Parasitism: Interactions in which one organsism is harmed, but the other benefits. A parasite may weaken its host; it rarely kills it host. More than 100 parasites live in or on the human species. When it causes a disease and sometimes the death of host, it is known as pathogen. Crown gall diease, caused by a bacterium, occurs in many plants.
· Mutualism: Interactions in which both participants are benefited. The interdependent association between nitrogen fixing bacteria of the genus rhizobium and legume, is an example. Another example is the association between reef building coral animals and microscopic alage. The symbiotic alga is called Zooxan- thellae. Mycorrhizae is such an association between fungi and roots of 80% plants.
· Commensalism: Interactions in which one participant benefits but the other is unaffected , e.g; relationship between two insects; silverfish and army ants, relationship between a tropical tree and many epiphytes, smaller plants such as mosses, orchids and ferms that live attahed to the bark of the tree’s branches. The epiphytes anchor itself to the tree to obtain adequate light and watr not for obtaining nutrients rom the tree.
Predation Predator-Prey interactions
