Kidneys | GCSE Biology

Homeostasis and response

Lesson overview

This lesson introduces the core biology idea, the useful equipment and the calculation or data skills used on this page.

Focuskidneys, water balance and temperature control

Time45-60 minutes

EquipmentNotebook, calculator and a pen for labelled diagrams.

Practical linkurine concentration, sweating and temperature data

Maths tagsconcentration, volume, rate and feedback

What you will learn

Describe the key biology ideas behind kidneys, water balance and temperature control.
Use precise GCSE command-word language in explanations.
Apply the idea to unfamiliar cells, organisms, data or practical contexts.
Check answers using units, labelled diagrams, observations, calculations or biological evidence where relevant.

Core knowledge

Big idea: Homeostasis keeps internal conditions stable by detecting change and adjusting water, waste or temperature responses.
This lesson focuses on kidneys, water balance and temperature control. A strong answer explains the biology and points to evidence such as feedback graphs, receptor-effector pathways, hormone levels and response data.
Kidney: an organ that filters blood and helps control water, ion and urea levels.
Urea: a waste product made from excess amino acids and removed in urine.
ADH: a hormone that controls how much water the kidneys reabsorb.
Use the model as a thinking route: Understand kidneys, water balance and temperature control -> Use urine concentration, sweating and temperature data -> Process data with concentration, volume, rate and feedback.
Likely question evidence: urine concentration data, ADH graphs, sweating contexts, temperature responses and kidney diagrams. Use it to justify the explanation, not as decoration.
When numbers or graphs appear, show working with concentration, volume, rate and feedback and finish by saying what the result means biologically.

Homeostasis and response infographic

GCSE Biology infographic showing homeostasis, nervous responses, hormones, blood glucose and water balance. — Supplied GCSE Biology visual summary for homeostasis and response.Download visual

Kidneys practice set

Use the worked examples and practice questions on this page as a complete study task: learn the definitions of kidney and urea, summarise the infographic in your own words, then answer the questions using the data, equations and observations given here. Check every answer for concentration, volume, rate and feedback.

Clear explanation

First secure the anchor idea: kidneys, water balance and temperature control. In ordinary language, this means using kidney, urea and ADH to explain what is happening, not just spotting those words in the question.

Next look for the evidence. In this lesson it is likely to come from urine concentration data, ADH graphs, sweating contexts, temperature responses and kidney diagrams.

Then build the answer in order: Understand kidneys, water balance and temperature control then use urine concentration, sweating and temperature data then process data with concentration, volume, rate and feedback. This stops the answer becoming a list of disconnected facts.

If the question includes data, use concentration, volume, rate and feedback. Keep the unit or comparison visible, then link the result back to kidney or urea.

Exam-ready model sentence: The response returns the condition towards normal by changing water reabsorption, waste removal or heat loss.

Worked examples

Kidneys: from idea to explanation

Question: Explain kidneys, water balance and temperature control using the model.

Start with the idea: Understand kidneys, water balance and temperature control.

Add the mechanism: use urine concentration, sweating and temperature data.

Finish with the consequence: process data with concentration, volume, rate and feedback.

Reveal worked answer

Answer: A good answer uses kidney (an organ that filters blood and helps control water, ion and urea levels), urea (a waste product made from excess amino acids and removed in urine) and ADH (a hormone that controls how much water the kidneys reabsorb) in one connected explanation. For example: The response returns the condition towards normal by changing water reabsorption, waste removal or heat loss.

Kidneys: from evidence to marks

Question: A student has evidence from urine concentration data, ADH graphs, sweating contexts, temperature responses and kidney diagrams. What should their answer include?

Step 1: name the useful evidence rather than writing a general fact about the topic.

Step 2: process any data with concentration, volume, rate and feedback.

Step 3: explain what the evidence shows about kidney and urea.

Reveal worked answer

Answer: The answer earns marks by joining evidence, method or data to a biological reason. Avoid describing a change without showing how feedback or a response returns conditions towards normal.

Quick checks

Choose an answer, then check your thinking.

1. Which answer would make kidneys clearer?

Understand kidneys, water balance and temperature control and explain it using kidney Repeat the topic title without explaining it Ignore the evidence and write a memorised paragraph

2. What should you check before finishing an answer on this lesson?

Whether the answer sounds long enough Whether concentration, volume, rate and feedback and evidence such as urine concentration data, ADH graphs, sweating contexts, temperature responses and kidney diagrams have been used where needed Whether every keyword from the page has been copied

Practice questions

Question 1

Define kidney and use it in a complete sentence about kidneys, water balance and temperature control.

Reveal answer and marking guidance

Answer: Kidney means an organ that filters blood and helps control water, ion and urea levels. In kidneys, water balance and temperature control, it helps explain understand kidneys, water balance and temperature control.

Marking: Credit the definition and a sentence that uses the term in the lesson context.

Question 2

Explain the main sequence in Kidneys using the infographic.

Reveal answer and marking guidance

Answer: Understand kidneys, water balance and temperature control -> Use urine concentration, sweating and temperature data -> Process data with concentration, volume, rate and feedback. A strong answer says why the final step follows from the first two steps.

Marking: Credit the correct order plus a biological link between the steps.

Question 3

A question gives evidence such as urine concentration data, ADH graphs, sweating contexts, temperature responses and kidney diagrams. What should you do with that evidence?

Reveal answer and marking guidance

Answer: Identify the useful observation, method detail or data first. Then use concentration, volume, rate and feedback where relevant and explain what it shows about kidney, urea or ADH.

Marking: Credit evidence use, relevant data handling and a clear biology explanation.

Question 4

A student writes: 'kidney is involved, so the answer is correct.' What detail is missing?

Reveal answer and marking guidance

Answer: Kidney means an organ that filters blood and helps control water, ion and urea levels. A better answer also uses urea (a waste product made from excess amino acids and removed in urine) and explains the evidence route: Understand kidneys, water balance and temperature control then use urine concentration, sweating and temperature data. An exam-ready version could be: The response returns the condition towards normal by changing water reabsorption, waste removal or heat loss.

Marking: Credit a precise definition, a second linked term and use of evidence or model steps.

Practice ladder

FluencyRecall the key definition, symbol, structure, equation or observation.

ApplicationApply kidneys, water balance and temperature control to unfamiliar organisms, cells, systems, practicals or data.

Practical interpretationUse evidence, method quality, uncertainty or conclusion wording where asked to evaluate.

Maths skillUse units, ratios, graphs and significant figures accurately.

Answers and marking guidance

The exact practice answers are hidden under each question so you can try first. Marks come from using the correct biology model, choosing the right calculation where needed, keeping units with values, labelling diagrams clearly, and explaining changes with precise words such as cells, enzymes, hormones, genes, adaptation, rate, evidence and uncertainty.

Common mistakes

Using kidney, urea or ADH as labels without explaining what they mean.
Forgetting to connect the answer to likely evidence, such as urine concentration data, ADH graphs, sweating contexts, temperature responses and kidney diagrams.
Missing the maths or data habit: concentration, volume, rate and feedback.
Falling into the common trap of describing a change without showing how feedback or a response returns conditions towards normal.

Extension challenge

Create a focused revision card for kidneys, water balance and temperature control: three exact definitions, one model sequence, one evidence detail such as urine concentration data, ADH graphs, sweating contexts, temperature responses and kidney diagrams, one data check using concentration, volume, rate and feedback, one common misconception, and one exam-ready explanation sentence: The response returns the condition towards normal by changing water reabsorption, waste removal or heat loss.

Reveal answer

Example answer: A complete response names the biology model, uses accurate units or observations, and explains why the evidence supports the conclusion.