Year 8 Science · Unit 1 · Lesson 13
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Learning Goals
Match each word to its description
Write the matching letter in the middle column. Each letter is used once.
| Word | Letter | Description |
|---|---|---|
| Water | A. Parts linked to capturing light and exchanging gases. | |
| Minerals | B. Parts that take in water and minerals from the soil. | |
| Light | C. Dissolved in soil water; too little gives slow growth and yellow leaves. | |
| Roots | D. Taken in from the soil; too little makes the plant wilt. | |
| Leaves | E. An input that does not come from the soil at all. |
Odd one out
In each row, circle the one that does not belong. Give a reason.
| Row | Group | Odd one out and reason |
|---|---|---|
| 1 | sunlight · chewed food · water · minerals | |
| 2 | taking in water · taking in minerals · anchoring the plant · capturing sunlight | |
| 3 | taking in water from the soil · letting carbon dioxide in · capturing light · letting oxygen out |
1. Name the three key inputs a plant needs from its surroundings, and say which part of the plant takes in or captures each one.
Cause and effect
Scenario: a new fence shades a vegetable patch
A tall fence is built on the sunny side of a school vegetable patch. The soil and watering stay the same.
Complete the chain. Each box is caused by the box before it.
What is this plant short of?
Read about each plant. In the row below it, write the input it is most likely short of, the plant part linked to that input, and the clue that told you.
| Input it is short of | Linked plant part | Clue that told you |
|---|---|---|
| Plant 1: A fern on a sunny balcony. The soil is bone dry and the fronds are limp. | ||
| Plant 2: A pot plant in a windowless hallway. The soil is damp and fertilised. The stems are long, thin and pale. | ||
| Plant 3: Beans in full sun in damp soil that has not been fertilised for years. Growth is slow and the older leaves are yellow. | ||
Investigation: spinach grown without soil
An indoor farm grows spinach with its roots hanging in tanks of water instead of soil. The grower can choose how much mineral mix to dissolve in the water. Every tank gets the same lights for the same hours each day.
| Minerals in the tank water | Mean mass per plant (g) |
|---|---|
| none (plain water) | 9 |
| quarter strength | 38 |
| half strength | 64 |
| full strength | 81 |
Source: sample grower results.
2. Describe the pattern in Table 1. Then explain it, using the word roots.
3. The grower sells spinach only if a plant is at least 60 g. What is the weakest mineral mix in Table 1 that reaches this mass? Use the data to support your answer.
4. A worker turns off half of the lights over the full-strength tank. He says, “If I double the minerals, the spinach will still reach 81 g.” Explain why he is unlikely to be right.
5. After a wet winter, a wheat farmer’s crop has plenty of rain and sunshine but grows poorly. A soil test shows the soil is low in minerals. The farmer says, “Roots just hold the plant in the ground, so the soil can’t be the problem.” Explain to the farmer why the crop is growing poorly and what the roots really do.
Match each word to its description
Water → D; Minerals → C; Light → E; Roots → B; Leaves → A.
Odd one out
Row 1: chewed food (plants make their own food; the others are plant inputs). Row 2: capturing sunlight (a leaf job; the others are root jobs). Row 3: taking in water from the soil (a root job; the others are leaf jobs).
1. Water and minerals (both taken in by the roots) and light (captured by the leaves). [3 marks]
Cause and effect
Box 2: less light reaches the leaves. Box 3: the leaves make less food for the plant.
What is this plant short of?
Plant 1 (fern): water; roots; dry soil and limp fronds. Plant 2 (hallway): light; leaves; no window, and long, thin, pale stems. Plant 3 (beans): minerals; roots; no fertiliser for years, slow growth and yellow older leaves, even with sun and water.
Go Deeper
2. The more minerals in the water, the heavier the spinach (9 g with none, up to 81 g at full strength). The roots take in the minerals dissolved in the water, so more minerals are available for growth. [2 marks: 1 pattern, 1 roots take in minerals]
3. Half strength: 64 g is above 60 g, but quarter strength gives only 38 g. [2 marks: 1 answer, 1 data]
4. Light is now short, and extra minerals cannot replace it. The leaves capture less light, so they make less food and the spinach grows less. Every input is needed; adding more of one does not make up for another that is missing. [3 marks: light is now the missing input; leaves make less food; one input cannot replace another]
Show What You Know
5. Marking guide (points expected): 1 the three inputs (water, minerals, light); 1 minerals are the missing input here; 1 roots take in water and minerals from the soil, not only anchor the plant; 1 all three are needed, so plenty of water and light cannot make up for too few minerals; 1 a sensible action (add fertiliser with the missing minerals). [5 marks]
Common error to watch for: thinking a plant short of one input can be fixed by giving it more of another (more water, more light). Each input has its own job.