A simple food chain is:
algae → mosquito larvae → dragon fly larvae → perch
At the bottom of all food chains is a producer. This is almost always a plant or alga which can photosynthesise to convert carbon dioxide and water into glucose. This provides all the biomass for the food chain. Algae are the producers in the food chain above.
All following trophic levels relate to consumers, which cannot make their own food.
There may be additional carnivorous consumers which would be called tertiary and quaternary. The final level is a carnivore often called the top or apex predator - in this example, a perch. Organisms at the top of a food chain have no predators.
Decomposers are bacteria and fungi that break down dead plant and animal matter. They secrete enzymes on the surface of the dead organisms to break the organism down and then absorb the digested, smaller food molecules.
|Producers||Green plants - they make glucose during photosynthesis.|
|Primary consumers||Usually eat plant material - they are herbivores (or omnivores). For example, rabbits, caterpillars, cows and sheep.|
|Secondary consumers||Eat animal material - they are carnivores (or omnivores). For example, cats, dogs and lions.|
|Predators||Kill for food. They are either secondary or tertiary consumers.|
|Prey||The animals that predators feed on.|
|Scavengers||Feed on dead animals. For example, crows, vultures and hyenas are scavengers.|
|Decomposers||Feed on dead and decaying organisms, and on the undigested parts of plant and animal matter in faeces.|