This is an example of vestigial structure.
Vestigial structures are structures (cells, tissues and organs) found in an organism that has lost most or all of its primitive function through evolution. The vestigial structure has performed vital functions in the organism in the past but as there are changes in species as a result of natural selection, the structure became less important until it no longer functions. A reduced nonfunctional digit on the paws of dogs known as a dewclaw is an example of vestigial structure.
Answer:
photosynthesis
Energy enters the ecosystem via sunlight as solar energy. Primary producers (a.k.a., the first trophic level) turn that solar energy into chemical energy via photosynthesis. Common examples are land plants, photosynthetic bacteria and algae
