DSE Biology | Homeostasis Lesson-Prep Guide (Tutor Edition) | Temperature, Blood Glucose and the Kidney

2026-11-01

Tutor lesson-prep guides · Secondary Biology

Students say “the body keeps things stable” but cannot name the sensor, the coordinator or the effector. This lesson fits temperature, blood glucose and water balance into one sentence pattern so they see a single model instead of three paragraphs.

Objectives — Students can: (1) describe any negative feedback as deviation, sensor, coordinator, effector, correction; (2) state normal ranges for temperature and blood glucose and the opposing hormones; (3) calculate daily filtrate volume and the percentage reabsorbed.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Osmosis	Which way water moves	Low solute to high solute
Unit conversion	How many cm3 in 1 dm3	1000 cm3
Percentages	How much of 180 is 1.5	0.83%

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-8 min	Recall: what stable means	A wobble, not a constant	Give a daily example
8-20 min	The five boxes	Deviation, sensor, coordinator, effector, correction	Students fill them
20-32 min	Temperature	Set point 37.0 C	Range 36.1-37.2
32-44 min	Blood glucose	Fasting 5.0, after a meal 7.0	Insulin against glucagon
44-54 min	Kidney figures	Filtration 125 cm3/min	180 dm3 a day, 99.2% reabsorbed
54-60 min	Exit check	Three questions, marked at once	Independent

03 Teaching script (read it out)

Scene 1: One negative-feedback model, three sets of parts

Temperature, blood glucose and water balance use the same sentence: value drifts, sensor detects, coordinator compares, effector acts, value returns to range. Students should say the sentence three times rather than memorise three blocks of text.

Board note: One negative-feedback model, three sets of parts

Scene 2: Temperature: losing and keeping heat are two ends of a rope

The set point is 37.0 C and normal drift stays inside 36.1-37.2 C. When temperature rises, vessels dilate and sweating starts; 0.5 dm3 of sweat evaporating carries away about 1200 kJ at roughly 2400 kJ per dm3. When it falls, vessels constrict and shivering generates heat.

Board note: Temperature: losing and keeping heat are two ends of a rope

Scene 3: The kidney filters everything, then takes back what it needs

At 125 cm3/min the glomeruli filter 180 dm3 in 1440 minutes, yet only about 1.5 dm3 leaves as urine, so 178.5 dm3 is reabsorbed: 99.17%. More ADH means more water reabsorbed, so less and more concentrated urine.

Board note: The kidney filters everything, then takes back what it needs

04 Question types and worked steps

Type	Example	Steps	Answer
Explanation	Five-box feedback	Deviation to correction	One sentence
Calculation	Daily filtrate	Rate x 1440 / 1000	180 dm3
Calculation	Percentage reabsorbed	(Filtrate – urine) / filtrate	99.2%
Comparison	Insulin and glucagon	One lowers, one raises	Antagonistic hormones

Sanity check (teach this): Stable means oscillating around a set point, so answers should quote a range, not a single number. Blood glucose is in mmol/dm3, not mg/dL; convert before comparing. The denominator for reabsorption is filtrate volume, not how much you drank.

05 Independent practice (3 questions)

Question	Answer	What to watch
Daily filtrate at 125 cm3/min	180 dm3	x 1440 / 1000
Reabsorption when 1.5 dm3 is passed	99.2%	(180 – 1.5) / 180
Heat lost by 0.5 dm3 of sweat	1200 kJ	x 2400
Which hormone rises after a meal	Insulin	From beta cells

06 Common mistakes and what to say

Mistake	Student writes	Say this
Treating stable as unchanging	Answering 37.0 C always	“It drifts between 36.1 and 37.2, it is not nailed down.”
Mixing up positive and negative feedback	Calling sweating positive feedback	“Sweating lowers temperature, so it pulls the value back: negative.”
Using fluid intake as the denominator	Answering 90%	“The denominator is the 180 dm3 filtered, not what you drank.”
Mixing glucose units	Comparing mg/dL with mmol/dm3	“Convert first; the factor is 18.”

07 Homework (paper, section and question numbers)

DSE Biology practice paper (human physiology) — Questions 9-12
DSE Biology practice paper (excretion) — Questions 13-14

08 Exit check (last 5 minutes)

Question	Answer	Decision
Daily filtrate volume	180 dm3	Wrong: redo units
Percentage reabsorbed	99.2%	Wrong: revisit the denominator
Which feedback sweating is	Negative feedback	Wrong: redraw the five boxes

09 Tutor FAQ

Do students need every hormone name?

Insulin, glucagon and ADH cover most questions; the direction of change matters more than the list.

Why can urine volume vary tenfold?

ADH changes water permeability of the collecting duct, so the reabsorbed fraction shifts sharply.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.