Commensalism

Commensalism is a close relationship between organisms of different species where one organism benefits and the other organism does not benefit but is not harmed. Let us look at a few examples of commensalism.

The photo below shows several fish called remoras on a shark. The remoras have a special suction cup on top of their heads that they use to attach to the shark. This does not harm the shark at all. The remoras benefit from the relationship. They are carried along as the shark swims. This means they do not have to use their energy to swim. When the shark catches prey, the remoras eat the scraps that are dropped by the shark. The shark does not benefit from the relationship but it is not harmed.

The photo below shows some cattle egrets near a cow. As the cow moves around, it stirs up small animals such as grasshoppers which the egrets eat. The cow does not benefit from this relationship but it is also not harmed.

The plant seen below is an orchid. Orchids can often be seen growing on tree trunks. They use the trees as support. Growing on trees also allows the orchid to get more light than if it was growing on the forest floor. The tree is not harmed by the orchid and it does not benefit from the orchid either.

Remember that in commensalism one organism benefits while the other does not benefit and is not harmed.