What organisms are at the bottom of food pyramids because the provide energy for all other organisms?

At the bottom of food pyramids are primary producers, primarily plants and phytoplankton, which capture energy from the sun through photosynthesis. These organisms convert solar energy into chemical energy in the form of glucose, forming the foundation of the food chain. Herbivores then consume these producers, transferring energy up the pyramid, while decomposers break down organic matter, recycling nutrients back into the ecosystem.