AP BIOLOGY

Detailed explanation-1: -The answer is tiny organisms known as cyanobacteria, or blue-green algae.

Detailed explanation-2: -Dutch-born British physician and scientist Jan Ingenhousz is best known for the discovery of the process of photosynthesis, by which green plants in sunlight absorb carbon dioxide and release oxygen.

Detailed explanation-3: -Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.

Detailed explanation-4: -The rise in oxygen is attributed to photosynthesis by cyanobacteria, which are thought to have evolved as early as 3.5 billion years ago.