📚 GCSE WJEC Biology: End-of-Term Revision Outline | GCSE WJEC 生物：期末复习提纲
This guide provides a comprehensive overview of the key topics covered in the GCSE WJEC Biology specification. It is designed to help you structure your end-of-term revision by breaking the content into manageable sections, each with essential concepts, terminology and applications. Use this outline to check your understanding, identify any gaps and practise applying knowledge to exam-style questions.
本提纲为 GCSE WJEC 生物课程的核心内容提供了系统梳理，旨在帮助你高效组织期末复习。我们将知识点拆分为若干小节，涵盖关键概念、术语和实际应用。你可以参照各节内容自查掌握程度，发现薄弱环节，并针对性地练习考试题型。
1. Cell Structure and Specialisation | 细胞结构与特化
All living organisms are composed of cells, the basic units of life. In eukaryotic cells, such as those of plants and animals, the genetic material is enclosed within a nucleus. Key organelles include mitochondria (site of aerobic respiration), ribosomes (protein synthesis) and chloroplasts (photosynthesis in plant cells). Plant cells possess a rigid cell wall made of cellulose, a large permanent vacuole and chloroplasts, which distinguish them from animal cells. Bacteria are prokaryotes; their DNA floats freely in the cytoplasm as a circular chromosome, and they may contain small rings of DNA called plasmids. Microscopy skills are essential: you must be able to calculate total magnification (eyepiece lens × objective lens) and convert between millimetres, micrometres and nanometres.
所有生物体均由细胞构成，细胞是生命的基本单位。在动植物等真核细胞中，遗传物质被包裹在细胞核内。重要的细胞器包括线粒体（有氧呼吸的场所）、核糖体（蛋白质合成）和叶绿体（植物细胞中进行光合作用）。植物细胞具有由纤维素组成的细胞壁、一个大中央液泡和叶绿体，这些结构使其区别于动物细胞。细菌属于原核生物，其 DNA 以环状染色体的形式游离在细胞质中，还可能含有称为质粒的小型 DNA 环。显微镜技能十分重要：你必须能够计算总放大倍数（目镜放大倍数 × 物镜放大倍数），并会在毫米、微米和纳米之间进行单位换算。
Cells are often specialised to perform particular functions. For example, sperm cells have a streamlined head and a tail for swimming to the egg, and are packed with mitochondria for energy. Root hair cells in plants have a long, thin extension to increase surface area for water and mineral absorption. Ciliated epithelial cells line the airways and use tiny hairs to sweep mucus away from the lungs. Understanding how a cell’s structure relates to its function is a central theme in biology.
细胞通常会特化以行使特定功能。例如，精子细胞具有流线型的头部和便于游动的尾部，并含有大量线粒体以提供能量。植物根毛细胞拥有细长的突起，能增大表面积，从而更有效地吸收水分和矿物质。纤毛上皮细胞排列在呼吸道内，借助微小的纤毛将黏液扫离肺部。理解细胞结构如何与其功能相适应，是生物学中的一个核心命题。
2. Transport Across Cell Membranes | 物质跨膜运输
Substances move into and out of cells by diffusion, osmosis and active transport. Diffusion is the net movement of particles from an area of high concentration to an area of low concentration, down a concentration gradient, and is a passive process requiring no energy. Factors affecting diffusion rate include temperature, concentration gradient and surface area. Osmosis is a special case of diffusion that refers only to the movement of water molecules across a partially permeable membrane from a dilute to a more concentrated solution. Animal cells can burst (lyse) in a very dilute solution and shrivel (crenate) in a concentrated one. Plant cells become turgid in dilute solutions, which supports the plant, and undergo plasmolysis when water leaves the cell. Active transport moves substances against the concentration gradient using energy from respiration and carrier proteins. It is essential for the uptake of mineral ions by root hairs and for glucose absorption in the small intestine.
物质通过扩散、渗透和主动运输进出细胞。扩散是指粒子顺着浓度梯度从高浓度区域向低浓度区域的净移动，属于被动过程，不需要能量。影响扩散速率的因素包括温度、浓度梯度和表面积。渗透是扩散的一种特殊情况，特指水分子通过部分透性膜从较稀溶液向较浓溶液的移动。动物细胞在极稀溶液中会吸水胀破（溶血），在浓溶液中会失水皱缩。植物细胞在稀溶液中变得硬挺，从而支撑植株；当水分流出时会发生活质壁分离。主动运输利用呼吸作用提供的能量和载体蛋白，逆浓度梯度运移物质。它是根毛吸收矿质离子和小肠吸收葡萄糖所必需的。
3. Enzymes and Digestion | 酶与消化系统
Enzymes are biological catalysts made of protein. They speed up chemical reactions by lowering the activation energy, and their specific shape means that each enzyme can bind only to particular substrates at its active site. The lock-and-key model explains this specificity. Enzyme activity is affected by temperature and pH. As temperature increases, the rate of reaction rises until an optimum is reached; beyond this temperature the enzyme denatures, permanently changing the shape of the active site. Each enzyme also has an optimum pH; for example, pepsin works best in the acidic conditions of the stomach, while amylase in the mouth prefers a neutral pH. Digestive enzymes break down large food molecules into smaller, soluble ones that can be absorbed. Amylase digests starch into maltose and other sugars; proteases digest proteins into amino acids; lipases break down lipids (fats) into glycerol and fatty acids. Bile, produced by the liver and stored in the gall bladder, emulsifies fats to provide a larger surface area for lipase action and neutralises stomach acid.
酶是由蛋白质构成的生物催化剂。它们通过降低活化能来加速化学反应，其特定的形状意味着每种酶只能在活性部位与特定底物结合。锁钥模型解释了这种专一性。酶的活性受到温度和 pH 的影响。随着温度升高，反应速率会加快，直至达到最适温度；超过这一温度后，酶会变性，活性部位的形状永久改变。每种酶还有其最适 pH；例如，胃蛋白酶在胃的酸性环境中活性最高，而口腔中的淀粉酶则偏好中性 pH。消化酶将大分子食物分解为可吸收的小分子可溶物质。淀粉酶将淀粉消化为麦芽糖和其他糖类；蛋白酶将蛋白质消化为氨基酸；脂肪酶将脂类（脂肪）分解为甘油和脂肪酸。由肝脏产生并储存在胆囊中的胆汁，能将脂肪乳化成微小液滴，增大表面积以利于脂肪酶作用，同时中和胃酸。
4. The Circulatory System and Blood | 循环系统与血液
The human circulatory system comprises the heart, blood vessels and blood. It is a double circulation: the right side of the heart pumps deoxygenated blood to the lungs (pulmonary circuit), while the left side pumps oxygenated blood to the rest of the body (systemic circuit). The heart has four chambers – two atria and two ventricles – and valves prevent backflow. Arteries carry blood away from the heart under high pressure and have thick, muscular walls; veins return blood at lower pressure and possess valves; capillaries are one-cell thick to allow efficient exchange of substances. Blood consists of red blood cells (transport oxygen via haemoglobin), white blood cells (defence against pathogens), platelets (involved in clotting) and plasma (transports dissolved substances and heat).
人体循环系统由心脏、血管和血液组成。这是一种双重循环：右心将缺氧血泵送至肺部（肺循环），左心将富氧血泵送至全身（体循环）。心脏有四个腔室——两个心房和两个心室——瓣膜可防止血液倒流。动脉将血液在高压下带离心脏，管壁厚实且富有肌肉层；静脉在较低压力下将血液送回，并带有瓣膜；毛细血管仅由单层细胞构成，有利于物质高效交换。血液由红细胞（通过血红蛋白运输氧气）、白细胞（抵御病原体）、血小板（参与凝血）和血浆（运输溶解物质和热量）组成。
Coronary heart disease can occur if fatty deposits build up in the arteries supplying the heart muscle, reducing blood flow. Lifestyle factors such as diet, exercise and smoking influence cardiovascular health. You should be able to calculate cardiac output (heart rate × stroke volume) and evaluate the advantages and disadvantages of treatments like stents and statins.
如果为心肌供血的动脉中堆积了脂肪性沉积物，血流量减少，就可能发生冠心病。饮食、锻炼和吸烟等生活方式因素会影响心血管健康。你需要能够计算心输出量（心率 × 每搏输出量），并能评估支架和他汀类药物等治疗方案的优缺点。
5. Respiration and Gas Exchange | 呼吸作用与气体交换
Respiration is a chemical process that releases energy from glucose. It occurs in all living cells and should not be confused with breathing. Aerobic respiration uses oxygen and produces a large amount of energy:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ energy)
Anaerobic respiration in animals produces lactic acid, causing muscle fatigue and oxygen debt:
C₆H₁₂O₆ → 2C₃H₆O₃
In yeast and some plants, anaerobic respiration yields ethanol and carbon dioxide:
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
呼吸作用是细胞从葡萄糖中释放能量的化学过程，发生在所有活细胞中，不可与“呼吸”（通气）混淆。有氧呼吸需要氧气，产生大量能量。动物体内无氧呼吸产生乳酸，可导致肌肉疲劳和氧债。在酵母和某些植物中，无氧呼吸则生成乙醇和二氧化碳。
Gas exchange in humans takes place in the alveoli. Features such as their large surface area, thin walls (one cell thick), moist lining and dense capillary network maximise the diffusion of oxygen into the blood and carbon dioxide out. Breathing involves the diaphragm and intercostal muscles changing the volume and pressure of the thoracic cavity. In plants, gas exchange occurs through stomata in the leaves, which can open and close via guard cells to balance carbon dioxide uptake and water loss.
人体的气体交换发生在肺泡中。肺泡具有极大的表面积、单细胞厚度的薄壁、湿润的内衬和密集的毛细血管网，这些特征最大限度地促进了氧气向血液的扩散以及二氧化碳的排出。呼吸运动依靠膈肌和肋间肌改变胸腔的容积和压力来实现。植物则通过叶片上的气孔进行气体交换，气孔可由保卫细胞控制开启或关闭，以平衡二氧化碳的吸收和水分蒸发的损失。
6. Nervous System and Hormones | 神经系统与激素
The nervous system enables rapid responses to stimuli. A reflex arc involves a receptor, sensory neurone, relay neurone in the central nervous system (CNS), motor neurone and effector (muscle or gland). Synapses are gaps between neurones where chemical neurotransmitters diffuse across to continue the impulse. Reflex actions are automatic and protective. The endocrine system uses hormones, chemical messengers produced by glands and carried in the blood to target organs. Compared with nerve impulses, hormonal responses are slower but longer lasting. For example, insulin is released by the pancreas when blood glucose is high, causing cells to take up glucose and the liver to store glycogen. Glucagon has the opposite effect. Adrenaline is released in ‘fight or flight’ situations, increasing heart rate and diverting blood to muscles. Type 1 diabetes, where the pancreas produces little or no insulin, is controlled by insulin injections. Type 2 diabetes involves cells becoming resistant to insulin and is often linked to lifestyle.
神经系统能对刺激作出快速响应。反射弧包括感受器、感觉神经元、中枢神经系统内的中间神经元、运动神经元和效应器（肌肉或腺体）。突触是神经元之间的间隙，化学神经递质通过扩散穿过突触以继续传递神经冲动。反射行为是自动的、具有保护作用。内分泌系统则利用激素这一化学信使，由腺体分泌后经血液运送到靶器官。与神经冲动相比，激素反应较慢但持续时间更长。例如，当血糖升高时，胰腺释放胰岛素，促使细胞吸收葡萄糖，肝脏将其转化为糖原储存；胰高血糖素则具有相反作用。在“战斗或逃跑”情境下，肾上腺素被释放，使心率加快并将血液重新分配到肌肉。1 型糖尿病是由于胰腺几乎不产生胰岛素，需通过注射胰岛素控制；2 型糖尿病则涉及细胞对胰岛素产生抵抗，通常与生活方式相关。
7. Homeostasis and Excretion | 稳态与排泄
Homeostasis is the maintenance of a constant internal environment. The body regulates temperature, blood glucose and water balance. Thermoregulation involves sweating, shivering, vasodilation and vasoconstriction to keep core temperature around 37°C. The skin plays a major role. Osmoregulation controls water content of the blood. The kidneys filter the blood, reabsorbing all glucose, some water and ions as needed, and excreting excess water, urea and salts as urine. The hormone ADH regulates the amount of water reabsorbed by the collecting ducts: more ADH increases water reabsorption, producing more concentrated urine. A negative feedback loop ensures any deviation from the norm is counteracted. Anti-diuretic hormone (ADH) is produced by the pituitary gland and acts on the kidneys. Kidney failure may be treated by dialysis or transplant.
稳态是指维持恒定的内环境。身体对体温、血糖和水分平衡进行调节。体温调节通过排汗、颤抖、血管扩张和血管收缩等机制，使核心体温维持在 37°C 左右。皮肤在其中发挥着重要作用。渗透调节控制血液中的水含量。肾脏过滤血液，根据身体需要重吸收全部葡萄糖、部分水分和离子，并将多余的水分、尿素和盐分以尿液的形式排出体外。抗利尿激素（ADH）调节集合管对水分的重吸收量：ADH 越多，水重吸收越多，尿液越浓。负反馈回路确保任何偏离正常水平的趋势都能被抵消。ADH 由垂体分泌并作用于肾脏。肾衰竭可通过透析或移植进行治疗。
8. Plant Transport and Photosynthesis | 植物运输与光合作用
Plants have two main transport systems. Xylem tubes transport water and dissolved minerals from the roots to the leaves. The movement is driven in part by transpiration – the evaporation of water from leaf surfaces through stomata – which creates a tension pulling water up the plant. Xylem cells are dead, hollow and strengthened by lignin. Phloem tubes transport sucrose and amino acids from sources (such as leaves) to sinks (growing regions and storage organs) in a process called translocation. Phloem consists of living cells with sieve plates and companion cells.
植物具有两大运输系统。木质部导管将水分和溶解的矿物质从根部运输至叶片。这一运动部分由蒸腾作用驱动——水分从叶片表面的气孔蒸发，产生拉力将水向上牵引。木质部细胞是死细胞，中空并由木质素加固。韧皮部则将蔗糖和氨基酸从源（如叶片）运送到库（生长区域和储存器官），这一过程称为输导。韧皮部由活细胞构成，具有筛板和伴胞。
Photosynthesis is the process by which plants produce glucose using light energy. It takes place in chloroplasts containing chlorophyll. The word equation is:
carbon dioxide + water → glucose + oxygen
The balanced chemical equation is:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Light intensity, carbon dioxide concentration and temperature all affect the rate of photosynthesis; any of these can become a limiting factor. The glucose produced is used for respiration, converted into starch for storage, or used to make cellulose, proteins and lipids for growth.
光合作用是植物利用光能产生葡萄糖的过程，发生在含叶绿素的叶绿体中。文字方程式为二氧化碳 + 水 → 葡萄糖 + 氧气。光照强度、二氧化碳浓度和温度都会影响光合速率，其中任一项都可能成为限制因子。产生的葡萄糖可用于呼吸作用，转化为淀粉储存，或用来制造纤维素、蛋白质和脂质以支持生长。
9. Cell Division and Inheritance | 细胞分裂与遗传
Mitosis is cell division for growth and repair, producing two genetically identical daughter cells with the same number of chromosomes as the parent (diploid). Meiosis produces gametes (sperm and eggs) for sexual reproduction. It involves two divisions, resulting in four genetically different haploid cells, each with half the chromosome number. This introduces genetic variation through independent assortment and crossing over. DNA is a double helix polymer made of nucleotides. A gene is a section of DNA that codes for a specific protein. Chromosomes carry many genes.
有丝分裂是用于生长和修复的细胞分裂，产生两个遗传物质相同的子细胞，染色体数目与亲代细胞相同（二倍体）。减数分裂产生用于有性生殖的配子（精子和卵子）。它包括两次分裂，最终形成四个遗传物质不同的单倍体细胞，每个细胞的染色体数目减半。这一过程通过独立分配和交叉互换引入遗传变异。DNA 是由核苷酸聚合而成的双螺旋结构。基因是编码特定蛋白质的一段 DNA。染色体上携带着许多基因。
Some characteristics are determined by single genes with different alleles. Alleles can be dominant or recessive. Genetic diagrams (Punnett squares) predict the probability of offspring inheriting particular traits. For example, if ‘R’ represents dominant red flowers and ‘r’ recessive white flowers, a cross between two heterozygous (Rr) plants gives an expected phenotype ratio of 3 red : 1 white. Inherited disorders such as cystic fibrosis (recessive) and polydactyly (dominant) can be traced using family pedigree charts.
有些性状由具有不同等位基因的单个基因决定。等位基因可分为显性或隐性。遗传图解（庞纳特方格）可预测后代继承特定性状的概率。例如，若“R”代表显性的红花，“r”代表隐性的白花，则两个杂合子（Rr）植株的杂交后代预期表现型比例为 3 红 : 1 白。囊性纤维化（隐性遗传）和多指症（显性遗传）等遗传疾病可通过家系图谱进行追踪。
10. Variation, Evolution and Natural Selection | 变异、进化与自然选择
Variation within a species can be continuous (e.g. height, controlled by many genes and influenced by environment) or discontinuous (e.g. blood group, determined by a single gene with little environmental influence). Mutations are changes in the DNA sequence and are the original source of genetic variation. Most mutations have no effect or are harmful; a very few are beneficial. Charles Darwin proposed the theory of evolution by natural selection. Individuals in a population show variation, and those with characteristics better suited to the environment are more likely to survive and reproduce, passing on their favourable alleles to the next generation. Over many generations, the frequency of these alleles increases, leading to adaptation and eventually speciation.
物种内部的变异可能是连续的（如身高，由多基因控制并受环境影响），也可能是不连续的（如血型，由单个基因决定，几乎不受环境影响）。突变是 DNA 序列的改变，也是遗传变异的原始来源。大多数突变没有效果或有害，极少数是有益的。查尔斯·达尔文提出了自然选择进化论。在一个种群中，个体间存在变异，那些具有更适应环境的性状的个体更有可能存活并繁殖，将其有利等位基因传递给下一代。经过许多代，这些等位基因的频率增加，导致生物适应并最终形成新物种。
Evidence for evolution comes from fossils, comparative anatomy and antibiotic resistance in bacteria. MRSA provides a clear example: bacteria resistant to an antibiotic survive exposure, reproduce, and the resistance allele spreads rapidly. You should be able to explain why overuse of antibiotics accelerates this process and how it relates to natural selection.
进化的证据来自化石、比较解剖学和细菌对抗生素产生的耐药性。MRSA 提供了一个清晰的例子：对抗生素具有抗性的细菌在药物作用下存活下来并进行繁殖，使抗性等位基因迅速传播。你应能解释为什么滥用抗生素会加速这一过程，以及它如何与自然选择相关联。
11. Ecosystems and Nutrient Cycles | 生态系统与物质循环
An ecosystem includes all the organisms in a habitat plus the physical environment. Organisms can be classified as producers (plants, algae that photosynthesise), consumers (primary, secondary, tertiary) and decomposers (bacteria and fungi). Food chains and webs show feeding relationships and the transfer of energy. At each trophic level, energy is lost through respiration, movement and as heat, so biomass and energy decrease along the chain. Pyramids of biomass and pyramids of number represent this data. Carbon is cycled via photosynthesis, respiration, feeding, decomposition and combustion. Microorganisms break down dead material, returning mineral ions to the soil, which plants then take up.
生态系统包括栖息地中的所有生物以及物理环境。生物可划分为生产者（进行光合作用的植物和藻类）、消费者（初级、次级、三级消费者）和分解者（细菌和真菌）。食物链和食物网展示了取食关系以及能量的传递。在每个营养级，能量都会因呼吸作用、运动以及热的形式而损耗，因此生物量和能量沿食物链递减。生物量金字塔和数量金字塔用来表示这类数据。碳通过光合作用、呼吸作用、摄食、分解和燃烧等过程循环。微生物分解死去的生物体，将矿质离子归还土壤，再由植物吸收利用。
The nitrogen cycle is equally important. Nitrogen-fixing bacteria in root nodules of legumes convert atmospheric nitrogen into nitrates. Other bacteria convert ammonia from decay into nitrites and then nitrates (nitrification). Denitrifying bacteria return nitrogen to the atmosphere. Human activities such as deforestation and burning fossil fuels disrupt these cycles, increasing carbon dioxide levels and contributing to climate change. Biodiversity can be measured by sampling techniques like quadrats and transects.
氮循环同样重要。豆科植物根瘤中的固氮细菌将大气中的氮气转化为硝酸盐。其他细菌将腐烂产生的氨转化为亚硝酸盐，再进一步转化为硝酸盐（硝化作用）。反硝化细菌则使氮返回大气。人类活动如砍伐森林和燃烧化石燃料会扰乱这些循环，导致二氧化碳水平升高并加剧气候变化。生物多样性可使用样方和样线等取样技术进行测量。
12. Micro-organisms and Disease | 微生物与疾病
Micro-organisms include bacteria, viruses, fungi and protists. Not all are harmful; many are essential for processes such as decomposition and food production (yoghurt, bread). Pathogens are micro-organisms that cause infectious diseases. Bacteria, such as Salmonella and Mycobacterium tuberculosis, release toxins that damage tissues. Viruses, such as influenza and measles, invade host cells and use the cellular machinery to replicate, eventually destroying the cell. Fungal diseases like athlete’s foot and rose black spot affect animals and plants respectively. Protists such as Plasmodium, which causes malaria, are often transmitted by vectors like mosquitoes.
微生物包括细菌、病毒、真菌和原生生物。并非所有微生物都有害；许多在分解和食品生产（酸奶、面包）等过程中必不可少。病原体是引起传染病的微生物。细菌（如沙门氏菌和结核分枝杆菌）释放毒素损伤组织。病毒（如流感和麻疹病毒）侵入宿主细胞并利用细胞机制进行复制，最终摧毁细胞。脚癣和玫瑰黑斑病等真菌病分别影响动物和植物。引起疟疾的原生生物（如疟原虫）通常由蚊子等媒介传播。
The body defends itself through non-specific defences, like intact skin, mucus, and stomach acid, and through the specific immune system. White blood cells can engulf pathogens (phagocytosis), produce antitoxins or secrete antibodies that recognise antigens on a pathogen’s surface. Memory cells give long-term immunity. Vaccination introduces a harmless form of an antigen, prompting the body to produce memory cells without causing illness. Antibiotics kill bacteria but are ineffective against viruses because they do not have the metabolic targets that antibiotics attack. Aseptic techniques and the work of pioneers such as Semmelweis, Pasteur and Lister are key historical contexts.
人体依靠非特异性防御（如完整的皮肤、黏液和胃酸）以及特异性免疫系统进行自我保护。白细胞能吞噬病原体（吞噬作用），产生抗毒素或分泌能识别病原体表面抗原的抗体。记忆细胞可提供长期免疫力。疫苗接种引入无害的抗原，刺激机体产生记忆细胞而不会引发疾病。抗生素能杀死细菌，但对病毒无效，因为病毒没有抗生素所攻击的代谢靶点。无菌操作技术以及塞麦尔维斯、巴斯德和李斯特等先驱的工作是重要的历史背景。
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