There are three major categories for organisms within a food chain : producers, consumers and saprobionts.
Producers are photosynthetic organisms that manufacture organic substances using light energy, water, carbondioxide and mineral ions.
Consumers are organisms that obtain their energy by consuming other organisms, rather than directly using sunlight. They can be divided into primary, secondary and tertiary consumers.
Primary consumers eat greenplants, whilst secondary consumers will consume the primary consumers. Similarly, tertiary consumers will consume secondary consumers.
Saprobionts (decomposers) are a group of organisms that breakdown the complex materials in dead organisms into simple ones. This releases valuable minerals and elements back into the soil for plants to absorb.
Saprobionts are typically bacteria or fungi.
A food chain describes a feeding relationship in which producers are eaten by primary consumers (then secondary consumers, then tertiary consumers etc).
Each individual stage in a food chain is known as a trophic level.
The arrows on food chain diagrams represent the direction of energy flow.
Foodwebs are a complex network of different foodchains from within a single habitat.
