Lichen anatomy and physiology the Ascomycota, with about 40% of species forming such an association. Some of these lichenized fungi occur in orders with nonlichenized fungi that live as saprotrophs or plant parasites (for example, the Leotiales, Dothideales, and Pezizales). Other lichen fungi occur in only five orders in which all members are engaged in this habit (Orders Graphidales, Gyalectales, Peltigerales, Pertusariales, and Teloschistales). Lichenized and nonlichenized fungi can even be found in the same genus or species. Overall, about 98% of lichens have an ascomycetous mycobiont. Next to the Ascomycota, the largest number of lichenized fungi occur in the unassigned fungi imperfecti. Comparatively
Parasites in fiction but not others. Parasites, represented as extraterrestrial aliens or unnatural beings, are seen in science fiction as distasteful, in contrast to (mutualistic) symbiosis, and sometimes horrible. Practical uses can be made of them, but humans who do so may be destroyed by them. For example, Mira Grant's 2013 novel "Parasite" envisages a world where people's immune systems are maintained by genetically engineered tapeworms. They form readily understood characters, since, as Gary Westfahl explains, parasites need to exploit their hosts to survive and reproduce. The social anthropologist Marika Moisseeff argues that Hollywood science fiction favours insects as villain characters because of