Final answer:
Humans can respond directly to a change in the environment through rapid responses elicited by external signals such as shivering when we are cold and sweating when we are hot.
Step-by-step explanation:
Humans can respond directly to a change in the environment through rapid responses elicited by external signals. Examples of these responses include shivering when we are cold and sweating when we are hot. These responses help our bodies maintain a stable internal environment despite changes in the external environment.