Parasitism of parasitism and examples of each.

Parasitism describes a relationship between two organisms where one is harmed, and the other benefits. Learn about the different types of parasitism and examples of each.


Parasitism describes a relationship between two organisms where one benefits, and the other is harmed. The parasite is the organism that benefits from the relationship, while the host is harmed by the relationship.

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Parasites can be a number of things including plants, animals and even viruses and bacteria.It is useful to know about parasitism because, technically, anything that is benefited while we are harmed is considered a parasite. Yes, that pesky mosquito that keeps biting you just gained an official title. While some of the parasites that affect humans can be a nuisance, such as lice or bedbugs, there are other parasites that can make us really sick, such as a bite from a tick, which can cause Lyme disease, or giardia, which we ingest by drinking contaminated water.


Parasites are classified by how they interact with their host. Overall, parasites are much smaller than their hosts and reproduce at a faster rate.Parasites that live on their host are termed ectoparasites.

Examples of ectoparasites are fleas, ticks and mites. These parasites live on larger animals, like cats, dogs and deer. Parasites that live inside their host are termed endoparasites. These include things like parasitic worms, bacteria and viruses. One interesting case of an endoparasite is the hornworm caterpillar and the braconid wasp. The wasp lays eggs inside the hornworm, which then hatch and kill the host. This relationship is considered beneficial to humans, because hornworms eat the leaves on plants, such as tomatoes, eggplants and potatoes, and ruin a lot of crops for farmers.

Ectoparasitism and Endoparasitism

Special Cases

An epiparasite is a parasite that feeds on another parasite. A common example of this is a protozoan that lives in the digestive tract of a flea, which then parasitizes a dog or cat.A social parasite is a parasite that takes advantage of the interaction of other organisms. One example would be a fly taking food away from a colony of ants. The best example of a social parasitism is brood parasitism. This is an interaction where the parasite, typically a bird, deposits their eggs in the nest of another species.

The host then ‘babysits’ the egg in place of the parasite, allowing the parasite to deposit eggs in other nests instead of spending time hatching their own young. Most species of cuckoo bird are brood parasites, and there is even one species of fish (spotted catfish), which parasitizes the ‘nest’ of another fish species!

Brood parasitism

In some rare cases, parasitism can be considered beneficial. Tapeworms lay eggs in the intestine of their host and feed off the nutrients from food the host consumes. Because they consume the majority of the nutrients from their hosts’ food, the worm grows while their host starts to lose weight. Ingesting tapeworm eggs in order to lose weight has been utilized as a diet option for about a century.

Typically, the dieter would then take an antibiotic to kill the worm off. Yuck!


The most common defense against parasitism is behavior. Grooming can eliminate parasites such as ticks and mites. Being careful about what you eat and where you eat it from, are common ways to eliminate foods which can contain parasites, such as tapeworms. However, when that doesn’t work, society has developed medicines to combat most parasites, such as worms and bacterial infections.

Lesson Summary

Parasitism defines a relationship between two organisms where one is harmed, and the other benefits. There are several different types of parasitism, and these are defined by how the parasite interacts with the host. An ectoparasite is a parasite that lives on its host, an endoparasite is a parasite that lives within its host and an epiparasite is a parasite that feeds on another parasite. A social parasite is a special case of parasitism where the parasite takes advantage of the interaction between other organisms.

Learning Outcomes

After this lesson is finished, you should be able to:

  • Define parasitism
  • Name and describe the different types of parasites that exist
  • List some ways to protect yourself from parasites

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