When an ecosystem is healthy, this graph produces a standard ecological pyramid. This is because  in order for the ecosystem to sustain itself, there must be more energy at lower trophic levels than there is at higher trophic levels. This allows organisms on the lower levels to not only maintain a stable population, but also to transfer energy up the pyramid. The exception to this generalization is when portions of a food web are supported by inputs of resources from outside the local community. In small, forested streams, for example, the volume of higher levels is greater than could be supported by the local primary production. Energy usually enters ecosystems from the Sun. The primary producers at the base of the pyramid use the solar radiation to power photosynthesis which produces food. However most wavelengths in solar radiation cannot be used for photosynthesis, so they are reflected back into space or absorbed elsewhere and converted to heat. Only 1 to 2 percent of the energy from the sun is absorbed by photosynthetic processes , and converted into food.Gates DM, Thompson JN and Thompson MB (2018) Efficiency of solar energy utilization Encyclopædia Britannica. Accessed: 26 December 2019. When energy is transferred to higher trophic levels, on average only about 10\% is used at each level to build biomass, becoming stored energy. The rest goes to metabolic processes such as growth, respiration, and reproduction.Pauly, D. and Christensen, V (1995) "Primary production required to sustain global fisheries". Nature 374.6519: 255-257.
When an ecosystem is healthy, this graph produces a standard ecological pyramid. This is because , in order for the ecosystem to sustain itself, there must be more energy at lower trophic levels than there is at higher trophic levels. This allows organisms on the lower levels to not only maintain a stable population, but also to transfer energy up the pyramid. The exception to this generalization is when portions of a food web are supported by inputs of resources from outside the local community. In small, forested streams, for example, the volume of higher levels is greater than could be supported by the local primary production. Energy usually enters ecosystems from the Sun. The primary producers at the base of the pyramid use solar radiation to power photosynthesis which produces food. However most wavelengths in solar radiation cannot be used for photosynthesis, so they are reflected back into space or absorbed elsewhere and converted to heat. Only 1 to 2 percent of the energy from the sun is absorbed by photosynthetic processes and converted into food.Gates DM, Thompson JN and Thompson MB (2018) Efficiency of solar energy utilization Encyclopædia Britannica. Accessed: 26 December 2019. When energy is transferred to higher trophic levels, on average only about 10\% is used at each level to build biomass, becoming stored energy. The rest goes to metabolic processes such as growth, respiration, and reproduction.Pauly, D. and Christensen, V (1995) "Primary production required to sustain global fisheries". Nature 374.6519: 255-257.
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