📚 IGCSE WJEC Biology: Last-Minute Revision Notes | IGCSE WJEC 生物：考前冲刺笔记
This set of revision notes covers the most essential concepts, definitions and common pitfalls for the WJEC IGCSE Biology examination. Use them to sharpen your recall, connect ideas across topics, and reinforce key mark-scheme phrases that examiners look for.
这份冲刺笔记覆盖了WJEC IGCSE生物学考试中最关键的概念、定义以及常见易错点。用它来强化记忆、串联不同主题的思路，并巩固考官青睐的关键评分术语。
1. Cell Structure and Function | 细胞结构与功能
Prokaryotic cells (bacteria) have no nucleus; their genetic material floats freely as a circular DNA strand, and they contain small ribosomes and a cell wall made of peptidoglycan.
原核细胞（细菌）没有细胞核；遗传物质是一条游离于细胞质中的环状DNA，含有小型核糖体，细胞壁由肽聚糖构成。
Eukaryotic cells include animal and plant cells. Both have a nucleus, mitochondria, ribosomes and a cell membrane, but only plant cells have a permanent vacuole, chloroplasts and a cellulose cell wall.
真核细胞包括动物细胞和植物细胞。两者都有细胞核、线粒体、核糖体和细胞膜，但只有植物细胞具有永久大液泡、叶绿体和纤维素细胞壁。
Always calculate magnification using the formula: Magnification = Image size ÷ Actual size. Convert all units to the same scale (mm, µm or nm) before dividing. The mark scheme often requires working and the unit ‘times’ (×).
计算放大倍数的公式始终是：放大倍数 = 图像尺寸 ÷ 实际尺寸。计算前把所有单位统一（mm、µm或nm）。评分标准通常要求写出计算过程，单位用“倍”（×）表示。
| Organelle | Function | 中文功能 |
|---|---|---|
| Mitochondria | Site of aerobic respiration, releasing energy (ATP) | 有氧呼吸的场所，释放能量（ATP） |
| Ribosomes | Protein synthesis | 蛋白质合成 |
| Chloroplasts | Absorb light for photosynthesis; contain chlorophyll | 吸收光能进行光合作用；含有叶绿素 |
2. Biological Molecules and Enzymes | 生物分子与酶
Carbohydrates are made of simple sugars. Starch is a storage polysaccharide in plants, detected by iodine solution which turns blue-black. The Benedict’s test for reducing sugars requires heating and gives a brick-red precipitate.
碳水化合物由单糖构成。淀粉是植物体内的储存多糖，用碘液检测会变为蓝黑色。用本尼迪克特试剂检测还原糖需要加热，并产生砖红色沉淀。
Proteins are built from amino acids. The biuret test turns purple in the presence of protein. Lipids (fats and oils) are detected by the ethanol emulsion test, which gives a cloudy white layer.
蛋白质由氨基酸构成。双缩脲试验遇蛋白质呈紫色。脂质（脂肪和油）用乙醇乳化试验检测，会形成乳白色的浑浊层。
Enzymes are biological catalysts that lower activation energy. They have a specific active site, so the lock-and-key model explains substrate specificity. Denaturation (caused by extreme temperature or pH) changes the shape of the active site irreversibly, preventing binding.
酶是降低活化能的生物催化剂。酶具有特定的活性位点，锁钥模型解释了底物专一性。高温或极端pH引起的变性会不可逆地改变活性位点形状，使底物无法结合。
The effect of temperature on enzyme activity shows an increase to an optimum, then a sharp drop when the enzyme denatures. In an exam, state ‘kinetic energy increases collisions’ for the rise and ‘active site changes shape / denatures’ for the fall.
温度对酶活性的影响表现为：温度升高至最适温度活性上升，之后因酶变性急剧下降。答题时，上升阶段要说明“动能增加使碰撞频率提高”，下降阶段说明“活性位点变形/变性”。
3. Movement Across Membranes | 物质跨膜运输
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient. It is passive and does not require energy.
扩散是粒子从高浓度区域向低浓度区域的净移动，顺浓度梯度进行。它是被动过程，不需要能量。
Osmosis is specifically the net movement of water molecules through a partially permeable membrane from a dilute solution to a more concentrated solution. Always use the word ‘water’ and ‘partially permeable membrane’ in your definition.
渗透特指水分子通过半透膜从稀溶液向浓溶液的净移动。定义中必须提到“水”和“半透膜”。
Active transport moves substances against the concentration gradient, from low to high concentration, using carrier proteins and energy from respiration (ATP). Uptake of mineral ions by root hair cells is a classic example.
主动运输将物质逆浓度梯度（从低浓度到高浓度）转运，需要载体蛋白和呼吸作用提供的能量（ATP）。根毛细胞吸收矿质离子是典型的例子。
In an osmosis experiment with plant tissue, mass change indicates water movement. If mass increases, the external solution has a higher water potential than the cells. If mass decreases, water left the cells. Plot percentage change, not raw mass, to allow fair comparison.
在植物组织渗透实验中，质量变化指示水分移动。若质量增加，外界溶液的水势高于细胞；若质量减小，水从细胞流出。应绘制质量百分比变化图表而非原始质量，以便公平比较。
4. Photosynthesis | 光合作用
Photosynthesis is the process by which green plants produce glucose and oxygen from carbon dioxide and water, using light energy absorbed by chlorophyll.
光合作用是绿色植物利用叶绿素吸收光能，将二氧化碳和水转化为葡萄糖和氧气的过程。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Limiting factors include light intensity, carbon dioxide concentration and temperature. The rate is constrained by the factor in shortest supply; increasing other factors will have no effect until that limiting factor is raised.
限制因素包括光照强度、二氧化碳浓度和温度。光合作用速率受最缺乏的因素限制；在提升该限制因素之前，增加其他因素并无效果。
The leaf is adapted for photosynthesis: broad, flat surface for light capture; thin shape for short diffusion distance; stomata for gas exchange; and palisade mesophyll packed with chloroplasts. Learn to identify spongy mesophyll and guard cells in a cross-section diagram.
叶片适应光合作用的结构：宽而扁平的表面利于捕获光能；薄的结构缩短扩散距离；气孔进行气体交换；栅栏组织密布叶绿体。需能识别横截面图中的海绵组织和保卫细胞。
5. Respiration | 呼吸作用
Aerobic respiration uses oxygen to fully oxidise glucose, releasing a large amount of energy as ATP. The word equation is: glucose + oxygen → carbon dioxide + water (+ energy).
有氧呼吸利用氧气彻底氧化葡萄糖，释放大量能量以ATP形式储存。文字方程式：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。
Anaerobic respiration in animals produces lactic acid and a small amount of energy; in yeast and plants it produces ethanol and carbon dioxide. Learn the industrial use of yeast fermentation for bread and biofuel.
动物无氧呼吸产生乳酸和少量能量；酵母和植物无氧呼吸产生乙醇和二氧化碳。要掌握酵母发酵在面包制作和生物燃料生产中的应用。
Investigations on respiration often use a respirometer to measure oxygen uptake or carbon dioxide production. Coloured fluid moving towards the organisms indicates oxygen consumption. Add soda lime to absorb CO₂ and confirm O₂ usage.
呼吸作用实验常用呼吸计测量氧气消耗或二氧化碳产生。有色液体向生物体方向移动表示氧气被消耗。加入碱石灰吸收二氧化碳可确认利用的是氧气。
6. Human Nutrition and Digestion | 人体营养与消化
Large insoluble molecules are broken down by digestive enzymes into small soluble monomers that can be absorbed into the blood. Amylase digests starch into maltose; proteases digest proteins into amino acids; lipase digests lipids into fatty acids and glycerol.
大分子不溶性物质被消化酶分解为可吸收的小分子可溶性单体。淀粉酶将淀粉分解为麦芽糖；蛋白酶将蛋白质分解为氨基酸；脂肪酶将脂质分解为脂肪酸和甘油。
Bile is produced in the liver, stored in the gall bladder, and released into the small intestine. It emulsifies fats, increasing surface area for lipase action, and neutralises stomach acid to create an alkaline pH ideal for intestinal enzymes.
胆汁在肝脏中生成、储存于胆囊，排入小肠。它乳化脂肪，增大脂肪酶作用的表面积，并中和胃酸，营造适合肠道酶的碱性pH。
The small intestine is the main site of absorption. Its inner wall has villi with a single layer of epithelial cells, a lacteal for lipid absorption, and a dense capillary network. A large surface area, thin wall and good blood supply maximise absorption.
小肠是主要的吸收部位。其内壁的绒毛具有单层上皮细胞、吸收脂质的乳糜管和密集的毛细血管网。巨大的表面积、薄壁和丰富的血液供应最大限度地增强了吸收效率。
7. Transport in Plants and Animals | 植物与动物的运输
The human circulatory system consists of the heart, arteries, veins and capillaries. The heart is a double pump: the right side pumps deoxygenated blood to the lungs; the left side pumps oxygenated blood to the body. Valves prevent backflow.
人体循环系统由心脏、动脉、静脉和毛细血管组成。心脏是一个双泵：右侧将缺氧血泵向肺部，左侧将富氧血泵向全身。瓣膜防止血液倒流。
Arteries carry blood away from the heart under high pressure; they have thick muscular walls and elastic fibres. Veins return blood at low pressure and contain valves. Capillaries are one-cell thick, allowing efficient exchange of substances.
动脉将血液带离心脏，承受较高压力，管壁具有厚肌肉层和弹性纤维。静脉在低压下回流血液并含有瓣膜。毛细血管仅有一层细胞厚，利于物质交换。
In plants, xylem transports water and mineral ions from the roots; it is composed of dead, hollow cells and strengthened by lignin. Phloem transports sucrose and amino acids (translocation) and is made of living sieve tube elements and companion cells.
在植物中，木质部从根部向上运输水和矿质离子，由死细胞中空导管组成，并有木质素加厚。韧皮部运输蔗糖和氨基酸（输导作用），由活筛管分子和伴胞构成。
Transpiration is the loss of water vapour from leaves through stomata. It creates a pulling force (transpiration stream) that draws water up the xylem. Factors increasing transpiration: higher temperature, lower humidity, more wind, more light (stomata open).
蒸腾作用是水分以水蒸气形式通过气孔从叶片散失。它产生蒸腾拉力，将水沿木质部向上牵引。促进蒸腾的因素有：温度升高、湿度降低、风力增强、光照增强（气孔张开）。
8. Nervous System and Homeostasis | 神经系统与内稳态
The nervous system uses electrical impulses travelling along neurones. A reflex arc involves a receptor, sensory neurone, relay neurone in the spinal cord, motor neurone and effector. Synapses use chemical neurotransmitters to pass impulses; they ensure unidirectional transmission.
神经系统利用沿神经元传导的电脉冲。反射弧包括感受器、感觉神经元、脊髓中的中间神经元、运动神经元和效应器。突触通过化学神经递质传递冲动，确保单向传导。
Homeostasis is the maintenance of a stable internal environment. Blood glucose is controlled by insulin (lowers glucose by converting it to glycogen) and glucagon (raises glucose by converting glycogen back). Type 1 diabetes is treated with insulin injections.
内稳态是指维持稳定的内部环境。血糖通过胰岛素（降低血糖，将其转化为糖原）和胰高血糖素（将糖原分解为葡萄糖升高血糖）调控。1型糖尿病通过注射胰岛素治疗。
Thermoregulation involves sweating, vasodilation, shivering and vasoconstriction. The skin is a key effector; the hypothalamus monitors blood temperature. Include arteriole changes (histamine and muscle contraction) in your answers.
体温调节包括出汗、血管舒张、战栗和血管收缩。皮肤是关键的效应器，下丘脑监测血液温度。作答时应提到小动脉的变化。
The kidneys excrete urea and regulate water balance. ADH (antidiuretic hormone) makes the collecting duct more permeable to water, increasing its reabsorption when the body is dehydrated. A dialysis machine mimics kidney function by diffusion across a partially permeable membrane.
肾脏排出尿素并调节水平衡。抗利尿激素（ADH）使集合管对水的通透性增加，身体缺水时增强水的重吸收。透析机通过半透膜的扩散模拟肾脏功能。
9. Reproduction and Inheritance | 生殖与遗传
Asexual reproduction produces genetically identical offspring from one parent by mitosis. Sexual reproduction involves meiosis to produce gametes, resulting in variation. Meiosis halves chromosome number and introduces genetic variation through crossing over and independent assortment.
无性生殖通过有丝分裂由一个亲本产生遗传上完全相同的后代。有性生殖通过减数分裂产生配子，导致变异。减数分裂使染色体数目减半，并通过交叉和独立分配引入遗传变异。
DNA is a double helix of nucleotides; a gene is a section of DNA coding for a specific protein. The genetic code follows base pairing: A-T and C-G. In monohybrid inheritance, use Punnett squares and state phenotype/genotype ratios clearly (e.g. 3:1, 1:2:1).
DNA是双螺旋构成的核苷酸链；基因是编码特定蛋白质的一段DNA。遗传密码遵循碱基配对：A-T和C-G。在单因子杂交中，使用庞纳特方格，清晰表述表现型和基因型比例（如3:1，1:2:1）。
Genetic diagrams must include key symbols and a legend. When interpreting pedigree charts, shaded symbols represent individuals expressing the trait. Determine if the allele is dominant or recessive by looking for parents who don’t show the trait but have affected children.
遗传图解必须包含图例和符号说明。分析系谱图时，涂黑的符号表示表现出该性状的个体。可通过不表现性状的父母却生出患病子女的现象，判断等位基因是显性还是隐性。
10. Ecology and Sampling | 生态与取样
An ecosystem includes all the living organisms (community) and the non-living conditions in a defined area. Food chains show the transfer of energy; arrows point from the eaten organism to the eater. Energy is lost at each trophic level as heat and waste.
生态系统包含特定区域中所有生物（群落）和非生物条件。食物链表示能量传递；箭头从被吃者指向吃者。能量在每一营养级以热和废物的形式散失。
The carbon cycle involves photosynthesis, respiration, feeding, decomposition and combustion. The nitrogen cycle can be simplified for most WJEC answers: nitrogen-fixing bacteria turn atmospheric N₂ into nitrates; denitrifying bacteria convert nitrates back to N₂.
碳循环涉及光合作用、呼吸作用、摄食、分解和燃烧。在WJEC答题中，氮循环可简化为：固氮菌将大气中的N₂转化为硝酸盐，反硝化细菌将硝酸盐还原为N₂。
Sampling organisms in a habitat can be done with quadrats (for slow-moving or stationary species) to estimate population size or percentage cover. Always use random sampling or a transect to study zonation. Avoid bias by using a random number generator.
在栖息地取样生物可使用样方（针对移动缓慢或固着的物种）估算种群数量或覆盖率。始终采用随机取样或样线法研究带状分布。使用随机数表避免主观偏差。
Calculate the estimated population size using the Lincoln Index: (number in first sample × number in second sample) ÷ number of marked individuals in second sample. State assumptions: no immigration, emigration, births, deaths or marking effect during the study period.
使用林肯指数估算种群大小：（第一次捕获数 × 第二次捕获数）÷ 第二次捕获中已标记的个体数。陈述假设条件：研究期间无迁入、迁出、出生、死亡，且标记不影响个体。
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