Final answer:
Cyanobacteria gave rise to green plants and an oxygen-rich atmosphere and were capable of nitrogen fixation.
Step-by-step explanation:
The cyanobacteria, also known as blue-green algae, gave rise to green plants and an oxygen-rich atmosphere on Earth. They were able to convert solar energy into chemical energy through photosynthesis and released oxygen as a by-product. Cyanobacteria were also capable of nitrogen fixation, which is the process of converting atmospheric nitrogen into a form that plants can use.