Final answer:
Adaptive radiation refers to the rapid diversification of a single ancestral species into multiple new species, each adapted to a different niche, exemplified by the Hawaiian honeycreepers.
Step-by-step explanation:
An adaptive radiation is a process where a single ancestral species rapidly diverges into a number of different species that are each adapted to a specific niche or environment. This concept is central to understanding how species evolve and adapt to different ecological conditions. Examples of adaptive radiation can be seen in island ecosystems, such as the diversification of the Hawaiian honeycreepers, where from a single species, numerous species have evolved. These unique species have adapted to various niches and thus exhibit a wide range of forms and behaviors tailored to their specific environments.