What are the minimum requirements for an ecosystem to recycle nutrients?

Producers and Decomposers are the minimum requirements for an ecosystem to recycle nutrients.

Nutrient cycle is the movement of the nutrients from the physical environment into the living organisms and then back to the physical environment. Nutrient cycle involves both living as well as non-living components including biological, chemical and environmental interactions and processes.

By the process of obtaining food for energy the biotic factors are grouped as: producers or autotrophs, consumers or heterotrophs and decomposers.

Producers and decomposers are the most important factors which contribute in recycling the nutrients. Producers use the nutrients from physical environment through the process of photosynthesis and decomposers return back the nutrients into the physical environment as they obtain their food or energy by decaying or breaking down the dead remains of organisms chemically. Producers begin the food chain followed by consumers and then decomposers.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".