📚 Case Study Practical Drills | 案例分析实战演练
Case studies in KS3 Edexcel Biology help you apply scientific knowledge to real‑world scenarios. This revision drill walks you through five carefully selected examples – from antibiotic resistance to bioaccumulation – teaching you how to break down problems, link facts and write confident exam answers. Each case is followed by a guided analysis so you can practise the skill of data interpretation.
KS3 Edexcel 生物中的案例分析帮助你运用科学知识解决真实世界问题。本次复习实战将带你剖析五个精选案例——从抗生素耐药到生物累积——教你如何拆解问题、串联知识点并自信地书写考试答案。每个案例后均配有引导式分析，助你训练数据解读能力。
1. What Is a Biology Case Study? | 什么是生物案例分析？
A biology case study presents a realistic situation – such as a disease outbreak or an ecological problem – often supported by data, graphs or diagrams. Your task is to use subject knowledge to explain observations, predict outcomes and evaluate evidence. KS3 Edexcel frequently uses case studies to test AO2 (application) and AO3 (analysis) skills.
生物案例研究给出一个贴近真实的情境——比如疾病暴发或生态问题——通常配有数据、图表或示意图。你的任务是运用学科知识解释现象、预测结果并评估证据。Edexcel KS3 常借助案例考查 AO2（应用）与 AO3（分析）能力。
2. Case Study 1: The Rise of Antibiotic Resistance | 案例1：抗生素耐药性的抬头
In a hospital, the same bacterial infection kept returning in several patients despite treatment with penicillin. Doctors swabbed surfaces and cultured bacteria on agar plates containing penicillin. After 48 hours, many colonies grew around the antibiotic discs, while a control plate without penicillin showed a full lawn of bacteria. Only a few colonies survived near the strongest antibiotic disc.
在一家医院里，同一种细菌感染在多名患者身上反复出现，尽管使用了青霉素治疗。医生采集了表面拭子并在含青霉素的琼脂平板上培养细菌。48 小时后，抗生素纸片周围长出了许多菌落，而不含青霉素的对照平板则布满整片菌苔。只有最强效的抗生素纸片附近才见到寥寥几个存活菌落。
The graph of bacterial growth over time shows a sharp decline after the first dose, followed by a steady rise again after day three. The resistant population reproduces faster because sensitive bacteria are killed off, leaving resources and space for the resistant ones.
细菌生长的时间曲线图显示，第一次用药后数量急剧下降但第三天又开始稳步上升。耐药菌群繁殖更快，因为敏感菌被杀灭后，留下了充足资源和空间给耐药菌。
3. Antibiotic Resistance Analysis | 抗生素耐药性分析
Natural selection explains the pattern: random mutations in the bacterial DNA produce a few cells that can break down penicillin. When the antibiotic is used, these mutants survive and pass the resistance gene to their offspring via binary fission. Over generations, the resistant strain dominates. This is why completing a full course of antibiotics is crucial – stopping early leaves the most resilient bacteria alive.
自然选择可以解释这一规律：细菌 DNA 中的随机突变产生了少数能分解青霉素的细胞。使用抗生素后，这些突变体存活下来，并通过二分裂将耐药基因传给子代。经过多代繁殖，耐药菌株占据主导。这就是坚持用完整个疗程至关重要的原因——中途停药会让最强韧的细菌存活。
Exam tip: always link ‘resistance’ to ‘variation’ and ‘selection pressure’. State clearly that bacteria evolve, not individual patients. Use key terms: mutation, gene, susceptible, resistant, survival advantage.
考试技巧：始终将“耐药性”与“变异”和“选择压力”联系起来。明确指出是细菌在进化，而非患者本人。使用关键词：突变、基因、敏感、耐药、生存优势。
4. Case Study 2: Photosynthesis in a Greenhouse | 案例2：温室中的光合作用
A tomato grower measured the rate of photosynthesis under three different conditions: low light (200 µmol m⁻² s⁻¹), medium light (500 µmol m⁻² s⁻¹) and high light (800 µmol m⁻² s⁻¹). The carbon dioxide concentration was kept at 400 ppm and temperature at 25°C. Oxygen production bubbles were counted per minute as an indicator. Results: 8 bubbles/min, 18 bubbles/min and 21 bubbles/min respectively.
一位番茄种植者测量了三种条件下的光合速率：低光照（200 µmol m⁻² s⁻¹）、中光照（500 µmol m⁻² s⁻¹）和高光照（800 µmol m⁻² s⁻¹）。CO₂ 浓度保持在 400 ppm，温度为 25°C。以每分钟的氧气气泡数作为指标，结果分别为 8 气泡/分钟、18 气泡/分钟和 21 气泡/分钟。
The grower then raised CO₂ to 800 ppm while keeping light at 800 µmol m⁻² s⁻¹. Oxygen production jumped to 32 bubbles/min. However, when the temperature was increased to 40°C, bubble count dropped to 5 bubbles/min, and leaves began to wilt.
接着，种植者将 CO₂ 提升至 800 ppm，光照保持 800 µmol m⁻² s⁻¹。氧气产量跃升至 32 气泡/分钟。但当温度升至 40°C 时，气泡数降至 5 气泡/分钟，叶片开始萎蔫。
5. Photosynthesis Analysis | 光合作用分析
Light intensity initially limits the rate of photosynthesis: doubling light from low to medium nearly doubles oxygen output. Beyond a certain point, light is no longer the limiting factor – adding CO₂ further boosts the rate, proving CO₂ was the new bottleneck. At 40°C, enzymes such as rubisco denature, the stomata close to conserve water, and gas exchange is restricted, causing the sharp decline.
起初，光照强度是光合速率的限制因子：从低光加倍到中光，氧气输出几乎翻番。超过一定点后，光不再是限制因素——提高 CO₂ 进一步提速，证明 CO₂ 成为新的瓶颈。40°C 时，RuBisCO 等酶变性，气孔关闭以保存水分，气体交换受限，导致速率骤降。
This case highlights the interplay of limiting factors: light, CO₂ and temperature. Graphs would show a plateau until the next factor is adjusted. Remember to describe the shape of lines and use data points in your answer.
本案例凸显了限制因子间的相互作用：光、CO₂ 与温度。图表会显示在调整下一因子前出现平台。答题时记得描述曲线形状并引用数据点。
6. Case Study 3: Cystic Fibrosis Pedigree | 案例3：囊性纤维化家系图
A family tree shows a recessive genetic disorder, cystic fibrosis (CF). The parents in generation I are both healthy, but one of their three children has CF. In generation II, the affected son marries a healthy woman and they have two children, one boy with CF and one girl without. The healthy daughter from generation II marries a man with no family history of CF, and their three children are all healthy.
一个家族图谱展示了一种隐性遗传病——囊性纤维化（CF）。第 I 代父母均健康，但他们的三个子女中有一人患有 CF。第 II 代中，患病的儿子娶了一位健康女性，他们育有两个孩子：一个男孩患 CF，一个女孩不患病。第 II 代健康的女儿与一男性（无 CF 家族史）结婚，他们的三个孩子均健康。
7. Genetic Pedigree Analysis | 遗传家系图分析
CF is caused by a recessive allele on chromosome 7. Using the symbol F for normal and f for CF allele, the generation I parents must both be heterozygous (Ff). The affected son is ff, and his wife must be a carrier (Ff) to have an affected child. The healthy daughter from generation II is either FF or Ff, but since her husband is FF (no family history), all children are healthy – she is most likely FF, or if she is Ff, each child still had a 50% chance of being normal.
CF 由位于第 7 号染色体上的隐性等位基因引起。以 F 表示正常，f 表示 CF 等位基因，第 I 代父母必定均为杂合子（Ff）。患病的儿子为 ff，他的妻子要生出患病孩子必定是携带者（Ff）。第 II 代健康女儿为 FF 或 Ff，但由于其丈夫为 FF（无家族史），所有孩子均健康——她极有可能是 FF，若为 Ff，每个孩子仍有 50% 概率正常。
Pedigree analysis requires careful deduction of genotypes. Look for ‘skipping generations’ pattern typical of recessive disorders. Punnett squares help to calculate risk probabilities.
家系分析要求仔细推断基因型。留意隐性遗传病典型的“隔代遗传”模式。庞尼特方格有助于计算风险概率。
8. Case Study 4: Biological Washing Powders | 案例4：生物洗衣粉
A company tested its new enzyme‑based washing powder on protein‑stained cloth at four temperatures: 10°C, 30°C, 50°C and 70°C. The stain removal efficiency (%) after a 30‑minute wash was recorded. Results were: 15%, 68%, 94% and 12% respectively. The same experiment was repeated with a non‑biological powder, which showed results of 8%, 10%, 11% and 10%.
某公司测试其新型酶基洗衣粉对蛋白质污渍在四种温度下的去污效果：10°C、30°C、50°C 和 70°C。记录 30 分钟洗涤后的去污效率（%）：分别为 15%、68%、94% 和 12%。同样的实验用非生物洗衣粉重复，结果为 8%、10%、11% 和 10%。
9. Enzyme Detergent Analysis | 酶洗涤剂分析
The biological powder contains protease enzymes that break down protein stains into soluble amino acids. Enzyme activity increases with temperature up to an optimum near 50°C; at 10°C, molecules move too slowly, giving low collision rates. At 70°C, the enzyme’s active site denatures, losing its specific shape, so the substrate no longer fits – efficiency plunges. The control non‑bio powder removes hardly any protein stain regardless of temperature, confirming that temperature effect is due to enzyme action, not just hot water.
生物洗衣粉含有蛋白酶，可将蛋白质污渍分解为可溶性氨基酸。酶活性随温度升高而增强，最适温度约 50°C；10°C 时分子运动过慢，碰撞频率低。70°C 时酶活性位点变性，丧失特定形状，底物不再匹配——效率骤降。对照组非生物粉在任何温度下去除蛋白质污渍均极少，证实温度效应源于酶作用而非单纯热水。
This case links to digestion (protease in stomach and small intestine) and industrial biotechnology. Top‑tip: always state ‘optimum temperature’ and ‘denatured active site’ when explaining drops in enzyme activity.
本案例关联消化系统（胃与小肠中的蛋白酶）及工业生物技术。小贴士：解释酶活性下降时务必提及“最适温度”和“活性位点变性”。
10. Case Study 5: DDT in a Lake Food Chain | 案例5：湖中食物链的 DDT
A lake was sprayed with the pesticide DDT to control mosquitoes. Scientists measured DDT concentration (mg per kg body mass) in organisms at different trophic levels. Data: phytoplankton – 0.04 mg/kg, zooplankton – 0.5 mg/kg, small fish – 2 mg/kg, large fish – 10 mg/kg, and osprey (fish‑eating bird) – 80 mg/kg. Eggshell thinning was observed in the osprey population.
一个湖泊喷洒了杀虫剂 DDT 以控制蚊虫。科学家测量了不同营养级生物体内 DDT 浓度（mg/kg 体重）。数据：浮游植物 0.04 mg/kg、浮游动物 0.5 mg/kg、小鱼 2 mg/kg、大鱼 10 mg/kg、鱼鹰（食鱼鸟）80 mg/kg。鱼鹰种群中观察到蛋壳变薄现象。
11. Bioaccumulation Analysis | 生物累积分析
DDT is a persistent, fat‑soluble chemical. It is absorbed by producers and passed along the food chain. At each trophic level, the concentration increases because consumers eat many organisms from the level below, accumulating the toxin in their fatty tissues without breaking it down. This process, biomagnification, explains why top predators like osprey show the highest levels. Thinned eggshells reduce hatching success, threatening the population.
DDT 是一种持久性的脂溶性化学物质。它被生产者吸收后沿食物链传递。每上升一个营养级，浓度就增加，因为消费者会摄食大量下一级的生物，将毒素蓄积在脂肪组织中且不分解。这一过程称为生物放大，解释了为何鱼鹰等顶级捕食者体内浓度最高。蛋壳变薄会降低孵化成功率，威胁种群存续。
Graph the concentrations on a bar chart to visualise the dramatic increase. Use the terms: trophic level, persistent, toxin, accumulation, biomagnification. Relate to KS3 topics on ecosystems and interdependence.
用条形图绘出浓度数据，直观展示急剧上升趋势。使用术语：营养级、持久性、毒素、累积、生物放大。并联结 KS3 中生态系统与相互依存的知识点。
12. Exam Strategy and Summary | 应试策略与总结
When tackling a case study question, first identify the biology topic (disease, photosynthesis, genetics, enzymes, ecology). Highlight key data in the text, tables or graphs. Plan your answer using a short chain of reasoning: observation → scientific explanation → consequence. Support each point with specific figures from the case. Wherever relevant, discuss limitations or further investigations – this scores high marks for evaluation.
处理案例题时，首先识别所属生物学主题（疾病、光合作用、遗传、酶、生态）。圈出文本、表格或图表中的关键数据。用简短的推理链组织答案：观察 → 科学解释 → 后果。每个要点都要用案例中的具体数字支撑。在相关处讨论局限性或进一步研究方向——这会在评价能力上赢得高分。
Regular practice with case studies builds confidence in applying knowledge. Review these five drills, sketch the graphs, write out the genetic crosses and explain the enzyme curves – then you will be ready for any KS3 Edexcel Biology exam scenario.
定期做案例分析练习能增强知识应用的信心。重温这五个实战，自己绘制图表、书写遗传杂交并解释酶活力曲线——这样你就能从容应对任何 KS3 Edexcel 生物考试情境。
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