📚 Case Study Practice for Year 8 Cambridge Biology | 八年级剑桥生物学案例分析实战演练
Case studies bring biology to life. In Year 8 Cambridge Science, you will often be asked to interpret data, analyse real-world problems, and apply your knowledge of cells, body systems, ecosystems, and health. This article is a hands-on revision workout, guiding you through five detailed scenarios and four essential skills. Work through each one carefully — they are designed to mirror the style and challenge of your exam questions.
案例研究让生物学变得生动。在剑桥八年级科学课程中，你经常会被要求解读数据、分析现实世界的问题，并运用你对细胞、身体系统、生态系统和健康的知识。本文是一次动手操作的复习演练，将带你完成五个详细情境和四项必备技能。请认真完成每一个练习——它们都仿照你考试中可能出现的问题风格和难度设计。
1. Introduction to Biological Case Studies | 生物案例研究入门
A case study in biology is a detailed investigation of a real or hypothetical situation. It helps you practise the scientific method: observing, forming a hypothesis, collecting evidence, and drawing a conclusion. The cases below cover human health, ecology, genetics, plant physiology, and lifestyle diseases — all topics in the Cambridge Year 8 syllabus.
生物学中的案例研究是对真实或假设情况进行详细调查。它帮助你练习科学方法：观察、形成假设、收集证据和得出结论。以下案例涵盖人类健康、生态学、遗传学、植物生理学和生活方式疾病——全是剑桥八年级教学大纲的主题。
As you read each case, imagine you are a scientist. Look for clues in the data, link ideas from different topics, and support your answers with reasoning. The ability to think like this is what Cambridge examiners reward most.
当你阅读每一个案例时，想象自己是一位科学家。从数据中寻找线索，将不同主题的观点联系起来，并用推理论证你的答案。这样的思维方式正是剑桥考官最看重的。
2. Case Study: The School Canteen Outbreak | 案例分析：学校食堂疫情
On Monday, twelve students from Year 8 at Riverside School reported stomach pain, vomiting, and diarrhoea. By Tuesday, another nine students had fallen ill. The school nurse suspected food poisoning and investigated what the students had eaten the previous Friday. She surveyed the affected students and 30 healthy students who had also eaten in the canteen. The results are shown in the table below.
周一，河畔学校八年级有十二名学生报告腹痛、呕吐和腹泻。到周二，又有九名学生病倒。校护怀疑是食物中毒，并调查了这些学生上周五吃了什么。她调查了患病学生以及另外30名也在食堂就餐的健康学生。结果如下表所示。
| Food item | Ate it (ill students) / total ill = 21 | Ate it (healthy students) / total healthy = 30 |
|---|---|---|
| Chicken curry | 20 | 5 |
| Rice | 19 | 28 |
| Salad | 10 | 22 |
| Ice cream | 8 | 15 |
| Water | 21 | 30 |
Which food item is most strongly linked to the outbreak? Almost all ill students (20/21) ate chicken curry, while only 5 out of 30 healthy students ate it. This suggests chicken curry is the likely source. The pathogen may be Salmonella, a bacterium often found in undercooked chicken. Salmonella reproduces rapidly in the digestive system, causing the symptoms described.
哪种食物与本次疫情关联最强？几乎所有患病学生（21人中的20人）吃了鸡肉咖喱，而30名健康学生中只有5人吃过。这表明鸡肉咖喱很可能是源头。病原体可能是沙门氏菌，这是一种常见于未煮熟鸡肉的细菌。沙门氏菌在消化系统中迅速繁殖，导致所描述的症状。
Food poisoning links to the topic of microorganisms and the human digestive system. Bacteria such as Salmonella produce toxins that irritate the lining of the stomach and intestines. Boiling or cooking food thoroughly kills these pathogens, which is why food safety rules are crucial.
食物中毒与微生物和人体消化系统这两个课题相关。沙门氏菌等细菌会产生毒素，刺激胃壁和肠壁。彻底煮沸或煮熟食物能杀死这些病原体，这就是食品安全规则至关重要的原因。
3. Case Study: Coral Bleaching on the Great Barrier Reef | 案例分析：大堡礁的珊瑚白化
Marine biologists recorded sea surface temperatures and the percentage of bleached coral at five sites along the Great Barrier Reef over six months. Coral bleaching occurs when corals expel the tiny algae (zooxanthellae) living in their tissues, turning white. The algae provide most of the coral's energy through photosynthesis.
海洋生物学家在六个月里记录了大堡礁五个地点的海面温度和珊瑚白化百分比。当珊瑚排出其组织中生活的微小藻类（虫黄藻）时就会发生珊瑚白化，珊瑚由此变白。这些藻类通过光合作用为珊瑚提供大部分能量。
| Site | Average water temperature (°C) | Coral bleaching (%) |
|---|---|---|
| A | 26.5 | 5 |
| B | 29.0 | 32 |
| C | 30.5 | 68 |
| D | 27.0 | 10 |
| E | 31.2 | 85 |
The data show a clear positive correlation: as water temperature rises, the percentage of bleached coral increases. At site E, the warmest site, 85% of corals were bleached. This is strong evidence that elevated temperature stresses the coral–algae relationship. The stress causes the coral to expel the algae, losing its main food source.
数据显示明显的正相关：随着水温上升，珊瑚白化的百分比增加。在温度最高的地点E，85%的珊瑚出现白化。这是强有力的证据，说明温度升高使珊瑚与藻类的关系承压。这种压力导致珊瑚排出藻类，失去其主要食物来源。
In your ecology lessons, you learned that corals are animals that live in a mutualistic symbiosis with photosynthetic algae. If warm water persists, the coral starves and may die. This connects to food chains: a dead reef cannot support the fish, molluscs, and other organisms that depend on it, reducing biodiversity.
在你的生态课中，你已学过珊瑚是与光合藻类互惠共生的动物。如果温水持续，珊瑚会饿死。这与食物链有关：死去的珊瑚礁无法供养依赖它的鱼类、软体动物和其他生物，从而降低生物多样性。
4. Case Study: Anaemia in a Teenage Athlete | 案例分析：青少年运动员的贫血
A 13-year-old competitive swimmer, Mia, has been feeling unusually tired, breathless after short training sessions, and her skin appears pale. A blood test reveals a low haemoglobin concentration: 90 g/L (normal range for her age: 115–155 g/L). Her diet diary shows low intake of red meat, green leafy vegetables, and citrus fruits.
一名十三岁的竞技游泳运动员米娅最近异常疲倦，短时间训练后就气短，皮肤也显得苍白。验血显示血红蛋白浓度偏低：90 g/L（她年龄的正常范围是115–155 g/L）。她的饮食日记显示红肉、绿叶蔬菜和柑橘类水果摄入很少。
Haemoglobin is the protein in red blood cells that carries oxygen from the lungs to respiring muscles. Iron is a key component of haemoglobin, and vitamin C helps the body absorb iron from plant foods. Mia's diet is low in both iron and vitamin C, so her body cannot produce enough healthy red blood cells. This condition is called iron-deficiency anaemia.
血红蛋白是红细胞中负责将氧气从肺部输送到呼吸肌的蛋白质。铁是血红蛋白的关键成分，而维生素C帮助人体从植物性食物中吸收铁。米娅的饮食缺乏铁和维生素C，因此她的身体无法制造足够健康的红细胞。这种情况称为缺铁性贫血。
Oxygen transport is a core topic in the 'Respiration and Circulation' unit. Without enough haemoglobin, less oxygen reaches muscle cells for aerobic respiration. This explains Mia's fatigue and breathlessness. Treatment involves increasing iron-rich foods (lean red meat, spinach) and consumption of fruits high in vitamin C (oranges, kiwifruit).
氧气运输是“呼吸与循环”单元的核心主题。没有足够的血红蛋白，到达肌肉细胞进行有氧呼吸的氧气就更少。这就解释了米娅疲劳和气短的原因。治疗需要增加富含铁的食物（瘦红肉、菠菜）以及摄入维生素C含量高的水果（橙子、猕猴桃）。
5. Case Study: Cystic Fibrosis in a Family | 案例分析：一个家庭中的囊性纤维化
Cystic fibrosis (CF) is a genetic disorder that causes the body to produce thick, sticky mucus in the lungs and digestive system. It is caused by a recessive allele. A couple, both healthy, have a child with CF. They want to understand the probability of their next child being affected. The allele for normal mucus is represented by F, and the faulty allele by f.
囊性纤维化是一种遗传病，导致身体在肺部和消化系统中产生粘稠的粘液。它由隐性等位基因引起。一对健康的夫妇生了一个患CF的孩子。他们想了解下一个孩子患病的概率。正常粘液的等位基因用F表示，缺陷等位基因用f表示。
Because both parents are healthy but have a child with CF, they must be carriers. Their genotype is Ff. A genetic diagram (Punnett square) shows the possible combinations in their offspring:
因为父母都健康却有一个患CF的孩子，所以他们一定是携带者。他们的基因型是Ff。遗传图（旁氏表）展示了他们后代可能的基因组合：
Parents: Ff × Ff
| F | f | |
| F | FF | Ff |
| f | Ff | ff |
The chance of an affected child (ff) is 1 in 4, or 25%. The chance of a carrier child (Ff) is 2 in 4 (50%). The chance of a child who is neither affected nor a carrier (FF) is 1 in 4 (25%). This pattern applies to every pregnancy.
患病孩子（ff）的概率是四分之一，即25%。携带者孩子（Ff）的概率是四分之二（50%）。既非患病也非携带者的孩子（FF）的概率是四分之一（25%）。这种模式适用于每一次怀孕。
Genetic case studies link closely to your work on inheritance, alleles, and Punnett squares. Understanding probability helps families make informed choices, though it is important to remember that these probabilities are independent for each child.
遗传案例研究与你所学的遗传、等位基因和旁氏表密切相关。理解概率有助于家庭做出知情选择，但要记住这些概率对每个孩子都是独立的。
6. Case Study: The Mystery of the Wilting Sunflowers | 案例分析：向日葵枯萎之谜
A gardener notices that sunflowers in one part of her garden are wilting, while sunflowers in another part, only 5 metres away, are healthy. She measures soil moisture, light intensity, and checks for pests. The wilting plants' soil is very dry, whereas the healthy plants' soil is moist. Both receive the same amount of sunlight and show no signs of pests.
一位园丁发现她花园里某处的向日葵正在枯萎，而仅5米之外的另一处向日葵却十分健康。她测量了土壤湿度、光照强度，并检查了害虫。枯萎植株的土壤非常干燥，而健康植株的土壤湿润。两处接受的光照量相同，也都没有虫害迹象。
What is the most likely cause of wilting? Plants need water for support (turgor pressure in vacuoles) and for photosynthesis. When soil is dry, root hair cells cannot absorb enough water. The vacuole loses water, the cell becomes flaccid, and the whole plant droops. This connects to the topic of 'Plant Transport and Photosynthesis'.
最可能导致枯萎的原因是什么？植物需要水来维持支撑（液泡中的膨压）和进行光合作用。当土壤干燥时，根毛细胞无法吸收足够的水分。液泡失水，细胞变软，整株植物下垂。这与你学过的“植物运输与光合作用”课题相关。
The investigation also shows the importance of controlling variables. By comparing two groups where only soil moisture differed, the gardener can confidently conclude that lack of water caused the wilting. Always consider other possible factors, such as root disease or blocked xylem vessels, but here the evidence points clearly to water shortage.
这项调查也显示了控制变量的重要性。通过比较仅土壤湿度不同的两组植物，园丁可以自信地推断缺水导致了枯萎。当然还应考虑其他可能的因素，如根部病害或木质部导管阻塞，但这里的证据明确指向水分短缺。
7. Data Interpretation Skills | 数据解读技巧
Case studies often present data in tables, graphs, or diagrams. Learning to read these accurately is essential. Start by looking at the axis labels, units, and headings. Identify the independent variable (what is changed) and the dependent variable (what is measured). Look for patterns: does the line go up, down, or show a peak?
案例分析常以表格、图表或图示的形式呈现数据。学会准确阅读这些数据至关重要。首先看坐标轴标签、单位和标题。辨认自变量（改变的变量）和因变量（测量的变量）。寻找规律：线条是上升、下降还是出现峰值？
In the coral bleaching example, water temperature is the independent variable and bleaching percentage is the dependent variable. The pattern shows a steady rise. When describing data for Cambridge exams, use exact values, mention the range, and refer to 'correlation' rather than 'cause' unless the experiment controls all other factors.
在珊瑚白化的例子中，水温是自变量，白化百分比是因变量。其规律呈稳步上升。在剑桥考试中描述数据时，要使用准确数值，提及范围，并用“相关”而不是“导致”，除非实验控制了一切其他因素。
8. Drawing Conclusions from Evidence | 从证据得出结论
A conclusion must directly answer the question or hypothesis, be supported by the data, and use biological knowledge. For the school canteen outbreak, a suitable conclusion is: 'The chicken curry is the most likely source of the food poisoning because 20 out of 21 ill students ate it, compared with only 5 out of 30 healthy students. This suggests the presence of a pathogen such as Salmonella.'
结论必须直接回答问题或假设，有数据支持，并运用生物学知识。对于学校食堂疫情，合适的结论是：“鸡肉咖喱最可能是食物中毒的来源，因为在21名患病学生中有20人吃了它，而30名健康学生中只有5人吃了。这表明可能存在沙门氏菌等病原体。”
Always mention limitations. For example, 'The sample size was small, so the conclusion may not apply to all schools. Also, other factors like cross-contamination cannot be ruled out.' Recognizing weaknesses shows higher-level thinking and can earn marks in evaluation questions.
永远要提及局限性。例如，“样本量小，因此结论未必适用于所有学校。此外，无法排除交叉污染等其他因素。”认识到不足体现更高层次的思维，能在评估类问题中赢得分数。
9. Writing a Scientific Explanation | 撰写科学解释
A strong explanation states the cause, describes the process step by step, and links to the observable outcome. For anaemia: 'Low dietary iron means fewer haemoglobin molecules can be made in red blood cells. Haemoglobin carries oxygen, so less oxygen is transported to muscles for aerobic respiration. This causes fatigue and shortness of breath during exercise.'
一个好的解释会陈述原因，逐步描述过程，并联系到可观察的结果。以贫血为例：“饮食中铁摄入不足意味着红细胞中可制造的血红蛋白分子更少。血红蛋白运输氧气，因此输送到肌肉进行有氧呼吸的氧气减少。这导致运动中疲劳和气短。”
Use scientific vocabulary precisely: 'haemoglobin', 'aerobic respiration', 'red blood cells'. Link the microscopic (cellular level) to the macroscopic (symptoms). This approach works across all biology case studies, whether you are discussing enzyme action, diffusion, or genetic inheritance.
恰当使用科学术语：“血红蛋白”、“有氧呼吸”、“红细胞”。将微观（细胞层面）与宏观（症状）联系起来。这种方法适用于所有生物案例分析，无论讨论的是酶的作用、扩散还是遗传。
10. Practice Scenario: Investigating Enzyme Activity | 实践情境：酶活性探究
Try this on your own: A student wanted to test the effect of pH on the activity of amylase, an enzyme that breaks down starch. She set up test tubes with starch solution and amylase at pH 4, 7, and 10. She measured the time taken for the starch to disappear using iodine solution. Her results: pH 4 took 180 seconds, pH 7 took 30 seconds, pH 10 took 120 seconds.
请自己尝试：一名学生想测试pH值对淀粉酶（一种分解淀粉的酶）活性的影响。她设置了三个试管，分别含有淀粉溶液和pH为4、7和10的淀粉酶。她用碘液测量淀粉消失所需的时间。结果：pH 4用了180秒，pH 7用了30秒，pH 10用了120秒。
How would you describe the relationship? What conclusions can you draw about the optimum pH for amylase? What controls should she have included? (Answers: Amylase works fastest at pH 7, so its optimum is near neutral. Slower reaction at pH 4 and 10 suggests the active site of the enzyme changes shape and the enzyme denatures. A control tube without amylase, or with boiled amylase, would show whether starch breaks down on its own.)
你会如何描述这种关系？关于淀粉酶的最适pH，你能得出什么结论？她本应包括哪些对照？（答案：淀粉酶在pH 7时作用最快，因此其最适pH接近中性。pH 4和10反应较慢，表明酶的活性位点形状改变，酶变性。一个不含淀粉酶或含有煮沸淀粉酶的对照管，可以显示淀粉是否会自行分解。）
Published by TutorHao | Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图