One dim memory I have from sixth grade biology is that of the oxpecker, a small bird that sits on the back of the rhinoceros. Normally a dominating and irascible beast, the rhino tolerates the oxpecker because the bird does something the rhino cannot do for herself: relieve her of all the troublesome insects that worry her neck, back and hindquarters. As most sixth graders know, this relationship is an example of symbiosis, or the cooperation of two organisms to their mutual benefit.
