Define and differentiate between mutualism and commensalism.

Mutualism is a symbiotic relationship where both species benefit, while commensalism is where one species benefits and the other is unaffected.

Mutualism is a type of symbiotic relationship in which both species involved benefit from the interaction. This relationship can be obligatory, where the survival of one or both organisms depends on the relationship, or facultative, where the relationship is beneficial but not essential for survival. An example of mutualism is the relationship between bees and flowers. Bees collect nectar from flowers for food, and in the process, they help in the pollination of the flowers, which is essential for the reproduction of the plant.

On the other hand, commensalism is a type of symbiotic relationship where one species benefits and the other is neither harmed nor benefited. The species that benefits is known as the commensal, while the unaffected species is known as the host. This relationship can be seen in various ecosystems and often involves a larger host organism and a smaller commensal. An example of commensalism is the relationship between barnacles and whales. Barnacles attach themselves to the skin of whales and benefit by getting a free ride through nutrient-rich waters, feeding on the plankton in the water. The whales, however, are generally unaffected by the presence of the barnacles.

In summary, the key difference between mutualism and commensalism lies in the impact of the relationship on the species involved. In mutualism, both species benefit from the relationship, often leading to a close interdependence. In contrast, commensalism involves one species benefiting while the other remains unaffected, with no harm or benefit. Understanding these relationships is crucial in the study of ecology as they play a significant role in the survival and evolution of species.