Autotrophic group generating the molecular oxygen of earth

Question

a) Explain the main means through which the autotrophic beings consume the energy?

b) Describe which autotrophic group is responsible for generation of the most part of the molecular oxygen of earth?

Answer 1

a) The main means through which the autotrophs acquire energy is photosynthesis. (There are known as the chemosynthetic autotrophs.)

Image Diversity: photosynthesis

b) Algae and cyanobacteria of phytoplankton are the organisms, which contribute most for generation of the molecular oxygen.

Image Diversity: phytoplankton