1. Feeding Relationships - Pyramids
Showing feeding relationships quantitatively (in numbers).

2. What Food Chains and webs don’t tell us
A food chain tells us what eats what and shows the movement of energy
Food chains do not tell us how many organisms are involved, how much their mass is, or how much energy is transferred from organism to organism.
We use pyramids to show us values associated with each organism.

3. Pyramids of number

7. Pyramids of number
This shows us how many organisms are involved at each feeding (trophic) level.
Like a food chain a pyramid always starts (at the bottom) with a producer (plant) and builds itself up in the same order as a food chain.
Each block is in scale to show the numbers in each level.

9. Practicing Perfect Pyramids Please!
Try the following on graph paper. Go back and check the rules.
rose leaves 1000 greenfly (aphids)200 ladybirds100 spiders
oak leaves, 2000 caterpillars, 100 sparrows, 3 sparrow hawks
blades of grass, 200 rabbits, 20 foxes, 400 fleas

10. Pyramid of biomass

11. More biomass pyramids
Pyramids of Biomass show the mass of each organism on each level. The more the mass the wider the level.
For instance one pike has a similar mass to 3 water beetles which is why it's level is almost the same as the beetles.

13. Pyramid of number Pyramid of biomass

14. Pyramid of number Pyramid of biomass

15. Pyramids of energy These always are pyramid shaped.
These show the transference of energy up the feeding levels.
Energy should be lost as you move up the pyramid. Can you remember why?.

16. What happens to energy?
Flow of energy through a food chain. As energy passes to a higher tropic level, approximately 90% of the useful energy is lost.
High tropic levels contain less energy and fewer organisms than lower levels.

18. What happens to energy?
At each tropic level in a food chain, energy is used by the organisms at that level to maintain their own life process.
It is estimated that in going from one tropic level to the next, about 90 % of the energy is lost. In moving to the next tropic level, only 10 % of the original energy is available. By the third tropic level only 1% of the energy is available.