[GEMET] Any of the feeding levels through which the passage of energy through an ecosystem proceeds; examples are photosynthetic plants, herbivorous animals, and microorganisms of decay. , "[Henderson's] (1) a level in a food chain defined by the method of obtaining food, and in which all organisms are the same number of energy transfers away from the original source of the energy (e.g. photosynthesis) entering the ecosystem. see autotroph, herbivore, secondary con­sumer, tertiary consumer; (2) the nutrient status of a body of water. see eutrophic, oligotrophic.