Parasitismo

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Parasitismo es un forma de unilateral symbiosis.[1][2] Le parasitos vive de hoste. Ille pote, o non pote nocer le hoste. They may, or may not, harm the host. Parasitoides, per le altera latera, saepe occide suje hostes. on the other hand, usually kill their hosts. A parasitic relationship is the opposite of a mutualistic relationship.[3] Examples of parasites in humans include tapeworms and leeches. World-wide, the most serious cause of human death by a parasite is malaria.


Parasitism is a form of one-sided symbiosis.[4][5] The parasites live off the host. They may, or may not, harm the host. Parasitoids, on the other hand, usually kill their hosts. A parasitic relationship is the opposite of a mutualistic relationship.[6] Examples of parasites in humans include tapeworms and leeches. World-wide, the most serious cause of human death by a parasite is malaria.


A definition:

  • A parasite is an organism drawing nutrients from a living host. It lives in or on another organism, getting from it part or all of its food. It usually shows some degree of adaptive modification, and causes some degree of damage to its host.[7]

Parasites on humans[modificar | modificar fonte]

"Humans are hosts to nearly 300 species of parasitic worms and over 70 species of protozoa, some derived from our primate ancestors and some acquired from the animals we have domesticated or come in contact with during our relatively short history on Earth. Our knowledge of parasitic infections extends into antiquity".[8]

Biological context[modificar | modificar fonte]

When the above definition is applied, many organisms which eat plants can be seen as parasites, because they feed largely or wholly on one individual plant. Examples would include many herbivorous insects: the Hemiptera or true bugs (leafhoppers, froghoppers, aphids, scale insects and whiteflies). The larvae of Lepidoptera usually feed and mature on a single individual of the host plant species, and what they eat accounts for most of the food for their complete life span. Moreover, caterpillars can and often do serious damage to the host's foliage. Other orders also have many parasitic herbivores: Thysanoptera (thrips), Coleoptera (beetles), Diptera (flies).

Mites parasitising a harvestman

Parasites of larger animals account for much research done for veterinarian and medical purposes. These parasites include viruses, bacteria, protozoa, flatworms (flukes and tapeworms), nematodes (roundworms), arthropods (crustacea, insects, mites). Parasitic wasps and flies are of great interest to the entomologist, and may be used in biological control.

On the other hand, many blood-sucking insects (such as mosquitoes) have only brief contact with a host, and so perhaps should not be regarded as parasites.[9]p5

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  3. A relationship between two different organisms where both benefit.
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  6. A relationship between two different organisms where both benefit.
  7. Webster's Third International Dictionary, adapted; similar is the Oxford English Dictionary
  8. Cox F.E.G. 2002. History of human parasitology. Clinical Microbiology Reviews 15 (4) 595Patrono:Ndash612. [1]
  9. Price P.W. 1980. Evolutionary biology of parasites. Princeton N.J.