Food Chain

A food chain is a linear sequence of links in a food web starting from species that are called producers in the web and ends at species that are called decomposers in the web. A food chain also shows how the organisms are related with each other by the food they eat. A food chain differs from a food web, because the complex polyphagous network of feeding relations are aggregated into trophic species and the chain only follows linearmonophagous pathways. A common metric used to quantify food web trophic structure is food chain length. In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web and the mean chain length of an entire web is the arithmetic average of the lengths of all chains in a food web.

                                                                             Producers 

Plants are called producers. This is because they produce their own food! They do this by using light energy from the Sun, carbon dioxide from the air and water from the soil to produce food - in the form of glucouse/sugar.
The process is called photosynthesis.

                                                            

Consumers

Animals are called consumers. This is because they cannot make their own food, so they need to consume (eat) plants and/or animals. There are 3 groups of consumers.

Animals that eat only plants.

Animals that eat only animals.

Animals that eat both animals AND plants. Humans are also omnivores!

                   Decomposers

Bacteria and fungi are decomposers. They eat decaying matter - dead plants and animals and in the process they break them down and decompose them When that happens, they release nutrients and mineral salts back into the soil - which then will be used by plants!