What term describes a non-random change in direction or speed in response to a stimulus?

What term describes a non-random change in direction or speed in response to a stimulus?

• A. Kinesis
• B. Taxis
• C. Migration
• D. Instinct

Answer: (B)

A directed, non-random change in direction or speed in response to a stimulus is taxis. This means the organism moves with a purposeful orientation toward or away from a cue. For example, positive chemotaxis occurs when a bacterium moves toward a nutrient chemical, or positive phototaxis when an insect or worm moves toward light. The key idea is that movement is oriented relative to the stimulus, not random. In contrast, kinesis involves changes in movement that depend on the stimulus but are not directed toward or away from it—the organism’s speed or turning rate changes, but there isn’t a consistent orientation toward the cue. Migration refers to large-scale, often seasonal, movement of populations rather than a direct, moment-to-moment response to a local stimulus. Instinct is an inherited behavioral tendency, not a specific directed response to a stimulus in the moment.

A directed, non-random change in direction or speed in response to a stimulus is taxis. This means the organism moves with a purposeful orientation toward or away from a cue. For example, positive chemotaxis occurs when a bacterium moves toward a nutrient chemical, or positive phototaxis when an insect or worm moves toward light. The key idea is that movement is oriented relative to the stimulus, not random.

In contrast, kinesis involves changes in movement that depend on the stimulus but are not directed toward or away from it—the organism’s speed or turning rate changes, but there isn’t a consistent orientation toward the cue. Migration refers to large-scale, often seasonal, movement of populations rather than a direct, moment-to-moment response to a local stimulus. Instinct is an inherited behavioral tendency, not a specific directed response to a stimulus in the moment.