Which response describes a simple change in activity or turning rate in response to stimuli?

Kinesis refers to a non-directional response to a stimulus where the intensity of the stimulus influences the speed or frequency of movement of an organism. For example, in the presence of heat or light, an organism might increase its movement rate without moving towards or away from the stimulus. This results in a simple change in activity, often described as random movement patterns that are dependent on the level of the stimulus. The movement is characterized by an increase in activity rate when the stimulus is favorable and a decrease when it is not, thus demonstrating a simple response to environmental changes.

In contrast, phototropism is the directional growth of plants towards light, which is a growth response rather than a simple change in movement. Positive chemotaxis involves movement toward a chemical stimulus, indicating a specific and directed response rather than a simple activity change. Orthokinesis, while also related to kinesis, specifically indicates movement that changes direction more frequently in response to the intensity of a stimulus, rather than merely the overall activity level.