Year 8 Science · Unit 1 · Lesson 9
Apply Worksheet
Learning Goals
Match each part to its job
Write the matching letter in the middle column. Each letter is used once.
| Part | Letter | Job |
|---|---|---|
| Right ventricle | A. Tiny vessel with a wall one cell thick, where substances pass between blood and cells. | |
| Left ventricle | B. Heart chamber that pumps deoxygenated blood to the lungs. | |
| Vein | C. Thick-walled vessel that carries blood away from the heart. | |
| Capillary | D. Heart chamber that pumps oxygenated blood out to the body. | |
| Artery | E. Thinner-walled vessel with valves that carries blood back to the heart. |
Odd one out
In each row, circle the one that does not belong and give the reason.
| Row | Four items | Reason |
|---|---|---|
| 1 | artery · vein · capillary · lung | |
| 2 | pumps itself around the body · carries oxygen · carries wastes · carries nutrients | |
| 3 | right atrium · capillary · left ventricle · left atrium |
Cause and effect
Scenario: varicose veins
Blood in the leg veins must travel upward, against gravity, to reach the heart. In some people the valves in these veins become weak and no longer close properly, and the veins become swollen and twisted (varicose veins).
Complete the chain. Each box causes the next.
| Part of the circulatory system | Share of all the blood (%) |
|---|---|
| Veins of the body | 64 |
| Arteries of the body | 13 |
| Vessels in the lungs | 9 |
| Small arteries and capillaries of the body | 7 |
| Inside the heart | 7 |
Source: textbook estimates for an adult with about 5 L of blood.
1. Which type of vessel holds most of the blood? About what fraction of all the blood is this?
2. The adult has 5 L of blood. Calculate the volume of blood in the veins of the body.
Answer L
3. A student reads Table 1 and says: “Capillaries hold only a small share of the blood, so they must be the least important vessels.” Explain why the student is wrong.
4. A science museum builds a model of the circulatory system: an electric pump pushes red-coloured water around a closed loop of rubber tubing. Evaluate the model. Say which real part each model part stands for and what it does, then describe two important ways the model is not like the real system. Finish with a judgement about how useful the model is.
Match each part to its job
Right ventricle → B; Left ventricle → D; Vein → E; Capillary → A; Artery → C.
Odd one out
Row 1: lung (the others are blood vessels; the lung belongs to the respiratory system). Row 2: pumps itself around the body (blood is pushed by the heart; the others are things blood carries). Row 3: capillary (a blood vessel; the others are chambers of the heart).
Cause and effect
Box 2: blood slips backward, down the leg, instead of only moving up toward the heart. Box 3: blood collects (pools) in the lower part of the vein.
Go Deeper
1. The veins of the body (64%), which is nearly two-thirds of all the blood. [2 marks]
2. 64 ÷ 100 × 5 = 3.2 L. [2 marks: 1 method, 1 answer]
3. Capillaries are the only vessels where substances pass between the blood and the cells, because their walls are one cell thick. Arteries and veins only carry blood to and from them. Without capillaries, oxygen and nutrients would never reach the cells, so importance depends on the job done, not on how much blood a vessel holds. [3 marks: exchange site; thin wall; importance is about role, not volume]
Show What You Know
4. Marking guide: 1 pump = heart (pumps to keep blood moving); 1 tubing = blood vessels (pathways) and red water = blood (transport medium); 2 for two differences explained (any two: no capillaries with thin walls, so nothing could be exchanged with cells; the water carries no oxygen, nutrients or wastes; one pump and one loop, but the heart has four chambers and sends blood to the lungs and to the body; no valves; tubing is all the same, but arteries have thick walls and veins have thinner walls); 2 for a judgement that is weighed (useful for showing that a pump pushes a fluid through connected pipes, but it cannot show exchange with cells, which is the whole point of the system; 1 if the judgement has no reason). [6 marks]
Common error to watch for: in the match, swapping the two ventricles. The right ventricle sends blood only to the nearby lungs; the left ventricle sends it to the whole body.