Mutualism is a biological interaction between individuals of two different species, where both individuals derive a fitness benefit, for example increased survivorship. Similar interactions within a species are known as co-operation. Mutualism plays a key part in ecology and evolutionary biology. For example, mutualistic interactions are vital for terrestrial ecosystem function as more than 70% of land plants rely on mycorrhizal relationships with fungi to provide them with inorganic compounds… (More on Mutualism)