Final answer:
Commensalism is a symbiotic relationship in which one species benefits while the other is unaffected, such as birds nesting in trees or cattle egrets feeding on insects disturbed by grazing animals.
Step-by-step explanation:
Commensalism is a type of symbiotic relationship where one species benefits and the other is neither harmed nor benefits. A classic example of this is birds nesting in trees; the birds gain protection for their young without affecting the tree. Conversely, in mutualism, both species benefit, as seen in the relationship between termites and their gut protists, which helps them digest cellulose.
Commensalism contrasts with parasitism, where the parasite benefits at the expense of the host. Birds such as cattle egrets feeding on insects stirred up by grazing animals, mites hitching rides on flying insects, and pilot fish eating leftovers from sharks are all instances of commensal relationships.