📚 Food Chains for IGCSE AQA Biology: Key Points Revision | IGCSE AQA 生物：食物链 考点精讲
This article provides a comprehensive yet concise revision of food chains, food webs, energy transfer, pyramids and bioaccumulation – all essential for the AQA IGCSE Biology exam. We present each concept in a side-by-side bilingual format so you can master terminology and explanations in both English and Chinese.
本文为 AQA IGCSE 生物考试全面而精炼地复习了食物链、食物网、能量传递、金字塔和生物富集等核心内容。每个概念均采用中英对照讲解，帮助你在掌握知识的同时熟练双语术语。
1. What is a Food Chain? | 什么是食物链？
A food chain shows the feeding relationship between organisms in an ecosystem. It always starts with a producer (usually a green plant) which makes its own food by photosynthesis. Arrows in a food chain point from the organism being eaten to the organism that eats it, showing the flow of energy and biomass.
食物链展示生态系统中生物之间的摄食关系。它总是以生产者（通常是绿色植物）开始，生产者通过光合作用制造食物。食物链中的箭头从被吃掉的生物指向吃它的生物，表示能量和生物质的流动方向。
For example: Grass → Rabbit → Fox. Grass is the producer, rabbit is the primary consumer, and fox is the secondary consumer. You may also see quaternary consumers in longer chains.
例如：草 → 兔 → 狐狸。草是生产者，兔是初级消费者，狐狸是次级消费者。在更长的食物链中还可能出现四级消费者。
Decomposers (bacteria and fungi) are not usually shown in a food chain, but they break down dead organisms and waste, returning nutrients to the soil.
分解者（细菌和真菌）通常不画在食物链中，但它们能分解死去的生物和废物，将养分归还土壤。
2. Producers, Consumers and Decomposers | 生产者、消费者与分解者
Producers are organisms that make their own food using sunlight energy, e.g. plants and algae. They are also called autotrophs. Consumers are organisms that eat other organisms for energy. They are heterotrophs. Primary consumers eat producers, secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers.
生产者是利用光能自行制造食物的生物，例如植物和藻类，也称为自养生物。消费者是捕食其他生物以获取能量的生物，属于异养生物。初级消费者吃生产者，次级消费者吃初级消费者，三级消费者吃次级消费者。
Decomposers break down dead organic matter and waste, releasing mineral ions back into the soil. Without decomposers, nutrients would remain locked in dead bodies and life could not continue. In carbon and nitrogen cycles, decomposers play a vital role.
分解者分解死去的有机物和排泄物，将矿物离子释放回土壤。没有分解者，养分将被锁在尸体中，生命无法延续。在碳循环和氮循环中，分解者起着至关重要的作用。
3. Food Webs – More Realistic than Chains | 食物网 – 比食物链更真实
In reality, most organisms eat more than one type of food, and are eaten by more than one predator. A food web is a network of interconnected food chains. It shows all feeding relationships in a community and gives a more complete picture of energy flow.
在现实中，大多数生物不只吃一种食物，而且会被多种捕食者吃掉。食物网是由相互连接的食物链组成的网络。它展示了一个群落中所有的摄食关系，更全面地描绘了能量流动。
If one organism in a food web is removed, it can affect many other organisms. For example, if rabbits decline due to disease, foxes may switch to eating more voles, causing changes in vole and plant populations. AQA exam questions often ask you to interpret food web diagrams and predict the effects of a population change.
如果食物网中的某种生物消失，会影响许多其他生物。例如，如果兔子因疾病数量减少，狐狸可能会多吃田鼠，从而引起田鼠和植物种群的变化。AQA 考题经常会要求你解读食物网示意图，并预测种群变化的影响。
4. Trophic Levels and Energy Flow | 营养级与能量流动
Each step in a food chain is called a trophic level. Level 1: producers; Level 2: primary consumers; Level 3: secondary consumers; Level 4: tertiary consumers. Energy is transferred from one trophic level to the next, but very inefficiently.
食物链中的每一级称为一个营养级。第一营养级：生产者；第二营养级：初级消费者；第三营养级：次级消费者；第四营养级：三级消费者。能量从一个营养级传递到下一个营养级，但效率很低。
Only about 10% of the energy taken in at one trophic level is converted into biomass that becomes available to the next level. The rest is lost through respiration, movement, heat, undigested material and excretion. This is why food chains rarely have more than five trophic levels – there is simply not enough energy left to support another level.
大约只有 10% 的能量在某一营养级被转化为生物质，能提供给下一级。其余的能量通过呼吸作用、运动、散热、未消化的物质和排泄而散失。这就是为什么食物链很少超过五个营养级——没有足够的剩余能量来支撑更高的营养级。
5. Efficiency of Energy Transfer – The 10% Rule | 能量传递效率 – 10%定律
You should be able to calculate the efficiency of energy transfer between trophic levels using the formula:
你需要会使用下面的公式计算营养级之间的能量传递效率：
Efficiency (%) = (Energy available to next level ÷ Energy available to previous level) × 100
For example, if grass contains 10 000 kJ of energy and rabbits gain 1 000 kJ, the efficiency is (1000 / 10000) × 100 = 10%. In an exam, you may be given data in tables or diagrams and asked to complete calculations or explain why efficiency is low.
例如，草含有 10 000 kJ 的能量，兔子吸收了 1 000 kJ，则效率为 (1000 / 10000) × 100 = 10%。考试中可能会给出表格或图表数据，要求你完成计算或解释效率低的原因。
Major reasons for low efficiency: loss as heat from respiration, loss in undigested food (faeces), loss in urine, and energy used for staying alive (movement, repair, maintaining body temperature in mammals).
效率低的主要原因：呼吸作用中以热的形式散失的能量、未消化食物（粪便）的能量损失、尿液中的能量损失，以及用于维持生命活动的能量（运动、修复、哺乳动物维持体温）。
6. Pyramids of Numbers | 数量金字塔
A pyramid of number represents the number of organisms at each trophic level. Usually the producer level is wide and the top consumer level is narrow. However, this is not always the case. For example, one large oak tree can support thousands of insects; the pyramid would have a narrow base (one tree) and a wide second level (many insects), so it looks inverted.
数量金字塔表示每个营养级的生物个体数量。通常生产者一级较宽，顶级消费者一级较窄。但也有例外。例如，一棵大橡树可以供养成千上万只昆虫，这时金字塔底部窄（一棵树），第二层宽（许多昆虫），看起来像是倒置的。
When drawing a pyramid of number, bars are drawn to the same scale and centred. AQA exam papers may ask you to sketch a pyramid of numbers from given data, or to explain why the shape is not a perfect pyramid.
绘制数量金字塔时，条形宽度应按相同比例绘制并居中。AQA 考试可能会要求你根据所给数据画出数量金字塔，或者解释为什么形状不是标准的正金字塔形。
7. Pyramids of Biomass | 生物量金字塔
A pyramid of biomass shows the total dry mass of living material at each trophic level. It is almost always pyramid-shaped because biomass decreases along the food chain. It overcomes the problem of inverted pyramids of numbers caused by large producers.
生物量金字塔表示每个营养级中生物的总干质量。它几乎总是呈正金字塔形，因为生物量沿着食物链递减。它能克服由大型生产者引起的数量金字塔倒置问题。
Biomass is measured as dry mass (after removing all water) because water content varies greatly between organisms and would distort comparisons. In practice, you may need to estimate biomass by sampling a small area and scaling up.
生物量用干质量（去除所有水分后）来测量，因为生物体含水量差异很大，会扭曲比较。实际操作中，你可能需要通过对小面积取样并放大的方法来估测生物量。
8. Pyramids of Energy – The Most Informative | 能量金字塔 – 信息量最大
A pyramid of energy shows the energy content at each trophic level, usually measured in kJ per m² per year. This pyramid is always upright because energy is always lost to the environment as heat at each level. It never shows an inverted shape. This is the best representation of energy flow and ecosystem structure.
能量金字塔表示每个营养级的能量含量，通常以 kJ/m²/年 为单位。这种金字塔总是正立的，因为每个营养级总会有能量以热的形式散失到环境中，绝不会出现倒置形状。这是能量流动和生态系统结构的最佳表现形式。
Collecting energy data is difficult and time-consuming (requires bomb calorimetry), so in low-stakes exercises you often work with biomass pyramids instead. However, the concept of energy loss is crucial for explaining why food chains are short and why top predators are rare.
收集能量数据困难且耗时（需使用弹式量热计），因此在一般的练习中常用生物量金字塔代替。但能量损失的概念对于解释为何食物链较短、为何顶级捕食者稀少至关重要。
9. Why Does Energy Loss Matter for Food Production? | 能量损失对食物生产有何影响？
Because so much energy is lost at each trophic level, producing meat is far less energy-efficient than growing crops. For instance, to produce 1 kg of beef, a cow must eat many kilograms of plant material – yet most of that energy is used by the cow for respiration and lost as heat or manure.
由于每个营养级都有大量能量损失，生产肉类远比种植作物的能量效率低。例如，生产 1 kg 牛肉需要牛吃下很多公斤的植物，而其中大部分能量被牛用于呼吸并以热或粪便的形式散失。
This is why many people argue that eating lower down the food chain (more plants, less meat) can feed more people with the same area of land. In IGCSE Biology, you may be asked to link energy transfer efficiency to sustainable food production.
这就是为什么许多人提出，沿着食物链下层进食（多吃植物，少吃肉）可以在相同土地面积上养活更多人。在 IGCSE 生物考试中，可能会要求你将能量传递效率与可持续食物生产相联系。
10. Bioaccumulation and Food Chains | 生物累积与食物链
Some toxic substances, such as pesticides (e.g. DDT) and heavy metals (e.g. mercury), are not broken down by organisms. They accumulate in fatty tissues and cannot be excreted. As you move up the food chain, the concentration of these toxins increases dramatically – a process called bioaccumulation, or biomagnification.
一些有毒物质，如杀虫剂（例如 DDT）和重金属（例如汞），无法被生物体分解。它们会积累在脂肪组织中且无法排出体外。随着食物链升级，这些毒素的浓度急剧升高，这一过程称为生物累积或生物放大作用。
For example, DDT used on fields to kill insects enters the water system, is absorbed by microscopic algae, then eaten by zooplankton, small fish, large fish and finally birds of prey. The birds at the top may have DDT concentrations thousands of times higher than in the water. This can lead to thin eggshells and population collapse.
例如，用于田间杀虫的 DDT 进入水体，被微小的藻类吸收，然后被浮游动物、小鱼、大鱼，最后被猛禽捕食。处于顶端的鸟类体内的 DDT 浓度可能比水中高出数千倍，这会导致蛋壳变薄，种群崩溃。
AQA exam questions may ask you to explain how a poison ends up at high concentration in top predators, often using data from a food chain or a graph of toxin levels.
AQA 考题可能会要求你解释一种毒物如何在顶级捕食者体内达到高浓度，通常会借助食物链或毒素含量的图表数据。
11. Key Terminology for the Exam | 考试关键术语
Being precise with terminology is essential in IGCSE Biology. Make sure you can define and use these terms correctly: producer, consumer, primary/secondary/tertiary consumer, herbivore, carnivore, omnivore, decomposer, trophic level, biomass, efficiency, pyramid of number/biomass/energy, bioaccumulation.
在 IGCSE 生物中，术语的准确性至关重要。请确保你能正确定义和使用以下词语：生产者、消费者、初级/次级/三级消费者、草食动物、肉食动物、杂食动物、分解者、营养级、生物量、效率、数量/生物量/能量金字塔、生物累积。
Common command words in exam questions: ‘describe’ – give a step-by-step account; ‘explain’ – give reasons or mechanisms; ‘calculate’ – show your working; ‘draw’ – sketch a labelled diagram or graph; ‘suggest’ – apply your knowledge to a novel situation.
考试题干中常见的指令词：“describe” – 逐步描述；“explain” – 给出原因或机制；“calculate” – 写出计算过程；“draw” – 绘制带标注的草图或坐标图；“suggest” – 将知识应用于新情境。
12. Exam Tips and Common Mistakes | 考试技巧与常见错误
Always make sure arrows in a food chain point in the direction of energy flow (toward the eater). Writing them backwards is a frequent error. When labelling a food web, you might need to identify all producers, herbivores, and top carnivores – try not to miss any organism.
务必确保食物链中的箭头指向能量流动的方向（指向捕食者）。箭头方向写反是常见错误。在给食物网标注时，你可能需要找出所有生产者、草食动物和顶级肉食动物——不要遗漏任何生物。
In calculation questions, always check the units and show your working step by step. For efficiency, give your answer as a percentage to the appropriate number of significant figures. When explaining energy loss, avoid vague phrases like ‘energy is lost’ – specify how (respiration, heat, urine, faeces, movement).
在计算题中，务必核对单位并一步步写出计算过程。效率计算要以百分比给出，且保留适当有效数字。在解释能量损失时，避免含混地说“能量损失了”，而要具体说明如何损失（呼吸、热、尿液、粪便、运动）。
For pyramids of biomass, remember to label each bar with the trophic level and the organism name, and state the units (e.g. g/m²). In a food web question, if one organism is removed, think about competition and possible alternative food sources before answering.
绘制生物量金字塔时，记得在每个条形上标注营养级和生物名称，并注明单位（如 g/m²）。在食物网题目中，如果某种生物消失了，要先思考竞争关系和可能的替代食物来源再作答。
Finally, always link your answers back to the context of energy flow or carbon cycling, as AQA rewards “big picture” thinking. Practice past paper questions on food chains, energy efficiency, pyramids and bioaccumulation – these are common topics that appear in nearly every IGCSE Biology exam session.
最后，始终将你的答案与能量流动或碳循环的大背景相联系，因为 AQA 鼓励“全局思维”。多练习食物链、能量效率、金字塔和生物累积的历年真题——这些是几乎每次 IGCSE 生物考试都会出现的常见主题。
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