Year 8 Science · Unit 1 · Lesson 6
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Two words will not be used.
Every cell in a large organism still needs water, useful such as oxygen, and such as glucose. Its must also be taken away. In a single-celled organism, substances can pass straight across the cell’s surface by . In a large multicellular organism, many cells are deep the body, far from the surroundings, so the organism needs a system.
True or false? Fix the false ones
Circle T or F. Correct each false statement on its line.
1. All multicellular organisms use a heart and blood vessels to move substances around.
Correct it:
2. Cells deep inside a large animal still need oxygen and nutrients, and they still make wastes.
Correct it:
3. Diffusion alone is too slow to supply oxygen to the cells deep inside a large animal such as a blue whale.
Correct it:
4. A single-celled organism living in a pond needs a heart to supply its cell with oxygen.
Correct it:
5. Plants do not need a transport system, because they do not move around.
Correct it:
Match each substance to its journey
Write the matching letter in the middle column. Each letter is used once. The word in brackets tells you whether the row is about a human or a plant.
| Substance | Letter | Where it comes from → where it goes |
|---|---|---|
| Oxygen (human) | A. Made by body cells as they release energy → carried to the lungs and breathed out. | |
| Carbon dioxide (human) | B. A waste made in the body → carried in the blood to the kidneys and removed in urine. | |
| Water (plant) | C. Breathed in at the lungs → delivered to every body cell. | |
| Urea (human) | D. Enters the leaf from the air through tiny pores (stomata) → used by leaf cells in photosynthesis. | |
| Carbon dioxide (plant) | E. Taken in by the roots from the soil → carried up the stem to the leaves. |
Sort it
Write each living thing in the correct box. Each box gets exactly four.
Can rely on direct exchange with its surroundings
Needs a transport system
Read the data
Investigation: jelly-cube “organisms”
A class placed cubes of pink jelly (agar with an indicator) in weak acid. The acid moves in by diffusion and the pink colour disappears. They timed how long the acid took to reach the centre of each cube. Each cube models an organism; the acid stands for oxygen moving in from outside.
| Side length (cm) | Distance from surface to centre (cm) | Time for acid to reach the centre (min) |
|---|---|---|
| 1 | 0.5 | 9 |
| 2 | 1 | 34 |
| 4 | 130 |
Source: sample class results.
1. Fill in the missing distance in Table 1. Which cube took longest, and how long did it take?
2. Describe the pattern in Table 1, using the words “distance” and “time”.
3. Use the results to explain why cells in the middle of a large organism cannot rely on oxygen moving in from the surface.
4. A Paramecium is a single cell living in pond water; a saltwater crocodile is a large multicellular animal. Explain why the crocodile needs a transport system but the Paramecium does not. Use the terms diffusion, surface and internal cells.
Fill the gap
gases; nutrients; wastes; diffusion; inside; transport. Not used (2): movement, blood.
True or false
1. False: plants move substances without a heart or blood. 2. True. 3. True. 4. False: oxygen diffuses straight across the cell membrane from the water; it has no heart. 5. False: plant cells need substances moved through roots, stems and leaves; transport means moving substances, not moving the organism.
Match each substance to its journey
Oxygen (human) → C; Carbon dioxide (human) → A; Water (plant) → E; Urea (human) → B; Carbon dioxide (plant) → D.
Sort it
Direct exchange: a bacterium, a yeast cell, a Paramecium, a single-celled alga (single cells). Needs a transport system: a gum tree, a wombat, a wheat plant, a goldfish (multicellular).
Read the data
1. Missing distance: 2 cm. The 4 cm cube took longest, 130 minutes. [2 marks: 1 distance, 1 cube and time]
2. The greater the distance to the centre, the longer the time, and time grows much faster than distance: doubling the distance made the time about four times longer (9, 34, 130 min). [2 marks: 1 trend, 1 “much faster” or data quoted]
3. Cells in the middle of a large organism are far from the surface. The results show diffusion over a long distance is very slow, so oxygen would reach those cells too late (and wastes would leave too slowly). A transport system must carry substances to and from them. [3 marks: long distance; diffusion too slow, from data; transport needed]
Show What You Know
4. Marking guide: 1 cell needs (water, oxygen, nutrients in; wastes out); 1 Paramecium is one small cell touching the water all over; 1 diffusion across that surface is fast enough; 1 crocodile’s internal cells are far from the surface, so diffusion is too slow; 1 crocodile needs a transport system (heart, blood vessels, blood). [5 marks]
Common error to watch for: saying plants do not need transport “because they do not move”. Transport means moving substances through the organism, not moving the organism.