Final answer:
Phototaxis is an example of taxis, which is the directed movement towards or away from a stimulus. The planarian moving towards a light source is an example of positive phototaxis.
Step-by-step explanation:
Phototaxis, which is the movement of a planarian towards a light source, is an example of taxis. Taxis is the directed movement towards or away from a stimulus. In this case, the planarian is exhibiting positive phototaxis, as it is moving towards the light source.
Phototaxis specifically refers to the movement of an organism in response to light. Positive phototaxis involves movement toward a light source, while negative phototaxis involves movement away from light.