The Big Idea – Organisms require a supply of energy and materials for which they are often dependent on or in competition with each other.

This topic is about how the survival of one organism (including Humans) depends upon other organisms and how they are all linked together. If one organism disasters from a habitat it can have big effects on everything else in that habitat.

The Essentials

100% sheet Interdependence

You must be able to use and understand the following key words

Producer – The first thing in a food chain. It gets its energy from the sun by Photosynthesis

Primary consumer – eats the producer to gain energy

Secondary consumer – eats the primary consumer to gain energy

Herbivore – eats plants

Omnivore – eats plants and animals

Carnivore – eats animals

Eating plants and animals is the only way we cancan energy for growth, repair, movement and general living. However we have to eat every day because we lose energy through movement, excretion, growth etc.


Pyramids of numbers show us how many of each species there are at each level of the food chain. They usually look like this because energy is always lost between steps and predators eat more than one prey

pyramid of numbers

But BE CAREFUL. If a tree is in the chain then only 1 tree can be food for many insects and so it will look like this.


Deeper Understanding

It is important to carefully think about changes in food webs. If one organism suddenly disappears from a food web it can have complicated effects on every organism in the web, not just those directly linked. If one animals food disappears it may eat another animals food and cause it to decrease in number.

It is important for a habitat to have a wide diversity or organisms in it. This is called BIODIVERSITY. This helps animals have a wide range of food and so they will not be affected as much if there are changes to the habitat. Man is the main cause of decreasing biodiversity through farming, hunting and destroying habitats,

Other Links

BBC Bitesize – Interdependence

BBC – Food Chains Video

Review and Rate your Understanding

Have you learnt all the facts on the 100% sheet?

Have you completed the BBC Bitesize tutorial?

Have you been able to complete all the questions on the 100% sheet?

Do you know all of the key words?

Can you explain how energy is lost in each step of a food chain?

Can you explain the 2 different shapes of food pyramid?

Let us know how you feel about this topic in the comments section below. Any questions you have, just ask.


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