Longevity may refer to especially long-lived members of a population, whereas life expectancy is defined statistically as the average number of years remaining at a given age. For example, a population's life expectancy at birth is the same as the average age at death for all people born in the same year.
Elderly couple in Portugal
Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain the required amount of nutrients causes malnutrition. Nutritional science is the study of nutrition, though it typically emphasizes human nutrition.
An Amblypodia anita (purple leaf blue butterfly) gathering nutrients from guano
A bonobo fishing for termites with a prepared stick
A kingfisher eating a tadpole near the Ariège river, France
Image: Abr horta Antonio Cruz