Question

How was oxygen added to the atmosphere?

Answer 1

Millions of years ago, there was no oxygen in the earth and the atmosphere was reducing in nature. Later in due course of evolution various organisms developed who were responsible for the release of the oxygen in the atmosphere.

Complete step-by-step answer:
Very primitive photoautotrophs were responsible for carrying out the process of photosynthesis, but they were noy having any biochemical pathway to produce oxygen in the environment. At a later stage, oxygen releasing photosynthetic organisms developed. These were like the existing blue green algae called cyanobacteria. They used water to get hydrogen and release the oxygen gas in the atmosphere.
We should however remember that addition of oxygen to the atmosphere started oxidizing the methane and ammonia, which began to gradually disappear.

According to the great scientist David Biello the production of oxygen by the cyanobacteria took millions of years and the process involved was a complex process. Thus, we can say that it was cyanobacteria who firstly added oxygen in the reducing environment. Later and even in today’s world we know that plants are the major contributor of oxygen in the atmosphere. For example, Amazon forests are termed as lungs of the earth as they contribute nearly forty percent of oxygen in the atmosphere. We have learned in the junior classes that plants add oxygen in the environment during the process of photosynthesis, through which plants produce their own food.

Note: We should note that for the surplus release of oxygen in the environment, the products of photosynthesis should not be oxidized. This is the major concern of today’s world as increasing pollution, deforestation, mining etc. have disturbed this self-sustaining balance.