The sun is the source of energy for most ecosystems on earth. Autotrophs capture energy from the sun and make it available to the other living members of ecosystems. Eventually all of the energy captured will be lost to the environment in the form of metabolic heat. Autotrophs are referred to as producers. Trophic levels can be organized into food chains and food webs.
Food webs describe the complex interactions within ecosystems better than food chains.
The result is that diagrammatic representations of ecosystems based on energy, number, or biomass typically are shaped like pyramids. Study of energy transfers in real world ecosystems is difficult. A famous example is the study by Odum of a freshwater spring in Florida. The oceans, however, contribute the most to global productivity because of the vastness of the area they cover. 49.5 All of the figures and tables in these sections are important.