1. Energy transfer in ecosystems Re-cap
Draw a food chain
What does it show?
How much energy is lost between each organism?
How much energy is passed on at each level?
Energy in Ecosystems

2. Today we are learning about:
The different ways to represent organisms in a food
chain.
These include pyramids of:
Numbers
Biomass
Energy
Success criteria
Name the 3 alternative ways to express food chains.
Explain what they mean.
Explain why biomass and energy are more useful
than numbers to represent food chains.
Energy in Ecosystems

3. Pyramid of numbers
This represents the organisms in a food chain by the number at each level.
Numbers decrease because each level can support less than the one before.
Energy in Ecosystems

4. Exceptions to the usual shape are when the first
organism in a food chain is a bush or tree e.g.
Oak tree insect woodpecker
One Oak tree can
support many organisms in a
community.
Energy in Ecosystems

5. Pyramid of biomass
This represents the organisms in a food chain as the mass of living material (biomass) in each level.
The mass decreases
up the pyramid
Mass at each level
is measured in g/m2
Energy in Ecosystems

6. In living food chains biomass is often only a representative estimate.
Pyramid of biomass
In living food chains biomass is often only a
representative estimate.
This is because the best method of getting mass
is to use dry mass.
This would kill the organisms.
Dry mass is more valid and accurate than wet mass
as water content fluctuates widely.
Energy in Ecosystems

7. Pyramid of energy
This represents the organisms in a food chain by the energy transferred from each level.
Energy in Ecosystems

8. Pyramids of energy are always true pyramids.
They give a better representation of a food chain
as they are the energy passed on through the chain
Energy decreases because each level only passes on about 10%. It is measured in KJ/m2/year
Decomposers and energy
Energy is also used by decomposers for respiration.
They break down dead organisms and waste
(e.g. faeces) at each level.
Energy in Ecosystems

9. What are the ways to represent food chains?
What have we learned?
What are the ways to represent food chains?
Explain what each of them mean
Why is the pyramid of energy the truest form to
represent the food chain?
Energy in Ecosystems