Ecological Pyramids

1. Ecological Pyramids Pyramids of numbers, biomass and productivity

2. STARTER: Plot these values on a bar graph Colour the bars using the key below Producer– Green Primaryconsumer– Yellow Secondary consumer – Blue Tertiary consumer - Red

3. Ecological Pyramids • These are graphical models of the quantitative differences between the amounts of living material stored at each trophic level of a food chain. • They allow us to easily examine energy transfers and losses • There are three types which measure: • Number • Biomass • Productivity (Energy)

4. Pyramid of Numbers • A pyramid of numbers shows the number of organisms at each trophic level of the food chain

5. Now… • Cut out each of the bars and place them onto a separate piece of paper… • Which bar will go at the bottom? • Which bar will go at the top? • Stick them down…

6. Label! • Label each side of the pyramid with the following terms:

7. Pyramid of numbers • The length of each bar gives a measure of the relative numbers • Pyramids have producers at the bottom, usually in the greatest number

8. Pyramid of numbers • But some may have a large single plant, a tree, as the producer so the base is one individual

9. Pyramids of numbers

10. GROUP ACTIVITY

11. Pyramids of number

12. lettuce

14. snail

16. hedgehog

18. flea

19. If we start to think about how many of each organism there are, we can start to build a pyramid of numbers...

29. Is it really fair that 1 lettuce counts for the same size box as 1 flea?

30. Is it really fair that 1 lettuce counts for the same size box as 1 flea?

31. Pyramids of biomass

32. STARTER: Is it really fair that 1 lettuce counts for the same size box as 1 flea in a pyramid of number? Explain your reasoning? A better way is to look at the quantity of living material (biomass) at each feeding (trophic) level...

34. Pyramids of biomass are always “pyramid-shaped” as at each stage of a food chain energy (biomass) is lost through respiration and body waste. fleas hedgehogs snails lettuces

35. Pyramids of biomass • A pyramid of biomass contains the biomass (mass of each individual x number of individuals) at each trophic level. • The units of a pyramid of biomass are units of mass per unit area, often grams per square metre (g m -2) or volume of water (g m -3) or sometimes as energy content (joules, J) • A pyramid of biomass is more likely to be a pyramid shape

36. Pyramids of biomass

37. Pyramids of biomass

38. GROUP THOUGHT: Whatiswrongwiththispyramid of biomass?

40. STARTER Why are biomass and numbers SMALL at HIGHER trophiclevels?

42. Now try building a pyramid of biomass

43. STARTER: Energyloss in a foodchain

45. Pyramids of productivity show • That the amount of available energy decreases down the food chain • It takes a large number of producers to support a small number of primary consumers • It takes a large number of primary consumers to support a small number of secondary consumers

46. PYRAMIDS OF PRODUCTIVITY show theflow of energybetweentropiclevels

47. Pyramids of productivity

48. GroupActivity • Make a poster withtheinformationgiven in thehandout Thingstoinclude: • Unitsforthedifferentpyramids • Explanationsfortheshape of eachpyramid of number • Explanationforwhy a pyramid of biomassisalways ‘pyramidshaped’ • Description of how a pyramid of energy shows energyflowthrough a foodchain