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Parasitism: definition and examples

In nature, the relationships between each and every one of the different species of organisms are marked by the ultimate goal of survival. In this way, within each biological community, the species try to get the maximum benefit, both from the relationships they maintain with the rest of the individuals of their own species, as well as with those other organisms of different species and groups. In this context, parasitic organisms appear as experts in the benefit that they can obtain from other organisms, although this entails infection, damage, and sometimes even death, of those organisms from which they benefit.

The example of intestinal parasitism is probably one of the best known in humans, but the great biodiversity of parasites that nature harbors is really complex and surprising. In this interesting AgroCorrn article you can discover everything about parasitism: definition and examples .

You may also be interested in: What is commensalism: definition and examples
  1. Interspecific relationships: what they are and types
  2. What is parasitism – definition
  3. Types of parasitism
  4. Examples of parasitism

Interspecific relationships: what they are and types

Interspecific relationships are those that occur between organisms of different species that make up the same biological community. Depending on the type of interaction and its result, the organisms that participate in it may be benefited (+) or, conversely, harmed (-), as well as remain in a neutral state (0) in certain cases.

In this way, the different types of interspecific relationships that occur between different species are:

  • Relationships between species of the type (0) / (+): amensalism and antibiosis .
  • Interspecific relationships (+) / (0): epibiosis, thanatocresis, phoresia, commensalism and inquinilism.
  • Relations between species of the type (+) / (-): predation, exploitation and parasitism.
  • Interspecific relationships (+) / (+): symbiosis and mutualism.
  • Relations between species of the type (-) / (-) or (+): competences due to exploitation or interference.

Now that we know the different types of interspecific relationships that exist and we can differentiate them into one or another group, in the next section we will focus solely and exclusively on the interspecific relationship of parasitism .

In this other AgroCorrn article you can learn much more about interspecific relationships, their types and examples .

What is parasitism – definition

As we have indicated previously, parasitism is an interspecific relationship of the (+) / (-) type , in which one organism (parasite) benefits from another (host), which is harmed by the action and invasion of the other species, suffering damage to a greater or lesser extent, depending on the degree of parasitism.

For the parasitic organism, establishing this type of interspecific relationship with another species is its only way of life, since it depends on other organisms to supply its energy and food needs, as well as to reproduce and guarantee its survival and offspring. In this way, the parasite and the host coexist for a certain time, until one of the two dies.

In the next sections we will learn about the different types of parasitism that exist in nature, which are the main organisms that act as parasites, as well as several concrete examples that will allow us to better understand the complex process of parasitism relationships that are established between different species. .

Types of parasitism

When classifying and separating the different types of parasitism, it is necessary to adhere to one or another criterion. In this way, we name below some of the most common classifications that allow us to differentiate between different types of parasitism:

Classification of parasitism according to the host

Depending on the type of organism that the parasites infect, we can talk about:

  • Phytoparasites (infect plants).
  • Zooparasites (infect animals).

Classification of parasitism according to the degree of dependence

Depending on the degree of dependence that the parasite establishes with its host, we find different types of parasitism :

  • Obligate parasites: they depend completely for their survival and correct development on the presence of a host they infect.
  • Facultative parasites : these parasites are capable of surviving during certain stages of their development or under certain conditions without the need to invade and infect another organism to guarantee their survival.
  • Accidental parasites: sometimes parasites mistakenly infect another organism that is not their common host. Despite this, they manage to adapt to this new host and achieve their goal: to supply themselves and survive from the infected organism.
  • Erratic parasites: on other occasions, although the parasite has managed to infect its common host, it does so in some tissue and organ that is not usually the most suitable for its survival, so it makes a mistake when choosing its infection habitat and must adapt to survive.

Classification of parasitism according to its duration

Depending on the duration of the infection period by the parasite to the host, these parasites are considered, from longest to shortest time of permanence: permanent, periodic or temporary parasites.

Classification of parasitism according to location

Depending on the location that the parasite adopts in the host organism, we can find ectoparasites (outside the organism) or endoparasites (inside).

These are the basic classifications to be able to know well the types of parasites that there are, which also helps us to realize that some of them are well known to us, while the vast majority of us do not know them, as we will see in the examples that we will show below.

Examples of parasitism

The great diversity of parasitic organisms and their needs and parasitism processes make the examples of this type of interspecific interaction very varied. Here are some examples of parasitism :


  • Mites (Subclass Acari, Arachnids).
  • Fleas (Order Siphonaptera, Insects).
  • Ticks (Order Ixodida, Arachnids).
  • Bed bug ( Cimex lectularius , Insects).
  • Lice (Order Phthiraptera, Insects).
  • Guinea worm ( Dracunculus medinensis ).
  • Emerald cockroach wasp ( Ampulex compressa ).

Specifically, in the intestinal parasitism of many mammals, including humans, various zooparasites of the amoeba group are involved, such as the Entamoeba histolytica species , as well as flagellated protozoa such as Giardia lamblia, intestinal worms ( Ascaris lumbricoides ), pinworms ( Entervius vermicularis ) and tapeworms (genus Taenia).


  • Red Weevil ( Rhynchophorus ferrugineus, Insects).
  • Green bug ( Nezara viridula, Insects).
  • Termites (Infraorder Isoptera, Insects).
  • Aphids (Family Aphididae, Insects) .

If you want to read more articles similar to Parasitism: definition and examples , we recommend that you enter our Biology category .

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