A student suggests that homeostasis is only needed when a person is exercising. Evaluate this statement, using your knowledge of how the body monitors and responds to changes in its internal environment.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
During a biology lesson, a student states: 'The body only needs to regulate its internal conditions during exercise, because that is when conditions change the most.'
Model answer (5 marks)
Homeostasis is the maintenance of a constant internal environment.
It operates continuously, both at rest and during exercise.
An example is the regulation of core body temperature.
Temperature must be kept constant because enzymes and metabolic reactions have optimum temperatures; deviations reduce reaction rates and can denature proteins.
Thus the student’s statement is incorrect: exercise increases the challenge to homeostasis but does not initiate it; the body constantly monitors and responds to changes in its internal environment.
It operates continuously, both at rest and during exercise.
An example is the regulation of core body temperature.
Temperature must be kept constant because enzymes and metabolic reactions have optimum temperatures; deviations reduce reaction rates and can denature proteins.
Thus the student’s statement is incorrect: exercise increases the challenge to homeostasis but does not initiate it; the body constantly monitors and responds to changes in its internal environment.
Examiner tips
- Use the exact definition of homeostasis; mention continuous operation; give a specific regulated variable and explain its importance; conclude clearly that the statement is wrong but note exercise increases demand.
Common mistakes
- Confusing homeostasis with only exercise; omitting the definition; failing to explain why the variable is important; not concluding that the statement is incorrect.
Mark scheme (5 marks)
- Homeostasis is the maintenance of a constant internal environment
- Homeostasis operates continuously / at rest as well as during exercise
- Correct named example of a variable that is regulated at rest, e.g. blood glucose concentration / core body temperature / water content
- Explanation of why the named variable must be kept constant — linked to cells / enzymes / metabolic reactions
- Reasoned conclusion that the student's statement is incorrect / partially correct — e.g. acknowledging exercise increases the challenge to homeostasis but does not cause it to start
Key terms in this question
homeostasis · internal environment
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Evaluate" question →
- Decode the mark scheme abbreviations →
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