A pyramid is a graphical representation of the relationship between different organisms in an ecosystem. Each level of the ecological pyramid represents a trophic level (group of organisms which occupy the same level in a food chain). In every ecosystem, the base or first trophic level of the pyramid is occupied by autotrophs. They synthesis food through photosynthesis for themselves and they used as food for other organisms. Hence, they are producers of the ecosystem. Example, in a grassland ecosystem, autotrophs are grasses, herbs, and small trees.