Explain what is meant by the term trophic level.

A biologist collected data from a grassland ecosystem:

• Number of clover plants = 600
• Number of thrushes that feed on the snails = 18
• Number of snails that feed on the clover = 120
• Number of owls that feed on thrushes = 2

Draw and label a pyramid of numbers for this data.

The biologist collected this data during the summer months. Suggest why the number of snails might be different during the winter.

The total biomass of the organisms at each trophic level decreases as you move up the pyramid. Explain why.