A change in an organism's environment that causes a response is called a ______.

A change in an organism's environment that causes a response is called a ______.

• A. Trigger
• B. Prompt
• C. Stimulus
• D. Signal

Answer: (C)

A stimulus is any change in an organism’s environment (external or internal) that can be detected by its senses and elicit a response. It’s the initiating cause that a nervous system or other signaling system reacts to—for example, light prompting a plant to grow toward it or a hot surface causing a hand to withdraw. Terms like trigger or prompt are not the standard scientific terms for this initiating change, and a signal refers more to the information conveyed within a system rather than the external change that starts the response. So the correct word describes the initiating environmental change that brings about a reaction: stimulus.

A stimulus is any change in an organism’s environment (external or internal) that can be detected by its senses and elicit a response. It’s the initiating cause that a nervous system or other signaling system reacts to—for example, light prompting a plant to grow toward it or a hot surface causing a hand to withdraw. Terms like trigger or prompt are not the standard scientific terms for this initiating change, and a signal refers more to the information conveyed within a system rather than the external change that starts the response. So the correct word describes the initiating environmental change that brings about a reaction: stimulus.