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Food Chain & Food Web (Ecosystem)

Updated: Jun 11


Image of Grey Heron (HB23N2) from Educational Research Website - www.emkaycollection.co.uk

Importance of Food Chain and Food Web (Ecosystem)

[also Extinction and Over population]


Much of the research was composed by Duckster's Education Site.


Every plant and animal species, no matter how big or small, depends to some extent on another plant or animal species for its survival. It could be bees taking pollen from a flower, photosynthesis of plants, deer eating shrub leaves or lions eating the deer. Every living plant and animal must have energy to survive. Plants rely on the soil, water and the sun for energy. Animals rely on plants as well as other animals for energy.


In an ecosystem, plants and animals all rely on each other to live. Scientists sometimes describe this dependence using a food chain or a food web. A food chain shows how energy is transferred from one living organism to another via food. It is important for us to understand how the food chain works, so that we know what are the important living organisms that make up the food chain and how the ecology is balanced. A food chain describes how different organisms eat each other, starting out with a plant and ending with an animal.


For example, you could write the food chain for a Barn Owl like this:

Grass --> Crickets --> Shrews --> Barn Owls

The Barn Owl eats Shrews. Shrews eat Crickets. Crickets eat Grass.

Photosynthesis is only the beginning of the food chain. There are many types of animals that will eat the products of the photosynthesis process. Examples are deer eating shrub leaves, rabbits eating carrots, or worms eating grass. When these animals eat these plant products, food energy and organic compounds are transferred from the plants to the animals. These animals are in turn eaten by other animals, again transferring energy and organic compounds from one animal to another.

Links of the Chain

There are names to help describe each link of the food chain. The names depend mostly on what the organism eats and how it contributes to the energy of the ecosystem.


Producers - Plants are producers. This is because they produce energy for the ecosystem. They do this because they absorb energy from sunlight through photosynthesis. They also need water and nutrients from the soil, but plants are the only place where new energy is made. Consumers - Animals are consumers. This is because they don't produce energy, they just use it up. Animals that eat plants are called primary consumers or herbivores. Animals that eat other animals are called secondary consumers or carnivores. If a carnivore eats another carnivore, it is called a tertiary consumer. Some animals play both roles, eating both plants and animals. They are called omnivores.

(Please note - ‘Animals’ does include amphibians, birds, fish, insects, mammals & reptiles etc.)


Decomposers - Decomposers eat decaying matter (like dead plants and animals). They help put nutrients back into the soil for plants to eat.

Examples of decomposers are worms, bacteria and fungi.


Using the above example - Grass --> Crickets --> Shrews --> Barn Owls

Grass – producer Crickets – primary consumers Shrews – secondary consumers

Barn Owls – tertiary consumers



Each Link is Important

Links higher up in the food chain rely on the lower links. Even though Ospreys or Bald Eagles don't eat grass, they wouldn't last long if there wasn't any grass because any herbivore prey wouldn't have anything to eat.

Food Web

In any ecosystem there are many food chains and, generally, most plants and animals are part of several chains. When you draw all the chains together you end up with a food web.



Diagram was composed by Duckster's Education Site.

There are many examples of the need for culling of some tertiary consumers, or in some cases the secondary consumers as the next level down have no ‘apex’ predator, so they expand at such a fast rate that grass, bushes or trees suffer badly through over-population.


Example - In the UK – Grey Wolves were once the apex predator. They were removed from the ecosystem; now we are over-populated by ’in particular’ Red Deer, which are hungry herbivores. There are many other major imbalances in ecosystems the world over, mostly created by GUESS WHO.


Yes US - human beings.


Ecosystems, Food Chains and Food Webs are very important to our Planet and indirectly

to US as well.


Please ensure that all ecosystem evaluations are only decided by knowledgeable and learned individuals or organisations, to make the FINAL decisions, in order to prevent major

ecosystem destabilisations occuring in the future.


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