Primary producers are autotrophs that can capture sunlight energy and incorporate it into organic compounds. Consumers are heterotrophs that feed on tissues of other organisms. Herbivores eat plants. Carnivores eat animals. Parasites reside in or on living hosts and extract energy from them.
Omnivores eat a variety of organisms.
Decomposers are also heterotrophs and include fungi and bacteria that extract energy from the remains or products of organisms. An ecosystem is a complex of organisms interacting with one another and with the physical environment. Ecosystems are open systems through which energy flows and materials are cycled. B. Structure of Ecosystems 1. Decomposers feed on organisms from all levels.