6.1 - 6.2 - Photosynthesis

6.1 - From producers to biomass

A producer makes organic food from substances in its surroundings instead of obtaining all of its food by eating other organisms. Photosynthetic organisms, including plants and algae, are the main producers in most ecosystems. They bring food into food chains by making glucose from carbon dioxide and water.

The link between food and biomass is a material link. Carbon atoms from carbon dioxide become part of glucose. A producer can use some of this glucose to build new cell material, so its biomass increases. A consumer may then eat the producer, or eat another consumer that fed on a producer, so much of the food and biomass in a food web can be traced back to photosynthesis.

Photosynthetic organisms are described as the main producers, not the only possible producers. The important idea for this lesson is that photosynthesis supplies most ecosystems with newly made organic food.

6.2 - The photosynthesis reaction

In plants and algae, photosynthesis begins with carbon dioxide and water and ends with glucose and oxygen. It does not simply rearrange matter: it also needs an input of light energy.