Working Together

Different species within ecosystems work together in other ways, too. Some have an association called symbiosis.
 Symbiosis is a close relationship between organisms of different species in which one or both benefit.

There are three different kinds of symbiosis. One is called parasitism. An organism that benifits from its relationship with another organism while the other organism is harmed is called parasite.
An example of this fleas living on dogs.In this case a flea is the parasite. The animal on which the parasite lives, such as the dog, is called the host.
The fleas get food by drinking the dog's blood. However , the dog becomes very uncomfortble and it itches and scratches. In extreme cases, the dog can die from blood loss due to the fleas.