📚 IGCSE CCEA Biology: Ecology Revision – Mastering Key Concepts | IGCSE CCEA 生物：生态学 考点精讲
Ecology is one of the most accessible yet frequently examined topics in the IGCSE CCEA Biology specification. It bridges fieldwork, data interpretation and global environmental concerns. This article breaks down every essential concept—from food chains to nutrient cycles—so you can answer exam questions with confidence.
生态学是 IGCSE CCEA 生物大纲中既贴近生活又高频考查的主题之一，它将野外调查、数据解读与全球环境议题串联在一起。本文逐项拆解每一核心概念——从食物链到物质循环——帮助你在考试中稳操胜券。
1. What is Ecology? | 什么是生态学？
Ecology is the scientific study of the interactions between organisms and their environment. The environment is made up of living (biotic) and non-living (abiotic) components, and understanding these relationships helps us predict how ecosystems respond to change.
生态学是研究生物与其环境之间相互作用的科学。环境由生物因素和非生物因素构成，理解这些关系能帮助我们预测生态系统如何应对变化。
2. Key Ecological Terms | 生态学术语精要
A habitat is the specific place where an organism lives, such as a rock pool or forest floor. A population is a group of individuals of the same species living in the same area at the same time, whereas a community is all the populations of different species sharing a habitat. An ecosystem comprises the community plus its physical environment, and a niche describes the role an organism plays—what it eats, where it feeds and how it reproduces.
栖息地是生物具体生活的地点，比如岩池或林地表层。种群是同一时间在同一区域生活的同种生物个体的集合，群落则是共享栖息地的所有不同物种的种群集合。生态系统由群落加上其非生物环境组成，生态位则描述生物扮演的角色——它吃什么、在哪里觅食、如何繁殖。
3. Biotic and Abiotic Factors | 生物因素与非生物因素
Abiotic factors include light intensity, temperature, pH, water availability and mineral nutrients. Biotic factors encompass predation, competition, disease and human activity. In CCEA exams you may be asked to explain how a named factor affects organism distribution, using data from a practical investigation.
非生物因素包括光照强度、温度、pH、水分供应和矿质养分。生物因素涵盖捕食、竞争、疾病和人类活动。在 CCEA 考试中，你可能会被要求利用实验数据解释某一具体因素如何影响生物的分布。
4. Food Chains, Food Webs and Energy Flow | 食物链、食物网与能量流动
d web provides a more realistic network of interconnected chains. Energy enters ecosystems through photosynthesis; at each trophic level approximately 90% energy is lost as heat through respiration, movement and excretion, leaving only about 10% to be passed on. This limits food chain length.
食物链展示单一摄食途径，例如草 → 兔 → 狐。食物网则是相互连接的食物链构成的真实网络。能量通过光合作用进入生态系统；在每一营养级，约 90% 的能量以热、运动和排泄的形式通过呼吸作用散失，仅剩约 10% 传递到下一级，这限制了食物链的长度。
Energy transfer efficiency (%) = (Biomass at higher trophic level ÷ Biomass at lower trophic level) × 100
能量传递效率 (%) = (较高营养级的生物量 ÷ 较低营养级的生物量) × 100
5. Ecological Pyramids | 生态学金字塔
Pyramids of numbers count organisms, but can be misleading when one large producer supports many small consumers. Pyramids of biomass measure dry mass at each level and usually form a true pyramid in grassland and forest ecosystems. Pyramids of energy are always pyramid-shaped because energy is lost between trophic levels. You must be able to sketch and interpret all three types from given data.
数量金字塔统计个体数目，但当一株大型生产者支撑许多小型消费者时可能产生倒金字塔。生物量金字塔测量各营养级的干重，在草地和森林生态系统中通常呈现正金字塔形。能量金字塔则永远保持正金字塔形状，因为能量在级间不断散失。你必须能够根据给定数据绘制并解读这三种金字塔。
6. The Carbon Cycle | 碳循环
Carbon dioxide (CO₂) in the atmosphere is fixed by photosynthesis into organic compounds. Respiration by plants, animals and decomposers releases CO₂ back. Combustion of fossil fuels and decomposition of organic matter also return CO₂ to the air. Oceanic exchange and sedimentation lock carbon into limestone and fossil fuels over geological timescales. Diagrams in the exam typically show arrows labelled with these processes.
大气中的二氧化碳 (CO₂) 通过光合作用被固定为有机化合物。植物、动物和分解者的呼吸作用以及化石燃料的燃烧、有机物的分解都会将 CO₂ 释放回大气。海洋交换和沉积作用则在地质时间尺度上将碳锁定为石灰岩和化石燃料。考试中的示意图通常会用箭头标注上述过程。
7. The Nitrogen Cycle | 氮循环
Nitrogen gas (N₂) is fixed into ammonium (NH₄⁺) by nitrogen‑fixing bacteria living freely in soil or in root nodules of legumes (e.g. Rhizobium). Ammonium is then converted to nitrite (NO₂⁻) and subsequently to nitrate (NO₃⁻) by nitrifying bacteria. Plants absorb nitrate for protein synthesis. Denitrifying bacteria convert nitrate back to N₂ gas under anaerobic conditions. Decomposers produce ammonium from dead organic matter (ammonification).
氮气 (N₂) 被自由生活在土壤中或豆科植物根瘤内的固氮菌（如根瘤菌）固定为铵离子 (NH₄⁺)。铵随后被硝化细菌氧化为亚硝酸盐 (NO₂⁻) 并进一步氧化为硝酸盐 (NO₃⁻)。植物吸收硝酸盐用于合成蛋白质。反硝化细菌在缺氧条件下将硝酸盐还原为 N₂。分解者从死有机质中释放铵离子（氨化作用）。
8. Population Growth and Interactions | 种群增长与生物相互关系
Populations grow exponentially when resources are unlimited, but in nature logistic growth is the rule, levelling off at the carrying capacity of the environment. Predator–prey cycles often show linked oscillations: an increase in prey supports an increase in predators, which then reduce prey numbers, causing predator numbers to crash. Competition (intraspecific and interspecific) limits population size through reduced access to resources.
在资源无限时，种群呈指数增长，但自然界中逻辑斯蒂增长才是常态，种群数量在环境容纳量处趋于平稳。捕食者–猎物循环常表现出关联性波动：猎物增多使捕食者数量上升，随后捕食者压制猎物数量，自身也因食物短缺而下降。种内和种间竞争通过限制资源获取调控种群大小。
9. Sampling Techniques | 取样技术
at placed at random coordinates. Abundance can be expressed as percentage cover, density or frequency.
为估算种群大小和分布，生态学家使用样方（样框或点样方）和样带（线状或带状）。随机取样并使用大量重复可以减少偏差；带状样带可沿环境梯度记录物种分布。岩岸的帽贝可用 0.5 m × 0.5 m 样方在随机坐标处取样。丰度可以表示为盖度百分比、密度或频度。
10. Human Impact on Ecosystems | 人类对生态系统的影响
Deforestation removes habitats, reduces biodiversity and disrupts the water and carbon cycles. Burning forests releases CO₂, a major greenhouse gas. Intensive farming can lead to soil erosion and eutrophication when excess nitrate and phosphate fertilisers run off into water bodies, causing algal blooms that deplete dissolved oxygen and kill aquatic life. Acid rain, formed by sulphur dioxide (SO₂) and nitrogen oxides (NOₓ), damages vegetation and acidifies lakes.
森林砍伐破坏栖息地、降低生物多样性，并扰乱水循环和碳循环。森林燃烧释放大量温室气体 CO₂。集约化农业可能导致水土流失，过量的硝酸盐和磷酸盐肥料随径流进入水体，引发水体富营养化——藻类过度繁殖耗竭溶解氧，导致水生动物死亡。由二氧化硫 (SO₂) 和氮氧化物 (NOₓ) 形成的酸雨危害植被、酸化湖泊。
11. Conservation and Sustainability | 保护与可持续发展
Conservation is the management of the biosphere to maintain biodiversity and ensure resources are available for future generations. Strategies include establishing protected areas (SSSIs, national parks), captive breeding and seed banks, replanting hedgerows, enforcing fishing quotas and promoting sustainable forestry. CCEA questions often ask you to evaluate the ecological and economic arguments for a named conservation scheme.
保护指对生物圈进行管理，以维持生物多样性并确保资源可供后代利用。策略包括建立保护区（特殊科学价值地点、国家公园）、圈养繁殖与种子库、重植树篱、实施捕捞配额以及推广可持续林业。CCEA 试题常要求你评价某一具体保护计划的生态和经济论据。
12. Exam Technique for Ecology Questions | 生态学考题答题技巧
When analysing data, always quote figures and state trends clearly. Use the P.E.E. structure—Point, Evidence, Explain—when linking a result to an ecological concept. Common command words like "describe", "explain" and "suggest" demand different levels of detail. For graph-based questions, identify the axis labels and look for correlations or anomalies. Practise sketching pyramids and labelling stages of the carbon and nitrogen cycles under timed conditions.
分析数据时，务必引用具体数字并清晰陈述变化趋势。运用 P.E.E. 结构（观点–证据–解释）将结果与生态学概念联系起来。常见指令词如“描述”“解释”“建议”要求不同程度的详略。针对图表题，首先读懂坐标轴标题，然后找出相关性或异常点。在限时条件下练习手绘金字塔以及标注碳、氮循环的各步骤。
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