What characteristic defines Batesian mimicry?

Batesian mimicry is characterized by non-harmful animals evolving to resemble harmful or unpalatable species. This form of mimicry provides a survival advantage to the mimics, as potential predators may avoid them based on their resemblance to harmful species. The mimicking species gains protection despite being harmless, as predators have learned to associate the warning signals (like coloration) of the harmful species with negative consequences.

In contrast, the other options do not convey the essence of Batesian mimicry. Harmful animals appearing harmless pertains to a different concept and does not reflect the mimicking relationship central to Batesian mimicry. Similarly, beneficial animals mimicking other beneficial species typically refers to a more mutual advantage scenario, which is not the focus of Batesian mimicry. Finally, the idea of species evolving to look entirely different does not align with the concept, as Batesian mimicry specifically involves a resemblance to a harmful model rather than a complete transformation into something distinctly different.