How important are plants?

Do you know your consumers from your producers and your predators from your prey?

Can you describe food chains from a food web of an ecosystem?


Here we take a look at the different roles organisms have within an ecosystem and how they are linked together. We explore the keywords you need to know and their definitions, so you can name all organisms involved correctly. The aim is you can write out an entire food web and identify different food chains that exist within that food web.


It is vital that you understand the important role plants play in a food chain and food web. Green plants are called producers, this means they are an organism that is able to produce their own food. They do this by the chemical reaction of photosynthesis. Make sure you can remember (and write out) the word equation for photosynthesis; you will need this in KS3 and KS4 Biology. As the green plants are producers, they are found at the start of a food chain, then they are eaten by primary consumers, which can also be called herbivores (if they only eat plants).

Food Chains

Within an ecosystem there are many different feeding relationships between organisms, we represent these with food chains. A food chain shows what each organism eats, by linking them together with arrows. The arrows also show the direction of energy transfer from one organism to another. You will be expected to draw examples of a food chain and to complete a food chain your teacher gives you. To do this you need to have a good understanding of predator prey relationships and be able to explain the links.

Food Webs

A food web is made up of all the food chains present in an ecosystem, this shows all the relationships and links between organisms. You need to be able to identify specific food chains within a food web. This will also help you to understand how organisms depend on one another for survival. It is also worthwhile looking at what will happen if one organism dies out and the impact this has on other feeding relationships. As a predator will then have to look for another food source, which will affect any other organisms feeding on it.


There are many keywords and definitions you need to be confident using in this topic, the words below are the ones we think you need to understand and be able to use in the correct context.

    • Producer
    • Consumer
    • Primary consumer
    • Secondary consumer
    • Tertiary consumer
    • Herbivore
    • Carnivore
    • Omnivore
    • Predator
    • Prey

It is important that you can label organisms in a food web with these keywords, so you can recognise the differences and identify the different roles they have.


If you can draw a food web and food chain and explain the relationship between the organisms using the keywords mentioned then you will have a great understanding of Food Chains and Webs and should be able to answer assessment questions confidently.



Don’t forget to get in touch if you have any questions or would like some help with your KS3 science learning to fill in any knowledge gaps you have.



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