📚 IB Biology: End-of-Year Review Outline | IB 生物：期末复习提纲
As the IB Biology exam approaches, a structured review of the syllabus is essential for success. This outline distills the core concepts, practical skills, and cross‑topic connections you need to master, helping you focus your revision efficiently. Let’s build a solid framework for confident answering of Paper 1, 2, and 3 questions.
随着 IB 生物考试的临近，有条理地复习教学大纲是成功的关键。本提纲浓缩了核心概念、实验技能和跨主题联系，帮助你高效地集中复习。让我们构建一个扎实的框架，以自信应对试卷一、二和三的问题。
1. Cell Biology Essentials | 细胞生物学基础
Understand cell theory: all living things are composed of cells, the cell is the basic unit of life, and cells arise from pre‑existing cells. Contrast the structures of prokaryotic and eukaryotic cells, noting the lack of a nucleus and membrane‑bound organelles in prokaryotes.
理解细胞学说：所有生物都由细胞组成，细胞是生命的基本单位，细胞来自已有的细胞。对比原核细胞和真核细胞的结构，注意原核细胞没有细胞核及膜包裹的细胞器。
Memorise the functions of organelles: nucleus (stores DNA), rough ER (protein synthesis), smooth ER (lipid synthesis), Golgi apparatus (modifies and packages proteins), mitochondria (aerobic respiration), chloroplasts (photosynthesis), and vacuoles (storage). Use electron micrographs to identify these structures.
记住细胞器的功能：细胞核（储存 DNA）、粗面内质网（蛋白质合成）、光面内质网（脂质合成）、高尔基体（修饰和包装蛋白质）、线粒体（有氧呼吸）、叶绿体（光合作用）和液泡（储存）。利用电子显微照片识别这些结构。
Explain the fluid mosaic model of membrane structure: phospholipid bilayer with embedded proteins. Distinguish between passive transport (diffusion, facilitated diffusion, osmosis) and active transport (requires ATP, e.g., sodium‑potassium pump). Use the formula ψ = ψs + ψp for water potential in plant cells.
解释膜的流动镶嵌模型：磷脂双分子层及镶嵌蛋白。区分被动运输（扩散、易化扩散、渗透）和主动运输（需要 ATP，如钠钾泵）。植物细胞水势公式 ψ = ψs + ψp。
2. Molecular Mastery: Biomolecules and Enzymes | 分子精通：生物分子与酶
Describe the structure of water and its properties: cohesion, adhesion, high specific heat, high heat of vaporisation, and solvent abilities, linking each to biological significance (e.g., transport in xylem, temperature regulation).
描述水的结构及其性质：内聚力、附着力、高比热、高蒸发热和溶剂能力，并将每种性质与生物学意义联系起来（例如，木质部运输、温度调节）。
Compare the four main classes of organic molecules: carbohydrates (monosaccharides, disaccharides, polysaccharides like starch, glycogen, cellulose), lipids (triglycerides, phospholipids, steroids), proteins (amino acids → polypeptide → four levels of structure), and nucleic acids (DNA, RNA).
比较四类主要有机分子：碳水化合物（单糖、二糖、多糖，如淀粉、糖原、纤维素）、脂质（甘油三酯、磷脂、类固醇）、蛋白质（氨基酸→多肽→四级结构）和核酸（DNA、RNA）。
Enzyme kinetics: explain the induced‑fit model, the effect of temperature, pH, and substrate concentration on enzyme activity. Calculate Vmax and Km using Michaelis‑Menten plots, and distinguish competitive from non‑competitive inhibition.
酶动力学：解释诱导契合模型，温度、pH 和底物浓度对酶活性的影响。利用米氏方程图计算 Vmax 和 Km，区分竞争性抑制和非竞争性抑制。
3. DNA Structure, Replication and Protein Synthesis | DNA 结构、复制与蛋白质合成
State the Watson‑Crick double helix model: two anti‑parallel strands of nucleotides linked by hydrogen bonds between complementary bases (A=T, C≡G). The backbone consists of alternating deoxyribose sugar and phosphate groups.
阐述沃森‑克里克双螺旋模型：两条反向平行的多核苷酸链，由互补碱基之间的氢键连接（A=T，C≡G）。骨架由脱氧核糖和磷酸基团交替排列组成。
DNA replication is semi‑conservative, as proved by Meselson and Stahl. Outline the roles of helicase, DNA polymerase III, primase, ligase, and Okazaki fragments on the lagging strand. Ensure you can label a replication fork diagram.
DNA 复制是半保留复制，由梅塞尔森和斯塔尔实验证实。概述解旋酶、DNA 聚合酶 III、引物酶、连接酶以及后随链上的冈崎片段的作用。确保能标注复制叉示意图。
Protein synthesis: transcription (DNA → mRNA, catalysed by RNA polymerase, in nucleus) and translation (mRNA → polypeptide, on ribosomes, using tRNA and codons). Practice interpreting the genetic code table to predict amino acid sequences.
蛋白质合成：转录（DNA → mRNA，由 RNA 聚合酶催化，在细胞核内）和翻译（mRNA → 多肽，在核糖体上，利用 tRNA 和密码子）。练习使用遗传密码表预测氨基酸序列。
4. Cell Division and Mendelian Genetics | 细胞分裂与孟德尔遗传学
Differentiate mitosis (produces two genetically identical diploid daughter cells, for growth and repair) from meiosis (produces four genetically varied haploid gametes, for sexual reproduction). Focus on the behaviour of chromosomes during meiosis I: crossing over in prophase I and independent assortment in metaphase I generate genetic variation.
区别有丝分裂（产生两个遗传相同的二倍体子细胞，用于生长和修复）和减数分裂（产生四个遗传多样的单倍体配子，用于有性生殖）。重点关注减数分裂 I 中染色体的行为：前期 I 的交叉互换和中期 I 的自由组合产生遗传变异。
Apply Mendel’s laws: law of segregation (alleles separate during gamete formation) and law of independent assortment (alleles of different genes assort independently). Solve monohybrid and dihybrid crosses, using Punnett squares to determine genotypic and phenotypic ratios. Relate to pedigree charts for human disorders like cystic fibrosis (recessive) and Huntington’s disease (dominant).
应用孟德尔定律：分离定律（等位基因在配子形成时分离）和自由组合定律（不同基因的等位基因自由组合）。解答单基因和双基因杂交问题，使用庞纳特方格确定基因型和表现型比例。将遗传图谱与人类疾病如囊性纤维化（隐性）和亨廷顿病（显性）关联起来。
5. Evolution and Biodiversity | 进化与生物多样性
Explain natural selection as the mechanism for evolution: variation, overproduction, competition, differential survival and reproduction, leading to changes in allele frequencies. Provide examples like antibiotic resistance in bacteria and beak shape in Darwin’s finches.
解释自然选择作为进化的机制：变异、过度繁殖、竞争、差异存活和繁殖，导致等位基因频率的改变。提供例子，如细菌的抗生素抗性和达尔文雀的喙形。
Define species using the biological species concept (a group of organisms that can interbreed and produce fertile offspring). Distinguish allopatric speciation (geographic isolation) from sympatric speciation (reproductive isolation within the same area, e.g., polyploidy in plants).
使用生物学物种概念定义物种（能互相交配并产生可育后代的一组生物）。区分异域物种形成（地理隔离）和同域物种形成（同一区域内生殖隔离，如植物的多倍体）。
Cladistics: construct and interpret cladograms based on shared derived characteristics and molecular evidence. Use the principle of parsimony to choose the most likely evolutionary tree. Know the three‑domain classification: Bacteria, Archaea, Eukarya.
生物分类学：基于共享衍征和分子证据构建并解读分支图。使用简约性原则选择最可能的进化树。了解三域分类：细菌、古菌、真核生物。
6. Ecology: Matter and Energy Flow | 生态学：物质与能量流动
Describe the carbon cycle: photosynthesis fixes CO₂ into organic compounds, respiration releases CO₂, decomposition, combustion, and fossil fuel formation. Emphasise the role of methanogens in anaerobic environments (e.g., wetlands, cattle gut).
描述碳循环：光合作用将 CO₂ 固定为有机化合物，呼吸作用释放 CO₂，分解、燃烧和化石燃料形成。强调产甲烷菌在厌氧环境中的作用（如湿地、牛肠道）。
Energy flow: only about 10% of energy is transferred from one trophic level to the next (ecological pyramids of energy are always upright). Construct food chains and webs, and calculate ecological efficiency using the formula: (energy in biomass at trophic level n+1 / energy in biomass at trophic level n) × 100%.
能量流动：只有约 10% 的能量从一个营养级传递到下一个营养级（能量锥体总是正立）。构建食物链和食物网，并使用公式计算生态效率：（第 n+1 营养级生物量能量 / 第 n 营养级生物量能量）× 100%。
Analyse population growth: exponential (J‑shaped) versus logistic (S‑shaped, carrying capacity K). Factors limiting population size: density‑dependent (disease, competition) and density‑independent (fire, drought).
分析种群增长：指数增长（J 型）与逻辑斯谛增长（S 型，容纳量 K）。限制种群大小的因素：密度制约（疾病、竞争）和非密度制约（火灾、干旱）。
7. Human Physiology: Core Systems | 人类生理学：核心系统
Digestion: the breakdown of large insoluble molecules into small absorbable ones. Enzymes: amylase (starch → maltose), protease (proteins → amino acids), lipase (lipids → fatty acids + glycerol). Absorption of glucose and amino acids in the villi involves co‑transport with sodium ions.
消化：将大分子不溶物分解为可吸收的小分子。酶：淀粉酶（淀粉→麦芽糖）、蛋白酶（蛋白质→氨基酸）、脂肪酶（脂质→脂肪酸 + 甘油）。绒毛中葡萄糖和氨基酸的吸收涉及与钠离子的协同运输。
Circulation: double circulatory system in mammals. Structure of the heart (chambers, valves, cardiac cycle) and blood vessels (arteries, veins, capillaries). Control of heartbeat by the sinoatrial node. Explain the oxygen dissociation curve for fetal and adult haemoglobin.
循环：哺乳动物的双循环系统。心脏结构（腔室、瓣膜、心动周期）和血管（动脉、静脉、毛细血管）。窦房结对心跳的控制。解释胎儿和成人血红蛋白的氧解离曲线。
Immunity: non‑specific defences (skin, phagocytes) and specific immune responses. B‑lymphocytes produce antibodies (humoral), T‑lymphocytes (helper and killer) provide cell‑mediated immunity. Distinguish active from passive immunity, and natural from artificial methods of acquiring immunity.
免疫：非特异性防御（皮肤、吞噬细胞）和特异性免疫反应。B 淋巴细胞产生抗体（体液免疫），T 淋巴细胞（辅助性和杀伤性）提供细胞免疫。区分主动免疫和被动免疫，以及自然和人工获取免疫的方法。
8. Plant Biology (Higher Level Core) | 植物生物学（高水平核心）
Transport in xylem: transpiration‑cohesion‑tension mechanism. Water evaporates from leaf cells into air spaces, creating a negative pressure that pulls water up the xylem due to cohesion between water molecules. Factors affecting transpiration rate: light, temperature, humidity, wind.
木质部运输：蒸腾‑内聚力‑张力机制。水分从叶细胞蒸散到细胞间空气空间，产生负压，由于水分子间的内聚力将水向上拉。影响蒸腾速率的因素：光照、温度、湿度、风。
Transport in phloem: translocation of sucrose using pressure‑flow hypothesis. Active loading of sucrose at source (e.g., leaves) lowers water potential, water enters, increasing pressure; at sink, sucrose is unloaded, water leaves, reducing pressure. Use aphid stylets experiment as evidence.
韧皮部运输：使用压力流动假说解释蔗糖的转运。在源（如叶片）主动装载蔗糖，降低水势，水进入，增加压力；在库，蔗糖卸载，水流出，降低压力。以蚜虫口针实验为证据。
Reproduction: photoperiodism and the role of phytochrome (Pfr and Pr interconversion) in flowering of long‑day and short‑day plants. Germination: water uptake triggers gibberellin production, which stimulates amylase synthesis to break down starch.
生殖：光周期现象和光敏色素（Pfr 和 Pr 互变）在长日照和短日照植物开花中的作用。萌发：吸水引发赤霉素产生，刺激淀粉酶合成以分解淀粉。
9. Option Topic: Neurobiology and Behaviour (Example) | 选修主题：神经生物学与行为（示例）
Neuronal signalling: resting potential (−70 mV) maintained by Na⁺/K⁺ pump. Action potential: depolarisation (Na⁺ influx), repolarisation (K⁺ efflux), hyperpolarisation, return to resting. Saltatory conduction in myelinated axons speeds up transmission.
神经元信号：静息电位（−70 mV）由 Na⁺/K⁺ 泵维持。动作电位：去极化（Na⁺ 内流）、复极化（K⁺ 外流）、超极化、恢复静息。有髓轴突中的跳跃传导加速传递。
Synaptic transmission: arrival of action potential opens Ca²⁺ channels, vesicles release neurotransmitter into synaptic cleft, binding to receptors on postsynaptic membrane can cause EPSP or IPSP. Acetylcholine and cholinesterase as a classic example.
突触传递：动作电位到达，打开 Ca²⁺ 通道，囊泡释放神经递质到突触间隙，与突触后膜受体结合可引起 EPSP 或 IPSP。乙酰胆碱和胆碱酯酶是经典例子。
Innate and learned behaviour: taxis and kinesis, classical and operant conditioning using Pavlov’s dogs and Skinner boxes. Study ethology from Tinbergen’s four questions and bird song learning.
先天与习得行为：趋性（taxis）和动性（kinesis），经典条件反射和操作性条件反射，以巴甫洛夫的狗和斯金纳箱为例。研究动物行为学，可结合廷伯根四问和鸟类鸣叫学习。
10. Experimental Skills and Internal Assessment Recap | 实验技能与内部评估回顾
Know the command terms: “draw/label” requires a precise diagram; “describe” means give a detailed account; “explain” needs a reason or mechanism; “analyse” means look for patterns and draw conclusions; “evaluate” weighs strengths and limitations.
掌握指令术语：“draw/label”要求精确图示；“describe”意味着详细描述；“explain”需要说明原因或机制；“analyse”指寻找规律并得出结论；“evaluate”则权衡优势和局限性。
Design an investigation: identify independent, dependent, and controlled variables. Write a clear hypothesis. Explain how to collect data reliably, including repeats and statistical analysis (standard deviation, t‑test, correlation coefficient). For your Individual Investigation (IA), reflect on ethical considerations and procedural improvements.
设计探究：确定自变量、因变量和控制变量。写出清晰假设。说明如何可靠地收集数据，包括重复和统计分析（标准差、t 检验、相关系数）。对于个人调查（IA），反思伦理考量和步骤改进。
Microscopy skills: calculate magnification (magnification = size of image / actual size) and convert units (nm, µm, mm). Use a graticule to measure specimens. Prepare temporary mounts of onion epidermis or cheek cells.
显微镜技能：计算放大倍数（放大倍数 = 图像大小 / 实际大小）并转换单位（nm, µm, mm）。使用测微尺测量样本。制作洋葱表皮或口腔细胞临时装片。
11. Data–Based Questions and Graph Interpretation | 数据题与图表解读
For Paper 2 and 3, expect questions with graphs, tables, or diagrams. Always read the title and axes first. Identify trends, describe them precisely using quantitative language (e.g., “a three‑fold increase,” “plateau at 60 minutes”).
试卷二和试卷三会出现图表或数据表问题。一定要先读标题和轴。识别趋势，用定量语言精确描述（例如，“增加了三倍”，“在 60 分钟时达到平台期”）。
Calculate rates from tangent slopes or initial rates. For enzyme kinetics, determine Vmax and Km. When error bars are present, state whether differences are significant (non‑overlapping error bars suggest significance).
从切线斜率或初始速率计算速率。对于酶动力学，确定 Vmax 和 Km。存在误差棒时，说明差异是否显著（不重叠的误差棒表明可能显著）。
In ecology, use the Lincoln index to estimate population size: N = (M × C) / R, where M is the number originally marked, C is the total captured in the second sample, and R is the number of marked recaptures. Remember the assumptions of the mark‑release‑recapture method.
在生态学中，使用林肯指数估算种群大小：N = (M × C) / R，其中 M 是最初标记数，C 是第二次捕获总数，R 是重新捕获的标记数。记住标记‑释放‑重捕法的假设条件。
12. Final Examination Strategies | 期末应试策略
Paper 1 (Multiple choice): pace yourself (45 minutes for 30 questions HL). Elimination is your best friend. If unsure, mark the question and return later. Beware of “reverse” questions (which is NOT true?).
试卷一（选择题）：控制时间（高水平 30 题 45 分钟）。排除法是你的最佳助手。如果不确定，先标记，稍后返回。注意“反向”问题（哪个是不正确的？）。
Paper 2 (Short answer and extended response): Section A: data‑based and experimental skills; Section B: choose one essay from two options. Plan your essay for 5 minutes: outline key points, clearly define terms, use examples, and link concepts across topics. Draw diagrams whenever they add value.
试卷二（简答与拓展回应）：A 部分：数据题和实验技能；B 部分：从两题中选一题写作。用 5 分钟构思论文：列出要点，明确定义术语，使用实例，并跨主题联系概念。只要图表能加分，就画出来。
Paper 3 (Options and practical): Section A: compulsory core practical skills; Section B: option topic questions. Revise your option in depth, including all prescribed practicals. Use precise biological vocabulary and avoid vague terms. If the question asks for an “evaluation,” you must state both strengths and limitations.
试卷三（选修和实验）：A 部分：必修核心实验技能；B 部分：选修主题问题。深入复习你的选修内容，包括所有指定实验。使用精确的生物学术语，避免模糊词汇。如果问题要求“评价”，你必须陈述优势和局限性。
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