Which of the following defines a substance that provides nourishment essential for growth and maintenance of life?

The term that defines a substance providing nourishment essential for growth and maintenance of life is "nutrient." Nutrients are any chemical substances that organisms require for metabolic processes, growth, energy, and the repair of tissues. These can include macronutrients like carbohydrates, proteins, and fats, as well as micronutrients such as vitamins and minerals.

Understanding the role of nutrients is crucial in ecology, as they are fundamental for the survival of living organisms and the functioning of ecosystems. They are necessary for various physiological functions, including energy production, cell structure, and the regulation of bodily systems.

The other terms relate to ecological concepts but do not directly define a nourishing substance. A limiting nutrient refers to a nutrient that is in short supply and can limit the growth of organisms, particularly in an ecological context. A food web describes the complex network of feeding relationships among organisms in an ecosystem. Biomass refers to the total mass of living matter within a particular area or volume, which does not inherently denote nourishment but rather the quantity of organic material present.