Environmental Science: Key Revision Points | 环境科学考点精讲

📚 Environmental Science: Key Revision Points | 环境科学考点精讲

Environmental Science is a fascinating interdisciplinary subject that examines how the natural world works, how humans interact with it, and how we can protect it. This revision guide distils the most important concepts from IB and OCR specification points, covering ecosystems, energy flow, pollution, climate change, and sustainability. Each section presents key facts in English followed by a clear Chinese explanation, ensuring bilingual mastery of the material.

环境科学是一门迷人的跨学科科目，研究自然界的运行机制、人类与环境的互动方式以及我们如何保护地球。本文提炼了 IB 和 OCR 大纲中最重要的考点，涵盖生态系统、能量流动、污染、气候变化和可持续发展。每个要点均提供中英配对讲解，助你扎实掌握双语内容。

1. Ecosystems and Communities | 生态系统与群落

An ecosystem consists of all the living organisms (biotic factors) in a given area interacting with the non-living components (abiotic factors) such as sunlight, water, and soil. A community refers only to the populations of different species living and interacting in the same habitat. Producers (autotrophs) synthesise organic molecules using light or chemical energy; consumers (heterotrophs) obtain energy by feeding on other organisms; decomposers break down dead organic matter, recycling nutrients.

生态系统由特定区域内所有生物（生物因素）与非生物环境（如阳光、水分、土壤等非生物因素）的相互作用构成。群落则专指生活在同一生境并相互作用的各类物种种群。生产者（自养生物）利用光能或化学能合成有机物；消费者（异养生物）通过摄食其他生物获取能量；分解者分解死有机质，循环营养物质。

Trophic levels describe the position an organism occupies in a food chain: producers → primary consumers → secondary consumers → tertiary consumers. Food webs are more realistic interconnected networks of food chains within an ecosystem. Energy is lost at each trophic level – typically around 90% – as heat through respiration, movement, and undigested material, which limits the length of food chains.

营养级描述生物在食物链中的位置：生产者 → 初级消费者 → 次级消费者 → 三级消费者。食物网是生态系统中多条食物链相互交织形成的更真实网络。能量在每一营养级都会损失，通常约 90% 以热能形式通过呼吸、运动及未消化物质散失，这限制了食物链的长度。

Biotic factors: predators, prey, symbionts, competitors.
生物因素：捕食者、猎物、共生体、竞争者。
Abiotic factors: temperature, pH, salinity, light intensity.
非生物因素：温度、pH、盐度、光照强度。

2. Energy Flow and Nutrient Cycles | 能量流动与营养物质循环

Energy enters most ecosystems as sunlight and is captured by photosynthetic organisms. The gross primary productivity (GPP) is the total amount of chemical energy fixed by producers. Net primary productivity (NPP) is the energy that remains after producers use some for respiration: NPP = GPP – R (respiratory losses). NPP represents the energy available to the next trophic level.

能量以阳光形式进入大多数生态系统，被光合生物捕获。总初级生产力（GPP）是生产者固定的化学能总量。净初级生产力（NPP）是生产者呼吸消耗后剩余的能量：NPP = GPP – R（呼吸损失）。NPP 代表可供下一营养级利用的能量。

Nutrients such as carbon and nitrogen are recycled through biogeochemical cycles. In the carbon cycle, photosynthesis fixes CO₂ into organic matter, respiration returns it, and combustion of fossil fuels adds to atmospheric CO₂. The nitrogen cycle involves nitrogen fixation (N₂ → NH₃/NH₄⁺), nitrification (NH₄⁺ → NO₂⁻ → NO₃⁻), assimilation by plants, ammonification by decomposers, and denitrification (NO₃⁻ → N₂).

碳、氮等营养物质通过生物地球化学循环得以再循环。碳循环中，光合作用将 CO₂ 固定为有机物，呼吸作用将其归还，化石燃料燃烧增加大气 CO₂。氮循环包括固氮作用（N₂ → NH₃/NH₄⁺）、硝化作用（NH₄⁺ → NO₂⁻ → NO₃⁻）、植物同化、分解者的氨化作用以及反硝化作用（NO₃⁻ → N₂）。

NPP = GPP – R

3. Population Dynamics | 种群动态

Population size is determined by four factors: natality (birth rate), mortality (death rate), immigration, and emigration. When resources are unlimited, a population exhibits exponential growth described by dN/dt = rN, where r is the intrinsic rate of increase. Realistically, growth slows as resources become limiting, following logistic growth: dN/dt = rN(1 – N/K), where K is the carrying capacity.

种群大小由四个因素决定：出生率、死亡率、迁入和迁出。资源无限时，种群呈指数增长，描述为 dN/dt = rN，其中 r 为内禀增长率。现实条件下，资源限制使增长放缓，遵循逻辑斯蒂增长：dN/dt = rN(1 – N/K)，K 为环境容纳量。

dN/dt = rN

dN/dt = rN(1 – N/K)

Density-dependent factors (e.g. disease, competition, predation) affect larger populations more strongly, while density-independent factors (e.g. weather, natural disasters) impact populations regardless of size. K-strategists produce few offspring but invest heavily in parental care; r-strategists produce many offspring with little care, exploiting unstable environments.

密度制约因素（如疾病、竞争、捕食）对较大种群影响更强，非密度制约因素（如天气、自然灾害）则无论种群大小均会作用。K-对策者产生少量后代但倾注大量亲代抚育；r-对策者产生大量后代而照料少，利用不稳定环境。

4. Biodiversity and Conservation | 生物多样性与保护

Biodiversity encompasses species diversity, genetic diversity within species, and ecosystem diversity. High biodiversity increases ecosystem resilience, providing stability and services such as pollination, water purification, and climate regulation. Simpson’s Diversity Index (D = 1 – Σ(n/N)²) quantifies species diversity; a higher value indicates greater diversity.

生物多样性包括物种多样性、种内遗传多样性和生态系统多样性。高生物多样性增强生态系统恢复力，提供传粉、净水、气候调节等服务。辛普森多样性指数（D = 1 – Σ(n/N)²）可量化物种多样性，数值越高多样性越大。

Major threats to biodiversity include habitat destruction, overexploitation, invasive species, pollution, and climate change (HIPPO). Conservation strategies range from in-situ methods (protected areas, national parks) to ex-situ methods (zoos, seed banks). International agreements like CITES regulate trade in endangered species, while the IUCN Red List assesses extinction risk.

生物多样性的主要威胁包括生境破坏、过度开发、入侵物种、污染和气候变化（英文首字母缩写为 HIPPO）。保护策略涵盖就地保护（保护区、国家公园）和迁地保护（动物园、种子库）。CITES 等国际公约管制濒危物种贸易，IUCN 红色名录评估灭绝风险。

5. Pollution: Types and Effects | 污染的类型与影响

Pollution is the introduction of harmful substances or energy into the environment. Point source pollution comes from a single identifiable source (e.g. factory pipe), while non-point source pollution arises from diffuse sources (e.g. agricultural runoff). Primary pollutants are emitted directly (SO₂, CO, particulates); secondary pollutants form in the atmosphere through chemical reactions (e.g. ozone O₃, peroxyacetyl nitrate PAN).

污染是指有害物质或能量进入环境。点源污染来自单一可识别源（如工厂管道），面源污染则来自分散源（如农业径流）。一次污染物直接排放（SO₂、CO、颗粒物）；二次污染物在大气中经化学反应生成（如臭氧 O₃、过氧乙酰硝酸酯 PAN）。

Eutrophication results when excess nitrogen and phosphorus enter water bodies, causing algal blooms, oxygen depletion, and death of aquatic life. Acid deposition (pH < 5.6) arises from SO₂ and NOₓ emissions, harming forests, lakes, and buildings. Plastic pollution threatens marine organisms through ingestion and entanglement; microplastics can enter food chains.

富营养化由过量氮磷进入水体引起，导致藻华、缺氧和水生生物死亡。酸沉降（pH < 5.6）源于 SO₂ 和 NOₓ 排放，危害森林、湖泊和建筑。塑料污染通过摄入和缠绕威胁海洋生物；微塑料可进入食物链。

6. Climate Change: Greenhouse Effect | 气候变化：温室效应

The natural greenhouse effect is essential for life: greenhouse gases (GHGs) – H₂O, CO₂, CH₄, N₂O, O₃ – trap infrared radiation emitted by Earth’s surface, keeping the average temperature at about 15°C. The enhanced greenhouse effect, driven by human activities such as burning fossil fuels, deforestation, and agriculture, leads to global warming and climate change.

天然温室效应对生命至关重要：温室气体（GHGs）—— H₂O、CO₂、CH₄、N₂O、O₃ —— 捕获地表发射的红外辐射，使平均温度保持在约 15°C。人类活动（化石燃料燃烧、毁林、农业）驱动的增强温室效应导致全球变暖和气候变化。

Key evidence includes rising global temperatures, shrinking ice sheets, sea-level rise (thermal expansion and melting of land ice), and increased frequency of extreme weather events. Carbon dioxide concentration in the atmosphere has surpassed 420 ppm, compared to pre-industrial levels of about 280 ppm. Mitigation strategies involve reducing GHG emissions (renewable energy, carbon capture) and enhancing carbon sinks (reforestation).

关键证据包括全球气温上升、冰盖缩小、海平面上升（热膨胀和陆地冰融化）以及极端天气事件频率增加。大气二氧化碳浓度已超过 420 ppm，而工业化前约为 280 ppm。缓解策略包括减少温室气体排放（可再生能源、碳捕集）和增强碳汇（植树造林）。

7. Renewable and Non-renewable Resources | 可再生与不可再生资源

Non-renewable resources exist in finite quantities and cannot be replenished within human timescales. Fossil fuels (coal, oil, natural gas) supply the majority of global energy but release CO₂ and other pollutants. Nuclear power uses uranium, which is non-renewable; it produces low-carbon electricity but raises concerns about radioactive waste and safety.

不可再生资源存量有限，无法在人类时间尺度内再生。化石燃料（煤、石油、天然气）供应全球大部分能源，但释放 CO₂ 和其他污染物。核能利用不可再生的铀，产生低碳电力，但引发放射性废物和安全担忧。

Renewable resources are naturally replenished: solar, wind, hydroelectric, tidal, geothermal, and biomass. Solar photovoltaic cells convert sunlight directly into electricity; wind turbines harness kinetic energy of moving air. Their environmental impacts include land use, visual and noise effects, and dependence on climatic conditions. Energy security can be improved by diversifying the energy mix and developing storage technologies.

可再生资源自然再生：太阳能、风能、水力、潮汐能、地热能和生物质能。太阳能光伏电池直接将阳光转化为电能；风力涡轮机利用流动空气的动能。其环境影响包括土地利用、视觉和噪声效应以及对气候条件的依赖。通过能源结构多样化和开发储能技术可提升能源安全。

Energy Source 能源	Renewable? 可再生？	CO₂ Emissions 碳排放
Coal 煤	No	High
Solar 太阳能	Yes	Very low
Nuclear 核能	No	Very low

8. Waste Management and Sustainability | 废弃物管理与可持续性

Sustainable development meets present needs without compromising the ability of future generations to meet their own needs. It balances three pillars: environmental protection, economic viability, and social equity. Waste management follows the hierarchy: reduce, reuse, recycle, recover energy, and lastly dispose of safely (e.g. sanitary landfill).

可持续发展既满足当代人需求，又不损害后代满足其自身需求的能力。它平衡三大支柱：环境保护、经济可行性和社会公平。废弃物管理遵循层级：减量、再利用、回收、能量回收，最后安全处置（如卫生填埋）。

Landfills can produce leachate that contaminates groundwater and methane (a potent GHG) from anaerobic decomposition. Incineration reduces waste volume and can generate energy, but emits pollutants like dioxins if not properly controlled. Composting converts organic waste into nutrient-rich fertiliser. A circular economy aims to keep materials in use for as long as possible, designing out waste.

填埋场可产生污染地下水的渗滤液，以及厌氧分解产生的甲烷（强效温室气体）。焚烧减少废弃物量并可能发电，但若控制不当会排放二噁英等污染物。堆肥将有机废弃物转化为富含营养的肥料。循环经济旨在尽可能长久地将材料保持在利用状态，从设计阶段消除废弃物。

9. Environmental Impact Assessment | 环境影响评价

An Environmental Impact Assessment (EIA) is a process used to predict the environmental consequences of a proposed development before it proceeds. It includes baseline studies, identification of potential impacts, public consultation, and proposals for mitigation. EIAs are legally required for major projects in many jurisdictions and help decision-makers weigh environmental costs against economic benefits.

环境影响评价（EIA）是在开发项目实施前预测其环境后果的程序。它包括基线研究、潜在影响识别、公众咨询和缓解措施建议。许多司法管辖区法律要求重大项目进行 EIA，帮助决策者权衡环境成本与经济效益。

An Ecological Footprint measures the demand placed on nature by comparing human consumption of resources with Earth’s biocapacity. It is expressed in global hectares (gha) per person. The carbon footprint, a subset, quantifies total greenhouse gas emissions caused directly and indirectly by an individual, organisation, or product.

生态足迹通过比较人类资源消耗与地球生物承载力来衡量对自然的需求，以人均全球公顷（gha）表示。碳足迹是其中一部分，量化个人、组织或产品直接和间接造成的温室气体排放总量。

10. Key Case Studies and Exam Tips | 经典案例与考试技巧

Exam boards frequently ask students to apply knowledge to specific case studies. For climate change, the Arctic region shows rapid warming (Arctic amplification) with melting permafrost releasing methane. For conservation, Costa Rica reversed deforestation through payments for ecosystem services and ecotourism, doubling forest cover. For pollution, the Great Pacific Garbage Patch illustrates the persistence of plastics in oceans.

考试机构经常要求学生将知识应用于具体案例。气候变化方面，北极地区呈现快速变暖（北极放大效应），永冻层融化释放甲烷。保护方面，哥斯达黎加通过生态系统服务付费和生态旅游逆转了毁林，森林覆盖率翻倍。污染方面，大太平洋垃圾带展示了塑料在海洋中的持久性。

When answering questions, always use scientific terminology precisely. For ‘describe’ questions, state what happens; for ‘explain’, give reasons and mechanisms; for ‘evaluate’, weigh pros and cons and make a supported judgement. Use labelled diagrams where helpful, such as the carbon cycle or a pyramid of energy. Connect concepts – for example, link rising CO₂ to ocean acidification (H₂O + CO₂ → H₂CO₃ → H⁺ + HCO₃⁻), affecting coral reefs.

答题时，务必精准使用科学术语。遇到“描述”类问题，陈述现象；遇到“解释”，给出原因和机制；遇到“评估”，权衡利弊并给出有依据的判断。在合适时使用标注示意图，如碳循环或能量金字塔。联系概念——例如，将 CO₂ 上升与海洋酸化（H₂O + CO₂ → H₂CO₃ → H⁺ + HCO₃⁻）关联，影响珊瑚礁。

H₂O + CO₂ ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻

pH = –log₁₀[H⁺]

Remember common misconceptions: the ozone hole does not cause global warming; CFCs deplete stratospheric ozone, while greenhouse gases trap heat. Photosynthesis absorbs CO₂ but deforestation reduces this sink. Practise data-based questions: read axis labels, identify trends, calculate percentage change, and suggest reasons for anomalies.

记住常见误区：臭氧空洞并不导致全球变暖；CFCs 消耗平流层臭氧，而温室气体捕获热量。光合作用吸收 CO₂，但毁林削弱这一碳汇。练习数据分析题：读坐标轴标签、识别趋势、计算百分比变化、举出异常原因。

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Environmental Science: Key Revision Points | 环境科学考点精讲