Year 8 Science · Unit 1 · Lesson 12
Foundation Worksheet
Learning Goals
Match each word to its meaning
Write the matching letter in the middle column. Each letter is used once.
| Word | Letter | Meaning in a living system |
|---|---|---|
| Input | A. A substance leaving the living system. | |
| Output | B. A useful substance entering the living system. | |
| Balance | C. A substance made by cells that is not needed and must not build up. | |
| Waste | D. Keeping conditions inside the body within useful limits. |
Put the path of urine in order
Number the steps from 1 (first) to 5 (last).
| Order (1–5) | Step |
|---|---|
| Tiny filters in the kidney (nephrons) clean the blood and make urine. | |
| The bladder stores the urine. | |
| Blood carrying wastes flows into a kidney. | |
| Urine leaves the body through the urethra. | |
| Urine flows down a ureter. |
1. What is urea, and why must the body get rid of it?
Sort it
Write each item in the correct box. Each box gets three.
Input
Output
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. Cells use up everything they take in, so they make no waste.
Correct it:
2. Breathing out removes a waste gas from the body.
Correct it:
3. Sweat carries some water and salt out of the body.
Correct it:
4. Faeces are the main waste removed by the excretory system.
Correct it:
5. If both kidneys stop working, wastes build up in the blood.
Correct it:
2. A student says a pot plant “makes no waste, because it has no kidneys or bladder”. Explain why the student is wrong. Name one waste gas a plant gives off and the tiny pores in the leaf it leaves through.
Ella’s water diary
For four days, Ella measured how much water she drank and how much urine she made. On three days she had a normal school day. On Thursday it was hot and she played two hours of touch football, sweating a lot.
| Day | Water drunk (mL) | Urine made (mL) |
|---|---|---|
| Monday | 1500 | 1200 |
| Tuesday | 2500 | 2100 |
| Wednesday | 1000 | 700 |
| Thursday (hot, sport) | 2500 | 1100 |
Source: sample data.
3. Ella drank the same amount on Tuesday and Thursday. How much less urine did she make on Thursday?
Answer mL
4. Describe the pattern for Monday to Wednesday. Then use the idea of balance to explain why Thursday does not fit the pattern.
5. A student writes: “Waste does not matter, because the body only needs to focus on taking in useful things.” Rewrite this as a stronger scientific explanation.
Match each word to its meaning
Input → B; Output → A; Balance → D; Waste → C.
Put the path of urine in order
Reading down the table as printed: 2, 4, 1, 5, 3. (Blood enters the kidney; nephrons make urine; ureter; bladder; urethra.)
1. Urea is a waste made in the body and carried in the blood; if it built up it would stop cells working properly, so the kidneys remove it in urine. [2 marks: 1 what it is, 1 why removed]
Sort it
Input: water you drink, oxygen you breathe in, food you eat. Output: sweat, urine, carbon dioxide you breathe out.
True or false
1. False: cells make wastes, such as carbon dioxide and urea, when they use materials. 2. True. 3. True. 4. False: faeces are mostly undigested food; the excretory system removes wastes made by cells, such as urea in urine. 5. True.
2. Plants make wastes too; they just remove them without kidneys. Waste gas: oxygen (from photosynthesis, in light) or carbon dioxide (from respiration, in the dark), which leaves through the stomata. [2 marks: 1 waste gas, 1 stomata]
Go Deeper
3. 2100 − 1100 = 1000 mL less. [2 marks: 1 working, 1 answer with unit]
4. Monday to Wednesday: the more she drank, the more urine she made (1000 mL drunk, 700 mL urine; 2500 mL drunk, 2100 mL urine). On Thursday she lost a lot of water as sweat, so her kidneys kept more water and made less urine, keeping her body’s water in balance. [3 marks: 1 pattern with data; 1 water lost as sweat; 1 kidneys keep water to stay in balance]
Show What You Know
5. Marking guide (points expected): 1 the claim is wrong, because both inputs and outputs matter; 1 when cells use materials they make wastes; 1 if wastes build up, cells cannot work properly and the body becomes ill; 1 two wastes with organs, e.g. urea by the kidneys, carbon dioxide by the lungs; 1 removing outputs as inputs come in keeps the body in balance. [5 marks]
Common error to watch for: calling faeces the body’s main excretory waste. Faeces are mostly food that was never absorbed; excretion removes wastes made by cells.