1. Food Chains & Food Webs
D. Crowley, 2008

2. Wednesday, April 12, 2017
Food Chains & Food Webs
To understand food chains and food webs, and the transfer of energy within these

3. E.g. rabbit  fox means the rabbit is eaten by the fox
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

4. Food Chains
What is the food chain in the following habitat: -

5. 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

6. 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

7. 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

8. 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!

9. Food Webs chiffchaff owl blue tit stoat spider ladybird moth larva
vole
aphid
plants

10. Food Webs
You have 5 minutes to have an answer to every question (you do not need to write your answers down): -
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

11. Key terms
Producer - utilise the sun’s energy to produce their own food, e.g. plants and algae
Consumer - organisms that require eating 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…
Carnivore - an organism that eats other consumers, e.g. lion
Herbivore - an organism that eats other producers (plants), e.g. cow
Omnivore - an organism that eats both producers and consumers, e.g. human

12. Carnivore, Herbivore Or Omnivore?
Are the following carnivores, herbivores or omnivores?

13. Carnivore, Herbivore Or Omnivore?
Are the following carnivores, herbivores or omnivores?
Herbivore
Carnivore
Herbivore
Omnivore
Carnivore
Omnivore
Carnivore
Omnivore
Herbivore

14. Food Examples
Complete the food chains and food webs worksheet

15. Food Examples

16. 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…