Feeding Relationships

Food Chains

And Webs.

FOOD CHAINSYou need to be familiar with the idea of food chains. In its simplest sense, a food chain shows who eats what in a particular habitat, for example a cabbage is eaten by a caterpillar which is eaten by a blue-tit. A food chain is often referred to as a feeding relationship.Food chains give two other types of useful information:They show how materials (biomass) move through an ecosystem, as one organism feeds on another. They show how energy flows through an ecosystem. The food has to come from somewhere in the first place so remember that the first organism in a food chain must be a green plant (a producer) which can make its own food by photosynthesis. The other organisms in the food chain are called consumers, as they eat (consume) other organisms to get materials and energy.

Some useful terms to learn.Producer = a plant which makes its own food from the sunlight by photosynthesis.

Consumer = an organism which eats something else

Herbivore = an animal which eats only plant material

Carnivore = an animal which eats only meat/other animals

Omnivore = an animal which eats both plants and meat

Some useful terms to learn.Primary consumer = the first animal in the food chain

Secondary consumer = the second animal in the food chain

Tertiary consumer = the third consumer animal in the food chain

Top consumer = the last animal in the food chain

= the transfer of energy (and also what eats what)

Food Chains

Food chains always begin with the sun, as this is the source of energy.

You don’t need to include the sun however on a food chain when writing one out.

Food chain 2

The next thing in a food chain is always a plant.

This is because plants are the only organisms which can make their own food from light energy. This is known as photosynthesis

The plant is known as the producer.

Food chain 3

The next organism in the food chain must be an animal.

This animal is a herbivore.

The animal is also described as a primary consumer.

Food chain 4

The next organism must be a carnivore.

They are also described as a secondary consumer.

Food chain 5

Animals which eat secondary consumers are called tertiary consumers.

They are carnivores too.

Food chains are generally short as energy is lost each time it is transferred in the form of heat, in undigested food, urine, faeces etc. So the energy runs out.

Drawing food chains

(Sun)Plant Cow Human

e.g grass

Cabbage Greenfly lady bird spider sparrow

WRITE UNDERNEATH EACH FOOD CHAIN WHICH IS THE PRODUCER, CONSUMERS ETC.

Food Webs= Food chains joined together.Food websIn its natural habitat it is unusual for an animal to eat only one particular organism. A more realistic way of showing feeding relationships is to draw interconnecting food chains. This is called a food web. Look at this example of a food web by the seashore:                                            

Questions on the food web

Name 2 producers_________________

Name 2 primary consumers _________

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Name a secondary consumer__________

Name a tertiary (and top) consumer

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Effects on food webs.

What will be the effect of increasing the population of bladderrack?

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What will be the effect of sea urchins reducing in number I.e because of disease?

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