Loop Logic (PLD Level 2: 30%)
This term describes the "normal" or target value the body tries to maintain, such as 98.6°F for temperature.
Set point
When investigating heart rate response to exercise, this is the independent variable.
The intensity or duration of exercise
Looking at a data table, student A's pulse is 70, 120, and 75 BPM. Does this provide evidence of homeostasis?
Yes, because the heart rate returned near the starting baseline.
Predict the long-term impact on a human if their "sweat response" (effector) failed during a 5-mile run in the sun.
The body would overheat, leading to heatstroke/failure of homeostasis and potential death.
Explain how a graph of "Body Temperature vs. Time" in a cold room provides evidence of feedback mechanisms.
If the line stays relatively flat despite the cold room, it proves internal mechanisms like shivering are working.
In a feedback loop, this part detects a change in the environment, such as a drop in outside temperature.
Receptor/Sensor
Why must a student measure their "resting heart rate" before beginning the exercise portion of the lab?
To establish a baseline for comparison
Define the "Assessment Boundary" for this standard: What cellular process are we not required to explain when discussing heart rate?
Cellular respiration or specific ATP chemical pathways
Analyze how the circulatory and respiratory systems work together as a coordinated feedback mechanism during exercise.
The respiratory system increases O2 intake while the circulatory system speeds up to deliver that O2 to muscles and remove CO2.
In a stomate investigation, what evidence would support the claim that the plant is maintaining homeostasis?
Data showing the stomates closing during high heat to prevent dehydration.
This type of feedback loop works to reverse a change to bring the body back to its set point.
Negative feedback
List two factors that must be kept constant (controlled variables) to ensure the heart rate data is valid.
Type of exercise, environment temperature, or time spent resting
Provide evidence from a graph of blood glucose levels that a "positive feedback" loop is not occurring after a meal.
The glucose levels peak and then drop back down, rather than continuing to rise indefinitely.
Compare the feedback mechanism of "blood clotting" (Positive Feedback) to "temperature regulation" (Negative Feedback). Which one is more common for maintaining long-term stability?
Negative feedback is more common for stability; positive feedback amplifies a change to reach a specific endpoint.
Formulate a hypothesis for an investigation testing how water temperature affects the opening of stomates in a plant.
If the temperature increases, then the stomates will close to prevent water loss/maintain homeostasis.
When you are dehydrated, your kidneys reabsorb more water. Identify the effector in this scenario.
The kidneys
Predict the trend of a graph showing heart rate over time if a student exercises for 5 minutes and then rests for 10.
The graph will rise sharply and then gradually curve back down to the baseline.
A student concludes that exercise destroys homeostasis because heart rate changes. Explain why this conclusion is scientifically incorrect.
Homeostasis is a "dynamic equilibrium"; the change is the body's way of maintaining stability, not losing it.
Evaluation: A patient has a disease where their pancreas cannot produce insulin. Critique the claim: "This patient can maintain homeostasis without medical intervention."
The claim is false; without insulin, the feedback loop for blood sugar is broken, leading to dangerously high levels.
Identify a possible "source of error" in a heart rate investigation conducted by students in a classroom.
Miscounting the pulse, inconsistent exercise intensity, or not resting long enough between trials.
Explain why a thermostat in a house is a common analogy for a negative feedback loop.
It turns the heat on when it’s too cold and off when the set point is reached to maintain stability.
If a student's heart rate takes 15 minutes to return to baseline while another student's takes 2 minutes, what can you infer about their feedback efficiency?
The second student's body responded more quickly/efficiently to restore homeostasis.
In an investigation on root development, how does "water level" act as a feedback trigger for the plant?
Low water levels trigger the roots to grow deeper or more extensively to seek moisture.
If a feedback loop is "interrupted," identify the likely outcome for the organism.
Disease, instability, or death.
Describe the role of the "control center" (usually the brain) in a feedback mechanism.
It processes the signal from the receptor and sends instructions to the effector.