Question

The earliest oxygenic phototrophs are thought to be A. purple sulfur bacteria.B. green nonsulfur bacteria.C. purple nonsulfur bacteria.D. cyanobacteria.E. green nonsulfur bacteria AND purple nonsulfur bacteria.

Answer 1

Option (D).

Step-by-step explanation:

Cyanobacteria (also known as blue-green algae) represent a group of bacteria which make their food by the process of photosynthesis, during which they use carbon dioxide and release oxygen.

Due to their ability to produce oxygen as a byproduct of photosynthesis, Cyanobacteria are thought to be the earliest oxygenic phototrophs that changed the early low-oxygen atmosphere (reducing atmosphere) into an oxidizing atmosphere. It led to change in Earth's living forms and evolution.

Thus, the correct answer is option (D).