Definition and Kinds of Symbiosis

Symbiosis comes from two Greek words that mean “with” and “living.” It describes a close relationship between two organisms from different species. It is sometimes, but not always, beneficial to both parties.

Four Kinds of Symbiosis

There are several kinds of symbiosis to consider when looking for examples of symbiosis:

• Commensalism 
• Parasitism 
• Mutualism 
• Eendosymbiosis and ectosymbiosis

Commensalism

Commensalism is a type of relationship where one of the organisms benefits greatly from the symbiosis. The other is not helped but is not harmed or damaged from the relationship. In other words, this is a one-sided symbiotic relationship.  

• Example: The relationship between cattle egrets and cattle.

• The cattle egret will eat insects that have been disturbed when the cattle forage.  

In some of these commensalism relationships, the organism that is reaping the benefit will use the other for protection or transportation.  

• Example: A hermit crab taking up residence in an empty seashell.  
• Example: A spider building a web on a tree.   

Parasitism 

In parasitism, one organism benefits from the relationship but at the expense of the other. The organism may live inside the other’s body or on its surface. In some of these parasitic relationships the host dies and in others, it is important that the host remain alive.   

• Example: Fleas and mosquitoes feed on blood from other organisms.

• In this type of parasitic relationship, the host needs to stay alive and it is not damaged greatly.  

• Example: Barnacles that attach to the bodies of whales.

• The whale is not harmed greatly, but may have some pain or itching.  

• Example: Tapeworms

• Tapeworms do more damage to their hosts because they eat partially digested food and that deprives the host of some food and nourishment. 

• Example: Aphids

• Aphids eat sap from plants. 

Mutualism 

Mutualism is a close relationship where both parties benefit. Both species will benefit from the relationship and many of these relationships are ling-lasting.

• Example: Cleaning symbiosis

• In the ocean, certain species, like shrimps and gobies, will clean fish. They remove parasites, dead tissue, and mucous.

• Example: Dogs and humans have enjoyed a mutualistic symbiosis for centuries.

• The dogs supply protection and companionship and the humans provide food and shelter. 

• Example: The relationship between goby fish and shrimp.

• The shrimp digs a burrow into the sand and both organisms live there. Because the shrimp is almost blind, the goby fish will touch the shrimp when a predator is near.  

• Example: Humans and microorganisms

• Humans have a mutualistic relationship with microorganisms, primarily bacteria, in their digestive tract. 

Endosymbiosis and Ectosymbiosis 

Endosymbiosis is one species living inside another one.  

• Example: Protozoans that live inside termites and help them digest wood. 

Ectosymbiosis is one species living on the surface of the other species.  

• Example: Lice that feed on the skin, blood, or oil secretions of the host.