📚 IB Biology End-of-Term Review Outline | IB 生物期末复习提纲
This review guide is designed to help you consolidate the key concepts covered in the IB Biology course so far. It highlights the essential knowledge, common misconceptions, and connections across topics that are critical for success in the end-of-term examination. Use it alongside your class notes, textbook, and past paper questions for the most effective preparation.
这份复习指南旨在帮助你巩固 IB 生物课程至今所学的核心概念。它突出了关键知识、常见误区以及各主题之间的关联，这些都是期末考成功的关键。请结合课堂笔记、教科书和历年真题使用，以达到最佳备考效果。
1. Cell Theory and Ultrastructure | 细胞学说与超微结构
The cell is the basic unit of life. You must understand the three tenets of cell theory: all living things are composed of cells, the cell is the smallest unit of life, and all cells arise from pre-existing cells. Exceptions include striated muscle fibres, giant algae (e.g., Acetabularia), and aseptate fungal hyphae. Remember that unicellular organisms carry out all life functions within one cell, while multicellular organisms show emergent properties through cellular differentiation.
细胞是生命的基本单位。你必须理解细胞学说的三条原则：一切生物都由细胞构成，细胞是生命的最小单位，所有细胞都来源于已存在的细胞。例外情况包括横纹肌纤维、大型藻类（如伞藻）和无隔菌丝。记住单细胞生物在一个细胞内完成所有生命活动，而多细胞生物通过细胞分化展现出突现特性。
- Prokaryotic vs eukaryotic cells: Prokaryotes lack a membrane-bound nucleus and organelles (e.g., bacteria). Eukaryotes have compartmentalisation (nucleus, mitochondria, ER, etc.). Common features: cytoplasm, plasma membrane, ribosomes (70S in prokaryotes, 80S in eukaryotes), and DNA.
- 原核细胞与真核细胞：原核细胞没有膜包被的细胞核和细胞器（如细菌）。真核细胞具有区室化结构（细胞核、线粒体、内质网等）。共同特征：细胞质、质膜、核糖体（原核70S，真核80S）和DNA。
- Microscopy: l size. Electron microscopes have higher resolution than light microscopes. Understand how to interpret electron micrographs and identify organelles.
- 显微镜技术：放大倍数 = 图像大小 / 实际大小。电子显微镜分辨率高于光学显微镜。要会解读电子显微照片并识别细胞器。
2. Biological Molecules | 生物分子
Carbon’s ability to form four covalent bonds underpins the diversity of organic molecules. Focus on the four major classes: carbohydrates, lipids, proteins, and nucleic acids. For each, you need to know the monomers, polymers, types of bonds, and key functions.
碳原子可形成四个共价键，这奠定了有机分子多样性的基础。关注四大类分子：碳水化合物、脂质、蛋白质和核酸。对于每一类，你需要了解其单体、聚合物、键的类型和主要功能。
- Carbohydrates: Monosaccharides (e.g., glucose, ribose) are linked by glycosidic bonds to form disaccharides (maltose, sucrose) and polysaccharides (starch, glycogen, cellulose). Relate structure to function: cellulose’s beta-glucose orientation and hydrogen bonding give high tensile strength.
- 碳水化合物：单糖（如葡萄糖、核糖）通过糖苷键连接成二糖（麦芽糖、蔗糖）和多糖（淀粉、糖原、纤维素）。联系结构与功能：纤维素由β-葡萄糖取向及氢键赋予高抗张强度。
- Lipids: Triglycerides are formed by esterification of glycerol and three fatty acids. Use in long-term energy storage and thermal insulation. Phospholipids are amphipathic and form the basis of cell membranes. Steroids include cholesterol and hormones.
- 脂质：甘油三酯由甘油和三个脂肪酸经酯化形成。用于长期能量储存和隔热。磷脂是两性分子，构成细胞膜的基础。类固醇包括胆固醇和激素。
- Proteins: Amino acids linked by peptide bonds. Four levels of structure: primary, secondary (alpha-helix, beta-pleated sheet), tertiary (ionic, hydrogen, disulfide bonds, hydrophobic interactions), and quaternary (e.g., haemoglobin). Denaturation affects shape and function.
- 蛋白质：氨基酸通过肽键连接。四级结构：一级、二级（α-螺旋、β-折叠）、三级（离子键、氢键、二硫键、疏水相互作用）和四级（如血红蛋白）。变性影响形状和功能。
- Nucleic acids: DNA and RNA are polymers of nucleotides. DNA is double-stranded with complementary base pairing (A-T, C-G); RNA is single-stranded (A-U). Compare and contrast their roles and structures.
- 核酸：DNA和RNA是核苷酸的多聚体。DNA双链，碱基互补配对（A-T, C-G）；RNA单链（A-U）。比较它们的角色和结构。
3. Enzymes and Metabolism | 酶与代谢
Enzymes are globular proteins that act as biological catalysts, lowering activation energy without being consumed. Understand the induced-fit model: the active site is not a rigid shape but moulds around the substrate. Factors affecting enzyme activity include temperature, pH, and substrate concentration. Be able to interpret graphs and design experiments to investigate these factors.
酶是球状蛋白质，作为生物催化剂，降低活化能而自身不被消耗。理解诱导契合模型：活性位点不是刚性形状，而是围绕底物发生变化。影响酶活性的因素包括温度、pH值和底物浓度。要能解读图表并设计实验探究这些因素。
- Inhibitors: Competitive inhibitors bind at the active site and can be overcome by increasing substrate concentration. Non-competitive inhibitors bind at an allosteric site, altering the active site shape; Vₘₐₓ decreases, Kₘ unchanged.
- 抑制剂：竞争性抑制剂结合在活性位点，增加底物浓度可克服其作用。非竞争性抑制剂结合在别构位点，改变活性位点形状；Vₘₐₓ降低，Kₘ不变。
- Immobilised enzymes: Used in industry (e.g., lactose-free milk production). Advantages include enzyme reusability, product purity, and stability.
- 固定化酶：应用于工业（如生产无乳糖牛奶）。优点包括酶可重复使用、产物纯净和稳定性高。
4. Cellular Respiration | 细胞呼吸
Cellular respiration is the controlled release of energy from organic compounds to produce ATP. Distinguish between aerobic and anaerobic respiration. The four stages of aerobic respiration are glycolysis, link reaction, Krebs cycle, and the electron transport chain (ETC) / oxidative phosphorylation. Know the location, inputs, outputs, and ATP yield of each.
细胞呼吸是有机物受控分解释能生成ATP的过程。区分有氧呼吸和无氧呼吸。有氧呼吸的四个阶段是：糖酵解、连接反应、克雷布斯循环、电子传递链/氧化磷酸化。记住每个阶段的发生场所、投入物、产出物和ATP产量。
- Glycolysis: Occurs in cytoplasm. Glucose (6C) → 2 pyruvate (3C). Net gain: 2 ATP, 2 NADH.
- 糖酵解：发生在细胞质。葡萄糖（6C）→ 2丙酮酸（3C）。净收益：2 ATP, 2 NADH。
- Link reaction & Krebs cycle: eased, NADH formed). Krebs cycle: 2 CO₂, 1 ATP, 3 NADH, 1 FADH₂ per turn (×2 per glucose).
- 连接反应与克雷布斯循环：在线粒体基质。丙酮酸→乙酰辅酶A（释放CO₂，形成NADH）。克雷布斯循环：每轮产2 CO₂、1 ATP、3 NADH、1 FADH₂（每分子葡萄糖×2）。
- ETC and chemiosmosis: On inner mitochondrial membrane. NADH and FADH₂ donate electrons; H⁺ gradient drives ATP synthase. O₂ is final electron acceptor. Total ATP yield ~ 30-32 per glucose.
- 电子传递链与化学渗透：在线粒体内膜。NADH和FADH₂提供电子；H⁺梯度驱动ATP合酶。O₂是最终电子受体。每分子葡萄糖约产生30-32个ATP。
- Anaerobic respiration: D⁺). In yeast and plants, pyruvate → ethanol + CO₂. Both yield only 2 ATP from glycolysis.
- 无氧呼吸：动物体内，丙酮酸→乳酸（再生NAD⁺）。酵母和植物，丙酮酸→乙醇+CO₂。两者都仅从糖酵解获得2个ATP。
5. Photosynthesis | 光合作用
Photosynthesis uses light energy to convert CO₂ and H₂O into glucose and O₂. It occurs in chloroplasts. The two main stages are light-dependent reactions (in thylakoid membranes) and light-independent reactions (Calvin cycle, in stroma). Understand the role of pigments (chlorophyll a, accessory pigments) and the action/absorption spectra.
光合作用利用光能将CO₂和H₂O转化为葡萄糖和O₂。它发生在叶绿体中。两大阶段：光依赖反应（在类囊体膜上）和非光依赖反应（卡尔文循环，在基质中）。要理解色素的作用（叶绿素a、辅助色素）以及作用光谱/吸收光谱。
- Light-dependent reactions: Photolysis of water produces H⁺, electrons, and O₂. Non-cyclic photophosphorylation generates ATP and NADPH via photosystems II and I. Cyclic photophosphorylation produces only ATP.
- 光反应：水的光解产生H⁺、电子和O₂。非环式光合磷酸化通过光系统II和I生成ATP和NADPH。环式光合磷酸化只产生ATP。
- Calvin cycle: GP). Reduction of GP to triose phosphate using ATP and NADPH. Regeneration of RuBP. The first product is GP (3C), hence C3 pathway.
- 卡尔文循环：RuBisCO固定CO₂（RuBP + CO₂ → 2 GP）。利用ATP和NADPH将GP还原为磷酸丙糖。RuBP的再生。首产物是GP（3C）故称C3途径。
- Limiting factors: Light intensity, CO₂ concentration, temperature. Be able to explain graphs showing plateaus and optima.
- 限制因素：光强度、CO₂浓度、温度。能解释显示平台期和最适条件的图表。
6. Molecular Genetics | 分子遗传学
emi-conservative and involves helicase, DNA polymerase (III and I), primase, ligase, and Okazaki fragments on the lagging strand. Understand the Meselson-Stahl experiment that proved semi-conservative replication.
遗传信息的流向是DNA→RNA→蛋白质。DNA复制是半保留的，涉及解旋酶、DNA聚合酶（III和I）、引物酶、连接酶以及滞后链上的冈崎片段。理解证明半保留复制的梅塞尔森-斯塔尔实验。
- Transcription: In nucleus (eukaryotes). RNA polymerase synthesises mRNA using the antisense strand as template. mRNA is processed: 5' cap, poly-A tail, splicing (introns removed).
- 转录：在细胞核（真核生物）。RNA聚合酶以反义链为模板合成mRNA。mRNA加工：加5'帽、poly-A尾、剪接（去除内含子）。
- Translation: Ribosomes bind mRNA. tRNA anticodons pair with mRNA codons. Peptide bonds form between amino acids. Initiation, elongation, termination. The genetic code is degenerate and universal.
- 翻译：核糖体结合mRNA。tRNA反密码子与mRNA密码子配对。氨基酸间形成肽键。起始、延伸、终止。遗传密码是简并且通用的。
- Gene expression in prokaryotes: Lac operon as an example of gene regulation: regulator gene, promoter, operator, structural genes. Inducible system.
- 原核生物基因表达：乳糖操纵子作为基因调控实例：调节基因、启动子、操纵基因、结构基因。诱导型系统。
7. Genetics and Evolution | 遗传与进化
Meiosis produces haploid gametes and introduces genetic variation through crossing over (prophase I) and independent assortment (metaphase I). Compare mitosis and meiosis. Non-disjunction can lead to aneuploidy (e.g., Down syndrome, trisomy 21).
减数分裂产生单倍体配子，并通过交叉互换（前期I）和自由组合（中期I）引入遗传变异。比较有丝分裂与减数分裂。染色体不分离可导致非整倍体（如唐氏综合征，21三体）。
- Mendelian genetics: Monohybrid and dihybrid crosses. Dominant, recessive, codominant, sex-linked traits. Understand using Punnett squares and pedigree charts. Test cross to determine unknown genotypes.
- 孟德尔遗传：单基因和双基因杂交。显性、隐性、共显性、伴性性状。会使用庞纳特方格和系谱图。测交以确定未知基因型。
- Natural selection and evolution: Variation, overproduction, competition, survival of the fittest, and change in allele frequency. Evidence: fossil record, homologous structures, DNA sequences. Speciation: allopatric and sympatric.
- 自然选择与进化：变异、过度繁殖、竞争、适者生存、等位基因频率改变。证据：化石记录、同源结构、DNA序列。物种形成：异域和同域。
8. Ecology and Ecosystems | 生态与生态系统
s heat, so it is not recycled. Nutrients, however, are recycled within biogeochemical cycles (carbon and nitrogen).
理解关键术语：物种、种群、群落、生态系统、生物群系、生物圈。能量流经生态系统（光→生产者中的化学能→消费者），并以热的形式散失，因此不可循环。然而养分在生物地球化学循环（碳循环和氮循环）中被循环利用。
- Food chains and webs: Trophic levels (producer, primary consumer, etc.). Energy losses between levels (only ~10% transferred). Ecological pyramids of numbers, biomass, energy. Energy pyramid is always upright.
- 食物链与食物网：营养级（生产者、初级消费者等）。营养级间能量损失（仅约10%传递）。数量、生物量、能量金字塔。能量金字塔总是正立。
- Carbon cycle: Photosynthesis fixes CO₂; respiration, combustion, decomposition release it. Methane is produced by methanogens in anaerobic conditions. Peat formation sequesters carbon.
- 碳循环：光合作用固定CO₂；呼吸、燃烧、分解释放CO₂。甲烷由厌氧条件下的产甲烷菌产生。泥炭形成封存碳。
- Climate change: Enhanced greenhouse effect due to rising CO₂ and methane. Consequences: rising temperatures, sea level rise, changes in precipitation patterns. Evaluate data and models.
- 气候变化：CO₂和甲烷上升导致增强的温室效应。后果：气温升高、海平面上升、降水模式改变。评估数据和模型。
9. Human Physiology Overview | 人体生理学概要
This section consolidates key aspects of the digestive, circulatory, and immune systems. Focus on the processes, not just memorising names. Digestion: enzymes break down macromolecules (amylase for starch, proteases for proteins, lipases for lipids). Absorption in the small intestine is aided by villi and microvilli.
本小节串联消化、循环和免疫系统的关键方面。关注过程而非死记硬背名称。消化：酶分解大分子（淀粉酶分解淀粉，蛋白酶分解蛋白质，脂肪酶分解脂质）。小肠吸收通过绒毛和微绒毛促进。
- Heart and circulation: Double circulation in mammals. Sinoatrial node (SAN) initiates heartbeat; atrioventricular node (AVN) delays impulse. Cardiac cycle: atrial systole, ventricular systole, diastole. Arteries, veins, capillaries compared.
- 心脏与循环：哺乳动物的双循环。窦房结发起心跳；房室结延迟冲动。心动周期：心房收缩、心室收缩、舒张。比较动脉、静脉和毛细血管。
- Defence against disease: Skin and mucous membranes as barriers. Phagocytes (non-specific) and lymphocytes (specific). Antibodies are produced by B-cells. Antibiotics target bacteria, not viruses. Vaccination induces memory cell production.
- 对抗疾病：皮肤和粘膜作为屏障。吞噬细胞（非特异性）和淋巴细胞（特异性）。抗体由B细胞产生。抗生素针对细菌，对病毒无效。疫苗接种诱导记忆细胞产生。
- Be able to analyse data on blood pressure, ECG traces, and disease transmission.
- 要会分析血压、心电图描记和疾病传播的数据。
10. Data Analysis and Practical Skills | 数据分析与实验技能
IB Biology emphasises the scientific process. You should be able to plan investigations, identify variables, process data (mean, standard deviation, t-test), and draw conclusions. Be familiar with ethical considerations and the use of model organisms.
IB 生物强调科学探究过程。你应该能设计探究，确定变量，处理数据（平均值、标准差、t检验），并得出结论。要熟悉伦理考量和模式生物的使用。
- Graph drawing: Use appropriate scales, labelled axes with units, and best-fit lines or curves. Distinguish between continuous and discrete data.
- 绘图：使用合适的刻度，坐标轴标注及单位，最佳拟合线或曲线。区分连续数据和离散数据。
- Measuring techniques: Potometers (transpiration rate), respirometers (respiration rate), colorimeters (concentration), quadrats and transects (ecological sampling). Understand limitations and uncertainties.
- 测量技术：蒸腾计（蒸腾速率）、呼吸计（呼吸速率）、比色计（浓度）、样方和样线（生态取样）。理解局限性和不确定度。
- Data interpretation: Correlation vs causation. Evaluate claims with evidence. Use statistical tests where appropriate to assess significance (e.g., chi-squared for genetics ratios, t-test for comparing means).
- 数据解读：相关与因果关系。用证据评估主张。酌情使用统计检验来评估显著性（如卡方检验遗传比率、t检验比较平均值）。
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