Case Study Practice Drill | 案例分析实战演练

📚 Case Study Practice Drill | 案例分析实战演练

In CCEA Year 7 Biology, case studies help you apply your knowledge to real-world scenarios. This article provides a series of short case studies covering key topics such as ecosystems, cells, digestion, photosynthesis and adaptations. Each case presents an observation or problem, followed by a biological explanation. Work through each one, and use the dual-language analysis to check your understanding.

在 CCEA 七年级生物课程中，案例分析能帮助你将知识运用到真实情境中。本文提供一系列涵盖生态系统、细胞、消化、光合作用和适应性等重要主题的简短案例。每个案例先给出观察或问题，随后提供生物学解释。请逐一研读，并利用双语分析来检验你的理解。

1. Pond Water Micro‑Ecosystem | 池塘水微生物生态系统

A student collected a drop of pond water and observed it under the microscope. She noticed tiny green organisms, small fast‑moving creatures, and larger organisms feeding on the smaller ones. Later, she drew a food chain: green algae → water flea → small fish.

一名学生采集了一滴池塘水并在显微镜下观察。她注意到微小的绿色生物、游动迅速的小型生物，以及以小型生物为食的较大生物。随后她画了一条食物链：绿藻 → 水蚤 → 小鱼。

The green organisms are producers: they contain chlorophyll and carry out photosynthesis to make food. The water fleas are primary consumers, eating the algae. The small fish is a secondary consumer. This shows how energy passes along a food chain. If the algae population decreased, water fleas would have less food and their numbers might fall, affecting the fish as well. All organisms depend on each other in an ecosystem.

绿色生物是生产者：它们含有叶绿素，通过光合作用制造食物。水蚤是初级消费者，以藻类为食。小鱼是次级消费者。这表明了能量如何沿食物链传递。如果藻类数量减少，水蚤的食物就会减少，数量可能下降，进而影响小鱼。生态系统中所有生物都相互依存。

2. Sweet Taste While Chewing Bread | 咀嚼面包时的甜味

A student chewed a piece of plain white bread for several minutes without swallowing. She noticed that the bread began to taste slightly sweet. She wondered why a savoury food could become sweet in her mouth.

一名学生将一片白面包咀嚼了数分钟但不吞咽。她注意到面包开始有了一丝甜味。她好奇为什么一种不甜的食物在口中会变甜。

Bread contains a lot of starch. Human saliva contains an enzyme called amylase. Enzymes are biological catalysts that speed up chemical reactions. Amylase breaks down starch into smaller sugar molecules, such as maltose. It is this maltose that gives the sweet taste. This is an example of chemical digestion beginning right in the mouth. The longer you chew, the more starch is broken down.

面包含大量淀粉。人类唾液中含有一种叫做淀粉酶的酶。酶是生物催化剂，能加速化学反应。淀粉酶将淀粉分解为较小的糖分子，例如麦芽糖。正是麦芽糖带来了甜味。这是化学消化在口腔中就开始的例子。咀嚼时间越长，分解的淀粉就越多。

3. Pondweed Photosynthesis Bubbles | 水草光合作用气泡实验

A class placed a piece of pondweed in a beaker of water and shone a lamp on it. Students counted the number of oxygen bubbles produced per minute at different distances from the lamp. They recorded more bubbles when the lamp was closer.

一个班级将一段水草放入盛水的烧杯中，并用灯照射。学生们统计了灯在不同距离时每分钟产生的氧气泡数量。他们发现灯越近，气泡越多。

Pondweed photosynthesises using light energy. The equation for photosynthesis is:

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

The bubbles are oxygen, a by‑product. When light intensity is higher (lamp closer), the rate of photosynthesis increases, so more oxygen is released. However, beyond a certain light level, the rate may slow down as another factor (e.g., carbon dioxide concentration) becomes limiting. This investigation shows how light affects plant growth.

水草利用光能进行光合作用。光合作用的方程式为：

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

气泡是氧气，一种副产品。当光强度较高（灯更近）时，光合作用速率提升，因此释放更多氧气。但超过一定光照水平后，速率可能减慢，因为其他因素（如二氧化碳浓度）成为限制条件。此项调查说明了光如何影响植物生长。

4. Hand‑Washing and Bacterial Growth | 洗手与细菌生长

A student pressed his unwashed fingertip onto a nutrient agar plate, then washed his hands thoroughly and pressed another finger onto a second plate. Both plates were incubated at 30 °C for two days. The first plate showed many colonies; the second had very few.

一名学生将未洗的手指按在营养琼脂平板上，然后彻底洗手，再用另一根手指按在第二个平板上。两个平板均在 30 °C 下培养两天。第一个平板出现许多菌落；第二个菌落极少。

Microorganisms, including bacteria, are everywhere, especially on our skin. The nutrient agar provides food for the bacteria to grow into visible colonies. The unwashed finger transferred many bacteria, resulting in many colonies. Hand‑washing removes most germs, so far fewer colonies developed. This case demonstrates the importance of hygiene for preventing the spread of infectious diseases. In labs, aseptic technique is used to keep cultures pure.

微生物（包括细菌）无处不在，尤其在我们的皮肤上。营养琼脂为细菌提供食物，使其生长为可见的菌落。未洗的手指转移了许多细菌，因此形成了大量菌落。洗手去除了大部分病菌，因此菌落少得多。本案例说明了保持卫生对预防传染病传播的重要性。在实验室中，无菌技术用于保持培养物纯净。

5. Polar Bear vs. Camel Adaptations | 北极熊与骆驼的适应性对比

Arctic explorers observed that polar bears thrive in freezing temperatures, with thick white fur and a layer of blubber. In contrast, camels survive in hot deserts with little water. Students were asked to explain how each animal is adapted to its habitat.

北极探险者观察到，北极熊在严寒中生存良好，有厚实的白色皮毛和一层脂肪。相反，骆驼在几乎无水的炎热沙漠中生存。学生们被要求解释每种动物如何适应其栖息地。

Polar bears have thick fur with hollow, air‑filled hairs that trap heat efficiently. Their black skin underneath absorbs sunlight, and blubber insulates against the cold. White fur provides camouflage in snow. Camels have long eyelashes and hairy nostrils to keep out sand, wide feet to avoid sinking in sand, and humps that store fat (not water), which can be broken down for energy and water. They also produce very concentrated urine to conserve water. These are structural and physiological adaptations.

北极熊厚实的皮毛具有中空、充满空气的毛发，能有效锁住热量。其下的黑色皮肤吸收阳光，脂肪层隔绝寒冷。白色皮毛在雪地里提供伪装。骆驼有长长的睫毛和多毛的鼻孔阻挡沙粒，宽大的蹄防止陷入沙中，驼峰储存脂肪（而非水），可分解产生能量和水。它们还产生高度浓缩的尿液以节约水分。这些都是结构和生理上的适应性。

6. Observing Onion Epidermal Cells | 观察洋葱表皮细胞

A student peeled a thin layer of onion epidermis, placed it on a slide with a drop of water and iodine solution, and observed it under a light microscope. She noticed rectangular shapes, each containing a small round structure and a larger, lightly‑stained area.

一名学生撕取一层薄洋葱表皮，放在载玻片上，加一滴水和碘液，在光学显微镜下观察。她注意到矩形形状，每个内部有一个小圆形结构和一个较大的、轻度染色的区域。

Each rectangle is a plant cell. The outer boundary is the cell wall, which gives the plant cell a regular shape. Inside, the round structure is the nucleus, which controls the cell’s activities. The lightly‑stained area is the cytoplasm. The large, clear space is the permanent vacuole containing cell sap. Iodine stains starch granules and makes some features more visible. Plant cells also contain chloroplasts, but onion bulb cells usually lack chloroplasts because they grow underground and do not photosynthesise.

每个矩形是一个植物细胞。外部边界是细胞壁，它使植物细胞具有规则形状。内部的圆形结构是细胞核，控制细胞活动。轻度染色的区域是细胞质。大而透明的空间是含有细胞液的永久液泡。碘液可使淀粉粒染色，并使某些特征更明显。植物细胞还含有叶绿体，但洋葱鳞茎细胞通常不含叶绿体，因为它们生长在地下，不进行光合作用。

7. Sailors, Scurvy and Vitamin C | 水手、坏血病与维生素 C

In the 18th century, sailors on long voyages often suffered from bleeding gums, loose teeth and slow wound healing. A ship’s surgeon noticed that those who ate citrus fruits recovered quickly, while others did not.

18 世纪，长途航行的水手常出现牙龈出血、牙齿松动和伤口愈合缓慢的症状。一位船医注意到，食用柑橘类水果的船员很快康复，而未食用的则没有。

The disease was scurvy, caused by a severe deficiency of vitamin C (ascorbic acid). Vitamin C is needed to make collagen, a protein that strengthens skin, blood vessels, gums and bones. Without enough vitamin C, these tissues become weak. Citrus fruits like lemons and oranges are rich in vitamin C. Today, a balanced diet with fresh fruits and vegetables prevents deficiency diseases. This case highlights the importance of vitamins in maintaining health.

这种疾病是坏血病，由严重缺乏维生素 C（抗坏血酸）引起。维生素 C 是合成胶原蛋白所必需的，胶原蛋白是强健皮肤、血管、牙龈和骨骼的蛋白质。缺乏维生素 C 会导致这些组织变得脆弱。柠檬和橙子等柑橘类水果富含维生素 C。如今，含新鲜果蔬的均衡饮食可预防营养缺乏症。本案例突出了维生素在维持健康中的重要性。

8. Breathing Rate and Exercise | 运动与呼吸频率

A student measured her resting breathing rate: 16 breaths per minute. After running on the spot for two minutes, her breathing rate increased to 30 breaths per minute. Even after five minutes of rest, it remained slightly higher than her resting rate.

一名学生测量了她的静息呼吸频率：每分钟 16 次。在原地跑步两分钟后，她的呼吸频率增至每分钟 30 次。即使在休息五分钟后，仍略高于静息频率。

During exercise, muscles need more energy. Cells carry out aerobic respiration, using oxygen to release energy from glucose. The equation for aerobic respiration is:

Glucose + Oxygen → Carbon Dioxide + Water + Energy

The increased breathing rate brings more oxygen into the lungs and removes the extra carbon dioxide produced. The heart rate also increases to deliver oxygen faster. The slightly raised rate after exercise repays an ‘oxygen debt’ – the extra oxygen needed to break down lactic acid built up in muscles during vigorous activity.

运动时，肌肉需要更多能量。细胞进行有氧呼吸，利用氧气从葡萄糖中释放能量。有氧呼吸的方程式为：

葡萄糖 + 氧气 → 二氧化碳 + 水 + 能量

呼吸频率加快使更多氧气进入肺部，并排除多余的二氧化碳。心率也会加快以更迅速地运输氧气。运动后频率略微升高是在偿还“氧债”——需要额外氧气来分解剧烈运动时肌肉中积累的乳酸。

9. Dandelion Seed Dispersal Strategies | 蒲公英种子的传播策略

A child blew a dandelion clock and watched the tiny seeds with fluffy parachutes drift away. Some seeds landed on a nearby pond and sank, while others were carried far across the field by the wind.

一个孩子吹散了一株蒲公英绒球，看着带有绒毛降落伞的小种子飘远。一些种子落在附近的池塘中沉没，另一些则被风吹过田野飘向远方。

Dandelion seeds are adapted for wind dispersal. Each seed is attached to a pappus (a parachute of fine hairs) that increases air resistance and allows the seed to stay aloft longer. This increases the chance that the seed lands in suitable soil, away from the parent plant, reducing competition for light, water and nutrients. Seeds falling into water may fail to germinate due to lack of oxygen. Successful dispersal helps the species colonise new areas. Many other plants use wind, water, animals or explosive mechanisms to spread seeds.

蒲公英种子适应风力传播。每粒种子连接着冠毛（由细毛构成的降落伞），增加了空气阻力，使种子在空中停留更久。这增加了种子落在远离母株的适宜土壤中的机会，从而减少对光、水和养分的竞争。落入水中的种子可能因缺氧而无法萌发。成功的传播有助于物种开拓新区域。许多其他植物利用风、水、动物或炸裂机制传播种子。

10. Smoking and the Effect on Cilia | 吸烟对纤毛的影响

A health video showed the lining of a healthy airway covered with tiny, hair‑like structures called cilia that beat rhythmically to sweep mucus and trapped particles upwards. In a smoker’s airway, these cilia were flattened and unable to move properly.

一段健康视频显示了健康气道内壁覆盖着被称为纤毛的微细毛发状结构，它们有节奏地摆动，将黏液及其粘附的颗粒向上扫出。在吸烟者的气道中，这些纤毛变得扁平，无法正常运动。

Cilia are essential for keeping the lungs clean. Tar and chemicals in cigarette smoke paralyse and eventually destroy cilia. Without functioning cilia, mucus and pathogens accumulate, leading to persistent coughs and higher risk of respiratory infections such as bronchitis. Smoking also damages alveoli, causing emphysema, and triggers uncontrolled cell growth that can lead to lung cancer. This case study explains why avoiding smoking is crucial for respiratory health.

纤毛对于保持肺部清洁至关重要。香烟烟雾中的焦油和化学物质会使纤毛麻痹并最终将其破坏。纤毛功能丧失后，黏液和病原体积聚，导致持续咳嗽，并增加患支气管炎等呼吸道感染的风险。吸烟还会损害肺泡，引起肺气肿，并引发不受控制的细胞生长，从而导致肺癌。本案例说明了为什么避免吸烟对呼吸系统健康至关重要。

Published by TutorHao | CCEA Year 7 Biology Revision Series | aleveler.com

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Case Study Practice Drill | 案例分析实战演练