The correct answer to this question isParasitism. This relationship is one between species. In parasitism, one organism, known as the parasite, lives on another, which is the host. The parasite is normally smaller than the host and causes the host harm, while using the host resources to benefit themselves.
Examples of parasites include lice, bats, and fungi. They have been around since ancient Rome and Greece, with the existance of tapeworms and roundworms. It is dated to be first observed by Antonie van Leeuwenhoek in 1681. There are various strategies of parasites including transmitted by contact, by being eating, parasitic castration, and micropredation.