The ability of a living organism to detect and respond to changes in the environment is referred to as

Step 1: Analyze the question The question asks for the term describing an organism's ability to detect and respond to changes in its environment (stimuli).

Step 2: Explain the concept Irritability (also called sensitivity) is one of the characteristics of living things. It is the ability to detect changes in the environment, called stimuli, and respond to them. Examples include:

• A plant shoot bending toward light
• You withdrawing your hand from a hot object
• A cat running when it hears a loud noise

Step 3: Evaluate each option

• A. Locomotion: movement of an organism from one place to another. It may be a response, but it is not the ability to detect and respond.
• B. Taxis: the movement of a whole organism toward or away from a directional stimulus (e.g., a Euglena moving toward light). It is a specific type of response, not the general term.
• C. Irritability: the general ability to detect and respond to stimuli. This matches the question exactly.
• D. Growth: a permanent increase in size, mass, or number of cells. It is not related to detecting stimuli.

Step 4: Answer The correct answer is **C.

Exam tip: Remember "IRRITABILITY = I React to Immediate Triggers" (stimuli). When you see "detect and respond to stimuli," think irritability or sensitivity. If the question says "movement of a whole organism in response to a directional stimulus," that is taxis.