Edexcel IGCSE生物核心术语精讲
一、课本第312页到底讲什么？ | What Is on Page 312?
很多同学拿到Edexcel IGCSE生物课本（Pearson版）后，会忽略书最后的词汇表。第312页正好是词汇表中D到E开头的部分，覆盖了从DNA、扩散、消化到生态系统、酶、排泄等三十多个高频考点词。这些词并不是随便挑选的：它们直接对应Edexcel考试局4BI1大纲的指定术语，定义题的答案往往就来自这些措辞。IGCSE生物试卷中，几乎每年都有1到2分的术语定义题，要求考生用准确的语言写出定义，例如酶是蛋白质，起到生物催化剂的作用。把第312页的词汇逐个吃透，等于提前锁定了这些送分题，也为后面的遗传、生态等大题储备了答题语言。
Many students ignore the glossary at the back of the Pearson Edexcel IGCSE Biology Student Book. Page 312 covers terms beginning with D and E, including DNA, diffusion, digestion, ecosystem, enzyme and excretion, more than thirty high-frequency exam terms in total. These words are not chosen randomly: they match the terminology required by the Edexcel 4BI1 specification, and the wording of definition questions often comes straight from them. In nearly every IGCSE Biology paper there are one or two mark definition questions that reward precise language, such as describing an enzyme as a protein that acts as a biological catalyst. Mastering the terms on page 312 banks these easy marks in advance and builds the vocabulary needed for long-answer questions on inheritance and ecology.
二、DNA与遗传术语：从双螺旋到显性等位基因 | DNA and Inheritance Terms
第312页的遗传学词汇密度很高。DNA的全称是deoxyribonucleic acid，即脱氧核糖核酸，由脱氧核糖、磷酸和四种碱基组成，呈双螺旋结构，四种碱基分别是A、T、C、G。diploid二倍体指体细胞中的染色体数，人体细胞含46条染色体，也就是23对同源染色体。dominant allele显性等位基因指在杂合子中也能表现出来的等位基因，只需一个拷贝就能决定性状。F1代是亲本杂交产生的第一代，F2代是F1个体互相交配产生的后代。考试中这些词常以填空和选择形式出现，例如给出碱基序列让考生配对，或者判断某基因型对应的表现型。
Page 312 is dense with genetics vocabulary. DNA stands for deoxyribonucleic acid, a double helix made of deoxyribose sugar, phosphate groups and four bases: A, T, C and G. Diploid refers to the chromosome number in body cells; human body cells contain 46 chromosomes, or 23 pairs of homologous chromosomes. A dominant allele is one that is expressed in the heterozygote, so a single copy is enough to determine the trait. The F1 generation is the offspring of a cross between parent organisms, while the F2 generation comes from breeding F1 individuals together. These words typically appear as gap-fill and multiple-choice items, such as matching base sequences or predicting the phenotype from a genotype.
三、细胞与分化术语：真核细胞与细胞分化 | Cell and Differentiation Terms
eukaryotic真核细胞是指有细胞核的细胞，所有生物除细菌外都是真核生物；细菌是prokaryotic原核细胞，没有真正的细胞核。differentiation分化发生在胚胎发育过程中，细胞逐渐特化，执行特定的功能，例如红细胞专门运输氧气，神经细胞专门传导冲动。embryo胚胎是受精卵zygote分裂形成的多细胞结构。这一组词经常一起出现在细胞与生物体章节的选择题中，考的就是谁有核、谁没有核，以及分化发生在什么时候。答题时注意区分原核与真核的典型特征，例如细菌没有线粒体、没有膜包细胞器，这些细节是Edexcel的高频考点。
Eukaryotic cells contain a nucleus; all living organisms except bacteria are eukaryotes, while bacteria are prokaryotic cells without a true nucleus. Differentiation happens during embryo development, when cells become specialised to carry out particular functions, such as red blood cells transporting oxygen or neurones conducting impulses. An embryo is the multicellular structure formed by division of a zygote. These terms often appear together in multiple-choice questions on cells and organisms, testing which cells have a nucleus and when differentiation occurs. Remember the typical prokaryotic features such as absence of mitochondria and membrane-bound organelles, a favourite Edexcel detail.
四、营养与消化术语：膳食纤维与二糖 | Nutrition and Digestion Terms
营养章节的术语同样集中在第312页。dietary fibre膳食纤维是不能被消化的植物材料，主要是纤维素，能预防便秘和肠道疾病。disaccharide二糖由两个单糖组成，例如蔗糖就是葡萄糖和果糖构成的二糖。digestion消化是把食物分解成能被吸收的更简单分子的过程，消化从口腔开始，在十二指肠duodenum中继续，十二指肠是小肠紧接胃的第一段。fatty acid脂肪酸与甘油一起构成脂质。faeces粪便则是经肛门排出的半固体残渣。这些词常考属于哪类营养物质的分类题，以及食物中缺失某种成分会引发什么疾病。
The nutrition chapter contributes many terms to page 312. Dietary fibre is indigestible plant material, mainly cellulose, which prevents constipation and bowel disease. A disaccharide is a sugar made of two monosaccharides; sucrose, for example, is a disaccharide of glucose and fructose. Digestion is the breakdown of food into simpler molecules that can be absorbed; it begins in the mouth and continues in the duodenum, the first part of the small intestine after the stomach. Fatty acids combine with glycerol to form lipids, and faeces are the semi-solid waste passed out through the anus. Classification questions about nutrients and deficiency diseases commonly test these words.
五、血液循环术语：红细胞与双循环系统 | Circulation and Transport Terms
erythrocyte红细胞就是red blood cell，没有细胞核，含有血红蛋白，形状为双凹圆盘状，这使它的表面积增大，能更高效地携带氧气。double circulatory system双循环系统是哺乳动物的血液循环特点：血液先离开心脏到肺部，返回心脏后再被泵到全身，也就是说血液每完成一次全身循环要两次经过心脏。Edexcel考试喜欢用为什么双循环比单循环更高效这类推理题考这个词，答案要点包括血压更高、血流更快、氧气运输效率更高。还要注意把红细胞与白细胞、血小板的功能区分开，白细胞参与免疫，血小板参与凝血。
Erythrocytes, or red blood cells, have no nucleus and contain haemoglobin; their biconcave disc shape increases surface area for efficient oxygen transport. The double circulatory system is a feature of mammals: blood leaves the heart to the lungs, returns to the heart, and is then pumped around the body, so blood passes through the heart twice per complete circuit. Edexcel likes reasoning questions such as why a double circulation is more efficient than a single one, with marking points about higher blood pressure, faster flow and more efficient oxygen delivery. Also separate the roles of white blood cells in immunity and platelets in clotting.
六、呼吸与疾病术语：膈肌与肺气肿 | Breathing and Disease Terms
diaphragm膈肌是分隔胸腔和腹腔的肌肉层，参与肺的通气：吸气时膈肌收缩变平，胸腔容积增大，气压下降，空气进入肺。emphysema肺气肿是肺泡壁破裂融合形成的疾病，肺泡融合成大气腔，表面积减小，导致呼吸困难，常与吸烟有关。肺泡alveoli是气体交换的场所，壁薄、表面积大、有丰富的毛细血管。这三个词连起来能考一道完整的呼吸系统大题：从膈肌的运动机制，到肺泡的适应结构，再到吸烟如何损害肺泡。作答时记得用上氧扩散进入毛细血管、二氧化碳反向扩散的关键描述。
The diaphragm is a muscular sheet separating the thorax from the abdomen; it drives ventilation, contracting and flattening during inhalation to increase thoracic volume, lower pressure and draw air into the lungs. Emphysema is a lung disease in which the walls of the alveoli break down and fuse, forming larger air spaces with reduced surface area and causing breathing difficulty, often linked to smoking. The alveoli themselves are thin-walled, well supplied with capillaries and provide a large surface area for gas exchange. These three terms can form a complete respiratory-system question chain; remember to describe oxygen diffusing into the capillaries and carbon dioxide diffusing in the opposite direction.
七、皮肤与神经术语：真皮、树突与背根 | Skin and Nervous System Terms
皮肤和神经系统在第312页的术语同样重要。dermis真皮是皮肤的中间层，含有感觉受体；epidermis表皮是皮肤最外层，由死细胞组成。神经系统中，dendron树突是神经元细胞质的延伸，负责把冲动传向细胞体；背根dorsal root从脊髓背面发出，背根神经节dorsal root ganglion内含感觉神经元的细胞体。effector效应器是作出反应的器官，通常是肌肉或腺体。反射弧的完整链条感受器、感觉神经元、中枢、运动神经元、效应器是Edexcel必考默写点，答题时顺序不能颠倒，还要说明冲动沿神经元的传导方向。
The dermis is the middle layer of the skin containing sensory receptors, while the epidermis is the outer layer made of dead cells. In the nervous system, a dendron is an extension of the cytoplasm of a neurone that carries impulses towards the cell body; the dorsal root emerges from the back of the spinal cord, and the dorsal root ganglion contains the cell bodies of sensory neurones. An effector is the organ that brings about a response, usually a muscle or a gland. The full reflex arc chain of receptor, sensory neurone, CNS, motor neurone and effector is a guaranteed recall point in Edexcel papers; keep the order correct and state the direction of impulse travel.
八、激素与酶术语：内分泌腺与糖尿病 | Hormones and Enzymes Terms
endocrine gland内分泌腺是没有导管的腺体，直接把激素分泌进血液，例如胰腺分泌胰岛素；exocrine gland外分泌腺则通过导管分泌产物，例如唾液腺。enzyme酶是蛋白质类生物催化剂，具有专一性，高温或过酸过碱会使酶变性失活。diabetes糖尿病是血液葡萄糖浓度无法正常控制的疾病，因缺乏胰岛素引起，胰岛素由胰腺分泌，促进细胞吸收血糖。Edexcel常考胰岛素分泌不足为什么会导致血糖升高的因果链，以及酶的最适温度和pH曲线，画图题中记得标出最适点并说明高温段活性骤降的原因。
Endocrine glands have no ducts and secrete hormones directly into the blood, such as the pancreas releasing insulin, whereas exocrine glands secrete through ducts, like the salivary glands. Enzymes are protein biological catalysts with specificity; high temperature or extreme pH denatures them. Diabetes is a disease in which blood glucose concentration cannot be properly controlled, caused by a lack of insulin, the hormone secreted by the pancreas that helps cells absorb glucose. Edexcel commonly asks the causal chain of why insulin deficiency raises blood glucose, plus temperature and pH curves for enzyme activity; in graph questions mark the optimum point and explain the sharp drop at high temperature.
九、植物学术语：双子叶植物与组织培养 | Plant Terms: Dicots and Micropropagation
植物学部分，dicot双子叶植物指种子有两片子叶的植物，单子叶植物只有一片。epidermis在植物中指叶片或其他非木质部位的外层细胞，与皮肤的epidermis是两个概念，考试常设陷阱。explant外植体是微繁殖micropropagation中使用的一小块植物组织，在无菌条件下培养成完整植株，属于克隆技术，能快速繁殖优良品种。Edexcel的生物资源章节会考微繁殖的步骤和优点，例如繁殖速度快、不受季节限制、保留优良性状，也常和基因工程作对比，注意克隆不改变遗传物质，而基因工程会引入新基因。
A dicot, or dicotyledonous plant, has two seed leaves, while monocots have only one. In plants, the epidermis is the outer layer of cells of a leaf or other non-woody parts, which is a different concept from the epidermis of the skin, a common exam trap. An explant is a small piece of plant tissue used in micropropagation, grown under sterile conditions into a whole plant; this cloning technique rapidly multiplies desirable varieties. The use-of-biological-resources chapter tests the steps and advantages of micropropagation, such as speed, independence from seasons and preservation of good traits; contrast it with genetic modification, noting that cloning does not change the genetic material.
十、生态学术语：生态系统与富营养化 | Ecology and Environment Terms
ecosystem生态系统是群落与其非生物环境的总和，群落则是某一区域所有生物种群的总称。eutrophication富营养化是水体因流入大量矿物质而出现的过程，矿物质主要来自污水或化肥中的氮磷：藻类暴发覆盖水面，遮挡阳光，水草死亡，分解者大量繁殖消耗氧气，鱼类缺氧死亡。denitrifying bacteria反硝化细菌在氮循环中把硝酸盐转化为氮气，而固氮细菌把氮气转化为氨。这组生态学术语是人类对环境的影响章节的必考点，富营养化的五步链条尤其要记熟，答题时按顺序写出每一步并注明因果关系。
An ecosystem is a community of living organisms together with their non-living environment, while a community is all the populations in one area. Eutrophication happens when an aquatic habitat receives large amounts of minerals from sewage or fertiliser: algae bloom and cover the surface, blocking light, plants die, decomposers multiply and use up oxygen, and fish suffocate. Denitrifying bacteria convert nitrates into nitrogen gas in the nitrogen cycle, whereas nitrogen-fixing bacteria convert nitrogen gas into ammonia. These ecology terms anchor the humans-and-the-environment chapter; memorise the five-step eutrophication chain in order and state the cause and effect at every step.
十一、用词汇表备考的三大方法 | Three Revision Methods with the Glossary
第一，按字母聚类记忆：把第312页的D到E词汇按主题归类，例如遗传组、消化组、循环组，每组编成一句话故事，比孤立背单词更牢。第二，自问自答定义题：把每个词的英文定义写在卡片正面，中文解释写在背面，每天抽十张自测，模拟考试中的定义题。第三，主动造句与联想：用每个术语写一个与Edexcel真题情境相关的句子，例如吸烟导致肺泡壁破裂，引发肺气肿。把词汇表当作考前一周的快速复习清单，逐一打勾，能显著减少术语失分。坚持下去，生物这门课就能从背单词开始稳步提分。
First, cluster by theme: group the D-to-E terms on page 312 into genetics, digestion and circulation sets, and turn each set into a short story, which sticks better than isolated memorising. Second, quiz yourself with definition cards: write the English definition on the front and the Chinese explanation on the back, then test ten cards a day to simulate definition questions. Third, use each term in a sentence tied to a real Edexcel scenario, such as smoking destroying alveolar walls and causing emphysema. Treat the glossary as a one-week pre-exam checklist and tick terms off one by one to cut terminology marks lost. With consistent practice, Biology revision can start with vocabulary and steadily raise your score.
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