Topic – Symbiosis

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Symbiosis is a long-term relationship between two different species. This means that the two species interact with each other over a long period of time. So these types of relationships do not include things such as one species eating another one.

There are three main types of symbiosis. These are mutualism, commensalism, and parasitism. These may seem difficult to understand at first, but you probably already know many examples of these relationships.


Mutualism comes from the word mutual, which means something that is shared by two or more organisms. In a mutual relationship, both organisms gain something. So you would have a mutual relationship with your best friend. Both of you benefit from the friendship. The same is true of mutualism in other species. In mutualism, both species have something to gain. Neither species is hurt by the relationship. There are many examples of this in the world. A honey bee collects pollen from flowers to make honey. While doing this, the bee pollinates the flower and helps it reproduce. The Plover bird cleans the teeth of a crocodile. The crocodile gets its teeth cleaned, and the bird gets something to eat. People even have symbiotic relationships with their pets. For example, a dog owner gives a dog food and shelter, and the dog gives the owner affection and companionship.


In commensalism, one species benefits from the relationship while the other species is not harmed. The Cattle egret, a type of bird, looks for food in fields where cattle live. The cattle stir up the ground as they move and eat the grass. This also brings insects to the surface. Egrets follow the cattle and eat the insects. So the egrets benefit by having their food “delivered,” and the cattle are not harmed in any way. People have similar relationships with domestic animals. For example, people get eggs from chickens, and the chickens are not harmed.


In biology, a parasite is an organism that lives on or in another organism (its host) and gets nourishment from it. In parasitism, the host is harmed in some way. One example is the tapeworm. A tapeworm gets inside the intestines of cows, pigs, and sometimes people. The tapeworm eats the host’s partly digested food so the host does not get the nutrients it needs from the food. Another very common example is the mosquito. A mosquito bites its host to get blood to help its eggs develop. Mosquito bites can cause swelling and itching on the host. The bites can also spread diseases to their hosts.

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