Parasitism Facts For Kids: Meaning, Types And Examples Explained

Parasitism takes place between two organisms, wherein one benefits at the expense of another.

Parasites are a broad range of organisms that belong to the animal kingdom and vary in different shapes, sizes, and other characteristics. The host body can be affected by parasitic infections, which can often turn deadly.

Some of these organisms can live freely outside the host body, while some of them cannot. They completely rely on the hosts for their survival. In fact, certain parasites can enter the stage of dormancy when living outside the body of a host. In most parasites, there is more than one host involved in their life cycle. Different stages of their life are completed in different host bodies.

Read on to learn more about parasitism and its different types.

Meaning Of Parasitism

Parasitism is a long-term relationship between the parasitic organism and the host species. It's a type of symbiotic relationship, in which one member benefits from the other, thereby harming the other member. The name 'parasite' itself means 'one who eats at the table of another', a term derived from the Greek word 'parasites'.

Each of the biological kingdoms has its own kind of parasite species and those belonging to the animal kingdom usually have a free-living form. For example, protozoans, mosquitoes, roundworms, ticks, and the different types of viruses, all can live freely outside the host's body. The only exception here is in the case of the viruses, which get activated only upon entering the body of its host. The host's fitness is reduced by these organisms because of the different parasitic infections caused by them. The ones that cause these infections are called pathogens. So, we can call this relationship a one-sided symbiosis, where the parasites live off the host organism. It is just the opposite of a mutualistic relationship where both the organisms benefit from each other.

Types Of Parasitism

Different forms of parasitism exist in the world. These organisms are grouped under various classifications, which are based on their relationship with the host, their individual characteristics, growth, life cycle, and several other factors. The most common types of parasitism are explained below.

Obligate Parasitism: It is a type of parasitism where the parasitic species are completely dependent on the host organism to complete their life cycle. Their evolution made them incapable of existing without the host body. One such example is fleas, which will not survive when removed from the scalp.

Facultative Parasitism: These parasitic worms don't depend on the host to complete their full life cycle. This means that these parasite species can survive alone. Certain animals, plants, and fungi can undergo facultative parasitism. An example of this is a roundworm called Strongyloides stercoralis, which causes strongyloidiasis in humans, is also able to live freely.

Ectoparasites: The parasite species that live outside or on the host body are called ectoparasites. They derive their nourishment from the host body while living and thriving on it. Head lice, fleas, and ticks are some common ectoparasites that draw blood from multiple hosts and can get easily transmitted upon contact.

Endoparasites: Intestinal worms like roundworms, flatworms, and other intracellular parasites are termed endoparasites. They live inside the body of humans and other animals and derive the essential nutrients from the food and blood of hosts. Liver fluke is a common endoparasite, which uses humans as an intermediate host species to complete their life cycle. Mesoparasites enter the host body through the external orifices such as the mouth or anus.

Apart from these forms of parasites, there are other species as well. Some of these are large and can be seen with the naked eye, which is called macroparasites, while some of these are tiny and invisible to the naked eye. These are called microparasites. For example, protozoans are microparasites, while roundworms are macroparasites.

Brood Parasitism: This is the practice of laying eggs in the nest of another species. An example of a brood parasite is the cuckoo bird, which does not build its own nest and lays the eggs in the nest of crows. Sometimes, the brood parasites even kick out the eggs of the host from the nest in order to make space for their own eggs. It occurs in certain fish species as well and is known as kleptoparasitism.

Social Parasitism: This involves certain parasites that take advantage of social insects like bees, ants, and termites. For example, an ant species called Tetramorium inquilinum, spends its whole life on the back of other ants and makes these species their slaves. They get their food and travel from one place to another on the back of the host ants and will die if they accidentally fall off from the host backs.

Characteristics Of Parasites

Parasites have separated habitats. They produce an enormous amount of spores or eggs, and thus, fertile females are dispersed in large numbers. They generally attach themselves as well as their eggs or spores to larger organisms. The spores can live for long periods in the dormant stage and can become active once they enter the body of the hosts. For example, nematodes can live for about 23 years in their dormant stage.

Inbreeding among the offspring and parthenogenesis are common characteristics seen in parasites. As a result of this, the flow of genetic material in these species is less. They are well adapted for their successful dispersion and reproduction.

Parasitic species are extremely specialized feeders and generally rely on more than one host in their life cycle, which is quite complex. Adaptive radiation is extensively seen in parasites. The lifespan of these organisms depends on the lifespan of their host. An interesting characteristic of parasites is that they develop themselves in order to cope with the defense mechanisms of their hosts. This phenomenon is called co-evaluation and is one reason for the large population of parasitic species.

Why do we need parasites?

Parasite species are important to maintain the ecosystem and community structures. The host population is regulated by these organisms.

Dominant species are controlled by these parasites, giving a chance for competition among the living organisms. Genes are also transferred by the parasite species and therefore, their presence in the host body shows chances of evolution and adaptation. The food web stability is maintained by the parasites. They are part of the global biodiversity and are essential for the smooth running of the ecosystem. Parasites contribute to nutrient cycling and also play a crucial role in wildlife population control.

FAQs

Q. What are four examples of parasitism?

A. Four examples of parasitism are:

Protozoan parasitism

Helminthic parasitism

Ectoparasite parasitism

Brood parasitism

Q. What are the characteristics of parasitism?

A. The commonly seen characteristics of parasitism are:

Parasites are much smaller than the host.

A rate of reproductivity is seen in parasites.

Parasites harm the host organisms.

Parasites generally have their own characteristic way of evading the host organism.

Q. What are parasites and why do we need them?

A. Parasites are organisms that live either on the body surface of the host or within the host's body and generally cause harm to the hosts by drawing all the vital nutrients. These organisms are part of the global biodiversity and are essential for the smooth flow and stability of the ecosystem. They contribute to nutrient cycling and play a crucial role in wildlife population control.

Q. What is the nature of parasitism?

A. Parasitism is a relationship between two organisms belonging to two different species, one of which benefits from the other. Usually, the host species are harmed by the parasites.

Q. Why is parasitism important in ecosystems?

A. The host population is regulated by the parasites. The food web stability is also maintained by the parasite species. This helps in shaping the community and ecosystem structures.

Q. How common is parasitism?

A. The most popular lifestyle on Earth is parasitism. More than 100 million human parasites only. About 40% of the total animal species on Earth are parasites.

Q. What are the effects of parasitism?

A. Parasites can affect the survival rate of the host's body including its reproductive and growth rates. It increases the host's competitive ability.