Mutualism is the positive interaction between two species. Types of mutualism include:
- Resource-resource interactions: example- rhizobia bacteria live in nodules on the roots of leguminous plants (peas, beans, lentils, clover, etc.). The bacteria fixate nitrogen, which is a limiting resource.
- Service-resource interactions: example- cleaner animals such as oxpeckers and cleaner fish will remove parasites from an animal in return for a food source.
- Service-service interactions: example- sea anemones provide a safe place for clown fish in their stinging tentacles and the clown fish will protect the anemones from predators.
Commensalism is much more rare. It is when one organism benefits and the other is unaffected. For example, hermit crabs inhabit the empty shells of other animals for protection, typically snail shells.
