Year 8 Science · Unit 1 · Lesson 10
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Two words will not be used.
The system exchanges gases with the . During gas exchange, enters the body and leaves it. Gas exchange alone is not enough. The system uses blood to these gases to and from cells all around the body.
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. Oxygen enters the body during gas exchange.
Correct it:
2. The circulatory system can replace gas exchange, so the lungs are not really needed.
Correct it:
3. Once oxygen is in the blood, it must still be transported to cells all over the body.
Correct it:
4. Cells need a steady supply of oxygen, so gas exchange and transport must both keep going.
Correct it:
5. Breathing and circulation are separate processes that do not affect each other.
Correct it:
Read the data
| Gas | Air breathed in (%) | Air breathed out (%) |
|---|---|---|
| Nitrogen | 78 | 78 |
| Oxygen | 21 | 16 |
| Carbon dioxide | 0.04 | 4 |
Source: rounded figures for dry air. The rest is mostly argon; breathed-out air also holds extra water vapour.
1. Which gas makes up a smaller share of air breathed out than of air breathed in? What is the difference between its two values?
2. About a quarter of the oxygen you breathe in is not breathed out again. Use Table 1 to check this, then explain where that oxygen goes. Name both body systems.
Follow the effect through the systems
Scenario: a length underwater
Jack swims a length underwater on one breath and comes up gasping. While he holds his breath, no fresh air enters his lungs. Complete the table for that time.
| Stage | What is happening |
|---|---|
| Circulatory system | |
| Leg muscle cells |
3. A student writes: “The respiratory system works alone, because breathing is separate from circulation.” Is the student correct? Answer with a claim, evidence and reasoning.
Fill the gap
respiratory; environment; oxygen; carbon dioxide; circulatory; transport. Not used: nitrogen, digestive.
True or false
1. True. 2. False: the circulatory system cannot replace gas exchange; the respiratory system must first take in oxygen and remove carbon dioxide, and then the circulatory system transports the gases. 3. True. 4. True. 5. False: the two systems interact; the respiratory system exchanges gases and the circulatory system transports them, so each depends on the other.
Read the data
1. Oxygen; 21 − 16 = a difference of 5 (%). [2 marks]
2. Check: 5 of the 21 parts is about a quarter (5 ÷ 21 ≈ 0.24). The oxygen passes from the air in the lungs into the blood (gas exchange by the respiratory system). The circulatory system then carries it in the blood to cells all over the body, which use it. [3 marks: 1 check, 1 into the blood in the lungs, 1 carried by the blood to cells]
Follow the effect through the systems
Circulatory system: the heart keeps pumping blood, but the blood cannot pick up fresh oxygen in the lungs or get rid of its carbon dioxide there, so it carries less oxygen and more carbon dioxide. Muscle cells: they receive less and less oxygen and carbon dioxide builds up around them, so they cannot keep working as well.
Show What You Know
3. Marking guide: 1 claim (the student is incorrect; the systems interact); 1 evidence for the respiratory role (it exchanges gases with the environment, for example oxygen drops from 21% to 16% in breathed air); 1 evidence for the circulatory role (it transports oxygen to cells and carbon dioxide back to the lungs); 1 reasoning (if either stops, as when Jack holds his breath, cells run short of oxygen); 1 “system interaction” used correctly. Model: “The student is incorrect. The respiratory system takes oxygen in and lets carbon dioxide out, but it cannot carry these gases to the cells. The circulatory system transports them in the blood. Because cells need both jobs done, the systems depend on each other: this is system interaction.” [5 marks]
Common error to watch for: in Q2, saying the lungs “use up” the oxygen. The lungs only pass it into the blood; cells all over the body use it.