Biology · Grades 9–12
Homeostasis and negative feedback
Describe regulation as a dynamic process, not a perfectly fixed value.
Learn the idea
Homeostasis
Internal conditions are regulated within workable ranges despite changes.
Feedback
Negative feedback tends to counter a deviation from a regulated state.
Pathway
A simple control model includes a sensor, a coordinating process and an effector.
Limits
Feedback models simplify physiology and are not diagnostic tools.
Worked examples
What does negative feedback tend to do?
The response reduces the triggering difference in a simple control model.
Counter a deviation.
Does homeostasis mean every internal value is exactly constant?
Biological values vary while being regulated.
No; regulation operates within ranges.
Check your understanding
A supplied control model has target 10 units and measurement 13 units. What is measurement minus target?
Which component detects a change in a simple feedback model?
- Only the worksheet title.
- Only the output label.
- Sensor.
Why can a delay in feedback produce overshoot?
Answers and marking notes
Answers and marking notes
- 3
13 − 10 = +3 units.
- Sensor.
A sensor obtains information about the regulated quantity.
- A response may continue after the system has approached its target because information or effects are delayed.
A causal explanation is needed.
Further reading and review references
- openstax.org · reference 1
- www.genome.gov · reference 2
- www.genome.gov · reference 3
- www.genome.gov · reference 4
- www.genome.gov · reference 5
- www.genome.gov · reference 6
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.