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GCSE Biology Tutor Booster: Food Chains

A Brief and Visual Explanation of the GCSE Science Topic, Food Chains.

· GCSE Science Notes
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A food chain tells us what eat what.

For example, the following food chain shows us that rabbits eat grass and foxes eat rabbits.

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A food chain begins with a green plant.

This is called the producer because green plants produce food from an abiotic source by photosynthesis.

Organisms following the producer are called consumers. Consumers get their food from a biotic source.

The first in the food chain being the primary consumer, the second the secondary consumer and the third the tertiary consumer.

Below shows how to build a food chain.

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aA predator is an animal that hunts and kills other animals.

Prey is the organism that is hunted and killed for food.

Predator/prey relationships are best represented in food chains and food webs.

For example, in the following food chain we can see that the rabbit is the prey, and the fox is the predator.

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A food web will give us a more detailed view of the different predator/prey relationships
within an ecosystem.

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This is a food web for a woodland habitat.

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It identifies that rabbits, mice, grasshoppers and birds as the prey and foxes and owls as the predators.

There is a continuous struggle between predators and their prey.

If the prey population of an ecosystem increases, then there will be more food available for the predators. This in turn will increase the predator population.

An increased predator population will eventually exhaust the prey population. This
food scarcity will in turn reduce the predator population.

Less predators means less of the prey will be eaten so they will increase again

This cycle is continuous and is known as the predator/prey cycle.

The graph below shows the typical predator/prey relationship.

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If an organism is removed from a food chain or food web all together due to, for example, over hunting there can be a catastrophic effect on the other populations within that ecosystem.