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A parasite is a plant or animal that lives off another plant or animal-- or, formally, a parasite is an organism that lives in or on an organism of another species (the host), and benefits by deriving nutrients from that host. To some extent, all creatures are parasites-- we eat plants and animals to survive, in a sense “stealing” their nutrients for ourselves-- but let’s not get too existential about it-- “parasite” refers to those that live on the host and do nothing but take nutrients without giving anything in return.
Some parasites are very harmful to their host and will actually, eventually, kill their host. At first glance, this may seem to make no sense, as the death of the host would, by necessity, result in the death of the parasite. But if the goal of the parasite is solely to reproduce-- to increase their numbers-- a common biological goal of all creatures-- then this kind of relationship can be a successful short term means of existence. For instance, many pathogens will kill their host, but before the host is dead, some will jump from that host to another host, increasing their numbers. This extreme type of relationship is rare, however, and most parasites will not kill their host-- some don’t even really do that much harm. Most derive only small amounts of nutrients from their hosts, allowing both to survive. There are instances, however, when a parasite does not kill its primary host but does kill its secondary host-- and one of the most deadly of these is the malaria parasite. This is a parasite whose primary host-- mosquitoes-- can infect their secondary host-- humans-- and while it does not harm the mosquito, it is typically fatal for humans who are infected. While most parasites are “selfish”, and only steal nutrients from the host for themselves, there are also symbiotic relationships where a species that’s attached to another can be beneficial for the host. A good example of this are the types formerly parasitic bacteria in animals that have evolved to help the animal live. This increases the longevity of both the parasite and host. Also, there are many bacteria in the human gut that scientists believe have evolved from parasites to symbiotes because of their mutual advantage to both the host and the parasite. Parasites have been around for as long as there have been hosts. There’s evidence that the host and the parasite co-evolved as bacteria as far back as 4 billion years ago. As a result, parasites can be as varied as any other life form. While most parasites are microorganisms, there’s a wide variety. Remora, or suckerfish, attach to a shark host and are symbiotic, as they remove other, more harmful parasites that live on the shark’s skin. Cordyceps-- a much more harmful parasite-- is a parasitic funugs that lands on and takes over the body of an ant. The fungus burrows into the ant’s brain and causes the ant to climb great heights to release more of the fungus, which falls down on other ants and perpetuates the cycle. Parasites, although not always deadly, are usually harmful. But not all parasites are physical. Humans have exploited other humans since the dawn of time for money, shelter, and goods. A true parasite finds a way to live off of others without killing their source of livelihood. In that regard, some might say humans-- like Huck’s abusive father Huck Finn-- are the deadliest parasite of all. If you’re gonna get existential about it. |
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GLOSSARY
Co-evolve two things influencing each other in their processes of development.
Derive to get something out of a specific source.
Existential a philosophy focused on human existence, especially the nature of existence.
Malaria Parasite protozoan parasite Plasmodium, which can be transmitted to people by mosquito bites.
Microorganism an organism that is microscopic.
Pathogen bacterium or virus that can cause a disease.
Perpetuate make (something, typically an undesirable situation or an unfounded belief) continue indefinitely.
Symbiotic Relationship any type of a close and long-term biological interaction between two different biological organisms.
Derive to get something out of a specific source.
Existential a philosophy focused on human existence, especially the nature of existence.
Malaria Parasite protozoan parasite Plasmodium, which can be transmitted to people by mosquito bites.
Microorganism an organism that is microscopic.
Pathogen bacterium or virus that can cause a disease.
Perpetuate make (something, typically an undesirable situation or an unfounded belief) continue indefinitely.
Symbiotic Relationship any type of a close and long-term biological interaction between two different biological organisms.
