Some examples of parasitism include protozoans, such as amoebas, living in humans and other vertebrate species and parasitic worms that live in and cause disease in humans and animals. Parasitism is the relationship between two species of plants or animals in which one benefits at the expense of the other.
In addition to parasitic worms, there are parasitic vertebrates and plants. One example of a vertebrate parasite is the lamprey that feeds itself by attaching to other fish and sucking blood and other fluids from them. Mistletoe is one example of a parasitic plant; it is spread by birds, then it attaches to a tree to utilize its resources.