Pyramids of Numbers, Biomass and Energy

IGCSE Edexcel Biology
4.6–4.9 Feeding Relationships and Energy Transfer
Instructions: Use the data to draw pyramids on squared paper. Any sensible scale is acceptable. Label each trophic level in order from producers at the base to top consumers. Show the scale on each pyramid.

Section A: Pyramids of Numbers

1 Woodland food chain: draw a pyramid of numbers. [4]
Trophic level Organisms Number of organisms
Producer Oak tree 2
Primary consumer Aphids 200
Secondary consumer Ladybirds 40
Tertiary consumer Thrushes 8
2 Grassland food chain: draw a pyramid of numbers. [4]
Trophic level Organisms Number of organisms
Producer Grass plants 5000
Primary consumer Rabbits 500
Secondary consumer Foxes 25

Section B: Pyramids of Biomass

3 Meadow ecosystem: draw a pyramid of biomass. [4]
Trophic level Biomass (g m-2)
Producers 820
Primary consumers 140
Secondary consumers 18
4 Aquatic ecosystem: draw a pyramid of biomass. [4]
Trophic level Biomass (g m-2)
Producers (phytoplankton) 30
Primary consumers (zooplankton) 55
Secondary consumers (small fish) 12
Tertiary consumers (large fish) 2

Section C: Pyramids of Energy

5 Heathland ecosystem: draw a pyramid of energy. [4]
Trophic level Energy (kJ m-2 yr-1)
Producers 12000
Primary consumers 1800
Secondary consumers 220
6 Pond ecosystem: draw a pyramid of energy. [4]
Trophic level Energy (kJ m-2 yr-1)
Producers 9000
Primary consumers 1200
Secondary consumers 120
Tertiary consumers 12

Total: 24 marks

Guiding Mark Schemes (examples of sensible scales)

Any sensible scale earns credit if it is shown clearly. Examples below are one possible choice.

  1. Q1 Pyramid of numbers (woodland):
    • Order: producers → primary → secondary → tertiary.
    • Inverted base acceptable (few producers, many primary consumers).
    • Relative widths reflect 2 → 200 → 40 → 8.
    • Example scale: 1 grid square = 2 organisms.
  2. Q2 Pyramid of numbers (grassland):
    • Upright pyramid, producers widest.
    • Relative widths reflect 5000 → 500 → 25.
    • Example scale: 1 grid square = 25 organisms.
  3. Q3 Pyramid of biomass (meadow):
    • Upright pyramid, producers widest.
    • Relative widths reflect 820 → 140 → 18.
    • Example scale: 1 grid square = 10 g m-2.
  4. Q4 Pyramid of biomass (aquatic):
    • Inverted base acceptable (primary consumers wider than producers).
    • Relative widths reflect 30 → 55 → 12 → 2.
    • Example scale: 1 grid square = 1 g m-2.
  5. Q5 Pyramid of energy (heathland):
    • Always upright; producers widest.
    • Relative widths reflect 12000 → 1800 → 220.
    • Example scale: 1 grid square = 200 kJ m-2 yr-1.
  6. Q6 Pyramid of energy (pond):
    • Upright pyramid with four levels.
    • Relative widths reflect 9000 → 1200 → 120 → 12.
    • Example scale: 1 grid square = 100 kJ m-2 yr-1.