Final answer:
Reciprocity is a form of cooperation that involves one-sided interactions and is observed in many animal species. It requires repeated encounters and punishes individuals who don't reciprocate.
Step-by-step explanation:
Reciprocity, or being reciprocal, is a form of cooperation that involves one-sided interactions. It is observed in many animal species, such as monkeys, where individuals engage in behavior that benefits both parties. An example of reciprocity is when a monkey allows another monkey to pick parasites from its fur and then later the roles are reversed and the first monkey grooms the second monkey. This type of interaction requires repeated encounters and punishes individuals who don't reciprocate.