Final answer:
The relationship between a barnacle and a whale is an example of commensalism, where the barnacle benefits without harming the whale.
Step-by-step explanation:
A barnacle grows on a whale, doing it no harm. This is an example of commensalism. Commensalism is a type of symbiotic relationship where one species benefits and the other is neither helped nor harmed. For instance, birds nesting in trees benefit from this protective environment while the tree does not suffer any impact. Similarly, when barnacles attach to whales, they gain mobility and access to nutrient-rich waters, whereas the whale remains unaffected by their presence.