High School Biology
Biodiversity and Classification生物多样性与分类
Life on Earth spans an estimated 8.7 million species. To make sense of this diversity, biologists classify organisms using a shared system: the taxonomic hierarchy from domain down to species, binomial nomenclature for universal naming, the three-domain tree of life, the kingdoms and their unifying characteristics, phylogenetic trees and cladograms to map evolutionary relationships, and dichotomous keys to identify unknown organisms. Ontario SBI3U Strand B is the most comprehensive treatment; BC Life Sciences 11 is nearly as strong; Alberta Biology 20 Unit B covers taxonomy and nomenclature explicitly; NGSS has no dedicated taxonomy PE and instead frames biodiversity through speciation, extinction, and human impact.地球上估计有 870 万种生物。为了理解这一多样性（生物多样性，生物多样性），生物学家采用统一的分类（分类，分类）系统：从域到物种的分类层级（分类学，分类学）、用于通用命名的双名法（双名法，双名法）、生命的三域树（域，域）、各界（界，界）及其统一特征、用于绘制进化关系的系统发育树（系统发育树，系统发育树）与分支图（分支图，分支图），以及用于鉴定未知生物的二歧检索表（二歧检索表，二歧检索表）。安大略 SBI3U B 单元最为全面；BC Life Sciences 11 内容几乎同样丰富；阿尔伯塔 Biology 20 Unit B 明确涵盖分类与命名；NGSS 无专门的分类学表现期望，而是从物种形成、灭绝与人类影响的角度看待生物多样性。
Read me first先读这里
How to use this guide如何使用本指南
Biodiversity and Classification is the unit where the four curricula diverge most sharply. Ontario SBI3U Strand B is the primary source: it expects binomial nomenclature, taxonomic hierarchy, phylogeny, kingdom characteristics, and dichotomous keys as required content. BC Life Sciences 11 Big Idea 3 is nearly identical in scope. Alberta Biology 20 Unit B GO1 explicitly requires taxonomy and binomial nomenclature at the kingdom and genus-species levels. NGSS, by contrast, has no dedicated taxonomy PE: its HS-LS4-5 and HS-LS2-7 address biodiversity through speciation, extinction, and human impact — not classification systems. If you are in a US NGSS school, use this guide for background richness but do not expect classification questions on your standardized assessments. The syllabus-note below the table makes this explicit.生物多样性与分类是四套大纲分歧最大的单元。安大略 SBI3U B 单元是主要来源：它要求双名法、分类层级、系统发育学、界的特征和二歧检索表作为必修内容。BC Life Sciences 11 大概念 3 的范围几乎相同。阿尔伯塔 Biology 20 Unit B GO1 明确要求在界级和属种级掌握分类学和双名法。相比之下，NGSS 没有专门的分类学 PE：其 HS-LS4-5 和 HS-LS2-7 从物种形成、灭绝和人类影响的角度处理生物多样性，而非分类系统。如果你在美国 NGSS 学校，可将本指南用于背景拓展，但不要期望标准化评估中出现分类题。下表后的大纲说明对此有明确标注。
NGSS divergence.NGSS 分歧。
NGSS has no PE for the taxonomic hierarchy, binomial nomenclature, kingdom characteristics, or dichotomous keys. The biodiversity-adjacent PEs (HS-LS4-5, HS-LS2-7) focus on speciation, extinction, and human impact on biodiversity — not on Linnaean classification. Ontario SBI3U B3.1–B3.3, BC Life Sciences 11 Big Idea 3, and Alberta Biology 20 `20–B1.5k` all have explicit classification content. US students will encounter some of this in AP Biology (Big Idea 1) but not in standard NGSS assessments.NGSS 没有关于分类层级、双名法、界的特征或二歧检索表的表现期望（PE）。与生物多样性相关的 PE（HS-LS4-5、HS-LS2-7）聚焦于物种形成、灭绝和人类对生物多样性的影响，而非林奈分类法。安大略 SBI3U B3.1–B3.3、BC Life Sciences 11 大概念 3 和阿尔伯塔 Biology 20 `20–B1.5k` 均有明确的分类内容。美国学生会在 AP Biology（大概念 1）中接触部分内容，但不会出现在标准 NGSS 评估中。
| 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 | §1 (why biodiversity matters — HS-LS4-5 framing); §6 (phylogenetic trees connect to HS-LS4-1 common ancestry evidence)§1（为何生物多样性重要 — HS-LS4-5 框架）；§6（系统发育树与 HS-LS4-1 共同祖先证据关联） | §2–§5, §7: NGSS has no PE for Linnaean taxonomy, kingdom classifications, binomial nomenclature, or dichotomous keys — read for AP Biology preparation or general literacy§2–§5、§7：NGSS 无林奈分类法、界分类、双名法或二歧检索表的 PE — 可为 AP Biology 或通识学习阅读 | NGSS HS Life Science — HS-LS4-5, HS-LS2-7; no taxonomy PE confirmed— HS-LS4-5、HS-LS2-7；无分类学 PE 已确认 |
| 🇨🇦 ON Grade 11 — SBI3U安大略 11 年级 — SBI3U | All 7 sections. SBI3U Strand B is the most complete taxonomy strand of the four curricula: B3.1 (taxonomy + phylogeny), B3.3 (kingdom characteristics), B2.4 (dichotomous keys), B2.1 (binomial nomenclature terminology), B3.5 (biodiversity and ecosystem viability)全部 7 节。SBI3U B 单元是四套大纲中最完整的分类学单元：B3.1（分类学 + 系统发育学）、B3.3（界的特征）、B2.4（二歧检索表）、B2.1（双名法术语）、B3.5（生物多样性与生态系统可存续性） | Nothing — this entire guide maps to SBI3U Strand B无 — 本整份指南对应 SBI3U B 单元 | Ontario SBI3U/4U Biology — SBI3U Strand B B2.1–B3.5— SBI3U B 单元 B2.1–B3.5 |
| 🇨🇦 BC Life Sciences 11BC Life Sciences 11 | All 7 sections. Big Idea 3 ("Organisms are grouped based on common characteristics") anchors the entire unit. Content bullets explicitly name kingdom, phylum, class, order, family, genus, species; phylogenetic tree (cladogram); dichotomous key; binomial nomenclature; domains and kingdoms全部 7 节。大概念 3（"生物体根据共同特征分组"）是整个单元的支柱。内容条目明确列出界、门、纲、目、科、属、物种；系统发育树（分支图）；二歧检索表；双名法；域与界 | Nothing — BC Life Sciences 11 covers all sections无 — BC Life Sciences 11 涵盖所有节 | BC Life Sciences 11 / Anatomy 12 — Life Sciences 11 Big Idea 3 + Content— Life Sciences 11 大概念 3 + 内容 |
| 🇨🇦 AB Biology 20阿尔伯塔 Biology 20 | §1 (species concept, `20–B1.1k`), §2–§3 (taxonomy + binomial nomenclature, `20–B1.5k`), §5 (kingdom-level nutrition modes, `20–B1.5k`)§1（物种概念，`20–B1.1k`）、§2–§3（分类学 + 双名法，`20–B1.5k`）、§5（界级营养方式，`20–B1.5k`） | §6–§7 (phylogenetic trees and dichotomous keys are not explicitly required by Alberta `20–B1.x` codes, though they support the taxonomy content)§6–§7（阿尔伯塔 `20–B1.x` 代码未明确要求系统发育树和二歧检索表，但有助于支撑分类学内容） | Alberta Biology 20/30 — Biology 20 Unit B GO1 `20–B1.1k`, `20–B1.5k`— Biology 20 Unit B GO1 `20–B1.1k`、`20–B1.5k` |
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。
If you are cramming the night before如果你在临阵磨枪
Know the taxonomic levels in order (Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species); the binomial naming rules (genus capitalized, species lowercase, both italicized); the three domains (Bacteria, Archaea, Eukarya); and the six kingdoms. Read every cram-cheat box. Skip the going-deeper sections on cladogram construction details.按顺序掌握分类层级（域 → 界 → 门 → 纲 → 目 → 科 → 属 → 物种）；双名命名规则（属名首字母大写，种名小写，两者均斜体）；三个域（细菌、古菌、真核生物）；以及六界。阅读每个速记框，跳过分支图构建细节的深入内容。
If you are going for the top mark如果你目标顶分
Be precise about why domains replaced kingdoms at the top level (rRNA evidence; Archaea more similar to Eukarya than to Bacteria). Know the unifying characteristics of each kingdom including their mode of nutrition. Explain how a cladogram shows shared derived characters (synapomorphies) rather than overall similarity. Be able to construct a simple dichotomous key from a set of organisms using one binary question per step. For SBI3U, link classification to biodiversity conservation: why losing a species is losing unique evolutionary history.精准掌握域为何取代界成为最高分类级别（rRNA 证据；古菌与真核生物比与细菌更相似）。了解每个界的统一特征，包括其营养方式。解释分支图如何展示共同衍征（共近裔性状）而非整体相似性。能够使用每步一个二元问题为一组生物构建简单的二歧检索表。SBI3U 学生还需将分类与生物多样性保护相联系：失去一个物种意味着失去独特的进化历史。
Section 1 · Why classify? Biodiversity第 1 节 · 为何分类？生物多样性
Why Classify? The Scope of Biodiversity为何分类？生物多样性的范畴
Three types of biodiversity — and why classification makes sense of all three.三种类型的生物多样性 — 以及分类学如何使三者都有意义。
- Genetic diversity:遗传多样性： variation in alleles and genotypes within a species. Higher genetic diversity means greater resilience to disease and environmental change.物种内等位基因和基因型的变异。遗传多样性越高，对疾病和环境变化的抵御能力越强。
- Species diversity:物种多样性： the variety of distinct species in an area. Estimated 8.7 million eukaryotic species on Earth; only ~1.5 million have been formally named. A species is a group of organisms that can interbreed and produce fertile offspring.某区域内不同物种的多样性。地球上估计有 870 万种真核生物；目前仅约 150 万种已被正式命名。物种是能够相互交配并产生可育后代的一组生物。
- Structural (ecosystem) diversity:结构（生态系统）多样性： variation in habitats, ecosystems, and ecological processes across a region. Tropical rainforests contain far more species than Arctic tundra.某区域内栖息地、生态系统和生态过程的变异。热带雨林包含的物种数量远多于北极冻原。
Why classify at all?为何要分类？ Without a shared naming system, the same organism has hundreds of local names in different languages and regions. Classification gives every species a unique, universal scientific name and groups related organisms so that discoveries about one can predict properties of its relatives. Ontario SBI3U B3.5 frames this directly: biodiversity classification is essential "to maintaining viable ecosystems" because it tracks what we have, what we are losing, and what is related to what.没有共享的命名系统，同一种生物在不同语言和地区有数百个地方名。分类学（分类学）为每个物种提供唯一的、通用的科学名称，并将相关生物归组，使关于某种生物的发现能预测其近亲的特性。安大略 SBI3U B3.5 直接说明了这一点：生物多样性分类对于"维持可存续生态系统"至关重要，因为它追踪了我们拥有什么、正在失去什么以及什么与什么相关。
Worked Example 1 · Identifying types of biodiversity例题 1 · 识别生物多样性类型
A tropical coral reef contains 500 species of fish, 200 species of coral, and 1,000 species of invertebrates. A nearby degraded reef contains 50 species of fish, 10 species of coral, and 100 species of invertebrates. A conservation report also notes that the remaining fish on the degraded reef show 40% less genetic variation than the fish on the healthy reef. Identify which types of biodiversity have been reduced.一处热带珊瑚礁含有 500 种鱼、200 种珊瑚和 1,000 种无脊椎动物。附近一处退化珊瑚礁含有 50 种鱼、10 种珊瑚和 100 种无脊椎动物。保育报告还指出，退化珊瑚礁上剩余鱼类的遗传变异比健康珊瑚礁鱼类少 40%。请识别哪些类型的生物多样性已减少。
Species diversity reduced:物种多样性减少： the degraded reef has approximately 10% of the species count across all groups.退化珊瑚礁各类群的物种数量约为原来的 10%。
Genetic diversity reduced:遗传多样性减少： the 40% reduction in genetic variation within the remaining fish population. Smaller, isolated populations lose alleles through genetic drift.剩余鱼类种群内遗传变异减少 40%。较小的孤立种群通过遗传漂变丢失等位基因。
Structural diversity also reduced:结构多样性也减少： fewer coral species means fewer habitat niches (branching corals vs massive corals provide different shelter structures), reducing the ecosystem's structural complexity.珊瑚物种减少意味着栖息地生态位减少（枝状珊瑚与块状珊瑚提供不同的庇护结构），降低了生态系统的结构复杂性。
The biological species concept defines a species as a group of organisms that…生物物种概念将物种定义为一组能够…的生物体
§1 · Q1
The biological species concept (Mayr, 1942) defines a species as organisms that can interbreed naturally and produce fertile offspring. Geographic isolation is not sufficient; two isolated populations of the same species can still interbreed if brought together.生物物种概念（迈尔，1942 年）将物种定义为能够自然交配并产生可育后代的生物。地理隔离不足以作为标准；同一物种的两个隔离种群若相遇仍可交配。
The biological species concept requires successful interbreeding and fertile offspring. DNA percentage thresholds and geography are not the definition, though they can be evidence.生物物种概念要求成功交配并产生可育后代。DNA 百分比阈值和地理位置不是定义，尽管它们可以作为证据。
A forest ecosystem contains 200 tree species but nearly all individual trees belong to just 3 dominant species. Which type of biodiversity is high, and which is low?一片森林生态系统含有 200 种树木，但几乎所有个体树木都属于仅 3 个优势物种。哪种生物多样性高，哪种低？
§1 · Q2
Species richness counts the number of different species (200 = high). Species evenness measures how evenly individuals are distributed among species (3 species dominate = low evenness). True species diversity combines both components.物种丰富度计算不同物种的数量（200 = 高）。物种均匀度衡量个体在物种间的分布均匀程度（3 个物种占主导 = 低均匀度）。真正的物种多样性同时包含这两个组成部分。
200 species present means high richness. But 3 dominant species means individuals are unevenly distributed — low evenness. Both matter for true species diversity.存在 200 种意味着丰富度高。但 3 个优势物种意味着个体分布不均匀——均匀度低。两者对真正的物种多样性都很重要。
Section 2 · The taxonomic hierarchy第 2 节 · 分类层级
The Taxonomic Hierarchy: Domain to Species分类层级：从域到物种
Eight levels, broadest to most specific — every biology exam has at least one.八个层级，从最宽泛到最具体 — 每次生物考试至少考一题。
- Domain域 — broadest; three domains: Bacteria, Archaea, Eukarya.— 最宽泛；三个域：细菌、古菌、真核生物。
- Kingdom界 — e.g. Animalia, Plantae, Fungi, Protista, Eubacteria, Archaebacteria.— 如动物界、植物界、真菌界、原生生物界、真细菌界、古细菌界。
- Phylum门 — e.g. Chordata (animals with a notochord at some stage).— 如脊索动物门（某阶段具脊索的动物）。
- Class纲 — e.g. Mammalia (endothermic, hair, nurse young).— 如哺乳纲（内温、有毛、哺育后代）。
- Order目 — e.g. Carnivora (flesh-eating mammals with specialized teeth).— 如食肉目（具特化牙齿的肉食性哺乳动物）。
- Family科 — e.g. Felidae (cats: retractile claws, specialized carnassials).— 如猫科（猫：可伸缩爪、特化裂齿）。
- Genus属 — e.g. Panthera (roaring big cats: lion, tiger, leopard, jaguar).— 如豹属（能咆哮的大型猫科动物：狮、虎、豹、美洲豹）。
- Species物种 — e.g. Panthera leo (lion). Most specific; members can interbreed and produce fertile offspring.— 如Panthera leo（狮子）。最具体；成员可相互交配并产生可育后代。
Memory trick:记忆技巧： "Dear King Philip Came Over For Good Soup" — Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species."域界门纲目科属种" — 共八级，从宽到窄。
Human classification — a complete worked example人类的分类 — 完整例题
| Rank分类层级 | Name名称 | Key shared feature关键共同特征 |
|---|---|---|
| Domain域 | Eukarya | Membrane-bound nucleus具膜性细胞核 |
| Kingdom界 | Animalia | Multicellular, heterotrophic, no cell wall多细胞、异养、无细胞壁 |
| Phylum门 | Chordata | Notochord, dorsal nerve cord, pharyngeal slits脊索、背神经管、咽裂 |
| Class纲 | Mammalia | Hair, endothermic, mammary glands, diaphragm毛发、内温、乳腺、横膈膜 |
| Order目 | Primates | Forward-facing eyes, grasping hands, large brain前向眼、抓握手、大脑 |
| Family科 | Hominidae | Great apes: bipedal tendency, no tail, large brain大猿：倾向双足行走、无尾、大脑 |
| Genus属 | Homo | Fully upright, language, tool use, large cranium完全直立、语言、工具使用、大颅腔 |
| Species物种 | Homo sapiens | Modern humans; can interbreed with each other现代人类；相互之间可交配 |
Two organisms belong to the same Order but different Families. Which of the following is true?两种生物属于同一目但不同科。下列哪项正确？
§2 · Q1
The hierarchy is nested: same Order means they already share Domain, Kingdom, Phylum, Class, and Order. Different Families means they diverge at the Family level (and all ranks below: Genus, Species). They cannot be in the same Genus if they are in different Families.分类层级是嵌套的：同一目意味着它们已共享域、界、门、纲和目。不同科意味着它们在科级（及以下所有级别：属、物种）分歧。如果它们在不同的科，就不可能属于同一属。
Sharing the same Order means they share all ranks above Order too: Domain, Kingdom, Phylum, Class. They differ only from Family downward.共享同一目意味着它们也共享目以上的所有级别：域、界、门、纲。它们只在科及以下级别存在差异。
Which pair of organisms is most closely related?哪对生物亲缘关系最近？
§2 · Q2
The lower the rank, the more specific the shared characteristics, and the more recently two organisms diverged from a common ancestor. Genus is the second-most specific rank (just above Species), so organisms sharing a genus are more closely related than those sharing only a Class, Phylum, or Kingdom.级别越低，共同特征越具体，两种生物从共同祖先分歧的时间越近。属是第二具体的级别（仅次于物种），因此共享同一属的生物比仅共享纲、门或界的生物亲缘关系更近。
Closer relationship = lower (more specific) shared rank. Genus is lower than Class, Phylum, or Kingdom, so same-Genus organisms are most closely related.亲缘关系越近 = 共享的级别越低（越具体）。属低于纲、门或界，因此同属生物亲缘关系最近。
Section 3 · Binomial nomenclature第 3 节 · 双名法
Binomial Nomenclature: The Universal Naming System双名法：通用命名系统
Linnaeus (1758) gave every known species a two-part Latin name — and the rules are strict.林奈（1758 年）给每个已知物种一个两部分的拉丁名称 — 规则严格。
- Format:格式： Genus species — two words only. Genus is capitalized; species epithet is lowercase. Both are italicized in print; underlined when handwritten.属名 种名 — 仅两个词。属名首字母大写；种名小写。印刷时均用斜体；手写时加下划线。
- Examples:例子：
- Homo sapiens — modern human (genus Homo, species epithet sapiens = "wise")Homo sapiens — 现代人类（属 Homo，种名 sapiens = "智慧的"）
- Panthera leo — lion; Panthera tigris — tiger (same genus, different species)Panthera leo — 狮子；Panthera tigris — 老虎（同属，不同物种）
- Acer saccharum — sugar maple; Acer rubrum — red mapleAcer saccharum — 糖枫；Acer rubrum — 红枫
- Why Latin / Greek?为何用拉丁语 / 希腊语？ Latin was the international language of science in the 18th century and is now a dead language — it cannot change meaning over time, making names stable across all living languages. The same species has hundreds of common names in different languages; its scientific name is universal.拉丁语是 18 世纪国际科学语言，现为死语言——随时间推移含义不会改变，使名称在所有现存语言中保持稳定。同一物种在不同语言中有数百个俗名；其科学名称是通用的。
- Abbreviated form:缩写形式： after first mention, the genus can be abbreviated: H. sapiens, P. leo. Never abbreviate the species epithet.首次提及后，属名可缩写：H. sapiens、P. leo。种名永不缩写。
Worked Example 2 · Applying binomial nomenclature rules例题 2 · 应用双名法规则
A student writes the name of the domestic dog as "canis lupus familiaris". Identify two errors in formatting and rewrite the name correctly.一名学生将家犬的名称写为"canis lupus familiaris"。找出两个格式错误，并正确改写名称。
Error 1:错误 1： The genus name (Canis) must be capitalized. It is written in lowercase as "canis."属名（Canis）必须首字母大写。被写成小写的"canis"。
Error 2:错误 2： The entire name must be italicized (or underlined if handwritten). The name is written in plain text.整个名称必须用斜体（手写时加下划线）。该名称以普通字体书写。
Corrected form:正确形式： Canis lupus familiaris (the domestic dog is a subspecies of the gray wolf Canis lupus; three-part names indicate subspecies).Canis lupus familiaris（家犬是灰狼 Canis lupus 的亚种；三部分名称表示亚种）。
Which of the following is written correctly according to binomial nomenclature rules?下列哪项符合双名法规则？
§3 · Q1
Homo sapiens is correct: genus capitalized (Homo), species lowercase (sapiens), both italicized. Option A has genus lowercase; option B has both capitalized but not italicized; option D has neither capitalized nor italicized.Homo sapiens 正确：属名首字母大写（Homo），种名小写（sapiens），两者均斜体。选项 A 属名小写；选项 B 两者大写但无斜体；选项 D 既无大写也无斜体。
Rules: Genus capitalized + species lowercase + both italicized. Only option C follows all three rules.规则：属名首字母大写 + 种名小写 + 两者均斜体。只有选项 C 遵守全部三条规则。
Panthera leo (lion) and Panthera tigris (tiger) share the same genus. What does this tell us?Panthera leo（狮子）和 Panthera tigris（老虎）属于同一属。这说明了什么？
§3 · Q2
Sharing a genus means sharing all higher ranks (Domain, Kingdom, Phylum, Class, Order, Family) and diverging only at the species level. They are more closely related to each other than to, say, a house cat (Felis catus, different genus). They cannot interbreed to produce fertile offspring — they are different species.共享同一属意味着共享所有更高级别（域、界、门、纲、目、科），仅在物种层面分歧。它们彼此之间的亲缘关系比与（例如）家猫（Felis catus，不同属）更近。它们不能交配产生可育后代——它们是不同物种。
Same genus → same Family, Order, Class, Phylum, Kingdom, Domain. Same genus does NOT mean they can interbreed (different species) or are identical in structure.同属 → 同科、目、纲、门、界、域。同属并不意味着可以交配（不同物种）或结构完全相同。
Section 4 · The three domains第 4 节 · 三个域
The Three Domains: Bacteria, Archaea, Eukarya三个域：细菌、古菌、真核生物
Woese and Fox (1977) proposed three domains based on ribosomal RNA (rRNA) sequences.沃斯和福克斯（1977 年）基于核糖体 RNA（rRNA）序列提出三域说。
- Domain Bacteria:细菌域： prokaryotic (no membrane-bound nucleus); peptidoglycan cell walls; most are unicellular; includes most familiar bacteria (E. coli, Streptococcus, cyanobacteria). rRNA distinct from Archaea.原核（无膜性细胞核）；肽聚糖细胞壁；多数单细胞；包括大多数常见细菌（E. coli、链球菌、蓝藻）。rRNA 与古菌不同。
- Domain Archaea:古菌域： prokaryotic; NO peptidoglycan in cell walls (different lipid chemistry); often found in extreme environments (thermophiles, halophiles, methanogens); rRNA sequences are more similar to Eukarya than to Bacteria — this is why Archaea were separated from Bacteria.原核；细胞壁中无肽聚糖（不同的脂质化学）；常见于极端环境（嗜热菌、嗜盐菌、产甲烷菌）；rRNA 序列与真核生物比与细菌更相似 — 这就是古菌从细菌中分离出来的原因。
- Domain Eukarya:真核生物域： eukaryotic (membrane-bound nucleus, membrane-bound organelles); includes Kingdoms Protista, Fungi, Plantae, and Animalia. All multicellular complex life belongs here.真核（具膜性细胞核、膜性细胞器）；包括原生生物界、真菌界、植物界和动物界。所有多细胞复杂生命都属于此域。
Why three domains replaced two kingdoms at the top?为何三域取代了顶层的两界？ The old system had only two kingdoms for prokaryotes (Monera). rRNA sequencing revealed that Archaea differ from Bacteria as much as either does from Eukarya — so a higher-level division was needed.旧系统对原核生物只有两界（原核界）。rRNA 测序揭示古菌与细菌的差异程度与两者和真核生物的差异相当 — 因此需要更高层次的划分。
Bacteria vs Archaea vs Eukarya — key comparisons细菌 vs 古菌 vs 真核生物 — 关键比较
| Feature特征 | Bacteria细菌 | Archaea古菌 | Eukarya真核生物 |
|---|---|---|---|
| Nucleus细胞核 | No无 | No无 | Yes有 |
| Cell wall细胞壁 | Peptidoglycan肽聚糖 | No peptidoglycan无肽聚糖 | Varies (cellulose/chitin/none)因种而异（纤维素/几丁质/无） |
| Membrane lipids膜脂 | Ester-linked酯键连接 | Ether-linked (unique)醚键连接（独特） | Ester-linked酯键连接 |
| rRNA similarityrRNA 相似性 | Distinct独特 | Closer to Eukarya更接近真核生物 | Closer to Archaea than to Bacteria比细菌更接近古菌 |
| Extremophiles?极端嗜好生物？ | Some部分 | Many (defining feature)许多（定义性特征） | Rare罕见 |
Why were Archaea separated from Bacteria into their own domain?为什么古菌被从细菌中分离出来成为独立的域？
§4 · Q1
Woese and Fox used rRNA sequence comparisons and found that Archaea are as genetically distant from Bacteria as from Eukarya. Both Bacteria and Archaea are prokaryotic (no nucleus), but their biochemistry (membrane lipids, cell wall composition, RNA polymerases) is fundamentally different, justifying a separate domain.沃斯和福克斯使用 rRNA 序列比较，发现古菌与细菌的遗传距离与和真核生物的距离相当。细菌和古菌都是原核生物（无细胞核），但其生化特性（膜脂、细胞壁成分、RNA 聚合酶）从根本上不同，这证明了独立域的合理性。
Archaea are prokaryotic like Bacteria (no nucleus, no membrane-bound organelles). The key evidence for the three-domain split is rRNA sequence data showing the Bacteria-Archaea split is as deep as either group's split from Eukarya.古菌像细菌一样是原核生物（无细胞核，无膜性细胞器）。三域分类的关键证据是 rRNA 序列数据，显示细菌-古菌分歧与任一类群和真核生物的分歧一样深。
Methane-producing microbes found in the guts of cows have no membrane-bound nucleus, but their cell walls lack peptidoglycan. Which domain do they belong to?在牛肠道中发现的产甲烷微生物无膜性细胞核，但其细胞壁缺乏肽聚糖。它们属于哪个域？
§4 · Q2
No membrane-bound nucleus = prokaryote (rules out Eukarya). No peptidoglycan cell wall = Archaea, not Bacteria (Bacteria have peptidoglycan). Methanogens are a classic Archaea example, living as extremophiles in anaerobic guts.无膜性细胞核 = 原核生物（排除真核生物）。无肽聚糖细胞壁 = 古菌，而非细菌（细菌有肽聚糖）。产甲烷菌是古菌的经典例子，作为极端嗜好生物生活在无氧肠道中。
No nucleus rules out Eukarya. No peptidoglycan rules out Bacteria. Both features together point to Archaea. Protista is a Kingdom within Eukarya, not a domain.无细胞核排除真核生物。无肽聚糖排除细菌。两个特征结合指向古菌。原生生物界是真核生物域内的一个界，而非域。
Section 5 · The kingdoms第 5 节 · 界
The Six Kingdoms: Unifying Characteristics六界：统一特征
Six kingdoms — know the key feature that unifies each one (SBI3U B3.3; BC Life Sciences 11 Content; AB Biology 20 `20–B1.5k`).六界 — 掌握统一每界的关键特征（SBI3U B3.3；BC Life Sciences 11 内容；AB Biology 20 `20–B1.5k`）。
- Eubacteria (Domain Bacteria):真细菌界（细菌域）： prokaryotic; peptidoglycan cell walls; diverse nutrition (autotrophic and heterotrophic); unicellular; e.g. E. coli, cyanobacteria, Lactobacillus.原核；肽聚糖细胞壁；多样化营养方式（自养和异养）；单细胞；例如 E. coli、蓝藻、乳酸杆菌。
- Archaebacteria (Domain Archaea):古细菌界（古菌域）： prokaryotic; no peptidoglycan; unusual membrane lipids (ether-linked); extremophiles (methanogens, thermophiles, halophiles); e.g. Methanobacterium, Thermus aquaticus.原核；无肽聚糖；特殊膜脂（醚键连接）；极端嗜好生物（产甲烷菌、嗜热菌、嗜盐菌）；例如 产甲烷菌属、水生栖热菌。
- Protista (Domain Eukarya):原生生物界（真核生物域）： eukaryotic; mostly unicellular; do NOT fit the other three eukaryote kingdoms; very diverse — includes algae, amoeba, Paramecium, Plasmodium (malaria). Mode of nutrition varies: autotrophic (algae), heterotrophic (amoeba), parasitic.真核；多数单细胞；不符合其他三个真核界的特征；非常多样 — 包括藻类、变形虫、草履虫、疟原虫（疟疾）。营养方式多样：自养（藻类）、异养（变形虫）、寄生。
- Fungi (Domain Eukarya):真菌界（真核生物域）： eukaryotic; cell walls of chitin (not cellulose); heterotrophic by absorption (secrete enzymes into substrate, absorb the digested nutrients); mostly multicellular (hyphae); e.g. mushrooms, moulds, yeasts.真核；几丁质细胞壁（非纤维素）；通过吸收进行异养（将酶分泌到基质中，吸收消化后的营养物质）；多数多细胞（菌丝体）；例如蘑菇、霉菌、酵母菌。
- Plantae (Domain Eukarya):植物界（真核生物域）： eukaryotic; cell walls of cellulose; autotrophic by photosynthesis; mostly multicellular; stationary; includes mosses, ferns, conifers, and flowering plants.真核；纤维素细胞壁；通过光合作用自养；多数多细胞；固着；包括苔藓、蕨类、针叶树和开花植物。
- Animalia (Domain Eukarya):动物界（真核生物域）： eukaryotic; no cell wall; heterotrophic by ingestion; multicellular; most are motile; includes invertebrates (insects, molluscs, worms) and vertebrates (fish, amphibians, reptiles, birds, mammals).真核；无细胞壁；通过摄食进行异养；多细胞；多数可移动；包括无脊椎动物（昆虫、软体动物、蠕虫）和脊椎动物（鱼、两栖类、爬行类、鸟类、哺乳类）。
Kingdom summary table — nutrition mode is the key column界汇总表 — 营养方式是关键列
| Kingdom界 | Cell type细胞类型 | Cell wall细胞壁 | Nutrition营养方式 | Example例子 |
|---|---|---|---|---|
| Eubacteria真细菌界 | Prokaryote原核 | Peptidoglycan肽聚糖 | Auto/Heterotrophic自养/异养 | E. coli |
| Archaebacteria古细菌界 | Prokaryote原核 | None / unique无/独特 | Auto/Heterotrophic自养/异养 | Methanobacterium |
| Protista原生生物界 | Eukaryote真核 | Varies因种而异 | Varies因种而异 | Amoeba |
| Fungi真菌界 | Eukaryote真核 | Chitin几丁质 | Absorption吸收 | Agaricus |
| Plantae植物界 | Eukaryote真核 | Cellulose纤维素 | Photosynthesis光合作用 | Quercus |
| Animalia动物界 | Eukaryote真核 | None无 | Ingestion摄食 | Homo sapiens |
A multicellular organism has eukaryotic cells, a cell wall made of chitin, and obtains nutrients by secreting enzymes into decaying material and absorbing the products. Which kingdom does it belong to?一种多细胞生物具有真核细胞，由几丁质构成的细胞壁，通过将酶分泌到腐烂物质中并吸收产物来获取营养。它属于哪个界？
§5 · Q1
Chitin cell wall + absorptive heterotrophy + eukaryotic = Fungi. Plantae have cellulose walls and photosynthesize; Animalia have no cell wall and ingest; Protista are mostly unicellular and varied.几丁质细胞壁 + 吸收性异养 + 真核 = 真菌界。植物界有纤维素细胞壁且进行光合作用；动物界无细胞壁且摄食；原生生物界多数单细胞且多样化。
The key identifiers for Fungi: chitin cell wall + absorptive nutrition (secreting enzymes externally, then absorbing products). No other kingdom combines all three features.真菌界的关键标识：几丁质细胞壁 + 吸收性营养（向外分泌酶，然后吸收产物）。没有其他界同时具备这三个特征。
Which feature distinguishes Fungi from Plantae?哪个特征区分真菌界与植物界？
§5 · Q2
Both Fungi and Plantae are eukaryotic and mostly multicellular. The key differences: cell wall composition (chitin in Fungi vs cellulose in Plantae) and mode of nutrition (absorptive heterotrophy in Fungi vs photosynthetic autotrophy in Plantae). Fungi do not photosynthesize.真菌界和植物界都是真核生物且多数是多细胞的。关键区别：细胞壁组成（真菌为几丁质，植物为纤维素）和营养方式（真菌为吸收性异养，植物为光合自养）。真菌不进行光合作用。
Both kingdoms are eukaryotic. Fungi are mostly multicellular. The real distinctions are chitin (Fungi) vs cellulose (Plantae) cell walls and absorption (Fungi) vs photosynthesis (Plantae) nutrition.两界都是真核生物。真菌多数是多细胞的。真正的区别在于几丁质（真菌）vs 纤维素（植物）细胞壁，以及吸收（真菌）vs 光合作用（植物）营养方式。
Section 6 · Phylogenetic trees and cladograms第 6 节 · 系统发育树与分支图
Phylogenetic Trees and Cladograms系统发育树与分支图
Phylogenetics — mapping evolutionary history (BC Life Sciences 11; SBI3U B3.4; NGSS HS-LS4-1 common ancestry).系统发育学 — 绘制进化历史（BC Life Sciences 11；SBI3U B3.4；NGSS HS-LS4-1 共同祖先）。
- Phylogenetic tree:系统发育树： a branching diagram showing inferred evolutionary relationships (ancestry and descent) among species or groups. Each branch point (node) represents a common ancestor.一种树状图，显示物种或类群之间推断的进化关系（祖先与后裔）。每个分支点（节点）代表一个共同祖先。
- Cladogram:分支图： a type of phylogenetic tree where branch lengths do not represent time or the amount of change; the topology (branching pattern) alone indicates relatedness. Groups are called clades: a clade contains an ancestor and ALL of its descendants.一种系统发育树，其中分支长度不代表时间或变化量；仅拓扑结构（分支模式）表示亲缘关系。类群称为分支（进化支）：一个分支包含一个祖先及其所有后代。
- Shared derived characters (synapomorphies):共同衍征（共近裔性状）： features that evolved in a common ancestor and were inherited by all members of a clade. Cladograms are built by identifying which taxa share derived characters. Example: all mammals share hair and mammary glands as derived characters.在共同祖先中进化形成并被该进化支所有成员继承的特征。分支图通过识别哪些分类单元共享衍征来构建。例如：所有哺乳动物共享毛发和乳腺作为衍征。
- Evidence used to build phylogenies:构建系统发育关系所用的证据：
- Morphology — structural similarities (homologous structures share evolutionary origin; analogous structures do not).形态学 — 结构相似性（同源结构共享进化起源；同功结构则不然）。
- Molecular data — rRNA and DNA sequences; the more similar the sequences, the more recently two taxa diverged. This is the strongest modern evidence.分子数据 — rRNA 和 DNA 序列；序列越相似，两个分类单元分歧的时间越近。这是现代最强有力的证据。
- Fossil record — provides dates for divergence events.化石记录 — 为分歧事件提供时间节点。
- Embryology — shared developmental stages suggest common ancestry.胚胎学 — 共同的发育阶段表明存在共同祖先。
Reading a cladogram: three key rules.读懂分支图：三条关键规则。
- Rule 1: Two taxa are more closely related if they share a more recent common ancestor (a node closer to the tips).规则 1：若两个分类单元共享更近的共同祖先（更靠近末梢的节点），则它们的亲缘关系更近。
- Rule 2: A clade includes the node (ancestor) and ALL branches descending from it. You cannot cherry-pick only some descendants.规则 2：一个进化支包括该节点（祖先）及其所有下行分支。不能只选择部分后代。
- Rule 3: The position of the root represents the most ancient ancestor. Organisms at the tips are all alive (or recently extinct); they are not ancestral to each other — they share ancestors at the nodes.规则 3：根的位置代表最古老的祖先。末梢处的生物都是现存的（或近期灭绝的）；它们彼此之间不存在祖先关系 — 它们在节点处共享祖先。
Worked Example 3 · Interpreting a cladogram例题 3 · 解读分支图
A cladogram shows four taxa: Lamprey, Shark, Salamander, and Human. The lamprey branches off first (closest to the root), then the shark branches off, then salamander and human share the most recent common ancestor. Which two taxa are most closely related? Is the human ancestral to the salamander?一张分支图显示四个分类单元：七鳃鳗、鲨鱼、蝾螈和人类。七鳃鳗最先分支（最靠近根），然后鲨鱼分支，然后蝾螈和人类共享最近的共同祖先。哪两个分类单元亲缘关系最近？人类是蝾螈的祖先吗？
Most closely related:亲缘关系最近： Salamander and Human. They share the most recent common ancestor (the node just before the tips). Lamprey diverged earliest from the others.蝾螈和人类。它们共享最近的共同祖先（末梢前的节点）。七鳃鳗是最早从其他类群中分歧出来的。
Is human ancestral to salamander?人类是蝾螈的祖先吗？ No. Both appear at the tips; they are both modern organisms that descended from a common ancestor. Tips never represent ancestors of other tips — only nodes represent ancestors.不。两者都出现在末梢；它们都是现代生物，源自共同祖先。末梢绝不代表其他末梢的祖先 — 只有节点代表祖先。
In a cladogram, which feature is used to group organisms into the same clade?在分支图中，哪个特征用于将生物体归入同一进化支？
§6 · Q1
Cladograms are built on shared derived characters (synapomorphies) — features that evolved once in a common ancestor and were inherited by all members of the clade. Overall similarity can be misleading (convergent evolution produces analogous structures without shared ancestry, e.g. dolphin and shark fins).分支图基于共同衍征（共近裔性状）构建 — 在共同祖先中一次性进化形成并被进化支所有成员继承的特征。整体相似性可能具有误导性（趋同进化产生无共同祖先的同功结构，如海豚和鲨鱼的鳍）。
Cladograms use shared derived characters (synapomorphies), not overall similarity or geography. Analogous structures from convergent evolution are specifically excluded because they reflect similar selection pressures, not common ancestry.分支图使用共同衍征（共近裔性状），而非整体相似性或地理位置。趋同进化产生的同功结构被特别排除在外，因为它们反映的是相似的选择压力，而非共同祖先。
Dolphins and sharks both have streamlined, fish-like bodies. Yet dolphins are grouped with whales and humans, far from sharks, on a cladogram. Why?海豚和鲨鱼都有流线型、类鱼的体型。然而在分支图上，海豚与鲸鱼和人类归为一组，远离鲨鱼。为什么？
§6 · Q2
The dolphin-shark similarity is convergent evolution: both evolved streamlined shapes independently for swimming, but they do not share recent common ancestry for that trait. Dolphins share derived characters with mammals (endothermy, hair, mammary glands, live birth, four-chambered heart) that reveal their true relationships, regardless of their fish-like appearance.海豚与鲨鱼的相似性是趋同进化：两者独立进化出流线型体形以适应游泳，但这一特征并非来自近期共同祖先。海豚与哺乳动物共享衍征（内温、毛发、乳腺、胎生、四腔心脏），这些特征揭示了其真正的亲缘关系，无论其外表多么像鱼。
The key is convergent evolution vs. shared ancestry. Dolphins are mammals (Class Mammalia, Domain Eukarya) with derived mammalian features; sharks are cartilaginous fish. Similar body shape reflects adaptation to the same environment, not common ancestry.关键在于趋同进化与共同祖先的区别。海豚是哺乳动物（哺乳纲，真核生物域），具有哺乳动物衍征；鲨鱼是软骨鱼。相似的体型反映了对相同环境的适应，而非共同祖先。
Section 7 · Dichotomous keys第 7 节 · 二歧检索表
Dichotomous Keys: Identifying Unknown Organisms二歧检索表：鉴定未知生物
A dichotomous key is a series of paired, mutually exclusive questions used to identify an unknown organism (SBI3U B2.4; BC Life Sciences 11 Content).二歧检索表是一系列成对的、相互排斥的问题，用于鉴定未知生物（SBI3U B2.4；BC Life Sciences 11 内容）。
- How to USE a key:如何使用检索表： Start at step 1. Read both choices. Select the one that matches your organism. Follow the instruction (go to step X or accept an identification). Repeat until you reach an identification.从第 1 步开始。阅读两个选项。选择与你的生物相符的选项。按照指示（跳转到第 X 步或接受鉴定）。重复直到得出鉴定结果。
- How to BUILD a key:如何构建检索表：
- Use observable, unambiguous characters (not "large" — use specific measurements).使用可观察的、明确的特征（不用"大" — 使用具体测量值）。
- Each question must have exactly two mutually exclusive options (dichotomous = two branches).每个问题必须有恰好两个相互排斥的选项（二歧 = 两个分支）。
- Start with broad, easily visible characters (e.g. number of legs) before narrowing to fine details.从宽泛的、易于观察的特征开始（如腿的数量），然后才缩小到细节特征。
- Test your key on all organisms in the set to ensure each reaches a unique identification.用集合中所有生物测试你的检索表，确保每种生物都能得到唯一的鉴定结果。
Worked Example 4 · Using a simple dichotomous key例题 4 · 使用简单二歧检索表
Use the following key to identify organism X, which has six legs, wings, and a hard outer shell covering its wings.使用以下检索表鉴定生物 X，它有六条腿、翅膀，翅膀上有坚硬的外壳覆盖。
1a. Six legs ………………………………… go to 2 1b. More than six legs or no legs ……… go to 5 2a. Wings present ………………………… go to 3 2b. No wings ……………………………… go to 4 3a. Wings covered by hard outer shell … Beetle (Order Coleoptera) 3b. Wings not covered by hard shell …… Fly (Order Diptera) 1a. 六条腿 ………………………………… 转至 2 1b. 腿多于六条或无腿 ………………… 转至 5 2a. 有翅膀 ………………………………… 转至 3 2b. 无翅膀 ………………………………… 转至 4 3a. 翅膀被坚硬外壳覆盖 ……………… 甲虫（鞘翅目） 3b. 翅膀无坚硬外壳覆盖 ……………… 苍蝇（双翅目）
Step 1: Organism X has six legs → 1a matches → go to 2.第 1 步：生物 X 有六条腿 → 1a 匹配 → 转至 2。
Step 2: Organism X has wings → 2a matches → go to 3.第 2 步：生物 X 有翅膀 → 2a 匹配 → 转至 3。
Step 3: Wings are covered by a hard outer shell → 3a matches → Beetle (Order Coleoptera).第 3 步：翅膀被坚硬外壳覆盖 → 3a 匹配 → 甲虫（鞘翅目）。
A student is building a dichotomous key to distinguish four tree species. Which of the following is the BEST first question?一名学生正在构建一个二歧检索表来区分四种树木。以下哪项是最佳的第一个问题？
§7 · Q1
A good first question is observable, unambiguous, and divides the set roughly equally. "Needle-like vs broad leaves" is directly observable and broadly splits conifers from broadleaf trees. "Beautiful" is subjective; "temperate region" requires external knowledge not always available; "exactly 10 m tall" is too specific and rarely true.好的第一个问题应该是可观察的、明确的，并将集合大致平均分开。"针状叶还是宽叶"是直接可观察的，大致将针叶树与阔叶树分开。"美丽"是主观的；"温带地区"需要外部知识，并非总是可获得；"恰好 10 米高"过于具体，很少成立。
A dichotomous key question must be observable and unambiguous. Leaf type (needle vs broad) is observable and binary, making it a strong first couplet for trees.二歧检索表问题必须是可观察的且明确的。叶型（针状与宽叶）是可观察的且二元的，使其成为树木的强有力第一对选项。
Using the worked example key above, what is organism Y if it has six legs and no wings?使用上述例题检索表，如果生物 Y 有六条腿且无翅膀，它是什么？
§7 · Q2
Step 1: six legs → 1a → go to 2. Step 2: no wings → 2b → go to 4. The key shown only provides steps 1–3, so the identification is not complete; the student would continue from step 4 (which is not shown). This illustrates that a key must cover all taxa in the set.第 1 步：六条腿 → 1a → 转至 2。第 2 步：无翅膀 → 2b → 转至 4。给出的检索表仅提供第 1–3 步，因此鉴定未完成；学生将从第 4 步继续（未显示）。这说明检索表必须覆盖集合中所有分类单元。
Trace the path: 6 legs → 1a → go to 2. No wings → 2b → go to 4. The key does not show step 4, so we can only say "proceed to step 4." The identification is not yet complete.追踪路径：6 条腿 → 1a → 转至 2。无翅膀 → 2b → 转至 4。检索表未显示第 4 步，所以只能说"进行到第 4 步"。鉴定尚未完成。
Exam Tactics考试策略
Exam Strategy and Common Pitfalls考试策略与常见陷阱
Nomenclature questions命名法问题
- Check all three rules every time:每次检查全部三条规则： (1) Genus capitalized, (2) species epithet lowercase, (3) both italicized. Any one error is a marking error in a nomenclature question.(1) 属名首字母大写，(2) 种名小写，(3) 两者均斜体。命名法题中任何一个错误都会扣分。
- Never abbreviate the species epithet.永远不要缩写种名。 "H. sapiens" is fine; "Homo s." is not. You can abbreviate the genus after first mention, but never the species."H. sapiens"是正确的；"Homo s."是不正确的。可以在首次提及后缩写属名，但绝不能缩写种名。
Classification and kingdom questions分类与界的问题
- Use cell wall material as the key discriminator between kingdoms:使用细胞壁材料作为界之间的关键区分标准： peptidoglycan = Eubacteria; no peptidoglycan, unusual lipids = Archaebacteria; cellulose = Plantae; chitin = Fungi; no cell wall = Animalia.肽聚糖 = 真细菌界；无肽聚糖、特殊脂质 = 古细菌界；纤维素 = 植物界；几丁质 = 真菌界；无细胞壁 = 动物界。
- Protista is a "catch-all" eukaryote kingdom.原生生物界是真核生物的"兜底"界。 If an eukaryotic organism does not fit Fungi, Plantae, or Animalia, it is likely Protista. Algae, amoeba, and Plasmodium all land here despite looking very different.如果一种真核生物不符合真菌界、植物界或动物界，它可能是原生生物界。藻类、变形虫和疟原虫尽管外观差异很大，都归入此界。
Cladogram and dichotomous key questions分支图与二歧检索表问题
- Tips on a cladogram are NOT ancestors of other tips.分支图末梢上的生物不是其他末梢生物的祖先。 A common error: "humans evolved from chimpanzees." Wrong — both are at tips and share a common ancestor at a node. The node is the ancestor, not either tip.常见错误："人类从黑猩猩进化而来。"错误 — 两者都在末梢，在一个节点处共享共同祖先。节点是祖先，而非任何一个末梢。
- In a dichotomous key, trace the path systematically — do not skip steps.在二歧检索表中，系统地追踪路径 — 不要跳过步骤。 Write out each step number as you go. If you cannot decide between two options, re-read the question for additional observable characters.一边进行一边写出每个步骤编号。如果无法在两个选项之间做决定，重新阅读问题以获取额外的可观察特征。
Active Recall主动复习
Flashcards闪卡
What are the three types of biodiversity?生物多样性的三种类型是什么？
1. Genetic diversity (allele variation within a species). 2. Species diversity (variety of species in an area). 3. Structural/ecosystem diversity (variety of habitats and ecosystems).1. 遗传多样性（物种内等位基因变异）。2. 物种多样性（某区域内物种多样性）。3. 结构/生态系统多样性（栖息地和生态系统的多样性）。
Biological species concept?生物物种概念？
A species is a group of organisms that can interbreed naturally and produce fertile offspring. Geographic isolation alone does not define a species.物种是能够自然交配并产生可育后代的一组生物。仅地理隔离不能定义物种。
Eight levels of taxonomic hierarchy (broadest to most specific)?八个分类层级（从最宽泛到最具体）？
Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species域 → 界 → 门 → 纲 → 目 → 科 → 属 → 物种
Three rules of binomial nomenclature?双名法的三条规则？
1. Genus capitalized. 2. Species epithet lowercase. 3. Both italicized (or underlined when handwritten). Example: Homo sapiens1. 属名首字母大写。2. 种名小写。3. 两者均斜体（手写时加下划线）。例：Homo sapiens
Three domains of life?生命的三个域？
Bacteria (prokaryote, peptidoglycan wall), Archaea (prokaryote, no peptidoglycan, extremophiles), Eukarya (eukaryote, includes all four eukaryote kingdoms).细菌（原核，肽聚糖细胞壁），古菌（原核，无肽聚糖，极端嗜好生物），真核生物（真核，包含全部四个真核界）。
Why were Archaea separated from Bacteria?古菌为何从细菌中分离？
rRNA sequencing showed Archaea are as different from Bacteria as either is from Eukarya. Also: no peptidoglycan cell wall, ether-linked membrane lipids, and RNA polymerase more similar to Eukarya.rRNA 测序显示古菌与细菌的差异程度与两者和真核生物的差异相当。此外：无肽聚糖细胞壁、醚键连接膜脂、RNA 聚合酶更接近真核生物。
Cell wall composition: Plantae vs Fungi vs Eubacteria?植物界 vs 真菌界 vs 真细菌界的细胞壁成分？
Plantae: cellulose. Fungi: chitin. Eubacteria: peptidoglycan. Animalia: no cell wall.植物界：纤维素。真菌界：几丁质。真细菌界：肽聚糖。动物界：无细胞壁。
How does Fungi obtain nutrition?真菌如何获取营养？
Absorptive heterotrophy: secretes digestive enzymes into the substrate, then absorbs the digested nutrients. Cannot photosynthesize. Includes mushrooms, moulds, and yeasts.吸收性异养：将消化酶分泌到基质中，然后吸收消化后的营养物质。不能进行光合作用。包括蘑菇、霉菌和酵母菌。
What is a phylogenetic tree / cladogram?什么是系统发育树/分支图？
A branching diagram showing inferred evolutionary relationships. Each node = common ancestor. Organisms at tips are NOT ancestors of other tips; they share ancestors at nodes.显示推断进化关系的树状图。每个节点 = 共同祖先。末梢处的生物不是其他末梢的祖先；它们在节点处共享祖先。
What are shared derived characters (synapomorphies)?什么是共同衍征（共近裔性状）？
Features that evolved in a common ancestor and were inherited by all members of a clade. Used to build cladograms. Example: hair is a shared derived character of all mammals.在共同祖先中进化形成并被进化支所有成员继承的特征。用于构建分支图。例：毛发是所有哺乳动物的共同衍征。
Convergent evolution — example and why it misleads classification?趋同进化 — 举例说明为何会误导分类？
Dolphins and sharks both have streamlined bodies (analogous structures), but dolphins are mammals and sharks are cartilaginous fish. Similar appearance reflects similar selection pressure, not shared ancestry. Cladograms use derived characters, not overall similarity.海豚和鲨鱼都有流线型身体（同功结构），但海豚是哺乳动物，鲨鱼是软骨鱼。相似外观反映相似选择压力，而非共同祖先。分支图使用衍征，而非整体相似性。
How to use a dichotomous key?如何使用二歧检索表？
Start at step 1. Read both paired choices. Select the one matching the organism. Follow the instruction (go to step X or accept identification). Repeat until identified.从第 1 步开始。阅读两个成对选项。选择与生物相符的选项。按照指示（转至第 X 步或接受鉴定）。重复直到得出鉴定结果。
NGSS stance on taxonomy and classification?NGSS 对分类学的立场？
NGSS has NO dedicated PE for taxonomic hierarchy, binomial nomenclature, kingdoms, or dichotomous keys. Biodiversity PEs (HS-LS4-5, HS-LS2-7) address speciation, extinction, and human impact instead.NGSS 没有专门的分类层级、双名法、界或二歧检索表的 PE。生物多样性 PE（HS-LS4-5、HS-LS2-7）转而关注物种形成、灭绝和人类影响。
What does sharing the same Genus tell you, compared with sharing the same Order?共享同一属与共享同一目，各自说明了什么？
Same Genus = same Domain, Kingdom, Phylum, Class, Order, Family — closely related, recently diverged from a common ancestor. Same Order = share higher ranks but differ from Family downward — less closely related.同属 = 同域、界、门、纲、目、科 — 亲缘关系近，近期从共同祖先分歧。同目 = 共享更高级别但在科及以下不同 — 亲缘关系较远。
Mixed Practice综合练习
Practice Quiz综合测验
A biologist discovers a microbe that has no membrane-bound nucleus and cell walls that lack peptidoglycan. It thrives in boiling hot springs at 90°C. Which domain does it belong to?一位生物学家发现了一种微生物，它没有膜性细胞核，细胞壁缺乏肽聚糖，在 90°C 的沸腾温泉中繁盛。它属于哪个域？
Q1
No nucleus = prokaryote (rules out Eukarya). No peptidoglycan + extreme thermophile = Archaea, not Bacteria. Bacteria have peptidoglycan cell walls. Archaea are the classic extremophile domain. Plantae is a Kingdom within Eukarya.无细胞核 = 原核生物（排除真核生物）。无肽聚糖 + 极端嗜热 = 古菌，而非细菌。细菌有肽聚糖细胞壁。古菌是经典的极端嗜好生物域。植物界是真核生物域内的一个界。
No nucleus rules out Eukarya. No peptidoglycan rules out Bacteria (which have peptidoglycan). Extreme thermophiles are hallmarks of Archaea.无细胞核排除真核生物。无肽聚糖排除细菌（细菌有肽聚糖）。极端嗜热是古菌的标志。
Which of the following scientific names is written correctly?下列哪个科学名称书写正确？
Q2
Panthera leo is correct: Genus capitalized (Panthera), species epithet lowercase (leo), both italicized. Option A: species epithet capitalized (wrong). Option B: genus not capitalized, not italicized. Option D: genus lowercase, species capitalized — both rules reversed.Panthera leo 正确：属名首字母大写（Panthera），种名小写（leo），两者均斜体。选项 A：种名首字母大写（错误）。选项 B：属名未大写，无斜体。选项 D：属名小写，种名大写——两条规则均颠倒。
Rules: Genus capitalized + species lowercase + both italicized. Only Panthera leo satisfies all three.规则：属名首字母大写 + 种名小写 + 两者均斜体。只有 Panthera leo 满足全部三条。
On a cladogram, sharks and dolphins are placed in very different clades, even though both have streamlined bodies. The most likely explanation is…在分支图上，鲨鱼和海豚被置于非常不同的进化支中，尽管两者都有流线型身体。最可能的解释是……
Q3
Convergent evolution produces analogous structures: similar traits that arose independently in unrelated lineages facing similar selection pressures. Dolphins share derived mammalian characters (hair, mammary glands, four-chambered heart, live birth) that reveal their true placement with whales and primates, far from sharks. Cladograms use shared derived characters, not overall body form.趋同进化产生同功结构：在面临相似选择压力的不相关谱系中独立出现的相似特征。海豚共享哺乳动物衍征（毛发、乳腺、四腔心脏、胎生），揭示了它们与鲸鱼和灵长类的真正关系，远离鲨鱼。分支图使用共同衍征，而非整体体型。
The streamlined body is an analogous structure from convergent evolution, not a shared derived character indicating common ancestry. Dolphins are mammals; sharks are cartilaginous fish.流线型身体是趋同进化的同功结构，而非表明共同祖先的共同衍征。海豚是哺乳动物；鲨鱼是软骨鱼。
Ontario SBI3U Strand B covers biodiversity and classification in detail. Which of the following expectations does it NOT include?安大略 SBI3U B 单元详细涵盖生物多样性与分类。以下哪项期望它不包含？
Q4
Hardy-Weinberg calculations are not in SBI3U Strand B at all. Hardy-Weinberg is required only in Alberta Biology 30 Unit D GO1 (`30–D1.3k`). NGSS explicitly excludes Hardy-Weinberg at HS level. Ontario does not include it in either SBI3U or SBI4U. Options A, C, and D are all actual SBI3U Strand B expectations.哈代-温伯格计算完全不在 SBI3U B 单元中。哈代-温伯格仅在阿尔伯塔 Biology 30 Unit D GO1（`30–D1.3k`）中为必修内容。NGSS 在高中层面明确排除哈代-温伯格。安大略在 SBI3U 和 SBI4U 中均不包含此内容。选项 A、C 和 D 都是实际的 SBI3U B 单元期望。
Hardy-Weinberg calculations are an Alberta Biology 30 exclusive in this curriculum set. SBI3U Strand B expectations include B2.4 (dichotomous keys), B3.3 (kingdom characteristics), B3.5 (biodiversity importance), B3.1 (taxonomy/phylogeny), and B2.1 (binomial nomenclature terminology).哈代-温伯格计算是这套大纲中阿尔伯塔 Biology 30 独有的内容。SBI3U B 单元期望包括 B2.4（二歧检索表）、B3.3（界的特征）、B3.5（生物多样性重要性）、B3.1（分类学/系统发育学）和 B2.1（双名法术语）。
Two organisms share the same Phylum but belong to different Classes. Which of the following must be true?两种生物共享同一门但属于不同纲。以下哪项必定正确？
Q5
The taxonomy hierarchy is nested. Sharing the same Phylum means they share all higher ranks: Domain, Kingdom, and Phylum. They differ from Class downward (Class, Order, Family, Genus, Species). They cannot be in the same Family, Order, Genus, or Species if they are in different Classes.分类层级是嵌套的。共享同一门意味着它们共享所有更高级别：域、界和门。它们从纲往下不同（纲、目、科、属、物种）。如果它们在不同的纲，就不可能在同一科、目、属或物种。
Sharing a Phylum means sharing Domain, Kingdom, and Phylum. Different Classes means they diverge at Class level, so they cannot share Family or Order. They are different species and cannot interbreed to produce fertile offspring.共享门意味着共享域、界和门。不同的纲意味着它们在纲级分歧，因此不能共享科或目。它们是不同物种，不能交配产生可育后代。
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。
0 / 11 mastered已掌握 0 / 11
- Define genetic diversity, species diversity, and structural diversity, and explain why each matters for ecosystem stability. 🇨🇦 ON SBI3U B3.5定义遗传多样性、物种多样性和结构多样性，并解释每种为何对生态系统稳定性重要。🇨🇦 ON SBI3U B3.5
- List the eight taxonomic ranks in order from broadest to most specific, and give one example organism placed at each level. 🇨🇦 ON SBI3U B3.1 🇨🇦 BC Life Sciences 11从最宽泛到最具体按顺序列出八个分类层级，并在每个层级各给出一个例子生物。🇨🇦 ON SBI3U B3.1 🇨🇦 BC Life Sciences 11
- Write the correct binomial name for any species given a genus and species epithet, following all three formatting rules. 🇨🇦 ON SBI3U B2.1 🇨🇦 AB 20–B1.5k给定属名和种名，遵循全部三条格式规则，正确写出任何物种的双名法名称。🇨🇦 ON SBI3U B2.1 🇨🇦 AB 20–B1.5k
- Name the three domains and explain the evidence that placed Archaea in a separate domain from Bacteria. 🇨🇦 BC Life Sciences 11说出三个域，并解释将古菌置于独立域的证据。🇨🇦 BC Life Sciences 11
- Describe the unifying characteristics of each of the six kingdoms, and classify an unknown organism into the correct kingdom given a set of observable features. 🇨🇦 ON SBI3U B3.3 🇨🇦 AB 20–B1.5k描述六界各自的统一特征，并根据一组可观察特征将未知生物归入正确的界。🇨🇦 ON SBI3U B3.3 🇨🇦 AB 20–B1.5k
- Read a cladogram: identify the most closely related pair, determine what a node represents, and explain why tips are not ancestors of other tips.读懂分支图：识别亲缘关系最近的一对，确定节点代表什么，并解释为何末梢不是其他末梢的祖先。
- Explain the difference between homologous structures (shared ancestry) and analogous structures (convergent evolution), with one example of each.用各一个例子解释同源结构（共同祖先）和同功结构（趋同进化）的区别。
- Name four types of evidence used to build phylogenies (molecular, morphological, fossil, embryological).说出构建系统发育关系所用的四种证据类型（分子、形态学、化石、胚胎学）。
- Use a given dichotomous key to identify an unknown organism by tracing the correct path step by step. 🇨🇦 ON SBI3U B2.4 🇨🇦 BC Life Sciences 11通过逐步追踪正确路径，使用给定的二歧检索表鉴定未知生物。🇨🇦 ON SBI3U B2.4 🇨🇦 BC Life Sciences 11
- Explain why NGSS has no dedicated taxonomy PE, and identify which PEs (HS-LS4-5, HS-LS2-7) cover biodiversity-adjacent content in a US curriculum. 🇺🇸 NGSS divergence解释为何 NGSS 没有专门的分类学 PE，并识别哪些 PE（HS-LS4-5、HS-LS2-7）在美国大纲中涵盖与生物多样性相关的内容。🇺🇸 NGSS 分歧
- Construct a simple dichotomous key for four or more organisms using observable binary characters, and verify that each organism reaches a unique identification. 🇨🇦 ON SBI3U B2.4使用可观察的二元特征为四种或更多生物构建简单的二歧检索表，并验证每种生物都能得到唯一的鉴定结果。🇨🇦 ON SBI3U B2.4
Next Steps后续衔接
What This Feeds Into本单元的去向
Feeder links are REMOVED for this unit. Biodiversity and Classification is not a direct prerequisite for other HS Biology units in the way that Cell Structure feeds into Biochemistry. Instead, the classification and phylogeny skills built here form a conceptual scaffold that enriches every biology unit: knowing kingdoms helps contextualize organisms in Ecology (Unit 9); understanding cladograms deepens the Evolution unit (Unit 7); taxonomy vocabulary appears throughout. When AP Biology and IB Biology HL products ship, this guide will connect directly to AP Biology Big Idea 1 (Evolution) and IB Biology HL Topic C (Ecology).本单元的衔接链接已移除。生物多样性与分类不像细胞结构为生物化学那样，是其他高中生物单元的直接先修课程。相反，此处建立的分类学和系统发育技能形成概念支架，丰富每个生物学单元：了解界有助于在生态学（第 9 单元）中理解生物背景；理解分支图深化了进化单元（第 7 单元）；分类学词汇贯穿始终。当 AP Biology 和 IB Biology HL 产品上线时，本指南将直接与 AP Biology 大概念 1（进化）和 IB Biology HL Topic C（生态学）相连。