This document discusses feeding relationships in ecosystems. It defines producers as organisms that can make their own food, such as plants, and consumers as organisms that cannot make their own food and must consume other organisms. Consumers are further divided into herbivores, carnivores, and omnivores based on whether they eat producers, other consumers, or both. Food chains show the transfer of energy as each organism eats the one below it. Producers are at the start of food chains, and consumers can be classified based on their trophic level as primary, secondary, or tertiary consumers depending on what they eat.

1. Feeding relationships in an
ecosystem
IGCSE Biology

3. Feeding types
Organisms can be grouped in several ways. One
way of doing this is based on how they obtain
their food.
Some organisms are producers. Producers
make their own food.
Plants produce their own food using light energy from the Sun. Some types of bacteria
can also make their own food by using light or chemical reactions.
Consumers cannot make their own food.
They must consume other organisms to
get the food that they need.

4. Can you sort out the
following organisms into
producers and
consumers?

5. Consumers
Consumers can be grouped into different types:
Herbivores:
These consumers eat producers. Herbivores include some types of
plants and bacteria.
Carnivores:
These consumers eat other
consumers.
Omnivores:
These consumers eat other consumers and producers.
Omnivores eat animals and plants. Most humans are
omnivores.

6. Can you sort out the
following into
herbivores, carnivores
and omnivores?

7. Food chains
A food chain is a sequence which shows how each individual feeds on the organism below
it in the chain. Each arrow means ‘eaten by’.
caterpillar
leaf bird fox
In this food chain a leaf is eaten by a caterpillar, which is then eaten by a bird,
which is then eaten by a fox.
Energy is transferred from one organism to another in the direction of the arrow,
showing the flow of energy through the chain.

8. Producer, herbivore or carnivore?
What are the feeding types of the animals in this food chain?
From a food chain, we can tell if an organism is a producer, a herbivore or a carnivore.
If the producer is a plant, only a small part of it might be involved in the food chain,
such as its seeds, fruits, leaves or even dead leaves.
Food chains always start with a producer. The source of energy for all food chains is
always the sun
snail
leaf bird owl

9. Ranking consumers
Consumers eat plants or animals, or both. A food chain can be used to rank
different types of consumers.
 Producers – make their own food.
 Primary consumers – eat producers.
 Secondary consumers – eat primary consumers.
 Tertiary consumers – eat secondary consumers.
producer primary
consumer
secondary
consumer
tertiary
consumer
seaweed limpet crab human

10. Group challenge
Can you use as many of these terms you have met correctly in labelling the
following food chain?
Producer
Green
plant
Primary
consumer Secondary
consumer
Tertiary
consumer
HERBIVORE CARNIVORE
If it also eats seeds and
nuts it would be an
TOP
CARNIVORE
OMNIVORE
Arrows show energy
flow

11. Now try your food chains!

16. Biomass = the total quantity or weight of organisms in a given area or volume