Ecological Pyramids

Question 1

What do ecological pyramids not take into account?

Answer 1

The fact that some organisms operate at more than one trophic level at once. E.g. A human eating an egg sandwich is a primary consumer of the wheat in bread, but a secondary consumer of the egg.

Question 2

Give 4 limitations of pyramids of numbers.

Answer 2

1. Doesn’t take into account size of organisms
2. Doesn’t recognise the difference between juvenile and adult forms
3. The range of numbers may make a scale difficult
4. The pyramid could be inverted.

Question 3

Why is a pyramid of energy the best?

Answer 3

It is the most accurate as it shows the energy transferred from one trophic level to the next, per unit area per unit time. They are never inverted.

Question 4

Give 5 limitations of pyramids of biomass.

Answer 4

1. They are difficult to measure e.g. Plant roots need to be included
2. They don’t indicate amount of energy flowing through
3. They may be inverted
4. Many organisms contain structures that don’t transfer to the next trophic level like fur and beaks, so look like they contribute more than they do
5. Species with similar biomass may have different lifespans

Question 5

Explain one inverted pyramid of biomass.

Answer 5

Phytoplankton reproduce very quickly, but are eaten immediately. Their standing crops biomass is therefore smaller than zooplankton