Case Study Practical Drills | 案例分析实战演练

📚 Case Study Practical Drills | 案例分析实战演练

Biology isn’t just about memorising facts – it’s about applying knowledge to real-world situations. The WJEC Year 9 course expects you to interpret data, evaluate evidence, and suggest logical explanations based on scientific principles. This article takes you through a series of practical case studies, each designed to strengthen your analytical skills and prepare you for exam-style questions.

生物学不仅仅是记忆知识点，更要求你把知识应用到真实情境中。WJEC 九年级课程希望你能解读数据、评价证据，并根据科学原理提出合理的解释。本文通过一系列实战案例，帮你提升分析能力，为考试做好准备。

1. Food Poisoning Outbreak | 食物中毒爆发调查

A school canteen reported that 45 students developed vomiting and diarrhoea within 24 hours after eating chicken sandwiches. The local health authority interviewed everyone who ate in the canteen and collected food samples. The pathogen suspected was a bacterium called Campylobacter, which multiplies rapidly between 20 °C and 45 °C. The investigation found that cooked chicken was left in a warm kitchen for over 4 hours before being made into sandwiches.

某学校食堂报告，45 名学生在食用鸡肉三明治后 24 小时内出现呕吐和腹泻。当地卫生部门对所有在食堂就餐的人员进行了询问并采集了食物样本。怀疑的病原体是一种叫做弯曲杆菌的细菌，它在 20 °C 至 45 °C 之间会迅速繁殖。调查发现，熟鸡肉在温暖厨房中放置超过 4 小时才制成三明治。

The pathogen’s optimal growth temperature range matched the kitchen conditions. / 病原体的最适生长温度范围与厨房条件吻合。
Incubation period of 12–24 hours is typical for Campylobacter. / 12–24 小时的潜伏期是弯曲杆菌的典型特征。
The canteen had not recorded the cooling time, breaking food safety protocols. / 食堂没有记录冷却时间，违反了食品安全规范。

Temperature / 温度	Bacterial Growth / 细菌生长
< 5 °C	Very slow / 很慢
20–45 °C	Rapid multiplication (danger zone) / 快速繁殖（危险区）
> 63 °C	Most bacteria killed / 多数细菌被杀死

The outbreak shows why the ‘danger zone’ principle is so critical. By keeping food below 5 °C or above 63 °C, the canteen could have prevented the incident.

这次爆发说明“危险区”原则为何如此关键。如果食堂将食物保持在 5 °C 以下或 63 °C 以上，本可以避免这起事件。

2. Enzyme Action in a Washing Powder | 洗衣粉中的酶作用实验

A student wanted to find the best temperature for a biological washing powder containing protease. She stained identical pieces of cloth with egg white (protein) and washed them at 10 °C, 20 °C, 30 °C, 40 °C, 50 °C and 60 °C. After 30 minutes, she measured how much stain remained using a light sensor. The results showed that the stain removal was most effective at 40 °C, moderate at 30 °C and 50 °C, poor at 20 °C and 60 °C, and very poor at 10 °C.

一位学生想找出含有蛋白酶的生物洗衣粉的最佳温度。她用蛋清（蛋白质）在相同的布片上染上污渍，然后在 10 °C、20 °C、30 °C、40 °C、50 °C 和 60 °C 下洗涤。30 分钟后，她用光线传感器测量了残留的污渍量。结果表明，40 °C 时去污效果最好，30 °C 和 50 °C 时效果中等，20 °C 和 60 °C 时较差，10 °C 时非常差。

At 40 °C, the enzyme and substrate have high kinetic energy and the enzyme’s active site is still the correct shape. Above 50 °C, the enzyme begins to denature – the active site changes shape so the substrate no longer fits. At 10 °C, molecules move too slowly for effective collisions.

在 40 °C 时，酶和底物具有较高的动能，酶的活性部位形状仍然正确。超过 50 °C 时，酶开始变性——活性部位形状改变，底物不再契合。10 °C 时，分子运动太慢，无法有效碰撞。

Stain removal % = (initial stain reading – final reading) ÷ initial stain reading × 100

She concluded that the enzyme has an optimum temperature around 40 °C, matching the human body temperature where the protease-producing bacteria naturally live.

她得出结论，该酶的最适温度约为 40 °C，这与产蛋白酶细菌自然生活的人体温度相符。

3. Diffusion in the Lungs – A Data Analysis | 肺部扩散数据分析

A scientist studied how oxygen moves from alveoli into the blood. He measured oxygen concentration in the alveolar air space and in the blood entering the lung capillaries. For a healthy person, the alveolar oxygen partial pressure was 13.3 kPa, while the blood entering had only 5.3 kPa. After gas exchange, the blood leaving the lungs had 12.6 kPa. The scientist then investigated a patient with emphysema, finding the alveolar oxygen only 10.0 kPa and the leaving blood only 8.9 kPa.

一位科学家研究了氧气如何从肺泡进入血液。他测量了肺泡气腔和进入肺毛细血管的血液中的氧浓度。健康人肺泡氧分压为 13.3 kPa，而进入的血液只有 5.3 kPa。气体交换后，离开肺部的血液为 12.6 kPa。科学家接着研究了一位肺气肿患者，发现其肺泡氧分压仅为 10.0 kPa，离开的血液仅为 8.9 kPa。

Steep concentration gradient in healthy lungs drives fast diffusion. / 健康肺中的陡峭浓度梯度推动快速扩散。
In emphysema, the alveolar walls are damaged, reducing surface area and trapping stale air. / 肺气肿患者的肺泡壁受损，表面积减少并滞留陈旧的空气。
The smaller gradient explains why the patient feels breathless. / 变小的梯度解释了患者为何感到气短。

The case reinforces that diffusion rate depends on concentration gradient, surface area, and thickness of the exchange surface.

这个案例强调了扩散速率取决于浓度梯度、表面积和交换表面的厚度。

4. Osmosis in Plant Cells – Carrot Lab Crisis | 植物细胞渗透作用——胡萝卜实验危机

A class placed carrot sticks in different sucrose solutions: 0.0 mol/dm³ (distilled water), 0.2, 0.4, 0.6, 0.8 and 1.0 mol/dm³. After 30 minutes, they recorded changes in length and mass. The carrot in distilled water gained mass (+12%) and became turgid. In 0.4 mol/dm³ solution, the mass barely changed. At 1.0 mol/dm³, the carrot lost 18% of its mass and became flaccid. One student accidentally left a carrot in 1.5 mol/dm³ solution overnight; the next morning it was so limp it could bend without breaking.

某班级将胡萝卜条放入不同蔗糖溶液中：0.0 mol/dm³（蒸馏水）、0.2、0.4、0.6、0.8 和 1.0 mol/dm³。30 分钟后，他们记录了长度和质量的变化。蒸馏水中的胡萝卜质量增加（+12%）并变得坚挺。在 0.4 mol/dm³ 溶液中，质量几乎不变。在 1.0 mol/dm³ 中，胡萝卜质量损失了 18%，变得松软。一位学生不小心将胡萝卜留在 1.5 mol/dm³ 溶液中过夜；第二天早上，胡萝卜软得可以弯折而不断裂。

Water moved in by osmosis because the cell sap had a lower water potential. / 水通过渗透进入，因为细胞液的水势较低。
0.4 mol/dm³ was roughly isotonic to the carrot cells – no net water movement. / 0.4 mol/dm³ 大致等渗于胡萝卜细胞——无水净移动。
The overnight case caused so much water loss that cells plasmolysed and lost turgor permanently. / 过夜情况导致水分大量流失，细胞发生质壁分离，永久失去膨压。

The experiment teaches the importance of water potential and the concept of isotonic, hypotonic, and hypertonic solutions.

该实验揭示了水势的重要性以及等渗、低渗和高渗溶液的概念。

5. Natural Selection – the Peppered Moth Story Updated | 自然选择——桦尺蠖故事的当代版

The classic case of the peppered moth (Biston betularia) involves the rise of the dark form during the Industrial Revolution when tree trunks were blackened by soot. In a recent long-term study, scientists recorded moth populations in a countryside area where pollution controls have cleaned the air. From 1970 to 2010, the proportion of dark moths fell from 90% to just 15%, while the pale speckled form rose to 85%.

经典案例桦尺蠖涉及工业革命期间树干被煤烟熏黑时深色型的增加。在最近的一项长期研究中，科学家记录了一个乡村地区的桦尺蠖种群，该地区的污染控制使空气变得清洁。从 1970 年到 2010 年，深色蛾的比例从 90% 下降到仅 15%，而浅色斑点型上升到 85%。

Year / 年份	% Pale moth / 浅色蛾 %	% Dark moth / 深色蛾 %
1970	10	90
1990	40	60
2010	85	15

Pale moths were now camouflaged against lichen-covered tree bark, so birds ate fewer of them. This is natural selection in action: the environment changed, shifting the selective advantage.

浅色蛾在地衣覆盖的树皮上得到了伪装，因此被鸟吃掉的更少。这就是自然选择在起作用：环境改变，选择优势随之转移。

6. Immune Response and Vaccination Timing | 免疫应答与疫苗接种时机

A child received her first dose of measles vaccine at 12 months. Blood antibody levels were measured for the next two years. After the first dose, antibody concentration rose slowly, peaking at about 50 arbitrary units after three weeks, then declining to 20 units by the time of the booster at 18 months. After the booster, the antibody level shot up to 180 units within a week and remained high.

一名儿童在 12 个月大时接种了第一剂麻疹疫苗。接下来的两年里监测了她的血液抗体水平。第一剂后，抗体浓度缓慢上升，三周后达到约 50 个任意单位的峰值，然后在 18 个月加强针时下降至 20 个单位。加强针后，抗体水平在一周内飙升至 180 个单位并保持高位。

Primary response activates memory B and T cells. / 初次应答激活了记忆 B 细胞和 T 细胞。
The booster triggers a much faster, stronger secondary response because memory cells are already present. / 加强针触发了更快、更强的二次应答，因为记忆细胞已经存在。
Without the booster, protection might wane below the protective threshold. / 没有加强针，保护力可能降至保护阈值以下。

This case explains why many vaccines require multiple doses to establish long-lasting immunity.

这个案例说明了为何许多疫苗需要多剂次接种才能建立持久的免疫力。

7. Photosynthesis and Limiting Factors | 光合作用与限制因素

An experiment used pondweed to measure the rate of photosynthesis by counting oxygen bubbles produced per minute at different light intensities and carbon dioxide concentrations. At 0.04% CO₂ (normal air), the rate increased with light intensity up to 14 bubbles/min at 40 arbitrary units of light, then plateaued. When CO₂ was increased to 0.12%, the rate reached 28 bubbles/min at the same light intensity.

一项实验利用水草测量光合作用速率，通过计数不同光照强度和二氧化碳浓度下每分钟产生的氧气气泡数。在 0.04% 的二氧化碳（正常空气）下，速率随光照强度增加而上升，在 40 个任意单位的光照下达到 14 个气泡/分钟，然后进入平台期。当二氧化碳增加到 0.12% 时，在相同光照强度下速率达到 28 个气泡/分钟。

Light intensity ∝ 1 ÷ distance² (inverse square law)

At low light, light intensity was the limiting factor. Once light was high enough, CO₂ became the new limiting factor. This illustrates how farmers might add extra CO₂ to greenhouses to boost crop yield.

在弱光下，光照强度是限制因素。一旦光照足够高，二氧化碳就成为新的限制因素。这说明农民如何可以向温室中添加额外的二氧化碳来提高作物产量。

8. Genetics of Cystic Fibrosis – A Family Case | 囊性纤维化的遗传——一个家庭案例

Cystic fibrosis (CF) is caused by a recessive allele on chromosome 7. Two healthy parents have a child with CF. The parents are understandably shocked. To understand the probability, the genetic counsellor drew a Punnett square using the alleles F (normal) and f (CF). Both parents were found to be heterozygous (Ff).

囊性纤维化是由第 7 号染色体上的隐性等位基因引起的。一对健康的父母生了一个患 CF 的孩子。父母自然很震惊。为了理解概率，遗传咨询师用等位基因 F（正常）和 f（CF）画了一个旁纳特方格。发现双亲都是杂合子 (Ff)。

Gametes / 配子	F (father / 父亲)	f (father / 父亲)
F (mother / 母亲)	FF (unaffected / 正常)	Ff (carrier / 携带者)
f (mother / 母亲)	Ff (carrier / 携带者)	ff (has CF / 患 CF)

Each pregnancy thus carries a 25% chance of an affected child, a 50% chance of a carrier, and a 25% chance of a child with two normal alleles. The case helps families understand inheritance patterns and make informed decisions.

因此每次怀孕有 25% 的概率孩子患病，50% 的概率为携带者，25% 的概率孩子有两个正常等位基因。这个案例帮助家庭理解遗传模式并做出知情选择。

9. Biodiversity Sampling in a School Pond | 校园池塘生物多样性采样

Year 9 students used kick sampling and a sweep net to survey macroinvertebrates in their school pond. They identified mayfly nymphs, caddisfly larvae, water boatmen, leeches, and rat-tailed maggots. The pond had a small inflow from a nearby busy road. A high number of rat-tailed maggots (tolerant of low oxygen) and very few mayfly nymphs (sensitive to pollution) suggested organic pollution, perhaps from road run-off containing oil and fertilisers.

九年级学生使用踢网和抄网调查了校园池塘中的大型无脊椎动物。他们识别出蜉蝣稚虫、石蛾幼虫、划蝽、水蛭和鼠尾蛆。池塘有一小股从附近繁忙道路来的入水。大量鼠尾蛆（耐低氧）和极少蜉蝣稚虫（对污染敏感）表明存在有机物污染，可能来自含有油类和肥料的道路径流。

Sensitive species like mayflies indicate clean water. / 像蜉蝣这样的敏感物种指示清洁水体。
Tolerant species like rat-tailed maggots indicate poor water quality. / 像鼠尾蛆这样的耐受物种指示水质差。
Using a biotic index, the pond scored poorly, warranting further chemical tests for nitrates and phosphates. / 使用生物指数，池塘得分很低，有必要进一步检测硝酸盐和磷酸盐。

This fieldwork exercise demonstrates how living organisms can serve as biological indicators of environmental health.

这次野外调查练习展示了生物如何作为环境健康的生物指标。

10. Hormonal Control – Diabetes and Insulin | 激素调控——糖尿病与胰岛素

A 13-year-old student was feeling constantly thirsty, tired, and losing weight. A blood test showed his fasting glucose level was 9.8 mmol/L (normal range 3.9–5.6 mmol/L). The doctor diagnosed Type 1 diabetes, where the pancreas fails to produce sufficient insulin. The student now injects insulin before meals and monitors his blood glucose using a continuous glucose monitor. He learned to calculate carbohydrate intake and adjust insulin doses accordingly.

一名 13 岁学生总感到口渴、疲倦且体重下降。血液检测显示其空腹血糖为 9.8 mmol/L（正常范围 3.9–5.6 mmol/L）。医生诊断为 1 型糖尿病，即胰腺无法产生足够的胰岛素。这名学生现在餐前注射胰岛素，并使用连续血糖监测仪监测血糖水平。他学会了计算碳水化合物摄入量并相应调整胰岛素剂量。

Insulin lowers blood glucose by signalling liver and muscle cells to take up glucose and convert it to glycogen. Without insulin, glucose accumulates in the blood, causing symptoms. The endocrine system’s feedback loop is disrupted.

胰岛素通过向肝脏和肌肉细胞发出信号，使其摄取葡萄糖并将其转化为糖原，从而降低血糖。缺乏胰岛素时，葡萄糖在血液中积累，引起症状。内分泌系统的反馈回路被打乱。

This real-life case connects classroom learning about hormones to a manageable but lifelong condition, emphasizing the importance of homeostasis.

这个真实案例将课堂上的激素学习与一种可控但终身的疾病联系起来，强调了稳态的重要性。

Published by TutorHao | Biology Revision Series | aleveler.com

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Case Study Practical Drills | 案例分析实战演练