Continuous and Discontinuous variations.

Mutualism is a sort of symbiotic connection in which both species gain from their association. The relationship between bees and flowers is an illustration of mutualism. The bees gather nectar from the flowers, which gives them sustenance, while the blooms gain from pollination.
Commensalism is a sort of symbiotic interaction in which one organism gains while the other is unaffected. The interaction between barnacles and whales is an illustration of commensalism. The whales are unaffected as the barnacles adhere to them and eat the food scraps they churn up while swimming.