Plants are called producers of food chain because they can use inorganic substances to produce organic substances and store energy through photosynthesis. By eating, consumers in the food chain can absorb the energy stored by plants, with an efficiency of about 30%.

Photosynthesis usually refers to the process that green plants (including algae) absorb light energy, synthesize carbon dioxide and water into high-energy organic matter, and release oxygen at the same time. It mainly includes two stages: light reaction and dark reaction, involving light absorption, electron transfer, photosynthetic phosphorylation, carbon assimilation and other important reaction steps, which is of great significance to realize natural energy conversion and maintain the balance of carbon and oxygen in the atmosphere.

Algae and bacteria

Eukaryotic algae, such as red algae, green algae and brown algae. Like higher plants, chloroplasts can also produce oxygen for photosynthesis. Light is absorbed by chlorophyll, and many algae have other different pigments in their chloroplasts, giving them different colors. ?

Photosynthetic bacteria have no chloroplasts, but are directly carried out by the cells themselves. Cyanobacteria (or "cyanobacteria") belonging to prokaryotes also contain chlorophyll, which produces oxygen and photosynthesis like chloroplasts. In fact, it is generally believed that chloroplasts evolved from cyanobacteria.

Other photosynthetic bacteria have a variety of pigments, called bacterial chlorophyll or bacteriocin, but do not oxidize water to produce oxygen, and use other substances (such as hydrogen sulfide, sulfur or hydrogen) as electron donors. Non-oxygen-producing photosynthetic bacteria include purple sulfur bacteria, purple non-sulfur bacteria, green sulfur bacteria, green non-sulfur bacteria and solar bacteria.