Year 8 Science · Unit 1 · Lesson 10
Apply Worksheet
Learning Goals
Match each term to its meaning
Write the matching letter in the middle column. Each letter is used once.
| Term | Letter | Meaning |
|---|---|---|
| Respiratory system | A. Oxygen moving into the body and carbon dioxide moving out. | |
| Circulatory system | B. When body systems depend on one another to do a larger job. | |
| System interaction | C. The body system that exchanges gases with the environment. | |
| Gas exchange | D. The body system that transports gases around the body in the blood. |
1. In which organs does breathed-in air come close to the blood? Which organ keeps the blood flowing?
Classify with a reason: which system is hit first?
For each emergency, write the system that is affected first. Then say what happens to body cells next.
| Emergency | System hit first | What happens to body cells next |
|---|---|---|
| A piece of food blocks the windpipe (choking) | ||
| The heart suddenly stops pumping | ||
| A room fills with thick smoke | ||
| A deep cut causes a large loss of blood |
Scenario: CPR
In CPR, a first-aider gives chest compressions (pushing hard on the chest to squeeze blood out of the heart) and rescue breaths (blowing air into the person’s lungs).
2. Use the idea of system interaction to explain why CPR includes both.
Read the data: a trek in the Himalaya
Mei treks high in Nepal, where each breath holds less oxygen than at sea level. A pulse oximeter on her finger shows how full of oxygen her blood is (% of the most it can carry). Complete the Zone column, using the zones given below the table.
| Height above sea level (m) | Blood-oxygen reading (%) | Zone |
|---|---|---|
| 0 (Sydney) | 98 | |
| 2800 | 93 | |
| 3900 | 88 | |
| 5000 | 81 |
Source: sample readings. Zones for this worksheet: 95 or more = normal; 90 to 94 = below normal; below 90 = low. Real advice comes from a doctor.
3. A student says: “If you just breathe faster at high altitude, your muscles will automatically get more oxygen.” Evaluate this statement. Say what is correct about it, explain what it leaves out, and use Table 1 as evidence. Finish with a judgement.
Match each term to its meaning
Respiratory system → C; Circulatory system → D; System interaction → B; Gas exchange → A.
1. The lungs; the heart. [2 marks]
Classify with a reason: which system is hit first?
Choking: respiratory; no air reaches the lungs, so no new oxygen enters the blood and cells run short of oxygen. Heart stops: circulatory; blood stops moving, so no oxygen is delivered to cells even though the lungs still hold air. Smoke: respiratory; the air breathed in carries less oxygen, so less enters the blood and cells get less. Blood loss: circulatory; less blood is left to carry oxygen, so cells receive less.
2. Rescue breaths do the respiratory system’s job: they put air with oxygen into the lungs so it can enter the blood. Compressions do the circulatory system’s job: they move the blood so the oxygen reaches cells, especially in the brain. The systems depend on each other, so doing only one would not get oxygen to cells. [3 marks: 1 breaths, 1 compressions, 1 interdependence]
Read the data: a trek in the Himalaya
Zones: 0 m normal; 2800 m below normal; 3900 m low; 5000 m low. The higher Mei goes, the lower her blood-oxygen reading.
Show What You Know
3. Marking guide: 1 correct part (faster breathing brings more air into the lungs, so more oxygen can enter the blood); 1 what is left out (the circulatory system must transport that oxygen to the muscles, and the heart rate rises too); 1 “automatically” is wrong, because each breath at altitude contains less oxygen, so even faster breathing may not bring the blood back to normal; 1 evidence from Table 1 (for example 88% at 3900 m, in the low zone); 2 justified judgement (the statement is only partly correct: muscles get enough oxygen only when gas exchange and transport work together; 1 if no reasoning). [6 marks]
Common error to watch for: saying there is “no oxygen” high in the mountains. There is still oxygen, but each breath brings in less of it than at sea level.