Final answer:
Parasites are classified into endoparasites, which live inside their hosts, including viruses and helminths, and ectoparasites, which live on the surfaces of their hosts.
Step-by-step explanation:
Classification of Parasites: Endoparasites and Ectoparasites
Parasites that live inside a host are known as endoparasites. These organisms, such as viruses and parasitic helminths (e.g., hookworms and tapeworms), depend on their hosts for sustenance and a place to reproduce. Viruses are unique among endoparasites because they are obligate intracellular parasites that lack their own cells and metabolic processes. To replicate, viruses must invade the cells of their hosts and co-opt the host's cellular machinery.
On the other hand, ectoparasites live on the surface of their hosts. They include a variety of organisms that engage in a complex relationship with their host, ranging from temporary to permanent residency. These ectoparasites exhibit adaptations that allow them to exploit their hosts for resources while navigating defensive responses from the hosts themselves.
Viruses, due to their dependence on intracellular environments to replicate and produce progeny, are classified as endoparasites. Examples include the flu virus, which targets specific host tissues like the respiratory tract in humans. In contrast, helminths such as hookworms and the beef tapeworm, Taenia saginata, also fall into the category of endoparasites as they live inside the host organism's body. Conversely, ectoparasites such as ticks, lice, and mites, live on the surface of their hosts and exhibit various adaptations to maintain their parasitic lifestyle without immediate access to the host's internal environment.