NEET BIOLOGY

Detailed explanation-1: -The answer is tiny organisms known as cyanobacteria, or blue-green algae. These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and, yes, oxygen.

Detailed explanation-2: -These microbes possessed the remarkable ability to perform photosynthesis, (i.e., they could generate energy from sunlight). Cyanobacteria possessed the machinery to utilize water as a fuel source by oxidizing it. More significantly, the by-product of photosynthesis happened to be oxygen.

Detailed explanation-3: -Cyanobacteria, formerly known as blue-green algae, are photosynthetic microscopic organisms that are technically bacteria. They were originally called blue-green algae because dense growths often turn the water green, blue-green or brownish-green.

Detailed explanation-4: -Cyanobacteria played an important role in the evolution of Early Earth and the biosphere. They are responsible for the oxygenation of the atmosphere and oceans since the Great Oxidation Event around 2.4 Ga, debatably earlier.

Detailed explanation-5: -Before about 2.4 billion years ago, Earth was a virtually oxygen-free environment. The appearance of cyanobacteria, or blue-green algae, changed all that. Cyanobacteria injected the atmosphere with oxygen, setting the scene for the development of complex life as we know it.