1. Energy Transfer in Food Chains
L.O: To understand how energy is transferred in food chains

2. Which pyramid of numbers represents each situation?
An oak tree supports lots of bird life; the birds are hunted by foxes.
A cornfield where field mice live; foxes prey on the field mice.
An oak tree is infected with beetles; bacteria infect the beetles.
Draw a pyramid of biomass for each?
Why are they these shapes?

3. Two activities …..
Eat a sweet without losing energy

4. Which diagram represents a cold bloode and warm blooded animal?
Warm blooded animal – body temperature is usually higher than the surroundings
Cold blooded animal – body temperature is usually lower than the surroundings
Faeces
Movement
Heat
Faeces
Movement
Heat

5. Sankey Diagrams for animals
Which diagram represents a carnivore and which represents a herbivore and why?
Which diagram represents a herbivore and which represents a carnivore and why?
Faeces
Faeces
Movement
Movement
Heat
Heat
Carnivore
Herbivore

6. Which diagram represents a battery farmed and free range chicken?
Faeces
Movement
Heat
Faeces
Movement
Heat

7. So how is energy lost in the food chain. http://www. bbc. co

8. Energy flow in a food chain
Consider the energy flow in this food chain:
100%
10% 1%
0.1%
Cabbage
Rabbit
Stoat
Fox
Clearly, not all of the ___’s energy that becomes stored in the _______ will end up in the fox. Only around ______ is passed on to the next stage in each food chain.
Energy is lost at each stage because of a number of reasons:
Each organism has to ____, respire, keep warm etc
Energy is lost through faeces (______)
Words – 10%, move, sun, waste, cabbage

9. Food Chain
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 (this is transferred to the next stage)
Respiration
Movement
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
Faeces
Movement
Heat

10. Efficiency
This animal has eaten 100 kJ of stored energy in the form of grass, and excreted 63 kJ in the form of faeces, urine and gas
The energy stored in its body tissues is 4 kJ – how much has been used up in respiration?
How much energy is passed on (energy efficiency percentage)

11. Efficiency = (4KJ ÷ 100KJ) × 100 = 4%
This animal has eaten 100 kJ of stored energy in the form of grass, and excreted 63 kJ in the form of faeces, urine and gas
The energy stored in its body tissues is 4 kJ – how much has been used up in respiration?
Energy taken in = 100KJ
Energy transferred to tissues + faeces etc… = 63KJ + 4KJ = 67KJ
Energy released by respiration = 100KJ – 67KJ = 33 kJ
Only 4 kJ of the original energy available to the animal is available to the next stage – the efficiency of this energy transfer is: -
Efficiency = (4KJ ÷ 100KJ) × 100 = 4%

12. Work out the percentage of energy passed between each trophic level of the food chain, and between the sun and producer. (using gross production) % % % %

13. Energy Transfer Questions
What do plants use a lot of their energy for?
Do all organisms loose the same amount of heat energy? Why?
Why doesn’t the whole of an organisms body get passed to the next stage of the food chain?
Food chains are rarely more than 5 trophic levels, why?
What happens to the energy lost in animal waste?
Why is food production more efficient with less stages in the food chain?
Explain using pyramids of biomass why it would be better to eat less meat and more plants with an increasing population

14. Energy Transfer Questions
What do plants use a lot of their energy for?
To make new cells
Do all organisms loose the same amount of heat energy? Why?
No warm blooded animals loose more as their body has to be kept at a constant temperature
Why doesn’t the whole of an organisms body get passed to the next stage of the food chain?
Some of it is inedible or can’t be digested e.g. bones and teeth, fibre and cell walls
Food chains are rarely more than 5 trophic levels, why?
So much energy is lost at each stage that there is not enough left to support the organisms after 4 or 5 stages

15. Energy Transfer Questions
What happens to the energy lost in animal waste?
It is recycled in the soil and eventually new plants will use it
Why is food production more efficient with less stages in the food chain?
Less material and less energy is wasted this means more food can be produced
Explain using pyramids of biomass why it would be better to eat less meat and more plants with an increasing population
More food would be made as less energy is lost, so in the limited land space enough food would be made to go around

16. What would a sankey diagram for veal look like?