Evolution and Decline of Oxygen on Earth

We all know that almost all living things need oxygen. They use oxygen during the process of creating energy in living cells. Oxygen is produced during the process of photosynthesis by the green plants. Most of the oxygen present in the atmosphere is produced by phytoplankton photosynthesis.

Phytoplankton is microscopic organisms that live in watery environments, both salty and fresh. Like land plants, phytoplankton has chlorophyll to capture sunlight, and they use photosynthesis to turn it into chemical energy. They consume carbon dioxide and release oxygen. The rest of the oxygen is produced by land plants such as herbs, shrubs, trees, and even grass.

Oxygen Evolution:

Do you know if there was any oxygen at the time of the earth’s formation? Now, you might have an infinity of questions sprawling your head, so let us go back a billion years and explore the early atmosphere. Geologists believe that at the time of the evolution of the earth, the atmosphere had begun to form by the gases released by volcanic eruptions, and the first billion years of earth had intense volcanic activity, consequently, the early atmosphere was covered with carbon dioxide and had little or no oxygen at all. Few other researchers claim that oxygen may have even disappeared from the atmosphere around 1.9 billion years ago. The fact is that oxygen happened to form only 2.33 billion years ago. It took billions of years for its airspace to form. 

Carboniferous Period:

Some 300 million years ago, Earth which was nearly devoid of oxygen took a leap to become a planet that had an abundance of oxygen. The oxygen level had peaked to a whopping 35% percent! Due to increased oxygen level all animals and insects became gigantic, they were thrice the size of present times.  

Multiple reasons led to the increased oxygen level on the earth; the most prominent ones being, biodiversification, the abundance of dense and matured forest areas. Additionally, aquatic plants covered the water bodies that contributed to oxygen production. Several pieces of researches indicate that stromatolites were largely responsible for increasing the amount of oxygen in the primeval Earth’s atmosphere through their continuing photosynthesis. Stromatolites conducted photosynthesis to breathe and released Oxygen as a by-product.

However, over the last 95 million years, the oxygen level has been continuously decreasing and has reached down to 21 percent. The oxygen level has been globally reducing due to the increased fossil fuel burning, the amount of reduction in the green cover on land, and increased carbon footprint.

Impact of reducing Oxygen:

Reducing Oxygen can adversely impact the global climate, it thins the atmosphere, allowing more sunlight to pass through. More sunlight leads to more water being evaporated from the Earth’s surface, which increases the level of humidity in the atmosphere. Because water vapor is a greenhouse gas, more heat gets trapped near Earth’s surface, and temperatures rise. The increased humidity and temperature also lead to increases in precipitation. On the other hand, when oxygen levels are higher, the atmosphere gets thicker and allowing less sunlight to pass through. As a result, there is less water vapor to trap heat.
If the oxygen level continues to decrease, it would take millions of years for it to form again. Oxygen is vital for the survival of all living beings and even organisms. It is crucial to understand that there is no life without oxygen. So, let us all together try to bring a change to the world! 

Interesting Fact- Did you know that blue-green algae became the first microbes to produce oxygen by the process of photosynthesis.

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