Which three processes contributed to reducing the level of carbon dioxide in the atmosphere when life evolved on Earth?

The correct choice highlights three significant processes that all played crucial roles in reducing atmospheric carbon dioxide as life evolved on Earth.

Photosynthesis is the primary process through which plants, algae, and some bacteria convert carbon dioxide from the atmosphere into organic matter, releasing oxygen as a byproduct. This process became increasingly prominent with the evolution of photosynthetic organisms, significantly lowering carbon dioxide levels and contributing to the development of an oxygen-rich atmosphere.

The formation of fossil fuels involves the accumulation of organic matter, typically from ancient plants and other living organisms. Over millions of years, this organic material is subjected to heat and pressure, transforming it into fossil fuels such as coal, oil, and natural gas. This process effectively sequesters carbon dioxide, as carbon that was once part of the atmosphere is locked away in these fossilized carbon sources.

The formation of sedimentary rocks happens as minerals and organic materials are deposited over time. Many sedimentary rocks contain carbonates, which are formed from carbon dioxide dissolved in water or from the decay of organisms. As these rocks are created, they can trap carbon, thereby removing it from the atmosphere.

Together, these processes contributed to a significant reduction in atmospheric carbon dioxide, fostering conditions conducive to the evolution of diverse life forms on Earth.