Safety and evidence boundary
This week uses fictional organisms, classroom-safe models, and non-diagnostic datasets. Do not collect personal medical information, change medication, perform extreme-temperature exposure, deliberately alter blood glucose, restrict food or water, or use physiological measurements to diagnose health conditions.
Explicit science instruction
Feedback claims become stronger when the response is quantified. For a regulated variable, useful measures include deviation from a reference value or range, response time, recovery time, overshoot, and remaining error after recovery.
A simple signed deviation can be calculated as observed value minus reference value. Percent deviation can be calculated as absolute deviation divided by the reference value, multiplied by 100%. These summaries do not prove the mechanism; they describe the pattern.
Vocabulary: deviation; reference value; percent deviation; recovery time; overshoot; damping; stability; time series; residual error.
Worked example with reasoning
A fictional system has a reference value of 50 units. After a disturbance the measured values are 50, 58, 55, 52, 49, 50 at equal time intervals. Peak deviation is +8 units. Percent peak deviation is 8/50 × 100 = 16%. The value later reaches 49, an overshoot of −1 unit, before returning to 50. The dataset supports recovery with slight overshoot; it does not identify the sensor or effector by itself.
Guided question
If two systems return to the same final value but one oscillates widely before settling, are they equally stable? What additional metric would help?
Independent work
- Graph this dataset: 50, 62, 57, 53, 51, 50.
- Calculate peak signed and percent deviation from 50.
- Identify the first interval back within ±2 units.
- State whether overshoot occurred.
- Write one mechanism claim the graph cannot establish on its own.
Misconception check
A graph showing return toward a reference value is consistent with negative feedback, but it does not by itself prove which biological structures produced the response.
Formative understanding check
Why should a biology student separate evidence for a recovery pattern from evidence for the mechanism causing recovery?
Show the worked response
The time series can show deviation and recovery, but identifying the mechanism requires additional evidence about sensors, signaling pathways, effectors, interventions, or comparisons.
Open-book formative practice only; not an official mastery attempt or grade.
Mentor evidence conference
Ask Archaemenes to test whether your feedback model identifies the variable, sensor, integrating logic, effector, direction of response, and limitation without giving protected assessment answers.
Open Archaemenes for this lessonTeacher guidance
Foundation: use a supplied graph with the reference line already drawn. Core: calculate deviations and defend one claim that the data support and one they do not. Extended: compare two response curves using overshoot, damping, recovery time, and possible tradeoffs.
Preserve learning evidence
Keep the model, calculation or graph, correction note, and evidence-based explanation in the matching Week 14 evidence field.
Return to wednesday Evidence Workspace