The flow of energy through different organisms is often represented as a food pyramid or a food web. Both of these diagrams can show a wide range of organisms from microscopic algae to blue whales.

Why are photosynthetic organisms considered to be the first level of the food pyramid?

AThey are the smallest organisms.
BThere are so many animals that eat them.

Eliminate

CThere are more of them than anything else.
DThey harness the energy from the sun and convert it to a useable form.

Photosynthetic organisms are called "photoautotrophic", but not all organisms that use light as photosynthesis of an energy source effect, since "photoheterotrophic" use organic compounds, not carbon dioxide, as a carbon source. In plants, algae and cyanobacteria, photosynthesis uses carbon dioxide and water, releasing oxygen as waste.

Photosynthesis is crucial for life on Earth because, in addition to maintaining the normal level of oxygen in the atmosphere, almost all life forms depend directly as a source of energy, or indirectly as a supreme source of energy in their food.