron-rich minerals and silica, indicating a change in the composition of the oceans due to the increase in oxygen levels. The formation of BIFs is believed to have occurred around the same time as the Great Oxidation Event, providing strong evidence for the role of photosynthetic organisms in changing the compositions of the atmosphere and oceans.