Food Chains in IGCSE OCR Biology | IGCSE OCR 生物：食物链考点精讲

📚 Food Chains in IGCSE OCR Biology | IGCSE OCR 生物：食物链考点精讲

A food chain shows the flow of energy and nutrients from one organism to another in an ecosystem. Understanding food chains is a fundamental concept in IGCSE OCR Biology, linking together ideas about photosynthesis, respiration, feeding relationships, and energy transfer. This revision guide will walk you through the key points you need to master food chains, food webs, and ecological pyramids, with clear explanations in both English and Chinese to support bilingual learning.

食物链展示了一个生态系统中能量和营养物质从一个生物体流向另一个生物体的过程。理解食物链是IGCSE OCR生物学的一个基本概念，它将光合作用、呼吸作用、摄食关系和能量传递等知识串联起来。这份复习指南将带你掌握食物链、食物网和生态金字塔的关键要点，并提供中英双语的清晰解释，支持双语学习。

1. What is a Food Chain? | 什么是食物链？

A food chain is a linear sequence of organisms through which energy and nutrients are passed as one organism eats another. In a food chain, arrows represent the direction of energy flow from the food source to the consumer. Each step in a food chain is called a trophic level.

食物链是一个线性的生物序列，能量和营养物质通过一个生物体吃掉另一个生物体而传递。在食物链中，箭头代表能量从食物来源流向消费者的方向。食物链中的每一步都被称为一个营养级。

A simple example of a terrestrial food chain is: grass → rabbit → fox. The grass is eaten by the rabbit, and the rabbit is eaten by the fox. The arrows show that energy moves from the grass to the rabbit and then to the fox.

一个简单的陆地食物链例子是：草 → 兔子 → 狐狸。草被兔子吃掉，兔子被狐狸吃掉。箭头表示能量从草转移到兔子，再转移到狐狸。

2. Producers – The Start of Every Chain | 生产者 – 每条链的起点

Producers are organisms that make their own food using energy from sunlight (or in rare cases, from chemicals) through the process of photosynthesis. In most ecosystems, green plants and algae are the primary producers. The chemical equation for photosynthesis is:

生产者是利用阳光（或在少数情况下利用化学物质）的能量通过光合作用制造自己食物的生物。在大多数生态系统中，绿色植物和藻类是主要的生产者。光合作用的化学方程式为：

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Producers form the base of every food chain and support all other trophic levels. Without producers, there would be no source of organic matter or energy for consumers.

生产者构成了每条食物链的基础，支撑着所有其他的营养级。如果没有生产者，消费者就没有有机物质或能量的来源。

In aquatic ecosystems, phytoplankton are key producers. They are microscopic organisms that float near the water surface and carry out photosynthesis. In grassland ecosystems, grasses and herbs fill this role.

在水生生态系统中，浮游植物是主要的生产者。它们是漂浮在水面附近的微小生物，进行光合作用。在草原生态系统中，草和草本植物承担这一角色。

3. Consumers – Primary, Secondary and Tertiary | 消费者 – 初级、次级和三级消费者

Consumers are organisms that obtain energy by feeding on other organisms. They are classified according to their position in the food chain. Primary consumers are herbivores that eat producers. Secondary consumers are carnivores that eat primary consumers. Tertiary consumers eat secondary consumers, and so on.

消费者是通过捕食其他生物来获取能量的生物。它们根据在食物链中的位置进行分类。初级消费者是吃生产者的食草动物。次级消费者是吃初级消费者的食肉动物。三级消费者吃次级消费者，以此类推。

For example, in the chain: grass → grasshopper → frog → snake, the grasshopper is the primary consumer, the frog is the secondary consumer, and the snake is the tertiary consumer. Apex predators are at the top and have no natural enemies.

例如，在食物链：草 → 蚱蜢 → 青蛙 → 蛇中，蚱蜢是初级消费者，青蛙是次级消费者，蛇是三级消费者。顶级捕食者位于最高营养级，没有天敌。

Consumers also include detritivores and decomposers, which break down dead organic matter. Although they are not usually shown in simple linear food chains, they are essential in recycling nutrients back to the environment.

消费者还包括食碎屑者和分解者，它们分解死亡的有机物。虽然它们通常不显示在简单的线性食物链中，但它们对于将营养循环回环境中至关重要。

4. Trophic Levels – Steps of Energy Transfer | 营养级 – 能量传递的阶梯

A trophic level is the position an organism occupies in a food chain. Producers occupy the first trophic level (T1), primary consumers occupy the second (T2), secondary consumers occupy the third (T3), and tertiary consumers occupy the fourth (T4). Decomposers process organic matter from all trophic levels, but they are often omitted from simple food chain diagrams.

营养级是一个生物在食物链中所处的位置。生产者占据第一营养级（T1），初级消费者占据第二营养级（T2），次级消费者占据第三营养级（T3），三级消费者占据第四营养级（T4）。分解者处理所有营养级的有机物，但在简单的食物链图中常常被省略。

Energy is passed from one trophic level to the next through feeding. However, only a small proportion of the energy – typically around 10% – is transferred to the next level. The rest is lost as heat from respiration, used for movement, or remains in undigested materials. This limits the length of food chains to usually no more than four or five trophic levels.

能量通过摄食从一个营养级传递到下一个营养级。然而，只有一小部分能量——通常约为10%——被传递到下一级。其余的能量在呼吸作用中以热的形式散失、用于运动，或者留在未被消化的物质中。这限制了食物链的长度，通常不超过四到五个营养级。

5. Energy Flow and the 10% Rule | 能量流动与10%法则

The flow of energy through a food chain is unidirectional and non-cyclical. Sunlight is the ultimate source of energy for almost all food chains. Producers convert only about 1–2% of the light energy reaching them into chemical energy through photosynthesis. At each subsequent trophic level, roughly 10% of the energy from the previous level is incorporated into new biomass.

食物链中的能量流动是单向且不可循环的。阳光是几乎所有食物链的最终能量来源。生产者仅将到达它们的光能的约1–2%通过光合作用转化为化学能。在每一后续营养级，大约只有前一级能量的10%被转化为新的生物量。

This low efficiency of energy transfer explains why there are fewer organisms at higher trophic levels. For instance, a field of grass can support many rabbits, but the same field can support only a few foxes. Pyramids of energy represent this loss and are always upright.

这种较低的能量传递效率解释了为什么高营养级的生物数量较少。例如，一片草地可以养许多兔子，但同一片草地只能养活少数狐狸。能量金字塔代表了这种能量损失，并且总是正立的。

6. Food Webs – Interconnected Chains | 食物网 – 相互连接的食物链

In a natural ecosystem, feeding relationships are rarely as simple as a single straight chain. Most organisms eat more than one type of food and are eaten by more than one type of predator. A food web is a network of interconnected food chains that shows all the possible feeding relationships in a community.

在自然生态系统中，摄食关系很少像单一直线的食物链那样简单。大多数生物吃多种食物，并且被多种捕食者吃掉。食物网是由相互连接的食物链组成的网络，显示了一个群落中所有可能的摄食关系。

Food webs provide a more realistic picture of energy flow and predator-prey dynamics. They also contribute to ecosystem stability: if one species declines, predators may still find alternative prey, reducing the risk of a complete collapse of the food web.

食物网提供了能量流动和捕食者-猎物动态的更真实图像。它们还有助于生态系统稳定性：如果一个物种数量下降，捕食者仍可能找到替代的猎物，从而降低食物网完全崩溃的风险。

For IGCSE OCR exams, you may be asked to interpret a food web diagram, identify producers, consumers, and state the number of trophic levels present. Practice identifying individual food chains within a given food web.

在IGCSE OCR考试中，你可能会被要求解读食物网图，识别生产者、消费者，并说明存在的营养级数量。练习从给定的食物网中找出单个的食物链。

7. Ecological Pyramids – Numbers, Biomass and Energy | 生态金字塔 – 数量、生物量和能量

Ecological pyramids are graphical representations used to show the relationship between different trophic levels in an ecosystem. There are three main types: pyramid of numbers, pyramid of biomass, and pyramid of energy. Each type has specific advantages and limitations.

生态金字塔是用来表示生态系统中不同营养级之间关系的图形。主要有三种类型：数量金字塔、生物量金字塔和能量金字塔。每种类型都有特定的优点和局限性。

A pyramid of numbers simply counts the number of organisms at each trophic level. It can sometimes be inverted, for example when one large tree supports many insects. A pyramid of biomass measures the dry mass of living material at each level. It is usually upright but can be inverted in aquatic ecosystems during certain seasons. The pyramid of energy always remains upright because energy is always lost at each transfer. In IGCSE, you may need to draw and interpret pyramids of numbers and biomass.

数量金字塔简单地计算每个营养级的生物个体数量。它有时可能是倒置的，例如一棵大树支撑许多昆虫。生物量金字塔测量每个营养级生物体的干重。它通常是正立的，但在某些季节的水生生态系统中可能倒置。能量金字塔始终是正立的，因为能量在每次传递中总是损耗。在IGCSE中，你可能需要绘制并解读数量金字塔和生物量金字塔。

8. Biomass and Energy Transfer Calculations | 生物量与能量传递计算

Biomass is the total dry mass of living material in an organism or a trophic level. Energy transfer efficiency between trophic levels can be calculated using the formula:

生物量是一个生物体或营养级中活体物质的总干重。营养级之间的能量传递效率可以用以下公式计算：

Efficiency (%) = (Energy transferred to next level ÷ Energy available at previous level) × 100

In OCR exam questions, you might be given data on the energy or biomass at each trophic level and asked to calculate efficiency. Remember to show your working and give your answer to an appropriate number of significant figures.

在OCR考试题中，你可能会得到每个营养级的能量或生物量数据，并被要求计算效率。记得展示你的计算过程，并给出适当有效数字的答案。

For example, if producers contain 20,000 kJ of energy and primary consumers contain 2,000 kJ, the efficiency is (2000 ÷ 20000) × 100 = 10%. This matches the typical 10% rule. Be familiar with these calculations.

例如，如果生产者含有20,000 kJ的能量，初级消费者含有2,000 kJ，那么效率为（2000 ÷ 20000）× 100 = 10%。这符合典型的10%法则。要熟悉这些计算。

9. Bioaccumulation – Toxins in the Food Chain | 生物累积 – 食物链中的毒素

Bioaccumulation is the build-up of toxic substances, such as pesticides (e.g., DDT) or heavy metals, in the tissues of organisms over time. When these substances are passed along a food chain, their concentration increases at each higher trophic level – a process known as biomagnification.

生物累积是指有毒物质，如杀虫剂（例如DDT）或重金属，在生物体组织中随时间积累的现象。当这些物质沿食物链传递时，它们在每一更高营养级的浓度会增加——这个过程被称为生物放大。

Top predators, such as birds of prey or large fish, are particularly affected by biomagnification. High concentrations of DDT caused thinning of eggshells in birds like the peregrine falcon, leading to population declines. Understanding bioaccumulation helps explain why some pollutants have far-reaching ecosystem impacts even at low initial releases.

顶级捕食者，如猛禽或大型鱼类，尤其受到生物放大的影响。高浓度的DDT导致游隼等鸟类的蛋壳变薄，致使种群数量下降。理解生物累积有助于解释为什么一些污染物即使在最初释放量很低的情况下也会对生态系统产生深远的影响。

10. Human Impact on Food Chains | 人类对食物链的影响

Human activities can disrupt food chains and entire food webs. Overfishing, deforestation, introduction of invasive species, and pollution all alter the balance of producers and consumers. For instance, overfishing removes top predators, which may cause an increase in smaller fish or plankton consumers, disrupting the whole marine food web.

人类活动可以扰乱食物链甚至整个食物网。过度捕捞、森林砍伐、入侵物种的引入和污染都会改变生产者和消费者之间的平衡。例如，过度捕捞移除了顶级捕食者，可能导致小鱼或浮游生物消费者的数量增加，从而破坏整个海洋食物网。

Fertiliser runoff from farms can lead to eutrophication in water bodies, causing algal blooms that block sunlight and kill aquatic plants, thereby affecting the producers at the base of the food web. Understanding these impacts is key for Conservation Biology and Sustainable Development topics in IGCSE.

来自农田的肥料径流可导致水体富营养化，引起藻华，遮挡阳光并杀死水生植物，从而影响食物网底部的生产者。理解这些影响对于IGCSE中保护生物学和可持续发展的主题至关重要。

11. Key Terms Summary | 关键术语总结

Here is a quick-reference list of essential vocabulary for the food chains topic. Make sure you can define each term clearly. | 下面是一个食物链主题基本词汇的快速参考列表。确保你能清晰地定义每个术语。

Producer – An organism that makes its own food via photosynthesis. | 生产者 – 通过光合作用制造自己食物的生物。
Consumer – An organism that gets energy by eating other organisms. | 消费者 – 通过吃掉其他生物来获取能量的生物。
Trophic level – A feeding position in a food chain. | 营养级 – 食物链中的摄食位置。
Herbivore – A consumer that eats only plants. | 食草动物 – 只吃植物的消费者。
Carnivore – A consumer that eats only animals. | 食肉动物 – 只吃动物的消费者。
Omnivore – A consumer that eats both plants and animals. | 杂食动物 – 既吃植物也吃动物的消费者。
Decomposer – An organism that breaks down dead matter. | 分解者 – 分解死亡物质的生物。
Food web – A network of interconnected food chains. | 食物网 – 相互连接的食物链网络。
Biomass – The total dry mass of living material at a trophic level. | 生物量 – 一个营养级活体物质的总干重。
Bioaccumulation – The accumulation of toxins in an organism’s body. | 生物累积 – 毒素在生物体内的积累。
Biomagnification – Increasing concentration of toxins up the food chain. | 生物放大 – 随食物链向上毒素浓度增加。
Pyramid of numbers – A diagram showing the count of organisms at each trophic level. | 数量金字塔 – 显示每个营养级生物数量的图表。
Pyramid of biomass – A diagram showing the dry mass at each trophic level. | 生物量金字塔 – 显示每个营养级干重的图表。

12. Exam Tips for Food Chains | 食物链的考试技巧

When answering food chain questions in OCR IGCSE Biology, always remember that arrows in a food chain represent the direction of energy flow, not who eats whom. A common mistake is drawing the arrow pointing from the predator to the prey – arrows should point from the food to the feeder. Label axes on pyramids clearly and state the units, such as ‘Number of organisms’ or ‘Biomass (g/m²)’.

在回答OCR IGCSE生物学的食物链问题时，永远记住食物链中的箭头代表能量流动的方向，而不是谁吃谁。常见的错误是把箭头从捕食者画向猎物——箭头应该从食物指向摄食者。清晰地标记金字塔的坐标轴，并注明单位，如“生物数量”或“生物量（g/m²）”。

In calculations, double-check whether the question asks for efficiency or total energy available. Always quote the 10% rule when appropriate, but use the given data if specific numbers are provided. Practice drawing and interpreting food webs – you may be asked to count the trophic levels, name a consumer, or predict the effect of removing one species. Use precise biological language in your answers.

在计算题中，仔细检查题目是问效率还是可用的总能量。在适当的时候引用10%法则，但如果给出了具体数据，则使用给出的数字。练习绘制和解读食物网——你可能会被要求计算营养级的数目，命名一个消费者，或者预测移除一个物种的影响。在答案中使用精确的生物学语言。

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Food Chains in IGCSE OCR Biology | IGCSE OCR 生物：食物链 考点精讲