Food chains show the feeding relationships in a habitat. Pyramids of biomass are charts that show the mass of living organisms at each step in a food chain. Energy is lost moving up in a food chain, and this limits the length of the chain.
A food chain shows what eats what in a particular habitat. For example, grass seed is eaten by a vole, which is eaten by a barn owl. The arrows between each item in the chain always point in the direction of energy flow - in other words, from the food to the feeder.
Radiation from the Sun is the ultimate source of energy for most communities of living things. Green plants and algae absorb some of the Sun’s light energy and transfer it into chemical energy. This happens during photosynthesis, and the chemical energy is stored in the substances that make up the cells of the plants or algae. The other organisms in a food chain are consumers, because they all get their energy and biomass by consuming (eating) other organisms.
It helps if you can recall the meaning of some common words used with food chains. The table shows some of these words.
|producers||Green plants and algae. They make food by photosynthesis.|
|primary consumers||Usually eat plant material - they are herbivores. For example rabbits, caterpillars, cows and sheep.|
|secondary consumers||Usually eat animal material - they are carnivores. 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.|
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