ParasitismParasitism describes a relationship between two life forms of different species. It occurs when one life form harms another. In order to be described as parasitism, the two life forms must live together for long periods of time. This does not include animals that hunt and eat their prey or the times when a mosquito feeds off its host.There are two major kinds of parasites: endo- and ecto-parasites. Endoparasites live inside the body of a host. An example is the hookworm, which lives in the stomach of a human or animal. Many of these parasites find their hosts by passive means. They live in the intestines. There they lay eggs, which are passed through waste products into the outer environment. Once outside the host, they are picked up by other people or animals in unclean areas.Ectoparasites develop complex ways of finding new hosts. Some aquatic leeches locate their hosts through their motion sensors.Theylearn their host's identity through the temperature of the skin and chemical cues. Once they haveconfirmedthat it is a desirable host, they use hook-like teeth to attach themselves. After they are attached, they dig through the skin and begin to suck blood.The way a parasite feeds off its host is also separated into two major distinctions, that of necrotrophs and biotrophs. Necrotrophs are parasites that consume their host's tissue until the host dies. In this relationship, the host usually dies from loss of tissue or nutrients. Biotrophic parasites cannot survive on a host once it has died. They must keep their hosts alive to survive themselves. Many viruses are biotrophic. They use their host's genetic and cellular processes to multiply.Biotrophic parasitism is a very common way for life forms to survive. At least half of all animals go through a phase of their life where they are parasitic. This includes human fetuses during the time they live inside their mother's womb. This behavior is also common amongst plants and fungi. All free-living animals are host to one or more types of parasites.Some parasites are social. They learn how to take advantage of the behavior of a social host species. Some parasitic insects like nematodes join ant or termite colonies. They are able to feed on colony members until the group is so weak that it ceases to exist. Many species of Cuckoo bird steal food caught by their host. They even use other birds as babysitters by depositing their eggs in the nests of other birds. The Cuckoo young are raised by the adults of the other bird species while the adult CuckoosfendforthemselvesAccording to the passage, how do social parasites like Cuckoo birds exploit their hosts...