Which of the following best defines nutrients in the context of ecosystems?

Nutrients are fundamental substances that provide essential elements required for the growth, maintenance, and overall functioning of living organisms within ecosystems. They play a critical role in various biological processes, such as metabolism, energy transfer, and the formation of cellular structures. Common nutrients include macronutrients like nitrogen, phosphorus, and potassium, as well as micronutrients like iron and magnesium, all of which are vital for the health of plants, animals, and microorganisms.

In the context of ecosystems, nutrients are directly linked to the productivity and sustainability of those ecosystems. For example, in terrestrial environments, plants absorb nutrients from the soil, which helps in their growth and development, while animals obtain their necessary nutrients by consuming plants and other animals. Thus, the availability and cycling of nutrients significantly influence ecosystem health and functioning.

The other choices do not accurately capture the broad definition of nutrients. Non-living factors affecting the habitat refer to abiotic components, energy sources pertain more specifically to the flow of energy through an ecosystem, and organisms that recycle nutrients play a role in nutrient cycling but are not themselves defined as nutrients. Therefore, the best definition of nutrients in this context is that they are elements essential for the growth and maintenance of life.