Pyramid of Numbers:
It is a graphical representation of the trophic structure and function of an ecosystem in terms of numbers.
In most ecosystems, the pyramid of numbers is upright i.e., producers are more in number than the herbivores and the herbivores are more in number than the carnivores.
But, there is an exception:
In the case of a parasitic food chain, the pyramid of numbers is inverted. In each trophic level, from the bottom to the top, the numbers of organisms increase and form an inverted pyramid of numbers.