Georgia Milestones Biology EOC Prep

Field Journal: Feedback Loops

Standard Alignment: SB1.a (Cellular structure, function, and homeostatic balance)

Lab Unit 1.2

Observer Name:

Class Period:

Date of Entry:

Negative Feedback (Stabilizes)

Response counteracts/reverses the stimulus, returning the system back to a set point. Essential for stability.

Positive Feedback (Amplifies)

Response reinforces/increases the stimulus, pushing system further from set point until target is met.

Q1

When body temperature drops below 37°C, sensory receptors signal the hypothalamus. The hypothalamus stimulates shivering (muscle contractions) and vasoconstriction (narrowing of blood vessels). How does this mechanism represent a homeostatic response?

A It is a positive feedback loop because it increases metabolic rate to generate immediate cellular energy.

B It is a negative feedback loop because the physiological response counteracts and reverses the original drop in temperature.

C It is a positive feedback loop because it constantly reinforces the heat loss process until shivering stops completely.

D It is a negative feedback loop because vasoconstriction increases blood flow to external extremities, releasing heat.

Q2

Following a carbohydrate-rich meal, blood glucose levels rise above normal. Beta cells in the pancreas detect this change and release the hormone insulin, which signals body cells to absorb glucose. As blood glucose levels decline, insulin secretion slows down. Which statement best analyzes this process?

A The insulin loop is a positive feedback system because the response speeds up target organ glycogen uptake continuously.

B The loop represents negative feedback because the target organ responses eventually reverse the initial rise in blood glucose levels.

C The pancreas operates on non-regulatory signaling pathways since glucose is fully eliminated in the process.

D It is a positive feedback loop because insulin amplification prompts the alpha cells to simultaneously trigger glucagon.

Field Naturalist Biology Assessment Series Page 1 of 4

EOC Target Practice Part 1: Scenario & Endocrine Data Analysis

Q3

[MULTI-SELECT] During childbirth, pressure of the baby’s head against the cervix stimulates receptors that signal the pituitary gland to secrete oxytocin. Oxytocin causes uterine contractions, pushing the baby further down, increasing cervical pressure, and triggering more oxytocin release. Identify TWO statements that accurately characterize this biological scenario:

A The mechanism represents positive feedback because uterine response amplifies and accelerates the initial labor stimulus.

B The loop stabilizes internal balance by ensuring uterine tissues immediately recover to pre-pregnancy set points during labor.

C The loop is driven toward an ultimate endpoint (birth) rather than maintaining a steady resting baseline.

D The scenario demonstrates negative feedback because oxytocin levels ultimately drop once the stimulus is removed.

Q4

The hormone aldosterone is secreted when blood sodium levels drop. Aldosterone targets the kidneys, stimulating sodium reabsorption, causing water to follow via osmosis, which increases blood volume and pressure. Based on this feedback mechanism, what would result from a medical condition that destroys the adrenal cortex's ability to secrete aldosterone?

A Uncontrolled retention of sodium in blood, leading to high water absorption and high blood pressure.

B Failure of kidney reabsorption, causing blood sodium levels and blood pressure to drop critically below normal ranges.

C An increase in oxytocin release to compensate for blood pressure failure, stimulating standard positive feedback.

D A transition of the system into an amplified positive feedback loop that stabilizes blood vessel dilation.

Field Naturalist Biology Assessment Series Page 2 of 4

EOC Target Practice Part 2: Advanced Data Analysis Scenarios

Q5

Thyroid-stimulating hormone (TSH) from the pituitary gland prompts the thyroid gland to release thyroxine (T4), which increases cellular metabolism. High levels of T4 inhibit the pituitary gland from releasing more TSH (negative feedback). A physician reviews endocrine blood panels for three patients:

Patient Status	TSH Level (Normal: 0.4 - 4.0 mIU/L)	T4 Level (Normal: 4.5 - 12.0 mcg/dL)
Healthy Patient	1.8 mIU/L (Normal)	8.2 mcg/dL (Normal)
Patient A	14.2 mIU/L (High)	1.5 mcg/dL (Low)
Patient B	0.1 mIU/L (Low)	22.4 mcg/dL (High)

Which statement best analyzes Patient A’s data through a feedback loop model?

A Patient A suffers from a positive feedback failure where high TSH continuously destroys circulating T4 proteins.

B Patient A’s damaged thyroid gland fails to produce T4; the lack of T4 removes the negative feedback signal, leaving TSH secretion uninhibited.

C Patient A shows standard negative feedback since high TSH is currently lowering the body's baseline core temperature.

D Patient A’s pituitary gland is damaged, making it unable to respond to standard metabolic hormone feedback indicators.

Q6

As tomatoes ripen, they release gaseous ethylene. Receptors on neighboring fruit cells detect the ethylene and trigger rapid cell ripening, which prompts those cells to emit even more ethylene into the surrounding space. A biology class tracks tomato softening in a sealed bag over 5 days:

Measurement Day	Ethylene Gas Concentration (ppm)	Mean Fruit Softness Index (1-10 Scale)
Day 1	0.2 ppm	1.2 (Firm)
Day 2	1.5 ppm	2.8
Day 3	8.9 ppm	5.5
Day 4	45.0 ppm	8.6
Day 5	190.0 ppm	9.8 (Fully Soft)

Which statement best explains the feedback mechanism shown by the tomatoes?

A It is negative feedback because increasing softness acts as an inhibitor to return ethylene back to a baseline level.

B It is positive feedback because the physiological response (ripening/softening) continually amplifies the initial stimulus (ethylene production).

C It is negative feedback because the tomato cells stabilize and delay softening when gaseous levels reach critical thresholds.

D It is positive feedback because ethylene concentrations fluctuate in waves, maintaining a rigid set point of cellular structure.

Field Naturalist Biology Assessment Series Page 3 of 4

EOC Target Practice Part 3: Free Response & Graph Simulation Analysis

Q7

[EOC Free Response] A student team records the body temperature of an athlete during an intensive 30-minute workout on a stationary bike:

Workout Time (Minutes)	0 min (Rest)	10 min	20 min	30 min (End)
Body Temp (°C)	37.0°C	37.8°C	38.2°C	37.2°C
Sweat Rate (mL/min)	0.2	1.8	3.2	1.4

Explain how the data provides evidence of a negative feedback mechanism. Identify the physiological stimulus and the response in your explanation.

Field Naturalist Biology Assessment Series Page 4 of 4

Feedback Loops Practice Worksheet

Feedback Loops Practice Worksheet

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