What type of organisms are considered parasites?

Parasites are defined as organisms that derive their nutrients and benefits from another organism, known as the host, while causing some degree of harm or disadvantage to that host. This relationship is characterized by the dependency of the parasite on the host for survival, growth, or reproduction, often leading to negative effects on the host's health.

The key aspect of this definition is the idea of living on or within another organism at the host's expense, which highlights the parasitic nature of this interaction. Examples of parasites include tapeworms that live in the intestines of animals, mosquitoes that feed on blood, and various types of fungi that can infect and consume living plants or animals.

In contrast, organisms that live independently of others do not engage in this parasitic interaction, making them distinct from parasites. Additionally, while some parasites may require specific hosts, not all do; many can infect multiple species or a range of hosts. Finally, organisms that assist in digestion do not exploit another organism but instead contribute positively to the host's digestive processes, differing fundamentally from the parasitic relationship.