📚 IB & Edexcel Biology: End-of-Term Revision Outline | IB & Edexcel 生物：期末复习提纲
This revision guide is designed for students preparing for end-of-term assessments in IB Biology (SL/HL) and Edexcel International A‑Level Biology. It consolidates the core themes, essential definitions, key experimental techniques, and frequently tested data‑analysis skills. Use it to check your understanding, fill gaps, and focus your final revision sessions.
本复习提纲适用于正在准备IB生物（SL/HL）和Edexcel国际A‑Level生物学期末考试的学生。它整合了核心主题、关键定义、重要实验技术以及常考的数据分析技能。你可以用它来检验理解、填补漏洞，并集中进行最后的复习。
1. Cell Structure & Function | 细胞结构与功能
Prokaryotic cells lack a membrane‑bound nucleus and organelles; they possess 70S ribosomes, a circular DNA molecule, and may have plasmids. Eukaryotic cells contain a true nucleus, membrane‑bound organelles such as mitochondria and the Golgi apparatus, and 80S ribosomes. In IB and Edexcel, you must be able to compare these two cell types and draw and label a typical bacterium, a liver cell, and a palisade mesophyll cell.
原核细胞没有膜包围的细胞核和细胞器；它们含有70S核糖体、一个环状DNA分子，并可能拥有质粒。真核细胞含有真正的细胞核、线粒体和高尔基体等有膜细胞器，以及80S核糖体。在IB和Edexcel考试中，你必须能够比较这两种细胞类型，并能画出并标注典型的细菌、肝细胞和栅栏叶肉细胞。
Electron microscopes reveal ultrastructure: transmission electron microscopes (TEM) give high‑resolution 2D images, while scanning electron microscopes (SEM) produce 3D surface views. Magnification = image size ÷ actual size; always convert to the same units before calculating.
电子显微镜可以揭示超微结构：透射电子显微镜（TEM）提供高分辨率二维图像，而扫描电子显微镜（SEM）生成三维表面视图。放大倍数 = 图像大小 ÷ 实际大小；在计算前务必转换成相同的单位。
The fluid mosaic model describes membranes as a phospholipid bilayer with embedded proteins, cholesterol (in animal cells), and glycoproteins. Membrane transport includes simple diffusion, facilitated diffusion via channel or carrier proteins, osmosis, and active transport using ATP. Endocytosis and exocytosis allow bulk transport. You must predict the effects of placing a cell in hypotonic, isotonic, or hypertonic solutions.
流动镶嵌模型将膜描述为由磷脂双分子层及嵌在其中的蛋白质、胆固醇（动物细胞中）和糖蛋白构成。膜运输包括简单扩散、通过通道蛋白或载体蛋白的协助扩散、渗透作用，以及利用ATP的主动运输。胞吞作用和胞吐作用实现大块物质的运输。你必须预判将细胞置于低渗、等渗或高渗溶液中的影响。
2. Biological Molecules | 生物分子
Water’s properties (cohesion, adhesion, high specific heat capacity, and solvent ability) stem from its polarity and hydrogen bonding. These properties are essential for life: transport in plants, temperature regulation, and metabolic reactions.
水的特性（内聚力、附着力、高比热容和溶剂能力）源于其极性和氢键。这些特性对生命至关重要：植物体内的运输、温度调节和代谢反应。
Carbohydrates include monosaccharides (glucose, galactose, fructose), disaccharides (maltose, sucrose, lactose), and polysaccharides (starch, glycogen, cellulose). Glycosidic bonds form by condensation and break by hydrolysis. You must be able to relate the structure of starch (amylose and amylopectin) and glycogen to their roles as energy stores, and the structure of cellulose to its role in plant cell walls.
碳水化合物包括单糖（葡萄糖、半乳糖、果糖）、二糖（麦芽糖、蔗糖、乳糖）和多糖（淀粉、糖原、纤维素）。糖苷键通过缩合反应生成，通过水解反应断裂。你必须能够将淀粉（直链淀粉和支链淀粉）和糖原的结构与其能量储存功能联系起来，以及将纤维素的结构与其在植物细胞壁中的作用联系起来。
Lipids: triglycerides are formed from glycerol and three fatty acids via ester bonds; phospholipids have a phosphate head and two fatty acid tails. Fats are hydrophobic and function in energy storage, insulation, and as components of cell membranes. Unsaturated fatty acids have one or more C=C double bonds (liquid oils), while saturated fatty acids have no double bonds (solid fats).
脂类：甘油三酯由甘油和三个脂肪酸通过酯键形成；磷脂具有一个磷酸头基和两个脂肪酸尾。脂肪具有疏水性，在能量储存、绝缘和细胞膜组成中起重要作用。不饱和脂肪酸含有一个或多个C=C双键（液态油），而饱和脂肪酸不含双键（固态脂肪）。
Proteins: amino acids are linked by peptide bonds; the four levels of structure (primary, secondary, tertiary, quaternary) determine the protein’s shape and function. Fibrous proteins (e.g., collagen) are structural, while globular proteins (e.g., enzymes, haemoglobin) are functional. Denaturation disrupts tertiary structure, usually irreversibly.
蛋白质：氨基酸通过肽键连接；四级结构（一级、二级、三级、四级）决定了蛋白质的形状和功能。纤维状蛋白（如胶原蛋白）起结构作用，而球状蛋白（如酶、血红蛋白）起功能作用。变性会破坏三级结构，通常是不可逆的。
Enzymes: biological catalysts that lower activation energy. The induced‑fit model describes substrate‑specific binding. Factors affecting enzyme activity include temperature, pH, substrate concentration, and inhibitors (competitive and non‑competitive). Be able to interpret Vmax and Km from graphs and design experiments investigating enzyme kinetics.
酶：降低活化能的生物催化剂。诱导契合模型描述了底物特异性结合。影响酶活性的因素包括温度、pH、底物浓度以及抑制剂（竞争性和非竞争性）。要能根据图表解读Vmax和Km，并设计研究酶动力学的实验。
3. Nucleic Acids & Molecular Genetics | 核酸与分子遗传学
DNA is a double helix of nucleotides (deoxyribose sugar, phosphate, base: A, T, C, G). The two strands are antiparallel and held by hydrogen bonds between complementary base pairs (A‑T two bonds, C‑G three bonds). RNA is usually single‑stranded and contains uracil instead of thymine. You must draw and label a simplified nucleotide and a section of DNA.
DNA是核苷酸（脱氧核糖、磷酸、碱基：A、T、C、G）组成的双螺旋结构。两条链反向平行，通过互补碱基对之间的氢键连接（A‑T两个氢键，C‑G三个氢键）。RNA通常是单链，含有尿嘧啶代替胸腺嘧啶。你需要能够画出并标注简化的核苷酸和一段DNA。
DNA replication is semi‑conservative and involves helicase, DNA polymerase, and ligase. Leading strand synthesis is continuous; lagging strand synthesis produces Okazaki fragments. Meselson and Stahl’s experiment proved semi‑conservative replication using nitrogen isotopes.
DNA复制是半保留的，涉及解旋酶、DNA聚合酶和连接酶。前导链是连续合成的；后随链合成产生冈崎片段。梅塞尔森和斯塔尔的实验利用氮的同位素证明了半保留复制。
Protein synthesis: transcription (DNA → mRNA) occurs in the nucleus; RNA polymerase synthesises mRNA complementary to the template strand. Translation occurs on ribosomes; tRNA anticodons match mRNA codons, bringing specific amino acids. The genetic code is degenerate but universal. Be able to use a codon table to determine amino acid sequences from DNA or mRNA.
蛋白质合成：转录（DNA → mRNA）在细胞核内进行；RNA聚合酶合成与模板链互补的mRNA。翻译在核糖体上进行；tRNA反密码子与mRNA密码子匹配，携带特定氨基酸。遗传密码是简并的但通用的。要能够使用密码子表从DNA或mRNA确定氨基酸序列。
4. Cell Division & Genetics | 细胞分裂与遗传学
Mitosis produces two genetically identical diploid daughter cells; stages: prophase, metaphase, anaphase, telophase, and cytokinesis. It is essential for growth, repair, and asexual reproduction. Meiosis produces four genetically different haploid gametes through two divisions; crossing over in prophase I and independent assortment in metaphase I generate variation.
有丝分裂产生两个遗传上相同的二倍体子细胞；阶段包括：前期、中期、后期、末期和胞质分裂。它对生长、修复和无性繁殖至关重要。减数分裂通过两次分裂产生四个遗传上不同的单倍体配子；前期I的交叉互换和中期I的独立分配产生遗传变异。
Mendelian genetics: key terms – allele, dominant, recessive, homozygous, heterozygous, genotype, phenotype, and test cross. Use Punnett squares for monohybrid and dihybrid crosses; predict phenotypic ratios (e.g., 9:3:3:1 for dihybrid). Understand co‑dominance, incomplete dominance, sex‑linkage, and multiple alleles (e.g., human blood groups). Pedigree analysis can reveal modes of inheritance.
孟德尔遗传学：关键术语——等位基因、显性、隐性、纯合子、杂合子、基因型、表现型和测交。利用庞尼特方格进行单基因杂交和双基因杂交；预测表现型比例（如双基因杂交的9:3:3:1）。理解共显性、不完全显性、伴性遗传和复等位基因（如人类血型）。谱系分析可以揭示遗传模式。
5. Evolution & Natural Selection | 进化与自然选择
Darwin’s theory of evolution by natural selection: variation exists within populations, more offspring are produced than can survive, individuals with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation. Over time, the frequency of favourable alleles increases.
达尔文的自然选择进化论：种群内存在变异，产生的后代数量超过了能够存活的数量，具有有利性状的个体更可能存活和繁殖，并将这些性状传递给下一代。随着时间的推移，有利等位基因的频率会增加。
Evidence for evolution includes fossil records, homologous structures (divergent evolution), analogous structures (convergent evolution), vestigial organs, and molecular similarities (DNA and protein sequence comparisons). Antibiotic resistance in bacteria and pesticide resistance in insects are modern examples of observable natural selection.
进化的证据包括化石记录、同源结构（趋异进化）、同功结构（趋同进化）、痕迹器官和分子相似性（DNA和蛋白质序列比对）。细菌的抗生素耐药性和昆虫的杀虫剂耐药性是可观察到的自然选择的现代实例。
Speciation occurs when populations become reproductively isolated. Allopatric speciation involves a geographical barrier; sympatric speciation occurs within the same area due to behavioural, temporal, or mechanical isolation. The Hardy–Weinberg principle: p + q = 1, p² + 2pq + q² = 1. Apply these equations to determine allele frequencies in a population that is not evolving.
当种群出现生殖隔离时就会形成物种。异域物种形成涉及地理障碍；同域物种形成发生在同一地区，由于行为、时间或机械隔离导致。哈代‑温伯格定律：p + q = 1，p² + 2pq + q² = 1。应用这些方程可以确定未进化种群中的等位基因频率。
6. Ecology & Energy Flow | 生态学与能量流动
An ecosystem includes the community (biotic) and its physical environment (abiotic). Food chains and food webs show feeding relationships. Energy enters most ecosystems as sunlight and is converted by producers (photoautotrophs) into chemical energy via photosynthesis. Energy flows through trophic levels but is lost as heat at each transfer (typical efficiency ~10%). Pyramids of energy, biomass, and numbers can be constructed.
生态系统包括生物群落和非生物环境。食物链和食物网展示摄食关系。在大多数生态系统中，能量以阳光形式进入，通过光合作用由生产者（光合自养生物）转化为化学能。能量流经各营养级，但在每次转移中会以热量形式损失（典型效率约10%）。可以构建能量金字塔、生物量金字塔和数量金字塔。
Nutrient cycles: carbon is recycled via photosynthesis, respiration, decomposition, and combustion. The nitrogen cycle involves nitrogen fixation, nitrification, assimilation, ammonification, and denitrification; bacteria play key roles (Rhizobium, Nitrosomonas, Nitrobacter). Be able to draw and label simple diagrams and discuss human impacts such as eutrophication caused by fertiliser run‑off.
营养物质循环：碳通过光合作用、呼吸作用、分解作用和燃烧进行循环。氮循环包括固氮作用、硝化作用、同化作用、氨化作用和反硝化作用；细菌起关键作用（根瘤菌、亚硝化单胞菌、硝化杆菌）。要能够绘制并标注简单示意图，并讨论人类活动的影响，如化肥流失引起的富营养化。
7. Plant Physiology | 植物生理学
Photosynthesis: light‑dependent reactions occur in the thylakoid membrane and produce ATP and reduced NADP; photolysis of water yields oxygen. The Calvin cycle (light‑independent) occurs in the stroma, uses ATP and NADPH to fix CO₂ and produce glucose. Limiting factors include light intensity, CO₂ concentration, and temperature; interpret graphs and design experiments with Elodea or alginate beads.
光合作用：光反应发生在类囊体膜上，产生ATP和还原态NADP；水的光解产生氧气。卡尔文循环（暗反应）发生在基质中，利用ATP和NADPH固定CO₂并生成葡萄糖。限制因素包括光照强度、CO₂浓度和温度；要能解读相关图表，并设计利用伊乐藻或海藻酸盐珠的实验。
Transpiration is the loss of water vapour from leaves, driven by the cohesion‑tension mechanism. Water moves through xylem vessels; mineral ions enter roots by active transport. Translocation of sucrose in the phloem is described by the pressure‑flow hypothesis. Factors affecting transpiration rate (light, temperature, humidity, wind) can be investigated using a potometer.
蒸腾作用是由内聚力‑张力机制驱动的叶片水蒸气损失。水分通过木质部导管运输；矿质离子通过主动运输进入根部。韧皮部中蔗糖的运输由压力流动假说解释。影响蒸腾速率的因素（光照、温度、湿度、风）可以使用蒸腾计进行探究。
8. Mammalian Physiology (Selected Systems) | 哺乳动物生理学（精选系统）
The circulatory system: the heart is a double pump; the cardiac cycle includes atrial systole, ventricular systole, and diastole. Control of heart rate involves the sinoatrial node (pacemaker) and the autonomic nervous system. Blood vessels: arteries carry blood away from the heart (thick muscular walls), veins return blood (with valves), and capillaries are the site of exchange.
循环系统：心脏是一个双泵；心动周期包括心房收缩期、心室收缩期和舒张期。心率控制涉及窦房结（起搏点）和自主神经系统。血管：动脉将血液带离心脏（厚肌层管壁），静脉将血液送回（具有瓣膜），毛细血管是物质交换的场所。
Gas exchange: in humans, alveoli provide a large surface area, thin walls, and a rich blood supply for efficient diffusion of O₂ and CO₂. In fish, counter‑current flow in gills maximises oxygen uptake. You must be able to interpret spirometer traces (tidal volume, vital capacity, breathing rate) and explain the effects of exercise.
气体交换：在人体中，肺泡提供了巨大的表面积、薄壁和丰富的血液供应，以实现O₂和CO₂的高效扩散。在鱼类中，鳃中的逆流交换最大限度提高氧气的吸收。你必须能够解读肺量计描记图（潮气量、肺活量、呼吸频率），并解释运动的影响。
Homeostasis: negative feedback maintains a stable internal environment. Examples include blood glucose regulation (insulin and glucagon), thermoregulation (vasodilation/vasoconstriction, sweating, shivering), and osmoregulation (ADH and kidney function). You must explain the control of blood glucose using the α cells and β cells of the pancreatic islets.
稳态：负反馈维持稳定的内环境。例子包括血糖调节（胰岛素和胰高血糖素）、体温调节（血管舒张/收缩、出汗、颤抖）和渗透调节（抗利尿激素和肾功能）。你必须能够解释胰岛中的α细胞和β细胞对血糖的控制。
9. Infectious Disease & Immunity | 传染病与免疫
Pathogens include bacteria, viruses, fungi, and protists. Transmission can be direct (contact, droplet) or indirect (vectors, contaminated food/water). Antibiotics target bacterial cell walls or metabolic pathways but do not affect viruses. The development of antibiotic resistance is accelerated by misuse and overuse.
病原体包括细菌、病毒、真菌和原生生物。传播方式可以是直接的（接触、飞沫）或间接的（媒介、受污染的食物/水）。抗生素以细菌细胞壁或代谢途径为靶点，但对病毒无效。滥用和过度使用抗生素加速了耐药性的发展。
The immune system: non‑specific defences include skin, mucous membranes, phagocytes, and inflammation. Specific immune responses involve lymphocytes: B cells produce antibodies (humoral immunity), while T cells help coordinate responses and kill infected cells (cell‑mediated immunity). Memory cells enable rapid secondary responses. Vaccination induces artificial active immunity.
免疫系统：非特异性防御包括皮肤、粘膜、吞噬细胞和炎症反应。特异性免疫反应涉及淋巴细胞：B细胞产生抗体（体液免疫），T细胞协助协调反应并杀死受感染细胞（细胞介导免疫）。记忆细胞使二次反应更快速。疫苗接种可诱导人工主动免疫。
10. Biotechnology & Gene Technology | 生物技术与基因技术
Genetic engineering involves isolating a gene of interest using restriction enzymes, inserting it into a vector (plasmid or virus), and introducing the recombinant DNA into a host organism. Gene transfer in agriculture produces genetically modified (GM) crops with traits like pest resistance or improved nutritional content (e.g., Golden Rice).
基因工程包括使用限制酶分离目标基因，将其插入载体（质粒或病毒）中，并将重组DNA引入宿主生物体内。农业中的基因转移产生了具有抗虫性或改善营养成分等性状的转基因作物（如黄金大米）。
Polymerase chain reaction (PCR) amplifies DNA in vitro; key steps: denaturation, annealing, extension (Taq polymerase). Gel electrophoresis separates DNA fragments by size; smaller fragments move faster through the gel. DNA profiling (fingerprinting) uses short tandem repeats (STRs) for identification. Be able to interpret gel electrophoresis results and discuss ethical issues.
聚合酶链式反应（PCR）可在体外扩增DNA；关键步骤：变性、退火、延伸（Taq聚合酶）。凝胶电泳根据大小分离DNA片段；较小的片段在凝胶中移动得更快。DNA指纹分析利用短串联重复序列（STR）进行身份识别。要能够解读凝胶电泳结果并讨论伦理问题。
11. Data Analysis & Practical Skills | 数据分析与实验技能
Examinations frequently present tables, graphs, and diagrams for interpretation. Be prepared to calculate rates, percentage changes, uncertainties, and mean values. Distinguish between accuracy and precision; identify systematic and random errors. Standard deviation and t‑tests (for comparing two means) are commonly required in IB; Edexcel may ask for chi‑squared tests in genetic crosses or ecology.
考试中经常出现表格、图表和示意图需要解读。准备好计算速率、百分变化率、不确定度和平均值。区分准确度和精确度；识别系统误差和随机误差。IB考试常考标准差和t检验（用于比较两个平均值）；Edexcel可能会要求对遗传杂交或生态学数据进行卡方检验。
Key practical skills: using a microscope and graticule to measure cell size; conducting food tests (iodine for starch, Benedict’s for reducing sugars, biuret for protein, ethanol emulsion for lipids); investigating enzyme activity with controls; using colorimeters to measure absorbance; and setting up respirometers to measure oxygen uptake. Always state independent, dependent, and control variables clearly.
关键实验技能：使用显微镜和测微尺测量细胞大小；进行食物测试（碘液检测淀粉、本尼迪克特试剂检测还原糖、双缩脲试剂检测蛋白质、乙醇乳浊液检测脂质）；设计有对照的酶活性实验；使用比色计测量吸光度；以及搭建呼吸计测量氧气吸收量。始终清楚地指出自变量、因变量和控制变量。
12. Exam Technique & Command Terms | 考试技巧与指令术语
Read the question carefully: ‘state’ requires a brief answer, ‘describe’ requires a factual account without explanation, ‘explain’ requires reasons or mechanisms, and ‘evaluate’ or ‘discuss’ requires arguments for and against with a conclusion. In data‑based questions, always quote figures from the text or graph to support your answer.
仔细审题：“state”要求简短回答，“describe”要求事实性叙述而不需解释，“explain”要求给出原因或机制，“evaluate”或“discuss”要求正反论点并得出结论。在数据题中，务必引用文本或图表中的数字来支持你的答案。
Time management: allocate time proportionally to marks. For long‑answer questions (e.g., extended response in IB Paper 2 or Edexcel 12‑mark questions), plan your answer briefly, use scientific terminology, and where relevant, include annotated diagrams. Check your workings for calculation errors and your units.
时间管理：按分值比例分配时间。对于长篇回答问题（如IB试卷2的扩展题或Edexcel的12分题），简要规划答案，使用科学术语，并在相关处附上带注释的示意图。检查计算过程和单位是否有误。
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