人类对环境的影响
爱德思国际GCSE生物· 4.12–4.18B· 20 分钟阅读
1. 空气污染（4.12）★★☆☆☆⏱ 3 min
✓ 计算器
本主题会考查两种关键空气污染物，你必须熟记它们各自对应的特定生物学后果，符合评分标准的答题要求。
空气污染物
由人类活动排放到大气中、会对生物或生态系统造成危害的物质
Sulfur dioxide: Released from burning fossil fuels (especially coal in power stations). It dissolves in rainwater to form acid rain, which damages plant leaves, acidifies lakes killing aquatic organisms, irritates human lung tissue, and erodes stone buildings.
Carbon monoxide: Released from incomplete combustion of fossil fuels (e.g. car engines, faulty gas boilers). It binds irreversibly to haemoglobin in red blood cells to form carboxyhaemoglobin, reducing the oxygen-carrying capacity of blood and leading to asphyxiation at high concentrations.
分别写出二氧化硫污染对水生生态系统的一项生物学后果，以及一氧化碳中毒对人体的一项后果。
- 1
- 二氧化硫会形成酸雨，降低湖泊的pH值，造成鱼类和水生无脊椎动物死亡。
- 2
- 一氧化碳与血红蛋白结合，减少血液中运输的氧气量，引发头晕、意识丧失甚至死亡。
2. 温室气体与全球变暖（4.13-4.15）★★☆☆☆⏱ 4 min
✓ 计算器
温室气体会自然截留地球大气中的热量，使行星温度维持在适宜生命生存的水平。人类活动提升了这类气体的浓度，进而引发温室效应增强。
温室效应增强
人类活动导致温室气体浓度高于自然水平，热量截留作用加剧，进而引发全球变暖的现象
Required list of greenhouse gases (memorize all 5): Water vapour, carbon dioxide, nitrous oxide, methane, CFCs
Human sources: Burning fossil fuels (CO₂), deforestation (reduced CO₂ removal), livestock farming/rice paddies (methane), nitrogen-based fertiliser use (nitrous oxide), old refrigerants/aerosols (CFCs)
Consequences of global warming: Rising sea levels (melting ice caps/thermal expansion), more frequent extreme weather events (droughts, floods, storms), habitat loss (e.g. melting Arctic sea ice), changing species distribution as organisms move to cooler areas
写出三种温室气体，以及分别会提升其浓度的一项人类活动。
- 1
- 二氧化碳：交通运输与发电过程中燃烧化石燃料释放
- 2
- 甲烷：畜牧养殖过程中牛的消化作用释放
- 3
- 一氧化二氮：农业作物种植过程中使用人工氮肥释放
3. 污水造成的水污染（4.16）★★★☆☆⏱ 4 min
✓ 计算器
未经处理的污水含有高浓度的有机营养物和病原体，排入河流或湖泊后会引发可预测的生态系统破坏序列。
Excess organic nutrients from sewage cause rapid growth of algae on the water surface (algal bloom)
Algal bloom blocks sunlight from reaching submerged aquatic plants, which die as they cannot photosynthesize
Aerobic decomposer bacteria multiply to break down dead plant matter, using large amounts of dissolved oxygen for respiration
Biological Oxygen Demand (BOD) increases, dissolved oxygen levels drop too low to support aquatic life, so fish and invertebrates die
解释为什么排入河流的未经处理的污水会导致下游数公里处的鱼类死亡。
- 1
- 污水向河流中输入过量营养物质，引发水面藻华，阻挡阳光照射到水下的沉水植物。
- 2
- 沉水植物因缺乏光照死亡，随后被大量增殖的好氧细菌分解，该过程耗尽了水体中的溶解氧。
- 3
- 溶解氧含量降至鱼类呼吸所需的阈值以下，因此当污染水流向下游时，鱼类会因缺氧死亡。
4. 肥料淋溶引发的富营养化（4.17）★★★☆☆⏱ 4 min
✓ 计算器
富营养化的耗氧过程与污水污染的耗氧序列一致，但过量营养物质的来源是大雨后从农用肥料中淋溶出的无机硝酸盐和磷酸盐。
描述紧邻使用人工肥料的小麦农场的湖泊发生富营养化的过程。
- 1
- 大雨将农田中过量的硝酸盐和磷酸盐肥料冲刷进入湖泊（淋溶过程），导致水体营养富集。
- 2
- 高营养水平导致湖泊表面出现水华，阻挡阳光照射到水下的水生植物。
- 3
- 沉水植物死亡，分解者细菌利用溶解氧分解死亡残体，因此氧含量下降，导致鱼类和其他水生生物死亡。
5. 生物专属内容：森林砍伐的影响（4.18B）★★☆☆☆⏱ 3 min
✓ 计算器
Soil degradation: Loss of tree roots that bind soil leads to increased soil erosion, and leaching of minerals from the topsoil making it less fertile
Water cycle disruption: Reduced evapotranspiration from tree leaves means less water is returned to the atmosphere, leading to changed rainfall patterns and increased risk of droughts or floods
Atmospheric gas imbalance: Less photosynthesis from removed trees means less CO₂ is removed from the atmosphere, increasing greenhouse gas concentrations, and less oxygen is released
Biodiversity loss: Destruction of forest habitats leads to extinction of plant, animal and fungal species that rely on forest ecosystems
说明大规模森林砍伐对碳循环的两点影响。
- 1
- 砍伐树木会降低光合作用的总发生量，因此从大气中吸收并以生物量形式储存在树木中的二氧化碳量减少。
- 2
- 如果被砍伐的树木被焚烧，其生物量中储存的碳会以二氧化碳的形式释放回大气，进一步提升温室气体的浓度。
6. 常见陷阱
错误做法:
Listing ozone as a greenhouse gas in answers
原因:
The Edexcel IGCSE Biology spec only requires you to recall 5 named greenhouse gases: ozone is not on the approved list and adding it will lose you marks.
正确做法:
Memorize the exact 5 gases: water vapour, carbon dioxide, nitrous oxide, methane, CFCs, and only list these in answers.
错误做法:
Skipping the light-blocking step when explaining eutrophication/sewage pollution
原因:
The mark scheme explicitly awards a mark for stating that algal blooms block sunlight leading to death of submerged plants: jumping straight to oxygen depletion will lose you this mark.
正确做法:
Always follow the full sequence: excess nutrients → algal bloom → light blocked → plant death → decomposers multiply → BOD rises → oxygen falls → aquatic life dies.
错误做法:
Stating that carbon monoxide reduces the number of red blood cells
原因:
Carbon monoxide binds to haemoglobin molecules inside red blood cells, it does not destroy red blood cells. This is a common misconception tested in multiple choice questions.
正确做法:
Explain that carbon monoxide forms carboxyhaemoglobin, which prevents haemoglobin from carrying oxygen, reducing the oxygen-carrying capacity of blood.
错误做法:
Stating that carbon dioxide causes acid rain
原因:
Carbon dioxide dissolves to form weak carbonic acid, but the acid rain examined in this topic is explicitly caused by sulfur dioxide pollution.
正确做法:
Pair sulfur dioxide with acid rain consequences, and carbon dioxide with the enhanced greenhouse effect and global warming.
错误做法:
Including deforestation content in Paper 1 answers
原因:
Deforestation is a Biology-only Paper 2 topic, it will never be tested on Paper 1 and including it in answers wastes time and will not get extra marks.
正确做法:
Only revise deforestation content if you are sitting Paper 2 for Single Award Biology, and do not reference it in Paper 1 responses.
7. 速查表
Topic | Key Exam Facts | Mark Scheme Keywords |
|---|---|---|
Sulfur dioxide pollution | Causes acid rain, irritates lungs | Acid rain, kills plants/aquatic life, lung irritation |
Carbon monoxide pollution | Binds irreversibly to haemoglobin | Carboxyhaemoglobin, reduced oxygen capacity, asphyxiation |
Greenhouse gases | Exact list of 5 required | Water vapour, CO₂, nitrous oxide, methane, CFCs |
Eutrophication/sewage | Full 6-step sequence required | Leaching, algal bloom, light block, BOD, oxygen depletion |
Deforestation (Paper 2 only) | 4 key effect categories | Soil erosion, disrupted carbon/water cycle, biodiversity loss |
8. 常见问题
我需要为考试熟记全部5种温室气体吗？
是的，评分标准明确要求你准确列出水蒸气、二氧化碳、一氧化二氮、甲烷和氟氯烃，完全按指定表述作答才能拿到这类题型的满分。
Paper 1会考查毁林相关内容吗？
不会，毁林（4.18B）是仅属于生物科目的考点，仅在Paper 2中考查。无论是单奖生物还是双奖科学的Paper 1都不会出现该考点。
污水污染和富营养化的区别是什么？
两者的氧气耗尽过程完全一致，但过量营养物质的来源不同：污水是来自人类聚居区的有机废弃物，而富营养化是由农业化肥中淋溶出的无机矿物质引发的。
下一步
Now that you have mastered all content for human influences on the environment, you are ready to practice exam-style questions to reinforce your understanding and memorize the mark scheme keywords for extended response questions. This topic is frequently tested in both short answer and 4-6 mark extended questions, so make sure you can write out the full eutrophication sequence and pollutant consequences without notes. You should also review the carbon cycle content to prepare for common cross-topic questions that link greenhouse gas emissions to natural carbon cycling processes. For Paper 2 students, practice deforestation extended response questions to maximize marks on Biology-only content.