The interactions are beneficial to atleast one of the two competing organisms. The other may be benefitted or not but it is seldom harmed. Important types of positive interactions are scavenging, commensalism, proto cooperation and mutualism.
a. Scavenging :
It is the phenomenon of feeding on flesh of dead animals and corpses. The corpse eaters are called scavengers. The best known scavenger is vulture followed by Carrion beetle.
b. Commensalism :
It is the interaction between the individuals of two different species in which one is benefitted while the other remains unaffected. The organism which is benefitted is called commensal while the unaffected organism which provides the benefit to the commensal is called the host. Example: Pilot fish and shark. Pilot fish follows Shark and feeds upon its left overs.
c. Proto cooperation :
It is a facultative mutually beneficial relationship that develops between individuals of two interacting populations. The association provides benefit to both the interacting organisms but this is not essential for their survival. Example: Sea anemone and Hermit crab. Sea anemone is sometimes found attached to the mollusk shell in which hermit crab resides. Hermit crab removes the sea anemone from its place of attachment over the rock and fixes it over the surface of its molluscan home . This is useful to Hermit crab as sea anemone provides it a camouflage and protect the Hermit crab from its predators. Sea anemone is also getting benefitted by moving to places where there are food sources. It also obtains food from the pieces dropped by the crab.
d. Mutualism or Symbioses :
It is an obligatory, physically close and mutually beneficial relationship that occurs between the interacting organisms. Both the interacting organisms fail to show normal growth in the absence of this association. Example: Lichens. Lichens are dual organisms formed of an algae and a fungus. The fungus helps in anchoring the lichen , absorption of water, minerals and provides a covering over the alga. The algal partner manufactures food using these raw materials both for self and fungal partner. Due to this association, lichen is abe to grow on barren substratum like bare rocks.