Question

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

Answer 1

Pyramid of number:

● An ecological pyramid constructed considering the number of organisms in each trophic level in a food chain in a sequential manner is known as pyramid of number.

● The pyramid can either be upright or inverted.

● For example:

○ Upright pyramid: In grassland ecosystems, the number of grasses (producers) will be high, the numbers of the consumers in the next level will keep on reducing.

○ Inverted pyramid: In a tree ecosystem, the number of individuals at the base of the pyramid is a tree, primary consumers are the insects (greater in number than the trees). The number of small birds feeding on the insects on the tree are further less. The number of larger birds eating the smaller birds are smallest in number. This gives an inverted pyramid



Pyramid of biomass:

● An ecological pyramid constructed considering the biomass of organisms in each trophic level in a food chain in a sequential manner is known as pyramid of biomass.

● The pyramid can be upright or inverted.

● Example:

○ Upright pyramid: In grassland ecosystems, the biomass of the producers is more than the successive trophic levels, hence, it is upright.

○ Inverted pyramid: In marine ecosystems, the second trophic level comprises the zooplanktons which have higher biomass than the lower phytoplankton. Further, the biomass of fishes is generally greater than that of zooplankton.