Primary 6 · Science · Systems: Respiratory & Circulatory
Systems: Respiratory & Circulatory questions for Primary 6 Science
9 questions to work through online, 2 of them written out the way the paper asks. Answer and you get the working straight away, then a score at the end. No sign-up, and you can retake it as often as you like.
- Oxygen-rich and oxygen-poor
- The double circuit
- Gas exchange
- Reasoning about exercise
- Why the lungs are built as they are
- Reasoning about a blockage
- Naming the exchange
- Naming the gas
- Applying the ideas
Same picture as the question above.
| Gas | Breathed in (%) | Breathed out (%) |
|---|---|---|
| oxygen | 21 | 16 |
| carbon dioxide | 0.04 | 4 |
| nitrogen | 78 | 78 |
| Time | Heartbeats per minute |
|---|---|
| at rest | 72 |
| during exercise | 160 |
| 1 min after | 126 |
| 4 min after | 88 |
| 8 min after | 73 |
Answers and explanations for all 9 questions
Every answer with the reasoning behind it. Worth reading after you have tried the set — or on its own, if you are a parent marking it.
Which statements about the diagram above are correct?
Answer: A, B and C only
Q and R are both oxygen-rich and S is oxygen-poor. The tempting rule about blood going to the heart fails at Q, which arrives from the lungs.
According to the diagram, how many times does the blood pass through the heart in one complete circuit?
Answer: 2
The blood goes heart to lungs, back to the heart, then out to the body and back again: 2 passes through the heart on each circuit.
Based on the table above, which statement is correct?
Answer: About a quarter of the oxygen breathed in is used by the body.
Oxygen falls from 21% to 16%, so 5 of the 21 parts are used — about a quarter. The rest is exhaled unused.
Based on the table above, which statement is correct?
Answer: The rate falls quickly at first and then more slowly as it nears the resting value.
160, 126, 88, 73 — the drops shrink as the rate approaches rest. The body catches up on its oxygen quickly at first and then tapers off.
Which two features of the lungs help oxygen enter the blood quickly?
Answer: A and B only
Oxygen crosses a surface, so a huge area and a very short distance to cross are exactly what make the exchange fast enough.
A blood vessel supplying part of the heart muscle becomes blocked. Why is this serious?
Answer: That part of the heart muscle stops receiving oxygen and is damaged.
The heart is a muscle and needs its own oxygen supply like any other. Blocking that supply starves the muscle, which is why it is damaged so fast.
In the lungs, oxygen crosses into the blood while carbon dioxide crosses out of it. This two-way swap is called gas ______ .
Answer: exchange
Oxygen in and carbon dioxide out at the lungs is gas exchange.
The blood at S in the diagram above is returning from the body carrying a waste gas. Which gas is it?
Answer: carbon dioxide
Blood returning from the body carries carbon dioxide, the waste gas made by the cells.
Why does someone who has smoked heavily for years become breathless climbing stairs?
Answer: Damage to the air sacs leaves less surface for oxygen to enter the blood.
Smoking destroys air sacs, cutting the surface available for gas exchange. Climbing stairs demands more oxygen than the damaged lungs can supply, so the person is left gasping.