There are two types of organisms: autotrophs and heterotrophs. Autotrophs can produce their own food through photosynthesis using carbon dioxide, water, soil, sunlight, and chlorophyll. Plants are autotrophs. Some plants lack chlorophyll and must get nutrition from other plants, making them heterotrophs. Examples of heterotrophic nutrition in plants include parasites like Cuscuta that live on a host, insectivores like pitcher plants that trap and digest insects, and saprophytes like fungi that get nutrients from dead and decaying plants. Some relationships, like that between crops and the Rhizobium bacteria that provide nitrogen in exchange for shelter and food, are examples of symbiosis