Question

Write a short note on pyramid of numbers and pyramid of biomass.

Answer 1

Pyramid of Number

• Pyramid of number deals with number of individuals in a trophic level.

Pyramid of numbers in a grassland ecosystem. Only three top carnivores are supported in an ecosystem based on production of nearly 6 millions plants

• In Grassland ecosystem only 3 top carnivores are supported in an ecosystem based on production of nearly 6 million plants.
• Pyramid of number in grassland or forest or pond ecosystem is upright.

• In parasitic food chain, the pyramid of number is inverted.
• In an ecosystem dominated by trees, the pyramid of number shaped/inverted.

• Among the grassland, pond and forest ecosystem, the number of primary producers per unit area would be maximum in the pond ecosystem.

Pyramid of Biomass

• Total amount of living material at various trophic level of a food chain is depicted by pyramid of biomass.

Pyramid of biomass shows a sharp decrease in biomass at higher trophic levels

• In most of the ecosystem, the pyramids of number and biomass are upright.
• In terrestrial ecosystem pyramid of biomass is generally upright.
• The pyramid of biomass in the sea or lake is generally inverted because the biomass of fishes exceeds that of phytoplankton.

Inverted pyramid of biomass-small standing crop of phytoplankton supports large standing crop of zooplankton