📚 Case Study Practice in Year 7 Biology | 七年级CAIE生物学案例分析实战演练
Case studies are an exciting way to apply your biology knowledge to real-life situations. In Year 7 CAIE Biology, you will often be given a short story or scenario and asked to explain what is happening using scientific ideas. This article provides ten worked examples covering key topics such as pollination, photosynthesis, digestion, food webs, respiration, classification, osmosis, the carbon cycle, enzymes and microbes. Each one shows you how to break down a problem, recall relevant facts and write a clear answer.
案例分析是将你的生物学知识应用于实际生活情境的一种令人兴奋的方式。在七年级 CAIE 生物学中，你经常会看到一个短篇故事或情景，并被要求用科学概念解释正在发生的事情。本文提供了十个范例，涵盖传粉、光合作用、消化、食物网、呼吸作用、分类、渗透、碳循环、酶和微生物等关键主题。每个范例都向你展示如何分解问题、回忆相关事实并写出清晰的答案。
1. Introduction: What Are Case Studies in Biology? | 引言：什么是生物学案例分析？
A biology case study presents a real or imaginary situation that links to a science concept. You need to spot the biology behind the story and use key terms to explain it. For example, a farmer noticing more fruit when bees are present is really about pollination. Case studies help you practise applying ideas rather than just memorising facts.
生物学案例分析给出了一个真实或虚构的情境，它与某个科学概念相联系。你需要发现故事背后的生物学原理，并使用关键术语进行解释。例如，一位农民注意到蜜蜂出现时会结出更多果实，这实际上与传粉有关。案例分析帮助你练习应用知识，而不仅仅是记忆事实。
In an exam, read the case study carefully and underline the science words. Think about which topic it fits into. Then plan your answer using PEEL: Point, Evidence, Explain, Link back to the question. Always use correct scientific vocabulary.
在考试中，要仔细阅读案例并划出科学词汇。想一想它属于哪个主题。然后使用 PEEL（观点、证据、解释、回扣题目）来规划答案。务必使用正确的科学术语。
2. Case Study 1: The Busy Bee and Pollination | 案例一：勤劳的蜜蜂与传粉
A gardener observes that his pumpkin plants produce many pumpkins when wild bees visit the large yellow flowers. One day he notices a bee crawling inside a flower, then flying off with yellow dust on its legs.
一位园丁观察到，当野生蜜蜂造访他南瓜植物上的大黄花时，会结出许多南瓜。一天，他注意到一只蜜蜂在一朵花里爬行，然后腿上沾着黄色粉末飞走了。
Question: Explain why the bee’s behaviour is essential for pumpkin formation.
问题：解释为什么蜜蜂的行为对南瓜的形成至关重要。
Answer: The yellow dust is pollen from the anther. When the bee visits another flower, pollen grains are transferred to the stigma. This is pollination. Pollination allows the male gamete to reach the ovule, leading to fertilisation. After fertilisation, the ovary develops into a fruit (the pumpkin) containing seeds. Without bees, pollination would be less likely, so fewer pumpkins would form.
答案：黄色粉末是来自花药的花粉。当蜜蜂拜访另一朵花时，花粉粒被传到柱头上。这就是传粉。传粉使雄性配子能够到达胚珠，从而发生受精。受精后，子房发育成果实（南瓜），内含种子。没有蜜蜂，传粉的可能性就会降低，因此南瓜的产量会减少。
Extension: This is an example of mutualism because the bee obtains nectar for food and the plant gets pollinated.
拓展：这是一个互惠共生的例子，因为蜜蜂获得花蜜作为食物，而植物得以传粉。
3. Case Study 2: A Plant Growing in the Dark | 案例二：黑暗中生长的植物
Sam places two identical potted geranium plants in different conditions. Plant A stays on a sunny windowsill and is watered regularly. Plant B is placed inside a dark cupboard but receives the same amount of water. After two weeks, Plant A has green leaves and has grown taller. Plant B has turned pale yellow and its stems are thin and leggy.
萨姆将两盆相同的天竺葵放在不同条件下。植物 A 放在阳光充足的窗台上并定期浇水。植物 B 放在黑暗的橱柜里，但浇水量相同。两周后，植物 A 叶片翠绿且长高了。植物 B 变成了淡黄色，茎细长而徒长。
Question: Why did Plant B become yellow and fail to grow well?
问题：为什么植物 B 变黄并且生长不良？
Answer: Plant B received no light, so it could not carry out photosynthesis. Photosynthesis produces glucose, which the plant uses for energy and growth. Without light, chlorophyll in the leaves breaks down and new leaves cannot make enough chlorophyll, causing yellowing. The plant had to use stored food reserves, so growth was poor. The spindly stems were due to etiolation – the plant grew tall searching for light.
答案：植物 B 没有获得光照，因此无法进行光合作用。光合作用产生葡萄糖，植物用它提供能量和生长。没有光，叶片中的叶绿素分解，新叶无法制造足够的叶绿素，导致变黄。植物不得不使用储存的养分储备，因此生长不良。细长的茎是由于黄化现象——植物长高以寻找光线。
4. Case Study 3: Digestion of a Cheese Sandwich | 案例三：一个奶酪三明治的消化之旅
Maria eats a cheese sandwich made of bread, butter and cheese. The bread contains starch, while the cheese and butter provide protein and fat. Describe the journey of the sandwich through the digestive system and explain how the main nutrients are broken down.
玛丽亚吃了一个由面包、黄油和奶酪做成的奶酪三明治。面包含有淀粉，奶酪和黄油提供蛋白质和脂肪。请描述三明治经过消化系统的旅程，并解释主要营养物质是如何被分解的。
Answer: In the mouth, teeth chew the sandwich into smaller pieces. Saliva contains the enzyme amylase, which begins to break down starch into maltose. The food then travels down the oesophagus to the stomach. In the stomach, gastric juice contains protease enzymes that start digesting, or breaking, the protein in cheese. The food then enters the small intestine. Here, more amylase from the pancreas continues starch digestion, protease finishes protein digestion, and lipase enzymes break down fats after bile from the liver emulsifies them. The small soluble molecules are absorbed into the blood through the villi.
答案：在口腔中，牙齿将三明治咀嚼成小块。唾液含有淀粉酶，开始将淀粉分解成麦芽糖。然后食物沿食道进入胃。在胃中，胃液含有蛋白酶，开始消化奶酪中的蛋白质。然后食物进入小肠。在这里，来自胰腺的更多淀粉酶继续消化淀粉，蛋白酶完成蛋白质消化，脂肪被胆汁乳化后由脂肪酶分解。这些可溶的小分子通过绒毛被吸收进血液。
Key: Large insoluble molecules are broken into small soluble ones so they can pass into the blood.
关键：大的不溶性分子被分解为小的可溶性分子，以便进入血液。
5. Case Study 4: Pond Life Food Web | 案例四：池塘食物网
A pond contains algae, water fleas, dragonfly nymphs, small fish and a heron. Algae are eaten by water fleas. Water fleas are eaten by dragonfly nymphs and small fish. Small fish are eaten by the heron, and dragonfly nymphs are also eaten by small fish.
一个池塘里有藻类、水蚤、蜻蜓幼虫、小鱼和苍鹭。藻类被水蚤吃。水蚤被蜻蜓幼虫和小鱼吃。小鱼被苍鹭吃，蜻蜓幼虫也被小鱼吃。
Question: Draw a food web and predict what might happen if the water flea population suddenly declines because of pollution.
问题：画一个食物网，并预测如果水蚤数量因污染而突然减少，可能会发生什么。
Answer: The food web has algae as producer. Water fleas are primary consumers. Dragonfly nymphs and small fish are secondary consumers, but small fish also eat dragonfly nymphs. The heron is the top predator. If water fleas decrease, dragonfly nymphs and small fish lose a food source. Some may starve, reducing their numbers. With fewer small fish, the heron may struggle to find food. Meanwhile, algae numbers might increase because fewer water fleas are eating them. This shows how a change in one population affects others in a community.
答案：食物网中藻类是生产者。水蚤是初级消费者。蜻蜓幼虫和小鱼是次级消费者，但小鱼也吃蜻蜓幼虫。苍鹭是顶级捕食者。如果水蚤减少，蜻蜓幼虫和小鱼就会失去一种食物来源。它们中的一些可能会饿死，数量减少。随着小鱼减少，苍鹭可能难以找到食物。同时，藻类的数量可能增加，因为吃藻类的水蚤变少了。这表明一个种群的变化会如何影响群落中的其他种群。
6. Case Study 5: Breathing During Exercise | 案例五：运动时的呼吸
Liam records his breathing rate at rest: 16 breaths per minute. After running 400 metres, his breathing rate increases to 35 breaths per minute. He also notices his heart beats faster and he feels hot.
利亚姆记录下他安静时的呼吸频率：每分钟 16 次。跑完 400 米后，他的呼吸频率增加到每分钟 35 次。他还注意到心跳加快并感到热。
Question: Explain why Liam’s breathing rate increased and relate this to respiration in his cells.
问题：解释为什么利亚姆的呼吸频率增加，并将其与他细胞中的呼吸作用联系起来。
Answer: During exercise, muscles contract more, needing more energy. Cells release energy through aerobic respiration, which uses oxygen and glucose and produces carbon dioxide and water. The equation is: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy. The increasing breathing rate brings more oxygen into the lungs and removes the extra carbon dioxide produced. The faster heart rate delivers oxygen and glucose to the muscles more quickly. Feeling hot is because respiration releases some energy as heat.
答案：运动时，肌肉收缩更频繁，需要更多能量。细胞通过有氧呼吸释放能量，这个过程需要氧气和葡萄糖，并产生二氧化碳和水。方程式为：C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 能量。呼吸频率增加能将更多氧气带入肺部，并排出额外产生的二氧化碳。心率加快能更快地将氧气和葡萄糖输送到肌肉。感到热是因为呼吸作用释放的部分能量以热能的形式散失。
7. Case Study 6: Classification Challenge – A Newly Discovered Organism | 案例六：分类挑战——新发现的生物
Scientists find a microscopic organism in a hot spring. It is single-celled, has a cell wall but no nucleus. It can move using a flagellum and survives in temperatures above 80 °C.
科学家在温泉中发现了一种微型生物。它是单细胞的，有细胞壁但没有细胞核。它能用鞭毛运动，并能在 80 ℃ 以上的温度中生存。
Question: Use the classification system to decide which kingdom this organism belongs to. Give reasons.
问题：使用分类系统判断这种生物属于哪个界。给出理由。
Answer: The organism is single-celled and lacks a nucleus, so it is a prokaryote. The kingdom Prokaryote (Monera) includes bacteria and archaea. Because it lives in extreme heat, it is likely an archaeon. Organisms with a nucleus belong to the kingdoms Protist, Fungus, Plant or Animal. Since this organism has no nucleus and has a cell wall, it fits best in the Prokaryote kingdom. It cannot be a plant or animal because it is single-celled and lacks a nucleus.
答案：该生物是单细胞且缺少细胞核，所以它是原核生物。原核生物界（或称无核生物界）包括细菌和古菌。由于它生活在极端高温下，很可能是一种古菌。有细胞核的生物属于原生生物界、真菌界、植物界或动物界。由于该生物没有细胞核且有细胞壁，它最适合归于原核生物界。它不可能是植物或动物，因为它既是单细胞的又没有细胞核。
8. Case Study 7: Osmosis in a Potato Strip | 案例七：土豆条的渗透作用
Alex cuts two identical strips from a potato. He places one strip in pure water and the other in a concentrated salt solution. After 30 minutes, the strip in pure water feels firm and has increased in length. The strip in salt solution has become soft and floppy.
亚历克斯从土豆上切下两条相同的土豆条。他将一条放入纯水中，另一条放入浓盐水中。30 分钟后，纯水中的土豆条摸起来较硬且长度增加。盐水中的土豆条变得柔软弯曲。
Question: Explain the results using the idea of osmosis.
问题：运用渗透作用的概念解释实验结果。
Answer: Osmosis is the movement of water molecules from a dilute solution (more water) to a more concentrated solution (less water) across a partially permeable membrane. In pure water, the water concentration outside the potato cells is higher than inside. Water enters the cells by osmosis, making them turgid and the strip firm. In strong salt solution, the water concentration outside is lower than inside the cells. Water leaves the cells, causing them to become flaccid, so the strip goes soft. This demonstrates that water moves to balance concentrations.
答案：渗透作用是水分子通过半透膜从稀溶液（水更多）向较浓溶液（水更少）的移动。在纯水中，土豆细胞外的水浓度高于细胞内。水通过渗透作用进入细胞，使细胞膨胀，土豆条变硬。在浓盐水中，细胞外的水浓度低于细胞内。水从细胞中流出，导致细胞失水变软，所以土豆条变得柔软。这表明水会向平衡浓度的方向移动。
9. Case Study 8: The Carbon Cycle in a Forest | 案例八：森林中的碳循环
A large oak tree absorbs carbon dioxide from the air and releases oxygen during the day. At night, it still takes in oxygen and gives out carbon dioxide. Leaves that fall to the ground are decomposed by fungi and bacteria. When the old wood is burned in a bonfire, carbon dioxide is also released.
一棵大橡树在白天从空气中吸收二氧化碳并释放氧气。到了晚上，它仍然吸收氧气并放出二氧化碳。落到地面的树叶被真菌和细菌分解。当旧木材在篝火中燃烧时，也会释放二氧化碳。
Question: Explain how these processes show the cycling of carbon.
问题：解释这些过程如何体现碳的循环。
Answer: During the day, the tree photosynthesises, removing CO₂ from the atmosphere and locking carbon in glucose and other organic compounds. At night, only respiration occurs (photosynthesis stops without light), so CO₂ is released back. When leaves decay, decomposers respire, returning CO₂ to the air. Burning wood (combustion) quickly releases the carbon stored in the tree as CO₂. This shows that carbon moves between the atmosphere, living things and the soil in a continuous cycle.
答案：白天，树木进行光合作用，从大气中移除二氧化碳，并将碳固定在葡萄糖和其他有机物中。到了晚上，只有呼吸作用发生（没有光照光合作用停止），因此二氧化碳被释放回大气。树叶腐烂时，分解者进行呼吸作用，将二氧化碳送回空气中。燃烧木材（燃烧）会快速将树木中储存的碳以二氧化碳形式释放。这表明碳在大气、生物和土壤之间不断循环移动。
10. Conclusion: How to Approach a Case Study Exam Question | 结论：如何应对案例分析考试题
When you see a case study, first identify the biology topic by looking for keywords like “bee”, “flower” (pollination) or “dark cupboard” (photosynthesis). Read the background and the question carefully. Then write your answer using complete sentences that include scientific terms. Always link the explanation back to the scenario given. Practice by writing your own case studies or explaining everyday observations with biology.
当你看到一个案例时，首先通过寻找关键词（如“蜜蜂”、“花”表明传粉，或“黑暗橱柜”表明光合作用）来确定生物学主题。仔细阅读背景和问题。然后用含有科学术语的完整句子写出答案。务
Published by TutorHao | Year 7 Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导