GENERAL GEOLOGY

Detailed explanation-1: -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.

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: -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-4: -Eventually, a simple form of bacteria developed that could live on energy from the Sun and carbon dioxide in the water, producing oxygen as a waste product. Thus, oxygen began to build up in the atmosphere, while the carbon dioxide levels continued to drop.

Detailed explanation-5: -And some evidence suggests cyanobacteria, the earliest photosynthetic organisms to release oxygen gas as a waste product-although not use it-may have arisen as early as 3.5 billion years ago.