📚 IB Biology: Final Review Outline | IB 生物期末复习提纲
This comprehensive revision outline covers the core themes, key concepts, and essential terminology for the IB Biology course at both Standard Level (SL) and Higher Level (HL). It is structured to help you efficiently review major topics, check your understanding of fundamental mechanisms, and build confidence ahead of your final examination. Cross-references between topics are emphasised, as synoptic thinking is regularly assessed in IB papers.
这份综合复习提纲涵盖了 IB 生物课程（标准级别 SL 与高级别 HL）的核心主题、关键概念及必要术语。提纲旨在帮助你有条理地回顾主要话题，检验对基础机制的理解，并在期末考试前建立信心。提纲特别强调跨主题的联系，因为综合性思维在 IB 试卷中经常被考查。
1. Cell Biology | 细胞生物学
All living organisms are composed of cells, the smallest units of life. You should be able to compare prokaryotic and eukaryotic cell structures, explain the functions of organelles, and describe membrane structure using the fluid mosaic model. Cell division, including mitosis and the cell cycle, is also fundamental to this topic.
所有生命体都由细胞组成，细胞是生命的最小单位。你需要能够比较原核细胞与真核细胞的结构，解释细胞器的功能，并用流动镶嵌模型描述膜的结构。细胞分裂（包括有丝分裂和细胞周期）也是本主题的基础内容。
Key skills include calculating magnification and actual size from micrographs, drawing cells according to biological drawing conventions, and evaluating the evidence for the endosymbiotic theory of mitochondrial and chloroplast origin.
关键技能包括从显微照片计算放大倍数和实际大小，根据生物绘图常规绘制细胞图，以及评估线粒体和叶绿体起源的内共生理论证据。
- Prokaryotic cell structure: naked DNA in a loop, 70S ribosomes, cell wall containing peptidoglycan, no membrane-bound organelles.
- 原核细胞结构： 裸露的环状 DNA、70S 核糖体、含肽聚糖的细胞壁、没有膜包被的细胞器。
- Eukaryotic organelles: nucleus (double membrane with pores, stores genetic information), rough ER (protein synthesis and transport), smooth ER (lipid synthesis), Golgi apparatus (modification and packaging), lysosomes (digestion), mitochondria (aerobic respiration), chloroplasts (photosynthesis, only in autotrophs).
- 真核细胞器： 细胞核（双层膜并有核孔，储存遗传信息）、粗面内质网（蛋白质合成与运输）、滑面内质网（脂质合成）、高尔基体（修饰与包装）、溶酶体（消化）、线粒体（需氧呼吸）、叶绿体（光合作用，仅限自养生物）。
- Membrane proteins: integral and peripheral; functions in transport (channels, pumps), enzymatic activity, cell recognition, and intercellular junctions.
- 膜蛋白： 内嵌蛋白和外周蛋白；具有运输（通道、泵）、酶活性、细胞识别和细胞间连接等功能。
- Mitosis phases: prophase, metaphase, anaphase, telophase; cytokinesis differs between animal (cleavage furrow) and plant cells (cell plate).
- 有丝分裂阶段： 前期、中期、后期、末期；胞质分裂在动物细胞（分裂沟）和植物细胞（细胞板）中不同。
2. Molecular Biology | 分子生物学
This topic connects biochemistry to living systems. Focus on the structure of the four major biological macromolecules, enzyme kinetics, DNA replication, transcription, and translation. Understanding the relationship between a gene and a polypeptide is central: the sequence of bases determines the sequence of amino acids, which in turn dictates the three-dimensional conformation and function of a protein.
本主题将生物化学与生命系统连接起来。重点关注四大生物大分子的结构、酶动力学、DNA 复制、转录和翻译。理解基因与多肽之间的关系至关重要：碱基序列决定氨基酸序列，而氨基酸序列又决定了蛋白质的三维构象和功能。
HL students need to analyse diagrams of the ribosome, tRNA activating enzymes, and the detailed steps of both transcription and translation, including base pair degeneracy.
HL 学生需要分析核糖体、tRNA 活化酶的图示，以及转录和翻译的详细步骤，包括碱基配对的简并性。
- Carbohydrates: monosaccharides (glucose, ribose), disaccharides (maltose, sucrose), polysaccharides (starch, glycogen, cellulose). Condensation and hydrolysis reactions.
- 糖类： 单糖（葡萄糖、核糖）、二糖（麦芽糖、蔗糖）、多糖（淀粉、糖原、纤维素）。缩合反应和水解反应。
- Lipids: triglycerides (ester bonds), phospholipids (amphipathic, form bilayers). Health implications of cis- and trans-unsaturated fatty acids.
- 脂质： 甘油三酯（酯键）、磷脂（两亲性，形成双分子层）。顺式与反式不饱和脂肪酸的健康影响。
- Proteins: primary structure (amino acid sequence), secondary (α-helix, β-pleated sheet), tertiary (3D folding, R-group interactions), quaternary (multiple polypeptides).
- 蛋白质： 一级结构（氨基酸序列）、二级（α‑螺旋、β‑折叠）、三级（三维折叠，R基相互作用）、四级（多条多肽）。
- Enzymes: active site, substrate specificity, lock-and-key vs. induced-fit models. Effects of temperature, pH, substrate concentration on rate. Competitive and non-competitive inhibition.
- 酶： 活性位点、底物特异性、锁钥模型与诱导契合模型。温度、pH、底物浓度对速率的影响。竞争性抑制与非竞争性抑制。
- DNA replication: helicase, DNA polymerase III (adding nucleotides in 5' → 3' direction), leading and lagging strands, Okazaki fragments, DNA ligase.
- DNA 复制： 解旋酶、DNA 聚合酶 III（沿 5' → 3' 方向添加核苷酸）、前导链与后随链、冈崎片段、DNA 连接酶。
- Transcription & translation: promoter, RNA polymerase, mRNA (codons), tRNA (anticodons), ribosomes (A, P, E sites). The genetic code is degenerate but universal.
- 转录与翻译： 启动子、RNA 聚合酶、mRNA（密码子）、tRNA（反密码子）、核糖体（A位、P位、E位）。遗传密码具有简并性但通用。
3. Genetics | 遗传学
Genetics covers inheritance patterns, meiosis, and sources of variation. Be prepared to construct and interpret Punnett grids for monohybrid crosses (including co-dominance, sex linkage) and dihybrid crosses. The difference between autosomal and X-linked inheritance is frequently tested. You should also understand the causes and consequences of gene mutations and chromosomal abnormalities.
遗传学涵盖遗传模式、减数分裂和变异来源。准备好构建和解读单基因杂交（包括共显性、伴性遗传）和双基因杂交的庞纳特方格。常染色体遗传与 X 连锁遗传的区别是常考内容。还应理解基因突变和染色体异常的成因及后果。
- Meiosis: reduction division; crossing over in prophase I, independent assortment in metaphase I, homologous chromosomes separate in anaphase I; sister chromatids separate in anaphase II.
- 减数分裂： 减数分裂；前期 I 的交叉互换、中期 I 的独立分配、后期 I 同源染色体分离；后期 II 姐妹染色单体分离。
- Mendelian ratios: monohybrid (3:1 for dominant-recessive), dihybrid (9:3:3:1 for unlinked genes). Test cross to determine unknown genotype.
- 孟德尔比例： 单基因杂合（显隐性 3:1）、双基因杂合（非连锁基因 9:3:3:1）。测交用于鉴定未知基因型。
- Coinheritance patterns: co-dominance (both alleles expressed, e.g., ABO blood group), incomplete dominance (blending), multiple alleles, sex linkage (e.g., haemophilia, colour blindness).
- 共遗传模式： 共显性（两个等位基因均表达，如 ABO 血型）、不完全显性（中间表型）、复等位基因、伴性遗传（如血友病、色盲）。
- Gene mutations: cell anaemia: GAG → GTG, glutamic acid to valine), insertion/deletion causing frameshifts.
- 基因突变： 碱基替换（镰刀型细胞贫血症：GAG → GTG，谷氨酸变缬氨酸）、插入/缺失导致移码突变。
- Chromosome mutations: non-disjunction causing aneuploidy (Down syndrome, trisomy 21). Karyotyping.
- 染色体突变： 不分离导致非整倍体（唐氏综合征，21 三体）。核型分析。
- Pedigree charts: deduce genotypes and inheritance patterns (autosomal dominant, autosomal recessive, X-linked recessive).
- 系谱图： 推断基因型与遗传模式（常染色体显性、常染色体隐性、X 连锁隐性）。
4. Ecology | 生态学
Ecological concepts bridge species and their environments. Key topics include energy flow through food chains and webs, nutrient cycling (carbon, nitrogen), population growth curves, and the statistical analysis of species distributions using quadrat sampling. The greenhouse effect and its consequences for climate change are essential case studies linking ecology to human impact.
生态学概念将物种与其环境联系起来。关键话题包括食物链和食物网中的能量流动、物质循环（碳循环、氮循环）、种群增长曲线，以及利用样方采样对物种分布进行统计分析。温室效应及其对气候变化的影响是连接生态与人类影响的重要案例。
- Autotrophs vs. heterotrophs: producers (photoautotrophs, chemoautotrophs), consumers (primary, secondary, tertiary), detritivores, saprotrophs.
- 自养生物与异养生物： 生产者（光合自养生物、化能自养生物）、消费者（初级、次级、三级）、食碎屑者、腐生生物。
- Energy pyramids: only about 10% of energy is transferred between trophic levels; energy is lost as heat through respiration.
- 能量金字塔： 营养级之间只有约 10% 的能量被传递；能量通过呼吸作用以热的形式散失。
- Carbon cycle: photosynthesis (fixation), respiration (release), combustion, decomposition, fossil fuel formation, ocean absorption.
- 碳循环： 光合作用（固定）、呼吸作用（释放）、燃烧、分解、化石燃料形成、海洋吸收。
- Greenhouse effect: short-wave solar radiation passes through atmosphere; Earth emits long-wave infrared; CO₂, methane, water vapour trap heat.
- 温室效应： 短波太阳辐射穿过大气层；地球发出长波红外辐射；CO₂、甲烷、水蒸气截留热量。
- Population growth: exponential (J-curve) vs. logistic (S-curve) growth; carrying capacity (K). Factors limiting population: density-dependent (disease, competition) and density-independent (natural disasters).
- 种群增长： 指数增长（J 型曲线）与逻辑斯蒂增长（S 型曲线）；环境容纳量 (K)。限制种群的因素：密度制约（疾病、竞争）与非密度制约（自然灾害）。
- Chi-squared test for distribution: used to test association between two species or habitat preferences, comparing observed vs. expected frequencies.
- 分布的卡方检验： 用于检验两个物种之间或与生境偏好的关联性，比较观察值与预期值。
5. Evolution and Biodiversity | 进化与生物多样性
Natural selection is the mechanism of evolution. Be able to explain how variation, overproduction, competition, and differential survival lead to a change in allele frequency over generations. Speciation can occur through geographic isolation (allopatric) or reproductive isolation within the same area (sympatric). Classification is based on cladistics and the binomial system.
自然选择是进化的机制。要能解释变异、过度繁殖、竞争和差异性生存如何导致逐代的等位基因频率改变。物种形成可通过地理隔离（异域）或同一区域内的生殖隔离（同域）发生。分类基于支序分类学和双名法。
- Evidence for evolution: fossil record, homologous structures, selective breeding, comparative DNA/amino acid sequences.
- 进化证据： 化石记录、同源结构、选择育种、DNA/氨基酸序列比较。
- Antibiotic resistance: a classic example of natural selection; bacteria with resistant genes survive and reproduce in the presence of antibiotics.
- 抗生素耐药性： 是自然选择的经典范例；存在耐药基因的细菌在抗生素存在时存活并繁殖。
- Speciation: allopatric (geographical barrier) and sympatric (behavioural, temporal, mechanical isolation; polyploidy in plants).
- 物种形成： 异域（地理屏障）与同域（行为、时间、机械隔离；植物中的多倍体化）。
- Binomial nomenclature: Genus species (italicised or underlined), e.g., Homo sapiens.
- 双名法： 属名 + 种加词（斜体或下划线），如 Homo sapiens。
- Cladistics: cladograms based on shared derived traits; monophyletic groups (clades). Keys to identify organisms.
- 支序分类学： 基于共源性状的支序图；单系群（支序）。用于鉴定生物的检索表。
6. Human Physiology (SL Core) | 人体生理学（SL 核心）
The SL physiology unit covers digestion, circulation, defence against infectious disease, gas exchange, neurons and synapses, and hormones. Focus on mechanisms and processes, such as peristalsis, the heart cycle, specific immune response, ventilation, nerve impulse transmission, and blood glucose regulation.
SL 生理学单元涵盖消化、循环、抗感染防御、气体交换、神经元与突触，以及激素。重点关注机制与过程，如蠕动、心动周期、特异性免疫应答、通气、神经冲动传递和血糖调节。
- Digestion: amylase (mouth, pancreas), pepsin (stomach, optimal pH ~2), lipase (pancreas, with bile salts). Absorption of glucose and amino acids in villi (active transport and facilitated diffusion).
- 消化： 淀粉酶（口腔、胰腺）、胃蛋白酶（胃，最适 pH ≈ 2）、脂肪酶（胰腺，需胆盐协助）。葡萄糖和氨基酸在绒毛中的吸收（主动运输和协助扩散）。
- Cardiac cycle: sinoatrial node (pacemaker), atrial systole, ventricular systole, diastole. Arteries vs. veins vs. capillaries.
- 心动周期： 窦房结（起搏点）、心房收缩、心室收缩、舒张。动脉、静脉与毛细血管的比较。
- Immune response: non-specific (skin, mucous membranes, phagocytes) and specific (antibody production by B-lymphocytes, cytotoxic T-cells). Antibiotics are ineffective against viruses.
- 免疫应答： 非特异性（皮肤、粘膜、吞噬细胞）和特异性（B 淋巴细胞产生抗体、细胞毒性 T 细胞）。抗生素对病毒无效。
- Ventilation: inhalation (diaphragm contracts and flattens, external intercostal muscles contract, thoracic volume increases, pressure decreases); exhalation is largely passive.
- 通气： 吸气（膈肌收缩变平、外肋间肌收缩、胸廓容积增大、压力下降）；呼气主要是被动的。
- Action potential: resting potential (−70 mV), depolarisation (Na⁺ channels open, threshold −50 mV), repolarisation (K⁺ channels open), refractory period. Propagation is saltatory in myelinated axons.
- 动作电位： 静息电位（−70 mV）、去极化（钠通道开放，阈电位 −50 mV）、复极化（钾通道开放）、不应期。有髓鞘轴突中为跳跃式传导。
- Blood glucose regulation: insulin (β-cells, lowers blood glucose), glucagon (α-cells, raises blood glucose). Diabetes: Type I (autoimmune β-cell destruction) and Type II (insulin resistance).
- 血糖调节： 胰岛素（β 细胞，降低血糖）、胰高血糖素（α 细胞，升高血糖）。糖尿病：I 型（自身免疫性 β 细胞破坏）与 II 型（胰岛素抵抗）。
7. HL Topic 7: Nucleic Acids | 高级主题 7：核酸
HL students extend their knowledge of DNA structure to include details of nucleosomes, the Hershey-Chase experiment, and non-coding DNA. The processes of DNA replication, transcription, and translation are examined in greater depth, including the role of the promoter, enhancers, silencers, and post-transcriptional modification in eukaryotes.
HL 学生将 DNA 结构知识扩展到核小体细节、Hershey-Chase 实验和非编码 DNA。DNA 复制、转录和翻译的过程被更深入地考查，包括启动子、增强子、沉默子的作用，以及真核生物中的转录后修饰。
- DNA packaging: DNA wraps around histone proteins to form nucleosomes, which coil to form chromatin fibres. This supercoiling allows DNA to fit inside the nucleus and regulates gene expression.
- DNA 包装： DNA 缠绕组蛋白形成核小体，核小体螺旋化形成染色质纤维。这种超螺旋化使 DNA 能容纳在细胞核内，并调控基因表达。
- Hershey-Chase experiment: used radioactive sulfur (¹³⁵S, labels protein) and phosphorus (¹³²P, labels DNA); confirmed DNA is the genetic material.
- Hershey-Chase 实验： 使用放射性硫（¹³⁵S，标记蛋白质）和磷（¹³²P，标记 DNA）；证实 DNA 是遗传物质。
- Replication details (HL): origins of replication, DNA primase, RNA primers, DNA polymerase I removes primers and replaces with DNA. Telomeres and telomerase.
- 复制细节（HL）： 复制起点、DNA 引发酶、RNA 引物、DNA 聚合酶 I 移除引物并用 DNA 替代。端粒和端粒酶。
- Transcription (HL): transcription factors bind to TATA box, RNA polymerase II. Post-transcriptional modification in eukaryotes: 5' cap, poly-A tail, splicing (introns removed, exons joined by spliceosomes).
- 转录（HL）： 转录因子与 TATA 盒结合，RNA 聚合酶 II。真核生物转录后修饰：5' 帽子、poly-A 尾、剪接（内容子切除，外显子通过剪接体连接）。
- Translation (HL): initiation complex, elongation (peptide bond formation catalysed by ribozyme activity of rRNA), termination. Polysomes. tRNA activating enzymes (proofreading).
- 翻译（HL）： 起始复合物、延伸（rRNA 的核酶活性催化肽键形成）、终止。多核糖体。tRNA 活化酶（校对功能）。
8. HL Topic 8: Metabolism, Cell Respiration & Photosynthesis | 高级主题 8：代谢、细胞呼吸与光合作用
Enzyme inhibition is revisited with more quantitative analysis. Metabolic pathways are controlled by end-product inhibition. The chemiosmotic theory underpins ATP synthesis in both respiration and photosynthesis. HL students must be able to draw and annotate the structure of a mitochondrion and chloroplast, linking structure to function.
酶抑制通过更定量的分析重新审视。代谢途径受最终产物抑制调控。化学渗透学说支撑呼吸作用和光合作用中 ATP 的合成。HL 学生必须能够绘制并注释线粒体和叶绿体的结构，将结构与功能联系起来。
- Enzyme kinetics: Michaelis-Menten plot (Vₘₐₓ, Kₘ). Lineweaver-Burk plot for identifying competitive vs. non-competitive inhibition.
- 酶动力学： 米氏图（Vₘₐₓ, Kₘ）。用于鉴定竞争性抑制与非竞争性抑制的 Lineweaver-Burk 图。
- Glycolysis: occurs in cytoplasm; glucose → 2 pyruvate, net gain of 2 ATP and 2 NADH.
- 糖酵解： 发生在细胞质中；葡萄糖 → 2 丙酮酸，净生成 2 ATP 和 2 NADH。
- Link reaction & Krebs cycle: NADH produced). Krebs cycle in mitochondrial matrix produces ATP by substrate-level phosphorylation, plus NADH and FADH₂.
- 连接反应与三羧酸循环： 丙酮酸 → 乙酰辅酶 A（释放 CO₂，产生 NADH）。线粒体基质中的三羧酸循环通过底物水平磷酸化产生 ATP，以及 NADH 和 FADH₂。
- Electron transport chain: inner mitochondrial membrane; electrons from NADH/FADH₂ passed through carriers, protons pumped into intermembrane space; chemiosmosis: ATP synthase uses proton gradient to make ATP. O₂ is the final electron acceptor, forming water.
- 电子传递链： 线粒体内膜；来自 NADH/FADH₂ 的电子通过载体传递，质子泵入膜间隙；化学渗透：ATP 合酶利用质子梯度制造 ATP。O₂ 是终末电子受体，生成水。
- Light-dependent reactions: trons), electron transport chain, photosystem I, production of NADPH and ATP via chemiosmosis.
- 光反应： 发生在类囊体膜；光系统 II（水的光解 → O₂、H⁺、电子）、电子传递链、光系统 I，通过化学渗透产生 NADPH 和 ATP。
- Calvin cycle: in stroma; carbon fixation (RuBisCO), reduction (using ATP and NADPH from light reactions), regeneration of RuBP. Glucose is not the direct product—G3P is.
- 卡尔文循环： 位于基质；碳固定（RuBisCO）、还原（利用光反应提供的 ATP 和 NADPH）、RuBP 的再生。直接产物是 G3P 而非葡萄糖。
9. HL Topic 9: Plant Biology | 高级主题 9：植物生物学
Plant biology at HL focuses on transport, phytohormones, and reproduction. Xylem and phloem structures are adapted for their functions: water transport under tension and active translocation of organic solutes. Photoperiodism and the control of flowering by phytochrome are key concepts.
HL 植物生物学重点为运输、植物激素和生殖。木质部和韧皮部的结构适应其功能：在张力下运输水分和有机物溶质的主动转运。光周期现象和光敏色素对开花的控制是关键概念。
- Xylem transport: cohesion-tension theory; transpiration pull generated by evaporation from stomata; cohesive and adhesive properties of water; continuous water columns in xylem vessels. Xerophyte adaptations to reduce transpiration.
- 木质部运输： 内聚力-张力理论；气孔蒸发产生的蒸腾拉力；水分子间的内聚力和与管壁的附着力；木质部导管中的连续水柱。旱生植物减少蒸腾作用的适应特征。
- Phloem translocation: pressure-flow hypothesis; active loading of sucrose at source (companion cells use proton pumps and co-transporter proteins); high osmotic pressure draws water into phloem, creating pressure gradient to sink.
- 韧皮部转运： 压力流动假说；在源端主动装载蔗糖（伴胞使用质子泵和协同转运蛋白）；高渗透压将水吸入韧皮部，产生流向库的压力梯度。
- Plant hormones: auxin (cell elongation, apical dominance, phototropism via asymmetric distribution); gibberellin (stem elongation, seed germination); abscisic acid (stomatal closure during drought).
- 植物激素： 生长素（细胞伸长、顶端优势、通过不对称分布实现向光性）；赤霉素（茎伸长、种子萌发）；脱落酸（干旱胁迫下气孔关闭）。
- Photoperiodism: es flowering in long-day plants (short nights) and inhibits flowering in short-day plants.
- 光周期现象： 光敏色素存在两种形式：Pr（无活性）和 Pfr（有活性）。红光使 Pr → Pfr；远红光使 Pfr → Pr。Pfr 促进长日植物（短夜）开花，抑制短日植物开花。
10. HL Topic 10: Genetics and Evolution | 高级主题 10：遗传与进化
This topic strengthens the SL foundation with linkage, recombination, and statistical analysis of genetic crosses (chi-squared test). Gene pools, allele frequencies, and the Hardy–Weinberg principle are used to detect evolutionary change. Speciation is linked to polyploidy and isolating mechanisms in more detail.
本主题通过连锁、重组和遗传杂交的统计分析（卡方检验）强化 SL 基础。基因库、等位基因频率和哈迪-温伯格原理用于检测进化改变。物种形成更详细地与多倍体化和隔离机制相关联。
- Linked genes: genes on the same chromosome do not assort independently; recombination frequency indicates map distance. Dihybrid crosses with linked genes produce parental-type gametes more frequently.
- 连锁基因： 同一染色体上的基因不遵循自由组合；重组频率指示图距。连锁基因的双因子杂交产生更多亲本型配子。
- Chi-squared test in genetics: pected Mendelian ratios; use critical values at p=0.05 and appropriate degrees of freedom.
- 遗传学中的卡方检验： 确定观察到的表型比是否与预期的孟德尔比例显著不同；使用 p=0.05 下的临界值和合适的自由度。
- Hardy–Weinberg equations: = 1. Conditions: large population, random mating, no mutation, no gene flow, no selection.
- 哈迪-温伯格方程： p + q = 1；p² + 2pq + q² = 1。条件：大种群、随机交配、无突变、无基因流动、无选择。
- Polyploidy: common sympatric speciation mechanism in plants; autopolyploidy (chromosome doubling within a species) and allopolyploidy (hybridisation between species followed by doubling).
- 多倍体化： 植物中常见的同域物种形成机制；同源多倍体（物种内染色体加倍）和异源多倍体（物种间杂交后加倍）。
11. HL Topic 11: Animal Physiology | 高级主题 11：动物生理学
This HL extension deepens the study of immunology, muscle contraction, kidney function, and sexual reproduction. Antibody structure, the roles of B-cells and T-cells, monoclonal antibodies, and vaccines are examined. The sliding filament model and osmoregulation are central integrative topics.
此 HL 延伸内容深化了免疫学、肌肉收缩、肾脏功能和有性生殖的研究。考查抗体结构、B 细胞与 T 细胞的作用、单克隆抗体和疫苗。肌丝滑动模型和渗透调节是核心综合主题。
- Specific immunity: antigen presentation by macrophages, activation of helper T-cells (CD4+), activation of B-cells and cytotoxic T-cells (CD8+). Memory cells provide long-term immunity.
- 特异性免疫： 巨噬细胞提呈抗原、辅助性 T 细胞（CD4+）的激活、B 细胞和细胞毒性 T 细胞（CD8+）的激活。记忆细胞提供长期免疫。
- Antibodies: Y-shaped proteins with variable regions that bind specific epitopes. Plasma cells produce large quantities. Monoclonal antibodies: produced by hybridoma cells, used in diagnostics and targeted therapy.
- 抗体： Y 形蛋白质，具有结合特定表位的可变区。浆细胞大量产生抗体。单克隆抗体：由杂交瘤细胞产生，用于诊断和靶向治疗。
- Muscle contraction: sarcomere shortening; actin (thin filament) and myosin (thick filament). Sliding filament model: myosin heads bind to actin, perform power stroke, ATP required for detachment. Calcium ions and troponin/tropomyosin regulate binding.
- 肌肉收缩： 肌节缩短；肌动蛋白（细丝）和肌球蛋白（粗丝）。肌丝滑动模型：肌球蛋白头部与肌动蛋白结合，执行动力冲程，需要 ATP 才能分离。钙离子和肌钙蛋白/原肌球蛋白调控结合。
- Nephron function: ultrafiltration in glomerulus (podocytes, fenestrated capillaries, basement membrane); selective reabsorption in proximal convoluted tubule (glucose, amino acids, water); loop of Henle (countercurrent multiplier creates medullary osmotic gradient); osmoregulation by ADH (aquaporins in collecting duct).
- 肾单位功能： 肾小球超滤（足细胞、有孔毛细血管、基膜）；近曲小管选择性重吸收（葡萄糖、氨基酸、水）；髓袢（逆流倍增器建立髓质渗透梯度）；抗利尿激素 ADH 调节渗透（集合管中的水通道蛋白）。
- Spermatogenesis and oogenesis: spermatogenesis produces four haploid sperm; oogenesis produces one ovum and polar bodies. Fertilisation: acrosome reaction, cortical reaction, fusion of nuclei.
- 精子发生与卵子发生： 精子发生产生四个单倍体精子；卵子发生产生一个卵子和极体。受精过程：顶体反应、皮层反应、核融合。
12. Exam Techniques and Command Terms | 考试技巧与指令术语
Mastering IB Biology examinations requires more than content recall—you must decode command terms precisely and manage your time strategically. Paper 1 consists of multiple-choice questions; Paper 2 includes data-based questions and short-answer/essay responses; Paper 3 examines the Option topic plus a section on experimental skills. HL students must also answer end-of-paper questions that go deeper.
掌握 IB 生物考试需要的不仅仅是回忆内容——你必须精确解读指令术语，并有策略地管理时间。试卷 1 为选择题；试卷 2 包含数据分析题和简答题/论述题；试卷 3 考查 Option 主题以及实验技能部分。HL 考生还需回答卷尾更深入的题目。
- Command terms – Objective 1 (recall): Define, Draw, Label, List, State. Provide clear, concise answers (e.g., "Define osmosis: the passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration across a partially permeable membrane.")
- 指令术语 – 目标 1（识记）： Define（定义）、Draw（绘图）、Label（标注）、List（列举）、State（陈述）。给出清晰、简洁的答案。
- Command terms – Objective 2 (understand & apply): Describe, Outline, Summarise, Distinguish, Compare. Use comparisons and sequences (e.g., "Compare
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