The trophic structure and function of an ecosystem can be represented in the triangular pyramids called ecological pyramid or Eltonian pyramid. Various types of pyramids related to different ecosystems are as follow. Ecosystem Shape of Pyramid [a] Pyramid of number Grassland - Upright Forest (Tree) - Inverted Aquatic (Pond) - Upright [b] Pyramid of biomass Grassland - Upright Forest - Upright Aquatic (Lake) - Inverted [c] Pyramid of energy All ecosystems - Upright.