📚 Case Study in Action: School Garden Investigation | 案例分析实战演练：学校菜园调查
Welcome to a hands-on science case study! In this activity you will act as a young scientist investigating why some plants in a school garden are not growing well. By following the steps of scientific inquiry, you will identify problems, design experiments, collect data, and draw evidence-based conclusions. This approach mirrors real-world scientific investigations and helps you develop key skills for the WJEC Year 7 Science curriculum.
欢迎参与这次动手实践的科学案例分析！你将扮演一名小科学家，调查学校菜园里某些植物生长不良的原因。通过遵循科学探究步骤，你将找出问题、设计实验、收集数据，并得出基于证据的结论。这种方法模拟了真实的科学调查，有助于培养WJEC七年级科学课程所要求的核心技能。
1. Case Background and Problem Identification | 案例背景与问题识别
The school gardening club has noticed that lettuce plants in Bed A are short and yellow, while those in Bed B are tall and green. The beds are side by side but may differ in several ways. The headteacher asks you to find out why and suggest improvements. Before jumping to conclusions, you need to gather information about the conditions in each bed — light, water, soil type, and possible pests.
学校园艺社团发现，A 菜床里的生菜矮小发黄，而 B 菜床里的则高大翠绿。两个菜床并排，但可能在许多方面不同。校长请你找出原因并提出改进建议。在匆忙下结论之前，你需要收集每个菜床的环境信息——光照、水分、土壤类型以及可能的害虫等。
2. Scientific Questions and Hypotheses | 科学问题与假设
From your observations, you can turn the problem into a testable scientific question: "Does the amount of sunlight reaching Bed A affect the growth of lettuce compared to Bed B?" A hypothesis is an informed prediction. You might state: "If lettuce in Bed A receives less sunlight than in Bed B, then it will grow shorter and have paler leaves, because sunlight is needed for photosynthesis."
根据观察，你可以将问题转化为一个可检验的科学问题：“与 B 床相比，A 床接收到的光照量是否会影响生菜的生长？”假设是基于知识的预测。你可以提出：“如果 A 床的生菜接收到的阳光少于 B 床，那么它会长得更矮、叶片更黄，因为光合作用需要阳光。”
3. Identifying Variables | 识别变量
In any fair test, you must identify three types of variables:
- Independent variable (what you change or compare): in this case, the amount of light (or which bed, A or B).
- Dependent variable (what you measure): plant height, number of leaves, or leaf colour.
- Control variables (what you keep the same): amount of water, type of soil, type of plant, time of planting, and no fertiliser added.
在任何公平测试中，必须识别三类变量：
- 自变量（你改变或比较的因素）：本例中为光照量（或哪个菜床，A 或 B）。
- 因变量（你测量的结果）：植株高度、叶片数量或叶片颜色。
- 控制变量（保持不变的因素）：浇水量、土壤类型、植物种类、种植时间以及不添加肥料等。
4. Experimental Design | 实验设计
To test the effect of light, you could set up a controlled experiment while also using the existing beds. Because we cannot move the beds, we can measure the light intensity at both beds over several days using a light meter. We will also ensure both beds receive the same amount of water (500 mL every two days) and that no fertiliser is applied. We will randomly select 5 lettuce plants from each bed and measure their height and leaf colour using a colour chart.
为了测试光照的影响，你可以设计一个对照实验，同时利用现有的菜床。由于无法移动菜床，我们可以使用光度计在数天内测量两个菜床的光照强度。我们还将确保两个菜床浇等量的水（每两天 500 毫升），且不施肥。再从每个菜床随机选取 5 株生菜，测量其高度并用比色卡记录叶片颜色。
5. Data Collection Methods | 数据收集方法
You will collect the following data:
- Light intensity (lux) at midday at plant level in Bed A and Bed B, repeated for three sunny days.
- Plant height in cm, measured from soil surface to highest leaf tip.
- Leaf colour rating on a scale of 1 to 5 (1 = very yellow, 5 = dark green).
Record all measurements in a table. Repeat measurements reduce random error.
你将收集以下数据：
- 正午时 A 床和 B 床植株高度的光照强度（勒克斯），在三个晴天重复测量。
- 植株高度（厘米），从土表量至最高叶尖。
- 叶片颜色评级，1 到 5 分（1 = 非常黄，5 = 深绿色）。
将所有测量值记录在表格中。重复测量可减少随机误差。
6. Safety Considerations | 安全注意事项
Before starting, always consider safety:
- Wash hands after handling soil.
- Be careful when using a light meter – do not point it directly at the sun.
- Handle rulers and other equipment sensibly.
- Be aware of allergies (e.g., pollen).
开始前，务必考虑安全：
- 接触土壤后洗手。
- 使用光度计时小心，不要将其直对太阳。
- 小心使用直尺和其他器材。
- 注意过敏（如花粉）。
7. Hands-on: Measuring Soil pH | 动手实践：测量土壤 pH
Light might not be the only factor. Soil pH can affect nutrient availability. You can test soil pH using a simple soil test kit or pH paper with distilled water and a soil sample. Mix a small spoon of soil with distilled water, let it settle, and dip the pH paper. Compare the colour to the chart. A pH between 6 and 7 is ideal for most vegetables.
光照可能不是唯一的因素。土壤 pH 值会影响养分有效性。你可以用简单的土壤测试盒或用蒸馏水和土样配制的溶液及 pH 试纸来测试土壤 pH。取一小勺土壤与蒸馏水混合，静置后蘸取 pH 试纸，将颜色与比色表对比。大多数蔬菜适宜的 pH 在 6 到 7 之间。
8. Data Recording and Tables | 数据记录与表格
Organising data in a table is essential. Here is an example:
| Bed | Plant | Height (cm) | Leaf Colour (1-5) | Light (lux) |
|---|---|---|---|---|
| A | 1 | 8.5 | 2 | 12000 |
| A | 2 | 9.0 | 2 | 11800 |
| B | 1 | 15.2 | 5 | 28500 |
| B | 2 | 14.8 | 4 | 29000 |
Make sure to include average values for each bed.
将数据整理成表格至关重要。示例见上表。务必计算每个菜床的平均值。
9. Analysing Results | 分析结果
00 lux; Bed B mean height = 15.1 cm, mean light = 28700 lux. You can also create a bar chart to compare the two beds. The results suggest that lower light in Bed A is linked to shorter plants and paler leaves. But is this proof of causation? Not yet — her factors might also differ, like soil moisture. You should check the control variables.
收集数据后，计算每个菜床的平均高度和平均光照强度。你可能得到：A 床平均高度 9.2 厘米，平均光照 11500 勒克斯；B 床平均高度 15.1 厘米，平均光照 28700 勒克斯。你还可以制作柱状图来比较两个菜床。结果显示 A 床光照较弱与植株较矮、叶片发黄有关联。但这能证明因果关系吗？还不能——其他因素也可能不同，例如土壤湿度。你应该检查控制变量。
10. Conclusions and Improvement Suggestions | 结论与改进建议
Based on the evidence, you can conclude that reduced light in Bed A is a likely cause of poor growth. To improve the situation, you might suggest:
- Trimming overhanging branches that shade Bed A.
- Moving the lettuce to a sunnier spot next season.
- Using reflective mulch to increase light.
Always note that more tests are needed to confirm, and that multiple factors can interact.
根据证据，你可以得出结论：A 床光照不足可能是生长不良的原因。为改善情况，你可以建议：
- 修剪遮挡 A 床的树枝。
- 下个季节将生菜移到更向阳的位置。
- 使用反光地膜增加光照。
请注意，需要更多测试来证实，并且多种因素可能相互作用。
11. Evaluation and Reflection | 评估与反思
Evaluate your investigation. Were there any uncontrolled variables? Perhaps Bed A was closer to a wall that reflected heat, or its soil drained faster. You could improve by measuring soil moisture daily. Also, sample size (5 plants) is small; measuring 10 plants would give more reliable results. Repeating the whole investigation in another season would be even better.
评估你的调查。是否有未控制的变量？也许 A 床靠近一堵会反射热量的墙，或者其土壤排水更快。你可以通过每天测量土壤湿度来改进。此外，样本量（5 株植物）较小；测量 10 株植物将得到更可靠的结果。在另一个季节重复整个调查会更好。
12. Extension: Investigating Other Factors | 知识拓展：探究其他因素
Now apply your skills to another factor. Design a new experiment to test the effect of soil pH or organic compost on plant growth, keeping light constant. Use the same variable-control structure. This practice builds your confidence in scientific inquiry and prepares you for more complex investigations in WJEC Science.
现在将你的技能应用到另一个因素上。设计一个新实验来测试土壤 pH 或有机堆肥对植物生长的影响，同时保持光照不变。运用相同的变量控制结构。这种练习能增强你对科学探究的信心，为 WJEC 科学课程中更复杂的调查做好准备。
Published by TutorHao | Science Revision Series | aleveler.com
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