College Board AP® Environmental ScienceUNIT 3 · CED TOPIC 3.1
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CED Topic 3.1 · 知识引导
Generalist and Specialist Species
ERT-3.ALearning Objective · 学习目标
Identify differences between generalist and specialist species.
区分广布种与特化种。
A raccoon: the textbook generalist — eats anything, lives anywhere
ESSENTIAL KNOWLEDGE · CED 原文（1 条，点开对照）
- ERT-3.A.1Specialist species tend to be advantaged in habitats that remain constant, while generalist species tend to be advantaged in habitats that are changing.
核心要点 · What actually gets tested
- Generalists have a broad niche — many foods, many habitats → win when the habitat is changing
- Specialists have a narrow niche — one food, one habitat → win when the habitat stays constant
- Habitat disturbance kills specialists first; they cannot switch
- Invasive species are almost always generalists — that's exactly why they invade
- 经典例子：raccoon / rat / coyote（广布）vs panda / koala / coral（特化）
Niche：物种的「职业」—— 它吃什么、住哪、什么时候活动、跟谁竞争。niche 越窄，越脆。
官方关键词 · Key Terms
generalist species 广布种specialist species 特化种niche 生态位
CED Suggested Skill1.BExplain environmental concepts and processes
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引导提问：深圳城里同时住着老鼠和某个只吃一种树的昆虫。旧城改造开工，谁先消失？为什么 APES 年年考这个逻辑？
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College Board AP® Environmental ScienceUNIT 3 · CED TOPIC 3.2
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CED Topic 3.2 · 知识引导
K-Selected r-Selected Species
ERT-3.BLearning Objective · 学习目标
Identify differences between K- and r- selected species.
区分 K 选择与 r 选择物种。
An elephant calf: few offspring, years of parental care — classic K-selected
ESSENTIAL KNOWLEDGE · CED 原文（5 条，点开对照）
- ERT-3.B.1K-selected species tend to be large, have few offspring per reproduction event, live in stable environments, expend significant energy for each offspring, mature after many years of extended youth and parental care, have long life spans/life expectancy, and reproduce more than once in their…
- ERT-3.B.2R-selected species tend to be small, have many offspring, expend or invest minimal energy for each offspring, mature early, have short life spans, and may reproduce only once in their lifetime. Competition for resources in r-selected species’ habitats is typically relatively low.
- ERT-3.B.3Biotic potential refers to the maximum reproductive rate of a population in ideal conditions.
- ERT-3.B.4Many species have reproductive strategies that are not uniquely r-selected or K-selected, or they change in different conditions at different times.
- ERT-3.B.5K-selected species are typically more adversely affected by invasive species than r-selected species, which are minimally affected by invasive species. Most invasive species are r-selected species.
核心要点 · What actually gets tested
- K-selected：体型大、寿命长、成熟晚、后代少、投入大量抚育（象、鲸、人）
- r-selected：体型小、寿命短、成熟早、后代极多、几乎不抚育（鼠、昆虫、多数鱼）
- Biotic potential = 理想条件下的最大繁殖速率（r 选的物种这项爆表）
- 记忆法：K = Keep care（少生优育），r = rapid reproduction
- 入侵物种几乎都是 r-selected；濒危物种几乎都是 K-selected —— 这句几乎每年考
Biotic potential：理想条件下（食物无限、无天敌、无病害）一个种群能达到的最大繁殖速率。现实中永远达不到。
官方关键词 · Key Terms
K-selected species K 选择物种r-selected species r 选择物种biotic potential 生物潜能parental care 亲代抚育
AP® EXAM TIP
看到题目给「产生 10,000 颗卵、亲代不照顾」，直接选 r-selected + Type III 存活曲线。给「每 3–5 年一胎、抚育数年」，选 K-selected + Type I。这两个是捆绑出现的。
CED Suggested Skill5.ADescribe patterns or trends in data
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引导提问：为什么捕捞业最先崩溃的总是鲨鱼（K 选择）而不是沙丁鱼（r 选择）？把答案压成一句话 —— 这就是 FRQ 的一个得分点。
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College Board AP® Environmental ScienceUNIT 3 · CED TOPIC 3.4
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CED Topic 3.4 · 知识引导
Carrying Capacity
ERT-3.DLearning Objective · 学习目标
Describe carrying capacity.
描述环境容纳量。
ERT-3.ELearning Objective · 学习目标
Describe the impact of carrying capacity on ecosystems.
描述环境容纳量对生态系统的影响。
A deer herd — the textbook case of overshoot and dieback
ESSENTIAL KNOWLEDGE · CED 原文（2 条，点开对照）
- ERT-3.D.1When a population exceeds its carrying capacity (carrying capacity can be denoted as K), overshoot occurs. There are environmental impacts of population overshoot, including resource depletion.
- ERT-3.E.1A major ecological effect of population overshoot is dieback of the population (often severe to catastrophic) because the lack of available resources leads to famine, disease, and/or conflict.
核心要点 · What actually gets tested
- Carrying capacity (K) = 环境能长期供养的最大种群数量
- Overshoot：短时间冲过 K → 资源被透支
- Dieback：资源崩掉后种群骤降（不是缓慢回落，是崩）
- 限制因素：食物、水、空间、疾病、捕食、光照 —— 任意一项先到顶，就决定了 K
- 人类同样受 K 约束，只是技术把 K 抬高了（Unit 9 会回扣这点）
Dieback：种群冲过 K 之后的急剧下降。写 FRQ 时用 dieback，别写 "population goes down"。
官方关键词 · Key Terms
carrying capacity 环境容纳量overshoot 超限dieback 崩溃limiting factor 限制因素
AP® EXAM TIP
MCQ 常给一张「冲过 K 又掉下来」的图问你叫什么。答案是 overshoot followed by dieback，两个词都要写 —— 只写其中一个拿不到分。
CED Suggested Skill5.EExplain what the data implies or illustrates about environmental issues
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引导提问：一片草原的 K 是 500 只鹿，现在有 800 只。描述接下来 2 年会发生什么 —— 用上 overshoot 和 dieback 两个词。
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College Board AP® Environmental ScienceUNIT 3 · CED TOPIC 3.7
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CED Topic 3.7 · 知识引导
Total Fertility Rate
EIN-1.BLearning Objective · 学习目标
Explain factors that affect total fertility rate in human populations.
解释影响总和生育率的因素。
Girls in school — the single strongest lever on total fertility rate
ESSENTIAL KNOWLEDGE · CED 原文（3 条，点开对照）
- EIN-1.B.1T otal fertility rate (TFR) is affected by the age at which females have their first child, educational opportunities for females, access to family planning, and government acts and policies.
- EIN-1.B.2If fertility rate is at replacement levels, a population is considered relatively stable.
- EIN-1.B.3Factors associated with infant mortality rates include whether mothers have access to good healthcare and nutrition. Changes in these factors can lead to changes in infant mortality rates over time.
核心要点 · What actually gets tested
- TFR = 一名女性一生中平均生育的子女数
- Replacement level ≈ 2.1（发达国家）；发展中国家更高（约 2.5–3.3，因为婴儿死亡率更高）
- TFR > 更替水平 → 人口增长；TFR < 更替水平 → 人口最终下降
- 压低 TFR 的因素：女性受教育年限、城市化、避孕可及性、养育成本、婴儿死亡率下降
- ⭐ APES 官方立场：降低人口增长最有效的手段是提高女性教育水平。这是 FRQ 的高频得分点
Replacement level fertility：让人口规模刚好不增不减的 TFR。发达国家约 2.1（多出的 0.1 补偿夭折风险）。写成 2.0 会失分。
官方关键词 · Key Terms
total fertility rate (TFR) 总和生育率replacement level 更替水平infant mortality 婴儿死亡率crude birth rate 粗出生率
AP® EXAM TIP
FRQ 问「如何降低人口增长」时，写 increasing educational access for women 或 empowering women。写 "family planning" 太笼统，写 "one-child policy" 会被认为是强制手段，不得分。
CED Suggested Skill5.ADescribe patterns or trends in data
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引导提问：为什么发达国家的更替水平是 2.1 而不是 2.0？多出来的 0.1 在补偿什么？
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College Board AP® Environmental ScienceUNIT 3 · CED TOPIC 3.8
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CED Topic 3.8 · 知识引导
Human Population Dynamics
EIN-1.CLearning Objective · 学习目标
Explain how human populations experience growth and decline.
解释人类人口如何经历增长与下降。
Density is not the same as impact — IPAT separates the two
ESSENTIAL KNOWLEDGE · CED 原文（4 条，点开对照）
- EIN-1.C.1Birth rates, infant mortality rates, and overall death rates, access to family planning, access to good nutrition, access to education, and postponement of marriage all affect whether a human population is growing or declining.
- EIN-1.C.2Factors limiting global human population include the Earth’s carrying capacity and the basic factors that limit human population growth as set forth by Malthusian theory.
- EIN-1.C.3Population growth can be affected by both density-independent factors, such as major storms, fires, heat waves, or droughts, and density-dependent factors, such as access to clean water and air, food availability, disease transmission, or territory size.
- EIN-1.C.4The rule of 70 states that dividing the number 70 by the percentage population growth rate approximates the population’s doubling time.
核心要点 · What actually gets tested
- 人口增长在全球极不均衡：增速最快的是最不发达国家
- 🧮 翻倍时间用 Rule of 70：70 ÷ 年增长率(%)
- 但人口多 ≠ 影响大。看 IPAT：I = P × A × T
- Population 人口 · Affluence 富裕度（人均消费）· Technology 技术
- 美国人均生态足迹约为印度的 8–10 倍 —— 同样一个人，影响天差地别
IPAT equation：Impact = Population × Affluence × Technology。FRQ 用它解释「为什么人口少的国家污染反而更严重」。这是把 Unit 3 和 Unit 6、9 串起来的那根线。
官方关键词 · Key Terms
IPAT equation IPAT 方程ecological footprint 生态足迹doubling time 翻倍时间per capita 人均
AP® EXAM TIP
别写 "more people = more pollution"。APES 要的是具体机制：per capita consumption、ecological footprint、IPAT。笼统表述一律不得分。
CED Suggested Skill7.ADescribe environmental problems
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引导提问：一个 3 亿人口的高消费国家 vs 一个 13 亿人口的低消费国家，谁的环境影响更大？用 IPAT 回答，别用感觉。
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