High School Biology

Ecology and Ecosystems生态学与生态系统

Ecology examines how living organisms interact with each other and with their physical environment. This guide moves from the hierarchy of ecological organization through energy flow in food webs and trophic pyramids, the biogeochemical cycles that recycle matter (carbon, nitrogen, water), population growth and carrying capacity, community interactions (competition, predation, symbiosis), ecological succession, and finally human impact on ecosystems and sustainability. Worked examples and KaTeX equations ground abstract concepts in real data.生态学（ecology，生态学）研究生物体之间及生物体与物理环境之间的相互作用。本指南从生态组织层次出发，历经食物网与营养级金字塔中的能量流动、生物地球化学循环（碳、氮、水的物质循环）、种群增长与环境容纳量、群落互作（竞争、捕食、共生）、生态演替，直至人类对生态系统的影响与可持续性。工作示例与 KaTeX 方程将抽象概念落实于真实数据。

7 sections7 节内容 US NGSS · ON · BC · ABUS NGSS · ON · BC · AB HS-LS2-1 to HS-LS2-8 strong NGSS unitNGSS HS-LS2-1 至 HS-LS2-8 核心单元
Read me first先读这里

How to use this guide如何使用本指南

Ecology and Ecosystems is the unit where all four curricula converge most strongly. US NGSS dedicates eight performance expectations (HS-LS2-1 through HS-LS2-8) to this topic area — more than any other HS biology unit. Alberta Biology 20 Unit A (energy and matter exchange) and Unit B (ecosystems and population change) together constitute roughly half of the Grade-11 course. Ontario covers ecology across SNC2D (Grade 10 foundations), SBI3U (succession, biodiversity), and SBI4U (quantitative population dynamics). BC Life Sciences 11 embeds ecological organization in its levels-of-organization Content bullet and Big Idea 2. The table below maps each section to your curriculum; each row cites the verified source document.生态学与生态系统是四套大纲汇聚最强的单元。US NGSS 为这一主题专设八个表现期望（HS-LS2-1 至 HS-LS2-8），超过任何其他 HS 生物单元。阿尔伯塔 Biology 20 的 A 单元（能量与物质交换）和 B 单元（生态系统与种群变化）合计约占 11 年级课程的一半。安大略跨 SNC2D（10 年级基础）、SBI3U（演替、生物多样性）和 SBI4U（定量种群动态）涵盖生态学。BC Life Sciences 11 在其组织层次内容条目和大概念 2 中嵌入生态组织内容。下表将各节映射到你的大纲；每行均注明已核实的来源文件。

If you are in…如果你在… Focus on these sections重点学习 Defer / lighter可推迟 / 减负 Source依据
🇺🇸 US NGSS HS Life Sciences美国 NGSS 生命科学 All 7 sections are core — HS-LS2 is the NGSS ecology family (HS-LS2-1 carrying capacity; HS-LS2-4 energy/matter flow; HS-LS2-6 ecosystem stability; HS-LS2-8 group behavior)全部 7 节均为核心 —— HS-LS2 是 NGSS 生态学系列（HS-LS2-1 承载量；HS-LS2-4 能量/物质流动；HS-LS2-6 生态系统稳定性；HS-LS2-8 群体行为） NGSS does not require deriving growth equations — carry capacity (HS-LS2-1) is assessed through graphs and data, not algebraic derivationNGSS 不要求推导增长方程——承载量（HS-LS2-1）通过图表和数据评估，而非代数推导 NGSS HS Life Science — HS-LS2 family PEs— HS-LS2 系列表现期望
🇨🇦 ON Grade 10 — SNC2D安大略 10 年级 — SNC2D §1 (organization), §2 (food webs, energy flow), §7 (human impact) — ecology foundations for Grade 10§1（组织）、§2（食物网、能量流动）、§7（人类影响）—— Grade 10 生态学基础 Quantitative population models (§4 going-deeper) — deferred to SBI4U定量种群模型（§4 深入内容）——推迟至 SBI4U Ontario SBI3U/4U Biology — SNC2D ecology strand— SNC2D 生态学单元
🇨🇦 ON Grade 12 — SBI4U Honors安大略 12 年级 — SBI4U 荣誉 All 7 sections in full. SBI4U F2.2 requires quantitative population models (exponential, logistic/sigmoid) — the going-deeper KaTeX in §4全部 7 节完整学习。SBI4U F2.2 要求定量种群模型（指数型、逻辑斯蒂型/S 型）——即 §4 的深入 KaTeX Nothing — this unit feeds directly into SBI4U Population Dynamics (Strand F)无 — 本单元直接衔接 SBI4U 种群动态（F 单元） Ontario SBI3U/4U Biology — SBI4U Strand F F3.1, F3.3, F2.2— SBI4U F 单元 F3.1、F3.3、F2.2
🇨🇦 BC Science 10 / Life Sciences 11BC Science 10 / Life Sciences 11 §1 (organization: population, community, ecosystem), §4 (population dynamics), §5 (species interactions) — BC Life Sciences 11 levels-of-organization Content bullet; Big Idea 2 (evolution at the population level)§1（组织：种群、群落、生态系统）、§4（种群动态）、§5（物种互作）—— BC Life Sciences 11 组织层次内容条目；大概念 2（种群层面的进化） Biogeochemical cycle fine detail (§3 going-deeper) — BC Life Sciences 11 addresses energy transformations but not full cycle chemistry生物地球化学循环细节（§3 深入内容）—— BC Life Sciences 11 涉及能量转化但不含完整循环化学 BC Life Sciences 11 / Anatomy 12 — Life Sciences 11 Big Ideas + Content— Life Sciences 11 大概念 + 内容
🇨🇦 AB Biology 20阿尔伯塔 Biology 20 All sections are core — Unit A (energy flow and matter cycling: 20–A1.3k trophic levels, 20–A2.1k biogeochemical cycles) and Unit B (ecosystems: 20–B1.1k organization, 20–B2 population change)全部各节均为核心 —— A 单元（能量流动和物质循环：20–A1.3k 营养级，20–A2.1k 生物地球化学循环）和 B 单元（生态系统：20–B1.1k 组织，20–B2 种群变化） Quantitative sinusoidal population models — those are Biology 30 Unit D GO3; use conceptual models at Biology 20 level定量正弦种群模型 ——属 Biology 30 Unit D GO3；Biology 20 层面使用概念模型即可 Alberta Biology 20/30 — Biology 20 Unit A GO1–GO3, Unit B GO1–GO2— Biology 20 Unit A GO1–GO3, Unit B GO1–GO2

Once you have located your row, use the two cards below for the approach that fits your timeline.找到所在行后，用下面两张卡片选择适合你时间安排的方式。

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If you are cramming the night before如果你在临阵磨枪

Know the five levels of ecological organization (organism → population → community → ecosystem → biosphere); the 10% energy rule between trophic levels; the three key biogeochemical cycles (carbon, nitrogen, water); the difference between exponential and logistic growth; and the three types of symbiosis (mutualism, commensalism, parasitism). Read every cram-cheat box. Skip the going-deeper KaTeX on logistic equations if you are not in SBI4U or Biology 30.掌握五个生态组织层次（生物个体→种群→群落→生态系统→生物圈）；营养级间 10% 能量传递规律；三大生物地球化学循环（碳、氮、水）；指数增长与逻辑斯蒂增长的区别；以及三种共生类型（互利共生、偏利共生、寄生）。读每个速记框，若不在 SBI4U 或 Biology 30，可跳过逻辑斯蒂方程的深入 KaTeX。

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If you are going for the top mark如果你目标顶分

Be able to sketch and annotate a logistic (S-shaped) growth curve, label the inflection point at $K/2$, and explain why carrying capacity ($K$) is reached. For NGSS HS-LS2-4, use proportional reasoning with pyramids of energy/biomass (not just numbers). Distinguish primary from secondary succession with real examples. For human impact (§7), link eutrophication, habitat fragmentation, and invasive species to ecosystem resilience (HS-LS2-6). Explain why the nitrogen cycle is often the rate-limiting step in ecosystem productivity.能够绘制并标注逻辑斯蒂（S 型）增长曲线，标记 $K/2$ 处的拐点，并解释为何达到环境容纳量（$K$）。对于 NGSS HS-LS2-4，用能量/生物量金字塔（而非仅数量金字塔）进行比例推理。用真实案例区分初级演替与次级演替。对于人类影响（§7），将富营养化、生境破碎化和入侵物种与生态系统韧性相联系（HS-LS2-6）。解释为何氮循环通常是生态系统生产力的限速步骤。

SBI4U going-deeper flag.SBI4U 深入级标记。 The quantitative population growth models in §4 (logistic equation, $\tfrac{dN}{dt} = rN\!\left(1-\tfrac{N}{K}\right)$, and sinusoidal patterns) carry the Honors SBI4U chip because Ontario SBI4U F2.2 requires calculating population growth using exponential, sigmoid, and sinusoidal models, while NGSS HS-LS2-1 explicitly does not require "deriving mathematical equations." If your curriculum is NGSS or Biology 20, read §4 conceptually and skip the derivation boxes.§4 中的定量种群增长模型（逻辑斯蒂方程 $\tfrac{dN}{dt} = rN\!\left(1-\tfrac{N}{K}\right)$ 及正弦模式）标注 荣誉 SBI4U，因为安大略 SBI4U F2.2 要求用指数型、S 型和正弦型模型计算种群增长，而 NGSS HS-LS2-1 明确不要求"推导数学方程"。若你的大纲是 NGSS 或 Biology 20，概念性阅读 §4，跳过推导框。
Section 1 · Levels of ecological organization第 1 节 · 生态组织层次

Levels of Ecological Organization生态组织层次

Five levels from individual to biosphere — each contains the one below.从个体到生物圈的五个层次 — 每个层次包含下方层次。
  • Organism:个体（organism）： a single living thing. The baseline unit of ecology.单个生物体，生态学的基本单位。
  • Population:种群（population）： all individuals of the same species living in the same area at the same time. Shares a gene pool.同一时间生活在同一地区的同一物种的所有个体，共享基因库。
  • Community:群落（community）： all populations of different species living together in an area and interacting with one another.生活在同一地区并相互作用的不同物种的所有种群。
  • Ecosystem:生态系统（ecosystem）： a community plus all the abiotic (non-living) factors it interacts with: soil, water, light, temperature, nutrients. Matter and energy flow through an ecosystem.群落加上其互动的所有非生物（abiotic）因素：土壤、水、光、温度、营养物质。物质和能量在生态系统中流动。
  • Biosphere:生物圈（biosphere）： all ecosystems on Earth combined; the global sum of all life and its physical environments.地球上所有生态系统的总和；所有生命及其物理环境的全球总体。
B
Biotic vs Abiotic factors生物因素 vs 非生物因素
Biotic (living)生物因素（有生命）Abiotic (non-living)非生物因素（无生命）
Producers (plants, algae)生产者（植物、藻类）Sunlight光照
Consumers (herbivores, carnivores)消费者（草食动物、肉食动物）Temperature温度
Decomposers (bacteria, fungi)分解者（细菌、真菌）Water / precipitation水 / 降水
Parasites, mutualists寄生生物、互利共生生物Soil chemistry, pH, nutrients土壤化学成分、pH、营养物质
Worked Example 1 · Identifying organizational level例题 1 · 判断组织层次

A student studies a lake. She observes bass, perch, algae, crayfish, bacteria, dissolved oxygen, sunlight, and sediment pH. Identify: (a) one population; (b) the community; (c) the ecosystem; (d) two abiotic factors.一名学生研究一个湖泊。她观察到鲈鱼、河鲈、藻类、小龙虾、细菌、溶解氧、阳光和沉积物 pH。请判断：(a) 一个种群；(b) 群落；(c) 生态系统；(d) 两个非生物因素。

(a) All bass in the lake = one population (same species, same area). (b) All bass + perch + algae + crayfish + bacteria together = the community (multiple species interacting). (c) The community + dissolved oxygen + sunlight + sediment pH = the ecosystem (living + non-living). (d) Dissolved oxygen and sediment pH are both abiotic factors.(a) 湖中所有鲈鱼 = 一个种群（同物种、同地区）。(b) 所有鲈鱼 + 河鲈 + 藻类 + 小龙虾 + 细菌在一起 = 群落（多物种互动）。(c) 群落 + 溶解氧 + 阳光 + 沉积物 pH = 生态系统（生命 + 非生命）。(d) 溶解氧和沉积物 pH 均为非生物因素。

Which of the following correctly describes a community?下列哪项正确描述了群落（community）？
§1 · Q1
All members of one species living in a given area生活在某地区的同一物种的所有成员
The living organisms in an area plus their abiotic surroundings某地区的生物体及其非生物环境
All populations of different species living together and interacting in an area生活在同一地区并相互作用的不同物种的所有种群
The entire global sum of all ecosystems on Earth地球上所有生态系统的全球总体
A community is all the interacting populations of different species in an area. It is biotic only. Adding abiotic factors makes it an ecosystem; one species is a population; all global ecosystems = the biosphere.群落是某地区所有不同物种的相互作用种群，仅包含生物因素。加入非生物因素即为生态系统；单个物种为种群；全球所有生态系统 = 生物圈。
A community is defined as all interacting populations of different species (biotic only). One species alone is a population. Community + abiotic = ecosystem. All ecosystems = biosphere.群落定义为所有不同物种的相互作用种群（仅生物）。单个物种是种群。群落 + 非生物 = 生态系统。所有生态系统 = 生物圈。
Soil pH, temperature, and rainfall are all examples of ___.土壤 pH、温度和降雨量都是___的例子。
§1 · Q2
Biotic factors生物因素
Limiting factors only仅限制因素
Community interactions群落互作
Abiotic factors非生物因素
Abiotic factors are the non-living physical and chemical components of an ecosystem. Soil pH, temperature, and rainfall are all non-living. They can also be limiting factors, but the broader term is abiotic.非生物因素是生态系统中非生命的物理和化学成分。土壤 pH、温度和降雨量均为非生命。它们也可以是限制因素，但更广泛的术语是非生物因素。
Biotic = living. Soil pH, temperature, and rainfall are non-living physical/chemical factors, so they are abiotic. They may also limit populations, but abiotic is the defining category.生物 = 有生命。土壤 pH、温度和降雨量是非生命的物理/化学因素，因此是非生物因素。它们也可能限制种群，但非生物因素是定义类别。
Section 2 · Energy flow and trophic levels第 2 节 · 能量流动与营养级

Energy Flow and Trophic Levels能量流动与营养级

Energy flows one way; matter cycles. The 10% rule governs transfer efficiency.能量单向流动；物质循环利用。10% 规律决定传递效率。
  • Producers:生产者（第一营养级）： autotrophs (plants, algae, cyanobacteria) that fix solar energy via photosynthesis. Base of every food chain.通过光合作用固定太阳能的自养生物（植物、藻类、蓝藻），每条食物链的基础。
  • Primary consumers:初级消费者： herbivores that eat producers. Second trophic level.以生产者为食的草食动物，第二营养级。
  • Secondary / tertiary consumers:次级 / 三级消费者： carnivores or omnivores. Energy diminishes at each step.肉食动物或杂食动物，每个步骤能量逐渐减少。
  • Decomposers:分解者： bacteria and fungi that break down dead organic matter, returning nutrients to the soil.细菌和真菌分解死亡有机物，将营养物归还土壤。
  • 10% rule:10% 规律： only about 10% of the energy stored at one trophic level is available to the next. The remaining ~90% is lost as heat (respiration, movement, excretion). This caps most food chains at 4–5 links.约 10% 的能量从一个营养级传递到下一个，其余约 90% 以热能形式散失（呼吸、运动、排泄）。这将大多数食物链限制在 4–5 个环节。
Energy transfer efficiency — proportional reasoning (NGSS HS-LS2-4)能量传递效率 — 比例推理（NGSS HS-LS2-4）

If producers fix $10{,}000$ kJ of solar energy, primary consumers receive $\approx 1{,}000$ kJ, secondary consumers $\approx 100$ kJ, tertiary consumers $\approx 10$ kJ. Each step multiplies by ~0.1.若生产者固定 $10{,}000$ kJ 太阳能，初级消费者获得约 $1{,}000$ kJ，次级消费者约 $100$ kJ，三级消费者约 $10$ kJ，每步乘以约 0.1。

$$\text{Energy at level }n \approx E_0 \times (0.10)^{n-1}$$

This explains why herbivore-dominated diets can support larger human populations per unit area than carnivore-dominated diets.这解释了为何以草食为主的饮食在单位面积上能支持比以肉食为主的饮食更多的人口。

Worked Example 2: A grassland fixes 50,000 kJ/m²/yr. Estimate the energy available to a top predator (4th trophic level).例题 2：一片草地每年每平方米固定 50,000 kJ。估算顶级捕食者（第四营养级）可获得的能量。

Level 1 (producers): 50,000 kJ → Level 2: 5,000 kJ → Level 3: 500 kJ → Level 4: 50 kJ. Only 50 kJ (0.1%) of the original energy reaches the top predator. Pyramids of energy always narrow; pyramids of numbers may invert (e.g., one tree supports many insects).第一营养级（生产者）：50,000 kJ → 第二营养级：5,000 kJ → 第三营养级：500 kJ → 第四营养级：50 kJ。只有原始能量的 0.1%（50 kJ）到达顶级捕食者。能量金字塔始终向顶端收窄；数量金字塔可能倒置（如一棵树支撑大量昆虫）。

W
Food webs vs food chains食物网（food web）vs 食物链（food chain）

A food chain is a single linear sequence (grass → rabbit → fox → eagle). A food web is the realistic network of all feeding relationships in a community. Most organisms feed at multiple trophic levels; removing one species can cascade through the web (a keystone species removal destabilizes the whole community).食物链是单一线性序列（草→兔→狐→鹰）。食物网（food web）是群落中所有取食关系的真实网络。大多数生物在多个营养级取食；移除一个物种可能会在网络中产生连锁反应（移除关键物种会破坏整个群落稳定性）。

A grassland ecosystem fixes 100,000 kJ of energy per year. Approximately how much energy is available to secondary consumers (3rd trophic level)?一个草地生态系统每年固定 100,000 kJ 能量。次级消费者（第三营养级）约可获得多少能量？
§2 · Q1
10,000 kJ10,000 kJ
1,000 kJ1,000 kJ
100 kJ100 kJ
50,000 kJ50,000 kJ
Applying the 10% rule twice: 100,000 × 0.1 = 10,000 kJ to primary consumers; 10,000 × 0.1 = 1,000 kJ to secondary consumers (3rd trophic level).两次应用 10% 规律：100,000 × 0.1 = 10,000 kJ 到初级消费者；10,000 × 0.1 = 1,000 kJ 到次级消费者（第三营养级）。
The 10% rule applies at each trophic step. From producers (100,000): ×0.1 = 10,000 (primary consumers); ×0.1 = 1,000 (secondary consumers). The 3rd trophic level is two steps from the base.10% 规律适用于每个营养级步骤。从生产者（100,000）：×0.1 = 10,000（初级消费者）；×0.1 = 1,000（次级消费者）。第三营养级距基础两个步骤。
Which statement about energy pyramids is always true?关于能量金字塔，以下哪项表述始终正确？
§2 · Q2
Energy decreases at each successive trophic level能量在每个连续营养级递减
Energy increases at each successive trophic level能量在每个连续营养级递增
Energy pyramids can be inverted, like number pyramids能量金字塔可以像数量金字塔一样倒置
All energy from one level passes to the next一个营养级的所有能量传递到下一营养级
Energy is always lost as heat at each trophic transfer (~90% lost), so energy pyramids always narrow toward the apex. They can never be inverted, unlike number or biomass pyramids.每次营养级传递都以热能形式损失能量（约损失 90%），因此能量金字塔始终向顶端收窄，不像数量或生物量金字塔那样可以倒置。
Energy always decreases at each trophic level due to heat losses (~90% per step). Energy pyramids cannot be inverted. Only ~10% passes upward.由于热量损失（每步约 90%），能量在每个营养级始终减少。能量金字塔不能倒置，只有约 10% 向上传递。
Going deeper — pyramids of numbers vs biomass vs energy (AB 20–A1.4k)深入 — 数量金字塔 vs 生物量金字塔 vs 能量金字塔（AB 20–A1.4k）

Alberta 20–A1.4k requires students to "explain, quantitatively, the flow of energy and the exchange of matter in aquatic and terrestrial ecosystems, using models such as pyramids of numbers, biomass and energy." All three pyramid types represent the same food web: (1) Numbers: count of organisms at each level — can invert (one oak tree hosts thousands of caterpillars). (2) Biomass: total dry mass at each level — nearly always narrows, but aquatic systems can invert when phytoplankton biomass is low despite rapid turnover. (3) Energy: kJ/m²/yr at each level — never inverts because thermodynamics mandates net heat loss at every transfer. NGSS HS-LS2-4 uses "proportional reasoning" with these pyramids (not derivation of equations).阿尔伯塔 20–A1.4k 要求学生"用数量金字塔、生物量金字塔和能量金字塔等模型，定量解释水生和陆地生态系统中的能量流动和物质交换。"三种金字塔类型代表同一食物网：(1) 数量金字塔：各层级生物个体数量——可倒置（一棵橡树寄宿数千条毛毛虫）。(2) 生物量金字塔：各层级总干重——几乎总是收窄，但当浮游植物生物量低而周转率高时，水生系统可倒置。(3) 能量金字塔：各层级每平方米每年的千焦——从不倒置，因为热力学规律要求每次传递净热量损失。NGSS HS-LS2-4 使用这些金字塔进行"比例推理"（而非推导方程）。

Section 3 · Biogeochemical cycles第 3 节 · 生物地球化学循环

Biogeochemical Cycles: Carbon, Nitrogen, and Water生物地球化学循环：碳循环、氮循环与水循环

Matter cycles; energy does not. Three cycles you must know.物质循环；能量不循环。必须掌握的三大循环。
  • Carbon cycle:碳循环（carbon cycle）： CO₂ is fixed by photosynthesis into organic compounds; released by respiration, decomposition, and combustion. Oceans act as the largest carbon sink. Fossil fuel burning adds ancient carbon to the active cycle, driving climate change.CO₂ 经光合作用固定为有机物；经呼吸、分解和燃烧释放。海洋是最大的碳汇。化石燃料燃烧将古代碳加入活跃循环，推动气候变化。
  • Nitrogen cycle:氮循环（nitrogen cycle）： N₂ gas (~78% of atmosphere) is unusable by most organisms. Nitrogen-fixing bacteria (e.g. Rhizobium) convert N₂ → NH₃ (ammonia). Nitrification: bacteria convert NH₃ → NO₃⁻ (usable by plants). Denitrification: bacteria return NO₃⁻ → N₂. Decomposers release ammonium from dead matter.N₂ 气体（约占大气 78%）大多数生物无法直接利用。固氮细菌（如根瘤菌）将 N₂ 转化为 NH₃（氨）。硝化作用：细菌将 NH₃ → NO₃⁻（植物可利用）。反硝化作用：细菌将 NO₃⁻ → N₂。分解者从死亡物质中释放铵盐。
  • Water cycle:水循环（water cycle）： evaporation + transpiration (evapotranspiration) → atmospheric water vapor → condensation → precipitation → runoff/infiltration → groundwater/oceans. Water is the universal solvent; its cycling transports nutrients and regulates temperature.蒸发 + 蒸腾（蒸散）→ 大气水蒸气 → 凝结 → 降水 → 径流/渗透 → 地下水/海洋。水是通用溶剂；其循环输送营养物质并调节温度。
Why the nitrogen cycle limits productivity (AB 20–A2.1k).为何氮循环限制生产力（AB 20–A2.1k）。 Nitrogen is a component of all amino acids and nucleic acids, so plant growth is often nitrogen-limited even when light and water are sufficient. Agricultural fertilizers (synthetic NO₃⁻, NH₄⁺) short-circuit the cycle to boost yields but can cause eutrophication when runoff enters waterways: algal blooms deplete dissolved oxygen, creating dead zones.氮是所有氨基酸和核酸的成分，因此即使光照和水分充足，植物生长往往仍受氮限制。农业化肥（合成 NO₃⁻、NH₄⁺）使循环短路以提高产量，但径流进入水体时会导致富营养化：藻华耗尽溶解氧，形成死区。
Which process in the nitrogen cycle converts N₂ gas directly into ammonia (NH₃) usable by living things?氮循环中哪个过程将 N₂ 气体直接转化为生物可用的氨（NH₃）？
§3 · Q1
Nitrification硝化作用
Denitrification反硝化作用
Decomposition分解作用
Nitrogen fixation固氮作用
Nitrogen fixation converts atmospheric N₂ → NH₃ (ammonia), making nitrogen available to organisms. Nitrification converts NH₃ → NO₃⁻; denitrification returns N to the atmosphere; decomposition releases ammonium from dead matter.固氮作用将大气 N₂ → NH₃（氨），使氮对生物可用。硝化作用将 NH₃ → NO₃⁻；反硝化作用将氮归还大气；分解作用从死亡物质释放铵盐。
Nitrogen fixation is the entry point: N₂ → NH₃. Nitrification is NH₃ → NO₃⁻ (a different step). Denitrification returns N₂ to the atmosphere. Decomposition releases ammonium from organic matter.固氮作用是入口：N₂ → NH₃。硝化作用是 NH₃ → NO₃⁻（不同步骤）。反硝化作用将 N₂ 归还大气。分解作用从有机物释放铵盐。
Burning fossil fuels increases atmospheric CO₂ because it:化石燃料燃烧增加大气 CO₂，因为它：
§3 · Q2
Increases the rate of photosynthesis globally增加全球光合作用速率
Fixes atmospheric nitrogen into carbon compounds将大气氮固定为碳化合物
Releases carbon stored in ancient organic matter back into the active carbon cycle将储存在古代有机物中的碳重新释放到活跃的碳循环中
Converts water vapor to CO₂ through condensation通过凝结将水蒸气转化为 CO₂
Fossil fuels are ancient organic carbon locked out of the active cycle for millions of years. Combustion returns this carbon as CO₂ faster than natural sinks (oceans, forests) can absorb it, raising atmospheric concentration.化石燃料是古代有机碳，已在活跃循环之外封存数百万年。燃烧以 CO₂ 形式释放这些碳的速度超过天然碳汇（海洋、森林）的吸收速度，导致大气浓度升高。
Fossil fuels release ancient stored carbon as CO₂ — this is why atmospheric concentrations are rising. It doesn't increase photosynthesis, fix nitrogen, or convert water to CO₂.化石燃料将古代储存的碳以 CO₂ 形式释放——这就是大气浓度上升的原因。它不会增加光合作用、固定氮，也不会将水转化为 CO₂。
Going deeper — phosphorus cycle and eutrophication (AB 20–A2.1k; NGSS HS-LS2-4)深入 — 磷循环与富营养化（AB 20–A2.1k；NGSS HS-LS2-4）

The phosphorus cycle has no significant atmospheric component — phosphorus moves from rock (weathering) → soil → organisms → decomposers → sediment. Alberta 20–A2.1k explicitly requires students to "explain and summarize the biogeochemical cycling of carbon, oxygen, nitrogen and phosphorus." Unlike nitrogen, phosphorus enters ecosystems only through weathering and leaves mainly by sedimentation, making it a frequent limiting nutrient in freshwater ecosystems. Agricultural runoff adding phosphate triggers eutrophication: rapid algal growth → algal die-off → decomposer respiration → oxygen depletion → dead zone. This is distinct from nitrogen-driven eutrophication in estuaries.磷循环没有显著的大气成分——磷从岩石（风化）→ 土壤 → 生物 → 分解者 → 沉积物移动。阿尔伯塔 20–A2.1k 明确要求学生"解释和总结碳、氧、氮和磷的生物地球化学循环。"与氮不同，磷只通过风化进入生态系统，主要通过沉积物离开，使其成为淡水生态系统中常见的限制营养素。农业径流添加磷酸盐触发富营养化：藻类快速增长 → 藻类死亡 → 分解者呼吸 → 氧气耗尽 → 死区。这与河口中由氮驱动的富营养化不同。

Section 4 · Population dynamics第 4 节 · 种群动态

Population Dynamics: Growth, Limits, and Carrying Capacity种群动态：增长、限制与环境容纳量

Two growth patterns: exponential (J-curve) and logistic (S-curve). Carrying capacity ($K$) is the ceiling.两种增长模式：指数增长（J 型曲线）和逻辑斯蒂增长（S 型曲线）。环境容纳量（$K$）是上限。
  • Exponential growth:指数增长： unlimited resources; population grows at a constant per-capita rate $r$. Rate equation: $\tfrac{dN}{dt} = rN$. Produces a J-shaped curve. Rare in nature for long periods; occurs after colonization of a new habitat.资源无限；种群以恒定人均增长率 $r$ 增长。速率方程：$\tfrac{dN}{dt} = rN$。产生 J 型曲线。在自然界中长期罕见；在殖民新栖息地后出现。
  • Logistic growth:逻辑斯蒂增长： resources are limited. Growth rate slows as $N$ approaches $K$. S-shaped (sigmoid) curve. Maximum growth rate occurs at $N = K/2$.资源有限。随 $N$ 趋近 $K$，增长率减慢。S 型（乙状）曲线。最大增长率发生在 $N = K/2$ 时。
  • Carrying capacity:环境容纳量（$K$）： the maximum population size a given environment can sustain indefinitely, set by food, water, space, disease, and other limiting factors (NGSS HS-LS2-1).特定环境可无限期维持的最大种群规模，由食物、水、空间、疾病和其他限制因素决定（NGSS HS-LS2-1）。
  • Limiting factors:限制因素： density-dependent (competition, predation, disease — intensify as $N$ rises) and density-independent (storms, drought, fire — affect all regardless of $N$).密度制约因素（竞争、捕食、疾病——随 $N$ 增大而加剧）和非密度制约因素（风暴、干旱、火灾——无论 $N$ 大小均影响所有个体）。
Logistic growth equation Honors SBI4U逻辑斯蒂增长方程 荣誉 SBI4U
$$\frac{dN}{dt} = rN\!\left(1 - \frac{N}{K}\right)$$

When $N \ll K$: the factor $(1 - N/K) \approx 1$, so growth is nearly exponential. When $N = K/2$: growth rate is at its maximum. When $N = K$: $(1 - N/K) = 0$, growth stops. SBI4U F2.2 requires calculating population sizes using this model; NGSS HS-LS2-1 requires only conceptual/graphical understanding.当 $N \ll K$ 时：因子 $(1 - N/K) \approx 1$，增长近乎指数型。当 $N = K/2$ 时：增长率最大。当 $N = K$ 时：$(1 - N/K) = 0$，增长停止。SBI4U F2.2 要求使用此模型计算种群规模；NGSS HS-LS2-1 仅要求概念性/图形理解。

A deer population on an island is currently at $N = K/2$. Which statement best describes the population growth at this moment?一个岛屿鹿种群目前处于 $N = K/2$。以下哪项最能描述此时的种群增长？
§4 · Q1
Growth has stopped because the population has reached its limit增长已停止，因为种群已达到其极限
Growth is exponential because resources are unlimited增长是指数型的，因为资源无限
Growth rate is at its maximum (inflection point of the S-curve)增长率处于最大值（S 型曲线的拐点）
The population is declining due to overshoot由于超调，种群正在下降
In logistic growth, the maximum rate of increase (fastest growth) occurs at $N = K/2$, the inflection point of the S-curve. Growth only stops at $N = K$; exponential growth occurs only when $N \ll K$.在逻辑斯蒂增长中，最大增长率（最快增长）发生在 $N = K/2$，即 S 型曲线的拐点。只有在 $N = K$ 时增长才会停止；指数增长只在 $N \ll K$ 时出现。
$N = K/2$ is the inflection point of the logistic S-curve where $\tfrac{dN}{dt}$ is largest. Growth stops at $N = K$, not at $K/2$.$N = K/2$ 是逻辑斯蒂 S 型曲线的拐点，此处 $\tfrac{dN}{dt}$ 最大。增长在 $N = K$ 时停止，而非 $K/2$。
A disease that kills more individuals as population density increases is an example of a ___ factor.随种群密度增大而杀死更多个体的疾病是___因素的例子。
§4 · Q2
Density-independent limiting非密度制约限制
Density-dependent limiting密度制约限制
Abiotic environmental非生物环境
Biotic potential生物潜能
Density-dependent factors intensify as population density increases — disease spreads more readily, competition for food increases, etc. Density-independent factors (storms, drought) affect the population regardless of its size.密度制约因素随种群密度增大而加剧——疾病更易传播、食物竞争加剧等。非密度制约因素（风暴、干旱）无论种群规模如何均会影响种群。
Density-dependent factors change in intensity with population density; density-independent factors do not. Disease spreading more at higher density is density-dependent.密度制约因素随种群密度变化而改变强度；非密度制约因素则不然。在较高密度下传播更广的疾病是密度制约因素。
Section 5 · Community interactions第 5 节 · 群落互作

Community Interactions: Competition, Predation, and Symbiosis群落互作：竞争、捕食与共生

How species affect each other: positive, negative, or neutral.物种如何相互影响：正面、负面或中性。
  • Competition:竞争： two species (interspecific) or individuals of the same species (intraspecific) compete for a shared limited resource. Outcome: competitive exclusion (one species eliminated) or niche partitioning (species coexist by using slightly different resources).两物种（种间竞争）或同物种个体（种内竞争）竞争共同的有限资源。结果：竞争排斥（一种物种被淘汰）或生态位分化（物种通过利用略有不同的资源共存）。
  • Predation:捕食： predator (+) kills and eats prey (-). Classic predator-prey cycles (Lotka-Volterra): prey increases → predator increases → prey decreases → predator decreases. Keystone predators regulate communities beyond their numerical abundance.捕食者（+）猎杀并吃掉猎物（-）。经典捕食者-猎物周期（Lotka-Volterra）：猎物增加→捕食者增加→猎物减少→捕食者减少。关键物种捕食者对群落的调控超出其数量比例。
  • Mutualism:互利共生： both species benefit (+/+). Examples: bees and flowers (pollination), mycorrhizal fungi and plant roots.两个物种均受益（+/+）。示例：蜜蜂与花（授粉）、菌根真菌与植物根部。
  • Commensalism:偏利共生： one species benefits (+), the other is unaffected (0). Example: barnacles on a whale.一种物种受益（+），另一种不受影响（0）。示例：鲸鱼上的藤壶。
  • Parasitism:寄生： parasite benefits (+), host is harmed (-). Similar sign pattern to predation but parasite rarely kills host immediately. Examples: tapeworms, mistletoe, ticks.寄生物受益（+），宿主受害（-）。符号模式与捕食相似，但寄生物很少立即杀死宿主。示例：绦虫、槲寄生、蜱虫。
S
Symbiosis summary table共生关系汇总表
Interaction互作类型Species A物种 ASpecies B物种 BExample示例
Mutualism互利共生++Clownfish & sea anemone小丑鱼与海葵
Commensalism偏利共生+0Barnacles on whale鲸鱼上的藤壶
Parasitism寄生+−Tapeworm in gut肠道绦虫
Predation捕食+−Wolf & moose狼与驼鹿
Competition竞争−−Lions & hyenas over prey狮子与鬣狗争夺猎物
Two species of barnacles occupy the same intertidal zone. Experiments show that when barnacle species A is removed, species B expands into A's former territory. When species B is removed, species A does not change. What type of interaction does this demonstrate?两种藤壶占据相同的潮间带。实验表明，当藤壶物种 A 被移除时，物种 B 扩展到 A 的前领地。当物种 B 被移除时，物种 A 没有变化。这展示了什么类型的互作？
§5 · Q1
Mutualism互利共生
Commensalism偏利共生
Parasitism寄生
Interspecific competition种间竞争
Species B is suppressed by species A (B expands when A is removed) but B does not suppress A (A unchanged when B is removed). This is asymmetric interspecific competition — both species compete for space, but A is the superior competitor. This is Connell's classic barnacle experiment.物种 B 受到物种 A 的抑制（A 被移除时 B 扩展），但 B 不抑制 A（B 被移除时 A 无变化）。这是不对称种间竞争——两个物种竞争空间，但 A 是优势竞争者。这是康奈尔经典藤壶实验。
This is competition: two species share a resource (space) and one suppresses the other. Mutualism would benefit both; commensalism would benefit one with no effect on the other; parasitism involves one harming the other in a different mechanism.这是竞争：两个物种共享资源（空间），一个抑制另一个。互利共生会使双方受益；偏利共生使一方受益而对另一方无影响；寄生涉及以不同机制损害另一方。
Mycorrhizal fungi grow into plant root cells and receive sugars from the plant, while the plant gains improved mineral absorption from the fungal hyphae network. This relationship is:菌根真菌生长进入植物根细胞，从植物获取糖分，而植物通过真菌菌丝网络获得更好的矿物质吸收。这种关系是：
§5 · Q2
Mutualism互利共生
Commensalism偏利共生
Parasitism寄生
Competition竞争
Both the fungus (gets sugars) and the plant (gets better mineral uptake) benefit. This is mutualism (+/+). Parasitism would harm the plant; commensalism would leave the plant unaffected.真菌（获得糖分）和植物（获得更好的矿物质吸收）都受益。这是互利共生（+/+）。寄生会损害植物；偏利共生会使植物不受影响。
Both species benefit: fungus gets carbohydrates; plant gets extended mineral absorption. That is the definition of mutualism (+/+).两个物种都受益：真菌获得碳水化合物；植物获得扩展的矿物质吸收。这就是互利共生（+/+）的定义。
Section 6 · Ecological succession第 6 节 · 生态演替

Ecological Succession生态演替

Succession: communities change directionally over time until a relatively stable climax community is reached.演替（succession）：群落随时间定向变化，直到达到相对稳定的顶极群落。
  • Primary succession:初级演替： begins on bare rock or substrate with no soil. Pioneer species (e.g. lichens, mosses) colonize first, breaking down rock and adding organic matter to form soil. Very slow (centuries). Example: lava field after volcanic eruption; newly exposed glacier bed.从裸岩或无土壤的基质开始。先锋物种（如地衣、苔藓）首先定殖，分解岩石并添加有机物以形成土壤，速度极慢（以世纪计）。示例：火山喷发后的熔岩地；新暴露的冰川床。
  • Secondary succession:次级演替： begins where a community was disturbed but soil remains. Faster than primary because soil seed bank and nutrients persist. Example: abandoned farmland, forest after fire or logging.从群落受干扰但土壤保留的地方开始，比初级演替快，因为土壤种子库和营养物质持续存在。示例：废弃农田、火灾或伐木后的森林。
  • Climax community:顶极群落： the relatively stable endpoint of succession in a given climate. Not truly permanent; disturbance resets succession. Alberta Biology 30 D2.2k notes communities "may change over time or remain as a climax community."在特定气候条件下演替的相对稳定终点。并非真正永久；干扰会重置演替。阿尔伯塔 Biology 30 D2.2k 指出群落"可能随时间变化或保持为顶极群落"。
  • Pioneer → intermediate → climax:先锋物种 → 中间阶段 → 顶极群落： each stage modifies the habitat, making it suitable for the next. Species richness and biomass generally increase. Dominant species shift from r-selected (fast-reproducing) to K-selected (slow-reproducing, competitive).每个阶段改变栖息地，使其适合下一阶段。物种丰富度和生物量通常增加。优势物种从 r 选择（快速繁殖）转向 K 选择（繁殖慢、竞争力强）。
A forest is destroyed by wildfire, leaving behind ash-covered soil. Which type of succession will occur?一片森林被野火摧毁，留下覆盖着灰烬的土壤。将发生哪种类型的演替？
§6 · Q1
Primary succession, because all organisms are killed初级演替，因为所有生物都被杀死
Secondary succession, because soil and seed banks remain次级演替，因为土壤和种子库保留
Primary succession, because lichens must colonize first初级演替，因为地衣必须首先定殖
No succession — the area will remain bare无演替——该地区将保持裸露
Secondary succession begins wherever soil (with its seed bank, nutrients, and microbial communities) is left intact. A wildfire destroys above-ground biomass but leaves soil behind. Primary succession requires starting on bare rock with no soil at all.次级演替发生在土壤（及其种子库、营养物质和微生物群落）完好保留的任何地方。野火摧毁地上生物量，但留下土壤。初级演替需要从完全没有土壤的裸岩开始。
The key distinction: primary succession starts with no soil (bare rock / fresh lava / exposed glacier). Secondary succession starts where soil survives — which includes post-fire sites. Fire leaves soil; lava flows do not.关键区别：初级演替从没有土壤的地方开始（裸岩/新鲜熔岩/暴露的冰川）。次级演替从土壤保留的地方开始——包括火灾后的地点。火灾留下土壤；熔岩流不留土壤。
Why do pioneer species such as lichens play a critical role in primary succession?为什么地衣等先锋物种在初级演替中起关键作用？
§6 · Q2
They outcompete all other species for nutrients它们在营养竞争中胜过所有其他物种
They provide food for tertiary consumers immediately它们立即为三级消费者提供食物
They fix atmospheric nitrogen into organic compounds它们将大气氮固定为有机化合物
They break down rock and add organic matter, forming soil for later species它们分解岩石并添加有机物，为后续物种形成土壤
Pioneer species like lichens tolerate extreme conditions and chemically erode rock while depositing dead organic matter. This process slowly builds a thin soil layer that allows mosses, grasses, and later shrubs and trees to establish. They "prepare the way" for subsequent successional stages.像地衣这样的先锋物种能耐受极端条件，化学侵蚀岩石，同时沉积死亡有机物。这个过程慢慢建立薄薄的土壤层，使苔藓、草类、以及后来的灌木和树木得以定殖。它们为后续演替阶段"铺路"。
Pioneers build soil by weathering rock and contributing organic matter — this is their defining ecological role in primary succession. They do not outcompete all others; they are quickly replaced by later-successional species once conditions improve.先锋物种通过风化岩石和贡献有机物来建造土壤——这是它们在初级演替中的决定性生态作用。它们不会胜过所有其他物种；一旦条件改善，它们很快被后期演替物种取代。
Section 7 · Human impact and sustainability第 7 节 · 人类影响与可持续性

Human Impact on Ecosystems and Sustainability人类对生态系统的影响与可持续性

Five major human threats to ecosystem resilience (NGSS HS-LS2-7; SBI3U B1.1–B1.2; AB 20–B1.4k).生态系统韧性面临的五大人类威胁（NGSS HS-LS2-7；SBI3U B1.1–B1.2；AB 20–B1.4k）。
  • Habitat loss and fragmentation:栖息地丧失与破碎化： the leading cause of species extinction globally. Reduces population size below minimum viable thresholds; isolates gene pools; disrupts migration.全球物种灭绝的主要原因。使种群规模降至最小可存活阈值以下；隔离基因库；破坏迁徙。
  • Invasive species:入侵物种： non-native organisms introduced to new ecosystems that disrupt food webs, outcompete natives, and reduce biodiversity (NGSS HS-LS2-7: "dissemination of invasive species").引入新生态系统的非本土生物，破坏食物网，在竞争中胜过本土物种，降低生物多样性（NGSS HS-LS2-7："入侵物种的传播"）。
  • Pollution and eutrophication:污染与富营养化： nutrient runoff (N, P) causes algal blooms → oxygen depletion → dead zones. Air pollutants (SO₂, NOₓ) cause acid rain, disrupting freshwater food webs. Plastics fragment into microplastics, entering food chains.营养物径流（N、P）导致藻华→缺氧→死区。空气污染物（SO₂、NOₓ）导致酸雨，破坏淡水食物网。塑料碎裂为微塑料，进入食物链。
  • Climate change:气候变化： rising temperatures shift species ranges poleward/upslope, disrupt phenology (flowering, migration timing), bleach coral reefs (ocean warming + acidification), and increase frequency of extreme weather events (HS-LS2-6: "changing conditions may result in a new ecosystem").温度升高使物种分布向极地/高海拔转移，破坏物候（开花、迁徙时机），漂白珊瑚礁（海洋变暖+酸化），并增加极端天气事件频率（HS-LS2-6："条件变化可能导致新的生态系统"）。
  • Overexploitation:过度开发： overfishing, poaching, and unsustainable harvesting reduce populations below recovery thresholds, sometimes causing trophic cascades (removal of apex predators triggers prey population explosions).过度捕捞、偷猎和不可持续的采集使种群减少到恢复阈值以下，有时导致营养级联（移除顶级捕食者引发猎物种群爆发）。
Ecosystem resilience and the NGSS HS-LS2-6 framing.生态系统韧性与 NGSS HS-LS2-6 框架。

HS-LS2-6 states: "complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem." Resilience = the ability of an ecosystem to return to a reference state after disturbance. Biodiversity is the primary driver of resilience: more species → more functional redundancy → more pathways to fill any role lost by disturbance. This is why habitat fragmentation (which reduces biodiversity) undermines resilience.HS-LS2-6 指出："生态系统中的复杂互动在稳定条件下维持相对一致的生物数量和类型，但条件变化可能导致新的生态系统。"韧性 = 生态系统在受干扰后恢复到参考状态的能力。生物多样性是韧性的主要驱动力：物种更多 → 更多功能冗余 → 更多途径填补干扰造成的任何角色缺失。这就是为什么降低生物多样性的栖息地破碎化会削弱韧性。

Wolves were reintroduced to Yellowstone National Park in 1995. Within a decade, elk populations decreased, riverside vegetation recovered, river banks stabilized, and beaver populations increased. This chain of effects is called a:1995 年，狼被重新引入黄石国家公园。十年内，麋鹿种群减少，河岸植被恢复，河岸稳定，河狸种群增加。这种连锁效应被称为：
§7 · Q1
A trophic cascade营养级联
Primary succession初级演替
Competitive exclusion竞争排斥
Nitrogen fixation固氮作用
A trophic cascade occurs when a change at one trophic level propagates through the food web, affecting organisms at other levels. Wolves (top predator) suppressed elk (primary consumer) → vegetation recovered → river banks stabilized → beavers benefited. This is a classic top-down trophic cascade driven by a keystone predator.营养级联发生在一个营养级的变化通过食物网传播，影响其他级别的生物时。狼（顶级捕食者）抑制麋鹿（初级消费者）→植被恢复→河岸稳定→河狸受益。这是由关键物种捕食者驱动的经典自上而下营养级联。
Trophic cascades are indirect effects that ripple through a food web when a predator changes prey behavior/abundance. The Yellowstone wolf reintroduction is a textbook trophic cascade example. Not succession (no directional community change), not competitive exclusion (no species eliminated), not nitrogen fixation.营养级联是当捕食者改变猎物行为/数量时通过食物网传播的间接效应。黄石公园狼的重新引入是教科书级的营养级联例子。不是演替（没有定向群落变化），不是竞争排斥（没有物种被淘汰），不是固氮作用。
Which of the following best explains why high biodiversity generally increases ecosystem resilience?以下哪项最能解释为什么高生物多样性通常能提高生态系统韧性？
§7 · Q2
More species means more competition, which drives adaptation物种越多意味着竞争越激烈，从而驱动适应
Diverse species produce more CO₂ for photosynthesis多样的物种产生更多的 CO₂ 用于光合作用
More species provide functional redundancy, so roles can be filled even if some species are lost物种越多提供越多功能冗余，因此即使某些物种丧失，角色也可以被填补
Diverse ecosystems have simpler food webs that are easier to maintain多样的生态系统拥有更简单的食物网，更容易维持
Functional redundancy means multiple species can perform similar ecological roles (e.g., several species of seed dispersers). If one is lost to disturbance, others continue the function. This keeps the ecosystem stable. High diversity = high redundancy = high resilience. This is the core argument for biodiversity conservation (NGSS HS-LS2-6, HS-LS2-7).功能冗余意味着多个物种可以执行类似的生态角色（例如多种种子传播者）。如果一种因干扰而丧失，其他种类继续发挥功能。这使生态系统保持稳定。高多样性 = 高冗余 = 高韧性。这是生物多样性保护的核心论点（NGSS HS-LS2-6，HS-LS2-7）。
Resilience comes from functional redundancy: multiple species fill the same roles, so disturbances that eliminate some species do not collapse the whole ecosystem. High biodiversity does NOT mean simpler food webs — it means more complex webs with more alternative pathways.韧性来自功能冗余：多个物种填充相同的角色，因此消灭部分物种的干扰不会使整个生态系统崩溃。高生物多样性并不意味着更简单的食物网——而是意味着具有更多替代途径的更复杂网络。
Exam Tactics考试策略

Exam Strategy and Common Pitfalls考试策略与常见陷阱

Energy calculation questions能量计算题
  • Apply the 10% rule step by step.逐步应用 10% 规律。 For each trophic level you move up, multiply by 0.1. A question asking "how much energy reaches the 4th trophic level from 50,000 kJ?" needs three multiplications: 50,000 × 0.1 × 0.1 × 0.1 = 50 kJ.每上升一个营养级，乘以 0.1。"从 50,000 kJ 中有多少能量到达第四营养级？"需要三次乘法：50,000 × 0.1 × 0.1 × 0.1 = 50 kJ。
  • Energy pyramids never invert; number pyramids can.能量金字塔从不倒置；数量金字塔可以。 If a question shows an inverted pyramid, it must be referring to numbers or biomass, not energy.若题目显示倒置金字塔，必定是指数量或生物量，而非能量。
Population growth questions种群增长题
  • Distinguish J-curve from S-curve by the phrase "unlimited resources" or "limited resources."用"资源无限"或"资源有限"区分 J 型曲线和 S 型曲线。 Exponential (J) = no carrying capacity mentioned. Logistic (S) = carrying capacity $K$ mentioned or implied.指数型（J）= 未提及环境容纳量。逻辑斯蒂型（S）= 提及或暗示环境容纳量 $K$。
  • Maximum growth rate is at $N = K/2$, not at $N = 0$ or $N = K$.最大增长率在 $N = K/2$，而非 $N = 0$ 或 $N = K$。 This is the inflection point of the S-curve — the most commonly tested point.这是 S 型曲线的拐点——考试中最常测试的点。
Succession and cycle questions演替与循环题
  • Primary vs secondary: the soil test.初级 vs 次级演替：土壤检验。 If soil is present, it is secondary succession. If only bare rock or fresh lava, it is primary succession. Wildfire → secondary (soil survives). Volcanic eruption with lava → primary (soil destroyed).若有土壤，则为次级演替。若只有裸岩或新鲜熔岩，则为初级演替。野火 → 次级（土壤保留）。熔岩火山喷发 → 初级（土壤被摧毁）。
  • In nitrogen cycle questions, name the specific bacteria and the conversion.在氮循环题中，说明具体细菌及其转化。 N₂ → NH₃ = nitrogen fixation (Rhizobium); NH₃ → NO₃⁻ = nitrification; NO₃⁻ → N₂ = denitrification. Three steps, three names.N₂ → NH₃ = 固氮作用（根瘤菌）；NH₃ → NO₃⁻ = 硝化作用；NO₃⁻ → N₂ = 反硝化作用。三个步骤，三个名称。
Active Recall主动复习

Flashcards闪卡

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Five levels of ecological organization (smallest to largest)?五个生态组织层次（从小到大）？
Organism → Population → Community → Ecosystem → Biosphere个体 → 种群 → 群落 → 生态系统 → 生物圈
What is the 10% rule?什么是 10% 规律？
Only ~10% of energy stored at one trophic level is available to the next. ~90% lost as heat. Limits most food chains to 4–5 links.约 10% 的能量从一个营养级传递到下一个，约 90% 以热能散失。将大多数食物链限制在 4–5 个环节。
Carbon cycle: four processes that release CO₂?碳循环（碳循环）：释放 CO₂ 的四个过程？
Cellular respiration, decomposition, combustion (fossil fuels + biomass), volcanism. Photosynthesis removes CO₂.细胞呼吸、分解作用、燃烧（化石燃料+生物量）、火山活动。光合作用吸收 CO₂。
Nitrogen fixation: what converts N₂ → NH₃?固氮作用：什么将 N₂ 转化为 NH₃？
Nitrogen-fixing bacteria (e.g. Rhizobium in legume root nodules; free-living Azotobacter). Lightning also fixes small amounts.固氮细菌（如豆科植物根瘤中的根瘤菌；自由生活的固氮菌）。闪电也可固定少量氮。
Logistic growth equation?逻辑斯蒂增长方程？
$$\frac{dN}{dt} = rN\!\left(1 - \frac{N}{K}\right)$$ Max rate at $N = K/2$. Growth stops at $N = K$.最大增长率在 $N = K/2$。增长在 $N = K$ 时停止。
Carrying capacity $K$ — definition?环境容纳量 $K$ — 定义？
Maximum population size a given environment can sustain indefinitely. Set by food, water, space, disease, and other limiting factors.特定环境可无限期维持的最大种群规模，由食物、水、空间、疾病和其他限制因素决定。
Three types of symbiosis — sign pattern?三种共生类型 — 符号模式？
Mutualism: +/+. Commensalism: +/0. Parasitism: +/−.互利共生：+/+。偏利共生：+/0。寄生：+/−。
Competitive exclusion principle?竞争排斥原理？
Two species competing for the same limited resource cannot coexist indefinitely — the superior competitor will eventually eliminate the other, unless they partition the niche.竞争同一有限资源的两个物种无法无限期共存——优势竞争者最终会消灭另一方，除非它们分化生态位。
Primary vs secondary succession — key distinction?初级 vs 次级演替 — 关键区别？
Primary: starts on bare rock / no soil (e.g. lava field, glacier retreat). Secondary: starts where soil remains after disturbance (e.g. post-fire forest, abandoned farmland).初级演替：从裸岩/无土壤开始（如熔岩地、冰川退缩）。次级演替：从干扰后土壤保留的地方开始（如火灾后森林、废弃农田）。
Pioneer species — role in succession?先锋物种 — 在演替中的作用？
First colonizers (e.g. lichens, mosses). Tolerate extreme conditions. Weather rock, add organic matter, build soil that allows later species to establish.首批定殖者（如地衣、苔藓）。耐受极端条件。风化岩石，添加有机物，建造使后续物种得以定殖的土壤。
Trophic cascade — what is it?营养级联 — 是什么？
Indirect effects that ripple through a food web when a top predator is added or removed. Example: wolves reintroduced to Yellowstone reduced elk → vegetation recovered → river bank stabilized.顶级捕食者添加或移除时通过食物网传播的间接效应。示例：狼重新引入黄石→麋鹿减少→植被恢复→河岸稳定。
Eutrophication — cause and consequence?富营养化 — 原因与后果？
Cause: excess N/P (fertilizer runoff) → algal bloom → algae die → decomposers use O₂ → hypoxia (dead zone). Kills fish and invertebrates.原因：过量 N/P（化肥径流）→藻华→藻类死亡→分解者耗尽 O₂→缺氧（死区）。导致鱼类和无脊椎动物死亡。
Density-dependent vs density-independent factors?密度制约 vs 非密度制约因素？
Density-dependent: intensify as N rises (disease, competition, predation). Density-independent: same impact regardless of N (drought, storm, fire).密度制约因素：随 N 增大而加剧（疾病、竞争、捕食）。非密度制约因素：无论 N 大小影响相同（干旱、风暴、火灾）。
Why does high biodiversity increase ecosystem resilience?为什么高生物多样性提高生态系统韧性？
Functional redundancy: multiple species fill similar ecological roles. If one is lost, others continue the function. More species → more redundancy → more stable after disturbance.功能冗余：多个物种填充相似的生态角色。若一种丧失，其他种类继续发挥功能。物种越多 → 冗余越多 → 干扰后越稳定。
Mixed Practice综合练习

Practice Quiz综合测验

A savanna ecosystem fixes 200,000 kJ/m²/yr. Approximately how much energy is available to a tertiary consumer (4th trophic level)?一个稀树草原生态系统每年每平方米固定 200,000 kJ。三级消费者（第四营养级）约可获得多少能量？
Q1
2,000 kJ2,000 kJ
200 kJ200 kJ
20 kJ20 kJ
2 kJ2 kJ
Three 10% steps from producers to 4th trophic level: 200,000 × 0.1 = 20,000 (primary consumers); × 0.1 = 2,000 (secondary); × 0.1 = 200 kJ (tertiary). Wait — the 4th trophic level is three steps from producers: 200,000 × 0.001 = 200 kJ.从生产者到第四营养级三个 10% 步骤：200,000 × 0.1 = 20,000（初级消费者）；× 0.1 = 2,000（次级）；× 0.1 = 200 kJ（三级）。
Three 10% steps: 200,000 → 20,000 → 2,000 → 200 kJ. The 4th trophic level is 3 steps above the producers (not 2, not 4).三个 10% 步骤：200,000 → 20,000 → 2,000 → 200 kJ。第四营养级在生产者上方 3 步（不是 2 步，也不是 4 步）。
In the logistic growth equation $\tfrac{dN}{dt} = rN(1 - N/K)$, what happens when $N$ equals $K$?在逻辑斯蒂增长方程 $\tfrac{dN}{dt} = rN(1 - N/K)$ 中，当 $N = K$ 时会发生什么？
Q2
$\tfrac{dN}{dt} = 0$; population growth stops$\tfrac{dN}{dt} = 0$；种群增长停止
$\tfrac{dN}{dt}$ is at its maximum$\tfrac{dN}{dt}$ 达到最大值
$\tfrac{dN}{dt}$ becomes negative; the population declines to zero$\tfrac{dN}{dt}$ 变为负数；种群下降至零
$\tfrac{dN}{dt} = rN$; exponential growth begins$\tfrac{dN}{dt} = rN$；指数增长开始
When $N = K$, the factor $(1 - N/K) = (1 - K/K) = 0$, so $\tfrac{dN}{dt} = rN \times 0 = 0$. The population is at carrying capacity and net growth is zero. Maximum growth is at $N = K/2$.当 $N = K$ 时，因子 $(1 - N/K) = (1 - K/K) = 0$，故 $\tfrac{dN}{dt} = rN \times 0 = 0$。种群处于环境容纳量，净增长为零。最大增长发生在 $N = K/2$ 时。
At $N = K$: $(1-N/K) = 0$, so growth rate = 0. Maximum growth is at $N = K/2$ (inflection point). Population does not go negative in basic logistic model unless N > K.当 $N = K$ 时：$(1-N/K) = 0$，增长率 = 0。最大增长在 $N = K/2$（拐点）。在基本逻辑斯蒂模型中，除非 N > K，否则种群不会变为负数。
Which of the following is an example of a density-independent limiting factor?以下哪项是非密度制约限制因素的例子？
Q3
An outbreak of disease that kills more individuals as the population grows denser随种群密度增大而杀死更多个体的疾病暴发
Increased competition for food as more rabbits share the same territory更多兔子共享同一领地时食物竞争加剧
Predators killing a higher percentage of prey when prey is more abundant猎物更丰富时捕食者杀死更高比例的猎物
A severe hurricane that destroys nesting habitats regardless of population size无论种群规模如何都摧毁筑巢栖息地的严重飓风
Density-independent factors affect the same proportion of individuals regardless of population density. A hurricane destroys habitat equally whether the population is 10 or 10,000. Disease, competition, and predation all intensify with density — they are density-dependent.非密度制约因素对个体的影响比例与种群密度无关。无论种群是 10 还是 10,000，飓风同等地摧毁栖息地。疾病、竞争和捕食都随密度加剧——它们是密度制约因素。
Density-independent = same impact regardless of N. Physical disturbances (storms, floods, fire) are classic density-independent factors. Disease, food competition, and predation all intensify with density.非密度制约 = 无论 N 大小影响相同。物理干扰（风暴、洪水、火灾）是经典的非密度制约因素。疾病、食物竞争和捕食都随密度加剧。
The Amazon rainforest undergoes deforestation. Ecologists observe that species richness drops sharply and the remaining ecosystem is far less able to recover from drought. This illustrates which principle?亚马逊雨林遭受砍伐。生态学家观察到物种丰富度急剧下降，剩余生态系统从干旱中恢复的能力大大减弱。这说明了哪项原则？
Q4
Competitive exclusion reduces ecosystem productivity竞争排斥降低生态系统生产力
High biodiversity provides functional redundancy that supports ecosystem resilience高生物多样性提供支持生态系统韧性的功能冗余
Primary succession is triggered by deforestation砍伐森林触发初级演替
The 10% rule limits recovery to primary consumers only10% 规律将恢复限制为仅初级消费者
When biodiversity is reduced, functional redundancy is lost — fewer species perform each ecological role. This makes the ecosystem fragile: a single drought can collapse the system when no redundant species can fill in for the lost ones. This is the ecological argument for biodiversity conservation (NGSS HS-LS2-6, HS-LS2-7).当生物多样性减少时，功能冗余丧失——执行每种生态角色的物种减少。这使生态系统变得脆弱：当没有冗余物种可以填补失去的物种时，单次干旱就可能使系统崩溃。这是生物多样性保护的生态论点（NGSS HS-LS2-6，HS-LS2-7）。
Biodiversity supports resilience through functional redundancy. Deforestation = secondary succession (not primary, since soil remains). The 10% rule applies to energy transfer, not recovery. Competitive exclusion is about interspecific competition.生物多样性通过功能冗余支持韧性。砍伐 = 次级演替（土壤保留，非初级）。10% 规律适用于能量传递，而非恢复。竞争排斥是关于种间竞争的。
Which biogeochemical cycle has NO significant gaseous phase and thus cycles primarily through rock weathering and sediment deposition?哪种生物地球化学循环没有显著的气态阶段，因此主要通过岩石风化和沉积物沉积循环？
Q5
Carbon cycle碳循环
Nitrogen cycle氮循环
Phosphorus cycle磷循环
Water cycle水循环
Phosphorus has no gaseous phase — it moves from rock (via weathering) → soil → organisms → decomposers → sediment. This makes it a frequent limiting nutrient in freshwater ecosystems (AB 20–A2.1k explicitly lists phosphorus in the biogeochemical cycling requirement). Carbon cycles via CO₂; nitrogen cycles via N₂; water cycles via water vapor.磷没有气态阶段——它从岩石（通过风化）→土壤→生物→分解者→沉积物移动。这使其成为淡水生态系统中常见的限制营养素（AB 20–A2.1k 明确列出磷在生物地球化学循环要求中）。碳通过 CO₂ 循环；氮通过 N₂ 循环；水通过水蒸气循环。
Phosphorus is the cycle without a gaseous reservoir. Carbon has CO₂ (atmosphere + dissolved); nitrogen has N₂ (78% of atmosphere); water has water vapor. Phosphorus is released only by rock weathering — this is why it can be a long-term limiting nutrient.磷是没有气态储库的循环。碳有 CO₂（大气 + 溶解）；氮有 N₂（大气的 78%）；水有水蒸气。磷只通过岩石风化释放——这就是为什么它可能是长期限制营养素。
Self-check自查

Readiness Checklist准备就绪清单

Tick each item when you can do it cold, without notes, on a first attempt.能在无笔记、首次尝试下完成，再勾选每一项。

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Next Steps后续衔接

What This Feeds Into本单元的去向

Ecology and Ecosystems is one of the most cross-connected units in the HS Biology sequence. The energy-flow framework from §2 builds directly on cellular respiration and photosynthesis (Unit 3). The population dynamics in §4 feed directly into Population Biology (Unit 12), where quantitative models extend to sinusoidal cycles (SBI4U F2.2) and Hardy-Weinberg equilibrium (Biology 30 D1). The biodiversity and human-impact content in §7 echoes themes from Biodiversity and Classification (Unit 8) and prepares students for Evolution and Natural Selection (Unit 7).生态学与生态系统是 HS Biology 序列中联系最广泛的单元之一。§2 的能量流动框架直接建立在细胞呼吸和光合作用（第 3 单元）之上。§4 的种群动态直接衔接种群生物学（第 12 单元），其中定量模型延伸至正弦周期（SBI4U F2.2）和 Hardy-Weinberg 平衡（Biology 30 D1）。§7 的生物多样性和人类影响内容呼应了生物多样性与分类（第 8 单元）的主题，并为进化与自然选择（第 7 单元）做好准备。

Feeds into AP Biology and IB Biology.衔接 AP Biology 与 IB Biology。

The energy-flow, nutrient-cycle, and population-dynamics content here maps directly to AP Biology Unit 8 (Ecology) and IB Biology HL Topic C (Ecology). AP Biology adds the quantitative logistic growth treatment and species interaction graphs (Lotka-Volterra). IB Biology HL extends biogeochemical cycles to include detailed nutrient-limitation effects on primary productivity and a deeper treatment of island biogeography and minimum viable population size.本指南的能量流动、营养循环和种群动态内容直接映射到 AP Biology 第 8 单元（生态学）和 IB Biology HL Topic C（生态学）。AP Biology 增加了定量逻辑斯蒂增长处理和物种互作图（Lotka-Volterra）。IB Biology HL 将生物地球化学循环扩展到包括营养限制对初级生产力的详细影响，以及对岛屿生物地理学和最小可存活种群规模的更深处理。

DINGRUI SCHOLARS

High School Biology · Ecology and Ecosystems · v1高中生物 · 生态学与生态系统 · v1