Which of the following is the best example of homeostasis in the human body?

• A. An increase in heart rate during exercise that remains elevated long after exercise stops
• B. Sweating when body temperature rises to help return temperature toward a set point
• C. A plant bending toward light to increase photosynthesis (phototropism)
• D. A sudden mutation that changes the amino acid sequence of an enzyme

Answer: (B)

Verified step by step guidance

1. Understand the concept of homeostasis: it is the process by which living organisms maintain a stable internal environment despite changes in external conditions.
2. Identify the key feature of homeostasis, which is the regulation of internal conditions to keep them within a narrow, optimal range or set point.
3. Analyze each option to see if it involves maintaining internal stability: - An increase in heart rate during exercise is a response, but if it remains elevated long after exercise, it does not reflect a return to balance. - Sweating when body temperature rises is a mechanism to cool the body and return temperature toward the set point, demonstrating regulation. - A plant bending toward light is a growth response to external stimuli, not internal regulation. - A sudden mutation changing an enzyme is a genetic change, not a regulatory process.
4. Conclude that the best example of homeostasis is the process that actively works to restore internal balance, which is sweating to regulate body temperature.
5. Summarize that homeostasis involves feedback mechanisms that detect deviations from a set point and trigger responses to correct those deviations, as seen in the sweating example.