Parasitism is a form of relationship between organisms in which one organism (the parasite) uses another (the host) as a source of food and/or habitat, causing harm to it. Parasites can be both simple organisms (viruses, bacteria, protozoa) and multicellular animals (worms, insects, arachnids).
Parasitism can be either temporary (for example, in some species of insects that live on plants) or permanent (for example, tapeworms in the human body). Parasites have a number of advantages over their hosts, such as rapid growth, reproduction and adaptation to the environment. However, parasites also cause serious harm to their hosts, which can lead to their death.
Parasites are an important part of ecosystems, as they play a role in regulating the populations of their hosts, as well as maintaining the diversity of species on Earth. However, excessive reproduction of parasites can lead to serious illness and even death of their hosts. Therefore, it is necessary to control the number of parasites and their distribution in ecosystems to maintain the balance and health of the environment.