Food Chains & Food Webs
D. Crowley, 2008
Key terms
means ‘eaten by’
Producer - utilise the sun’s energy to produce their own food, e.g. plants and
algae
Consumer - organisms that eat other organisms for their energy supply.
These can be primary consumers which eat the producers;
secondary consumers which eat the primary consumers;
or tertiary consumers which eat the secondary consumers etc…
Herbivore - an organism that eats other producers (plants), e.g. cow
Omnivore - an organism that eats both producers and consumers, e.g. human
Carnivore - an organism that eats other consumers, e.g. lion
Top predator – the organism at the top of the food chain: it isn’t eaten by other organisms
Food Chains & Food Webs
To understand food chains and food webs, and the transfer of energy within
these
Carnivore, Herbivore or Omnivore
Carnivore
Omnivore
Herbivore
Carnivore
Carnivore
Omnivore
Herbivore
Herbivore
Omnivore
Food Chains
What is a food chain?
A food chain shows what is eaten by what – each arrow means ‘eaten by’
E.g. rabbit  fox means the rabbit is eaten by the fox
Food Chains
What is the food chain in the following habitat: -
Food Chains
• This food chain shows a leaf is eaten by a caterpillar, which is eaten
by a bird, which is eaten by a cat
Producer
1° Consumer
(Herbivore)
2° Consumer
(Carnivore)
3° Consumer
(Carnivore)
• Why do the organisms eat one another?
• Energy is transferred from one organism to another, in the direction of
the arrow
Energy
• Food chains are never very long (usually only 4/5 stages at
most) – why is this?
• Remember the arrow shows the energy being transferred from
one organism to the next - between each step energy is ‘lost’
in a variety of ways, including: – Growth of the organism
– Reproductive costs
– Lost through waste products (poo)
– Lost through heat
• This is why food chains are never that long - as lots of energy is
‘lost’ from one stage to the next
Food Chains
• Your task is to make 3 food chains consisting of at least 3/4
organisms in each – e.g. leaf  caterpillar  bird  cat
• For each food chain draw out your animals, adding the key
words: producer, consumer (1°; 2°; 3°) and if you can: herbivore,
carnivore or omnivore
• Once you have done this complete a food chain for your
favourite celebrity / sports person / musician / actor etc… with a
paragraph underneath explaining how they live based on this
food chain
Food Webs
• In most habitats organisms normally eat / are eaten by more than
one other organism
• To represent this we use food webs (like food chains but they
interlink with one another), e.g. a pond
Here the producers are the
pondweed and the microscopic algae
Mayfly nymphs eat the pondweed
and microscopic algae, and
freshwater shrimp eat the
microscopic algae
Dragonfly nymphs and brown trout
eat the mayfly nymphs and
freshwater shrimp
Brown trout also eat the dragonfly
nymph!
Food
Webs
chiffchaff
owl
blue tit
stoat
spider
ladybird
moth larva
vole
aphid
plants
Food Webs
• You have 5 minutes to have an answer to every question (you do
not need to write your answers down): -
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
Name the producer
Name 2 herbivores
Name 2 top carnivores
How many 2° consumers
are there?
Which food chains include a
moth larva
Plants
Vole; moth larva; aphid
Stoat; owl
5 - stoat; spider; ladybird; blue tit;
owl
Blue and orange food chain
C: potato plant  beetle  mole  badger
E: peach tree  peach-potato aphid  spider  blue tit  cat
B: peach tree  peach-potato aphid  swallow  sparrowhawk
F: lettuce  rabbit  fox
G: lettuce  peach-potato aphid  hoverfly lava  blue tit  sparrowhawk
EXTENSION
Collect and cut up
these food chains
and use them to
create a food web.
Remember only stick
them down when you
are happy with the
position of all the
animals
Balance
Populations in a food chain are dependent upon one another – there is a balance
between the producers and consumers in the food chain
For example if there are lots of giraffes they will eat a large quantity of the trees
and shrubs until there may be insufficient amounts to support them. If this is the
case many will begin to starve and die.
Fewer giraffes means less food for lions, which will eventually
see a population decrease.
Less giraffes will allow more shrubs and tress to survive,
so the giraffe population recovers, leading to the lion
population recovering, until the process repeats itself…
Food Examples
• Complete the food chains and
food webs worksheet
Food Examples