Core Knowledge Revision for KS3 CCEA Biology | KS3 CCEA 生物核心知识点梳理

📚 Core Knowledge Revision for KS3 CCEA Biology | KS3 CCEA 生物核心知识点梳理

KS3 CCEA Biology builds a strong foundation in life science, covering cells, body systems, reproduction, plants, ecosystems, and more. This guide pulls together all the key concepts you need to understand, with clear explanations and useful revision snippets to help you feel confident.

KS3 CCEA 生物课程为生命科学打下坚实基础，涵盖细胞、人体系统、生殖、植物、生态系统等核心内容。本文梳理了所有必须掌握的关键知识点，并用清晰的解释和实用复习要点帮助你建立信心。

1. Cells: The Building Blocks of Life | 细胞：生命的基本单位

All living organisms are made of cells. Animal and plant cells share several common structures: a nucleus that controls the cell’s activities, cytoplasm where chemical reactions occur, a cell membrane that controls what enters and leaves, and mitochondria where respiration takes place. Plant cells have three extra features: a rigid cell wall made of cellulose, a large permanent vacuole containing cell sap, and chloroplasts that absorb light for photosynthesis.

所有生物都由细胞组成。动物细胞和植物细胞共享几种共同结构：控制细胞活动的细胞核、发生化学反应的细胞质、控制物质进出的细胞膜以及进行呼吸作用的线粒体。植物细胞还多了三个结构：由纤维素构成的坚硬细胞壁、含有细胞液的大液泡，以及吸收光能进行光合作用的叶绿体。

Under a light microscope, you can see the nucleus, cell wall, and vacuole clearly. Staining cells with iodine or methylene blue makes the structures more visible. Bacterial cells are much smaller and do not have a true nucleus; their DNA floats in the cytoplasm as a single circular strand. Some bacteria also have a slime capsule and flagella for movement.

在光学显微镜下，你可以清楚地看到细胞核、细胞壁和液泡。用碘液或亚甲基蓝给细胞染色可以让结构更清晰。细菌细胞要小得多，没有真正的细胞核；它们的 DNA 以一条环状链的形式漂浮在细胞质中。有些细菌还有荚膜和用于运动的鞭毛。

Animal cell structures: nucleus, cytoplasm, membrane, mitochondria
植物细胞结构：细胞核、细胞质、细胞膜、线粒体、细胞壁、液泡、叶绿体

Organelle	Function	Present in animal cell?	Present in plant cell?
Nucleus	Contains DNA, controls cell	Yes	Yes
Cytoplasm	Jelly-like substance where reactions happen	Yes	Yes
Cell membrane	Selectively permeable barrier	Yes	Yes
Mitochondria	Site of aerobic respiration	Yes	Yes
Cell wall	Provides structure (cellulose)	No	Yes
Vacuole	Stores cell sap, maintains turgor pressure	No (small temporary ones sometimes)	Yes (large permanent)
Chloroplasts	Contain chlorophyll for photosynthesis	No	Yes

2. The Digestive System and Nutrition | 消化系统与营养

Food provides the body with energy and materials for growth and repair. A balanced diet must include carbohydrates, proteins, lipids (fats), vitamins, minerals, water, and dietary fibre. Carbohydrates are the main energy source; proteins are used for growth and repair; fats provide insulation and a concentrated energy store. Vitamins and minerals are needed in small amounts for healthy functioning – for example, vitamin C prevents scurvy, and iron is needed for haemoglobin in red blood cells.

食物为身体提供能量以及生长和修复所需的物质。均衡饮食必须包含碳水化合物、蛋白质、脂类（脂肪）、维生素、矿物质、水和膳食纤维。碳水化合物是主要能量来源；蛋白质用于生长和修复；脂肪提供隔热层和浓缩的能量储备。维生素和矿物质需求量小但对健康功能至关重要——例如，维生素 C 可预防坏血病，铁是红细胞中血红蛋白所必需的。

Digestion breaks large insoluble molecules into small soluble ones that can be absorbed into the blood. Carbohydrates (starch) are broken down by amylase into sugars like glucose. Protease enzymes break proteins into amino acids. Lipase breaks fats into fatty acids and glycerol. Bile is produced in the liver, stored in the gall bladder, and released into the small intestine to neutralise stomach acid and emulsify fats, increasing their surface area for lipase action.

消化将大的不溶性分子分解成可被吸收进入血液的小分子。碳水化合物（淀粉）被淀粉酶分解成葡萄糖等糖类。蛋白酶将蛋白质分解为氨基酸。脂肪酶将脂肪分解为脂肪酸和甘油。胆汁在肝脏中产生，储存在胆囊中，释放到小肠内以中和胃酸并乳化脂肪，增大其表面积以便脂肪酶发挥作用。

The alimentary canal: mouth (chewing, saliva with amylase) → oesophagus → stomach (acid and protease) → small intestine (digestion completes, absorption) → large intestine (water absorption) → rectum → anus. Villi in the small intestine increase surface area for efficient absorption.

消化道路径：口腔（咀嚼、含淀粉酶的唾液）→ 食道 → 胃（胃酸和蛋白酶）→ 小肠（消化完成、吸收）→ 大肠（吸水）→ 直肠 → 肛门。小肠中的绒毛增大了吸收的有效表面积。

3. Breathing and Gas Exchange | 呼吸与气体交换

Breathing is the physical process of moving air in and out of the lungs. Respiration is the chemical process that releases energy from glucose. You must not confuse these two terms. Inhaled air contains about 21% oxygen, 0.04% carbon dioxide, and the rest mainly nitrogen. Exhaled air has less oxygen (about 16%) and more carbon dioxide (about 4%) because oxygen is used in respiration and carbon dioxide is produced.

呼吸是空气进出肺部的物理过程，而呼吸作用是从葡萄糖中释放能量的化学过程。这两个术语不能混淆。吸入的空气含有约 21% 的氧气、0.04% 的二氧化碳，其余主要是氮气。呼出的气体氧气含量较低（约 16%），二氧化碳含量较高（约 4%），因为呼吸作用消耗氧气并产生二氧化碳。

The respiratory system: air enters through the nose and mouth, passes down the trachea (windpipe) which contains rings of cartilage to keep it open, divides into bronchi, then smaller bronchioles, and finally reaches tiny air sacs called alveoli. Alveoli are surrounded by capillaries. Gas exchange happens by diffusion: oxygen moves from the alveoli into the blood, and carbon dioxide moves from the blood into the alveoli to be exhaled.

呼吸系统：空气通过口鼻进入，沿气管下行——气管中含软骨环以保持通畅，然后分为支气管，再分成更细的细支气管，最终到达称为肺泡的微小气囊。肺泡被毛细血管包围。气体交换通过扩散进行：氧气从肺泡进入血液，二氧化碳从血液进入肺泡被呼出。

Alveoli are adapted for gas exchange: they have very thin walls (one cell thick), a large surface area, a moist lining, and a rich blood supply. Inhaling involves the diaphragm contracting and flattening, and the intercostal muscles pulling the ribcage up and out, increasing chest volume and lowering pressure to draw air in.

肺泡适应气体交换的特点：壁极薄（一个细胞厚），表面积大，内衬湿润，血液供应丰富。吸气时膈肌收缩变平，肋间肌将肋骨向上向外拉，胸腔容积增大，压力降低，空气被吸入。

4. The Heart and Circulation | 心脏与血液循环

The circulatory system transports oxygen, nutrients, waste products, and hormones around the body. Humans have a double circulatory system: the right side pumps deoxygenated blood to the lungs (pulmonary circulation), and the left side pumps oxygenated blood to the rest of the body (systemic circulation). The heart is a muscular organ with four chambers: right atrium, right ventricle, left atrium, and left ventricle.

循环系统在全身输送氧气、营养物质、废物和激素。人类拥有双循环系统：右心将缺氧血泵至肺部（肺循环），左心将富氧血泵至全身各处（体循环）。心脏是一个具有四个腔室的肌肉器官：右心房、右心室、左心房和左心室。

Blood flows through the heart in a controlled sequence. Deoxygenated blood from the body enters the right atrium, moves to the right ventricle, and is pumped to the lungs via the pulmonary artery. Oxygenated blood returns via the pulmonary vein into the left atrium, moves to the left ventricle, and is pumped out through the aorta. Valves prevent backflow. The natural pacemaker in the right atrium controls the heartbeat rate.

血液按受控顺序流经心脏。来自身体的缺氧血进入右心房，流入右心室，然后通过肺动脉泵入肺部。富氧血通过肺静脉回流到左心房，再进入左心室，经主动脉泵出。瓣膜防止血液倒流。位于右心房的天然起搏器控制心跳速率。

Blood vessels: arteries carry blood away from the heart under high pressure, have thick muscular and elastic walls. Veins return blood to the heart under low pressure, contain valves, and have thinner walls. Capillaries are one cell thick and link arteries to veins, allowing exchange of substances with tissues. Blood contains red blood cells (carry oxygen using haemoglobin), white blood cells (defend against infection), platelets (clotting), and plasma (liquid transport medium).

血管：动脉将血液在高压下带离心脏，管壁肌肉层厚且富有弹性。静脉在低压下将血液带回心脏，内有瓣膜，管壁较薄。毛细血管仅有一个细胞厚，连接动脉和静脉，与组织进行物质交换。血液包含红细胞（利用血红蛋白运输氧气）、白细胞（抗感染）、血小板（凝血）和血浆（液体运输介质）。

5. Reproduction in Humans | 人类的生殖

Reproduction is the process that creates new individuals. Humans reproduce sexually, requiring a male gamete (sperm) and a female gamete (egg, or ovum). The male reproductive system includes testes that produce sperm and the hormone testosterone, the sperm duct, and the penis. The female system includes ovaries that release eggs and produce oestrogen, oviducts (fallopian tubes) where fertilisation occurs, the uterus where the baby develops, and the vagina.

生殖是产生新个体的过程。人类进行有性生殖，需要雄性配子（精子）和雌性配子（卵子）。男性生殖系统包括产生精子和睾酮的睾丸、输精管和阴茎。女性生殖系统包括释放卵子并分泌雌激素的卵巢、发生受精的输卵管、孕育胎儿的子宫以及阴道。

During sexual intercourse, sperm are deposited into the vagina and swim through the cervix and uterus to reach the oviduct. Fertilisation is the fusion of the nuclei of a sperm and an egg to form a zygote. The zygote divides and implants into the uterus lining. The placenta forms, allowing exchange of nutrients, oxygen, and waste between the mother and embryo, but preventing mixing of blood. The amniotic sac protects the developing fetus.

性交时，精子被送入阴道，游过子宫颈和子宫到达输卵管。受精是精子和卵子的细胞核融合形成受精卵的过程。受精卵分裂并植入子宫内膜。胎盘形成，使母体与胚胎之间能够交换营养、氧气和废物，但防止血液混合。羊膜囊保护发育中的胎儿。

The menstrual cycle prepares the uterus lining for possible pregnancy. If fertilisation does not occur, the lining breaks down and is shed as a period. Key hormones: FSH and LH from the pituitary gland, and oestrogen and progesterone from the ovaries.

月经周期为可能的怀孕准备子宫内膜。如果没有发生受精，内膜则会脱落形成月经。关键激素：垂体分泌的促卵泡激素 (FSH) 和黄体生成素 (LH)，以及卵巢分泌的雌激素和孕酮。

6. Plant Reproduction and Growth | 植物的生殖与生长

Flowering plants reproduce sexually using flowers. The male parts (stamens) consist of an anther that produces pollen grains (male gametes) and a filament. The female part (carpel) includes the stigma, style, and ovary containing ovules (female gametes). Pollination is the transfer of pollen from the anther to the stigma, which can be wind pollinated or insect pollinated. Fertilisation happens when a pollen tube grows down the style, and the male nucleus fuses with the egg in the ovule to form a zygote.

开花植物通过花进行有性生殖。雄性部分（雄蕊）由产生花粉粒（雄配子）的花药和花丝组成。雌性部分（心皮）包括柱头、花柱和含有胚珠（雌配子）的子房。传粉是花粉从花药转移到柱头的过程，可分为风媒传粉或虫媒传粉。当花粉管沿花柱向下生长，雄配子核与胚珠中的卵子融合形成受精卵时，便发生了受精。

After fertilisation, the ovule develops into a seed and the ovary becomes the fruit. Seeds contain an embryo, a food store, and a seed coat. Dispersal mechanisms help seeds spread away from the parent plant to reduce competition: wind, water, animal, and explosive dispersal. Germination requires water, oxygen, and a suitable temperature.

受精后，胚珠发育成种子，子房发育成果实。种子包含胚、营养储备和种皮。散布机制帮助种子远离母株以减少竞争：风力传播、水力传播、动物传播和弹射传播。萌发需要水、氧气和适宜的温度。

Plants also reproduce asexually, for example using runners in strawberries or tubers in potatoes. This produces genetically identical offspring (clones) and is faster than sexual reproduction.

植物也可以进行无性生殖，例如草莓的匍匐茎或马铃薯的块茎。这会产生遗传上完全相同的后代（克隆），且比有性生殖更快。

7. Photosynthesis and Plant Transport | 光合作用与植物运输

Photosynthesis is the process by which plants use light energy to convert carbon dioxide and water into glucose and oxygen. It takes place in the chloroplasts of plant cells. The overall word equation is:

光合作用是植物利用光能，将二氧化碳和水转化为葡萄糖和氧气的过程。它发生在植物细胞的叶绿体中。总文字方程式为：

carbon dioxide + water → glucose + oxygen

二氧化碳 + 水 → 葡萄糖 + 氧气

The chemical equation with symbols is:

使用化学符号的方程式为：

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Photosynthesis requires light, carbon dioxide, water, and chlorophyll. The rate can be limited by the factor that is in shortest supply – light intensity, carbon dioxide concentration, or temperature. Glucose produced is used for respiration, converted into starch for storage, used to make cellulose for cell walls, or combined with minerals to form proteins.

光合作用需要光、二氧化碳、水和叶绿素。速率会受到最缺乏的那个因素的限制——光照强度、二氧化碳浓度或温度。产生的葡萄糖用于呼吸作用，转化为淀粉储存，用于制造细胞壁的纤维素，或与矿物质结合形成蛋白质。

Water and minerals are transported up the plant in xylem vessels, which are hollow dead cells strengthened with lignin. The transpiration stream pulls water from roots to leaves where it evaporates through stomata. Sugars are transported in both directions in phloem (translocation). Stomata are tiny pores on the lower leaf surface that allow gas exchange; guard cells control their opening and closing.

水和矿物质通过木质部导管在植物体内向上运输，木质部是由木质素强化了的中空死细胞。蒸腾流将水从根部拉到叶片，水通过气孔蒸发。糖类则在韧皮部中双向运输（转运作用）。气孔是叶片下表面的小孔，允许气体交换；保卫细胞控制其开闭。

8. Ecosystems, Food Chains, and Interdependence | 生态系统、食物链与相互依存

An ecosystem is made up of a community of living organisms interacting with their non-living environment. Organisms are interdependent, meaning changes in one population affect others. Food chains show the feeding relationships and energy flow: producer (e.g. grass) → primary consumer (herbivore) → secondary consumer (carnivore) → tertiary consumer. The arrows represent the direction of energy transfer.

生态系统由生物群落及其与非生物环境相互作用构成。生物是相互依存的，意味着一个种群的变化会影响其他种群。食物链表示了捕食关系和能量流动：生产者（如草）→ 初级消费者（植食动物）→ 次级消费者（肉食动物）→ 三级消费者。箭头代表能量传递的方向。

Food webs are more realistic, showing interconnected food chains. A pyramid of numbers counts organisms at each trophic level, but may not be pyramid shaped if a large tree supports many insects. Energy is lost at each level via respiration, movement, and waste, so fewer organisms are usually supported at higher trophic levels.

食物网更为真实，显示了相互关联的食物链。数量金字塔计算每个营养级的生物数量，但当一棵大树养活许多昆虫时，它可能不是标准的金字塔形。每一营养级通过呼吸、运动和废物损失能量，因此较高的营养级通常能支撑的生物数量更少。

Populations can be estimated using quadrats and transects. Bioaccumulation occurs when toxic substances (e.g. pesticides) build up in organisms and concentrate along food chains, harming top predators. Human activity such as deforestation, pollution, and introduction of invasive species can disrupt ecosystems.

可以用样方和样线来估算种群数量。当有毒物质（如杀虫剂）在生物体内积累并沿食物链浓度升高时，会发生生物累积，危害顶级捕食者。人类活动，如森林砍伐、污染和引入外来入侵物种，会破坏生态系统。

9. Inheritance, DNA, and Variation | 遗传、DNA 与变异

Inheritance is the passing of genetic information from parents to offspring. DNA is the molecule that carries this information, arranged as a double helix structure. A gene is a section of DNA that codes for a particular protein and controls a characteristic. Chromosomes are long strands of DNA found inside the nucleus; humans have 23 pairs (46 in total).

遗传是指遗传信息从亲代传递给子代的过程。DNA 是携带这些信息的分子，呈双螺旋结构排列。基因是编码特定蛋白质并控制性状的一段 DNA。染色体是位于细胞核内的长链 DNA；人类拥有 23 对染色体（共 46 条）。

Variation within a species can be genetic, environmental, or a combination of both. Genetic variation arises through mutations and sexual reproduction (mixing of alleles). Some characteristics are determined by a single gene with two alleles, e.g. tongue rolling. An allele can be dominant or recessive. A dominant allele will be expressed even if only one copy is present (heterozygous), while a recessive allele needs two copies (homozygous) to show.

物种内的变异可以是遗传的、环境的或两者共同作用的结果。遗传变异来自基因突变和有性生殖（等位基因的组合）。有些性状由具有两个等位基因的单个基因决定，例如卷舌。等位基因可能是显性或隐性。显性等位基因即使只有一个拷贝（杂合）也能表达，而隐性等位基因需要两个拷贝（纯合）才会显现。

Using a Punnett square, we can predict the probability of offspring inheriting certain traits. For example, crossing a homozygous dominant (TT) with a homozygous recessive (tt) produces all Tt offspring expressing the dominant trait. Genetic disorders such as cystic fibrosis are caused by recessive alleles.

使用庞纳特方格，我们可以预测后代遗传特定性状的概率。例如，将纯合显性 (TT) 与纯合隐性 (tt) 杂交，产生的后代全部为 Tt，表现为显性性状。遗传性疾病如囊性纤维化由隐性等位基因引起。

10. Microorganisms and Defence Against Disease | 微生物与疾病防御

Microorganisms, or microbes, include bacteria, viruses, fungi, and protoctists. Some are useful, e.g. bacteria in yoghurt production and decomposers recycling nutrients; others cause disease. Pathogens are microorganisms that cause infectious diseases. Bacteria reproduce quickly and release toxins; viruses invade cells and take over their machinery to replicate.

微生物包括细菌、病毒、真菌和原生生物。有些是有益的，例如制作酸奶的细菌以及回收养分的分解者；另一些则引发疾病。病原体是引起传染病的微生物。细菌繁殖迅速并释放毒素；病毒则侵入细胞并接管其复制机制以进行繁殖。

Common diseases: bacterial – cholera, tuberculosis; viral – influenza, HIV, measles; fungal – athlete’s foot; protoctist – malaria. Transmission can be through air (droplets), direct contact, contaminated food/water, or vectors like mosquitoes. The body defends itself with physical barriers such as skin and mucus, chemical barriers like stomach acid, and the immune system. White blood cells engulf pathogens, produce antibodies, and form memory cells for long-term immunity.

常见疾病：细菌性——霍乱、肺结核；病毒性——流感、HIV、麻疹；真菌性——足癣；原生生物——疟疾。传播途径可通过空气（飞沫）、直接接触、受污染的食物/水或蚊子等媒介传播。身体通过皮肤、黏液等物理屏障，胃酸等化学屏障以及免疫系统自我防御。白细胞吞噬病原体，产生抗体，并形成记忆细胞以提供长期免疫力。

Vaccination introduces a dead or weakened form of the pathogen, stimulating antibody production and memory cell formation without causing illness. This provides immunity. Antibiotics can kill bacteria but are ineffective against viruses. Overuse of antibiotics leads to resistant strains. Hygiene, handwashing, and clean water help prevent the spread of disease.

疫苗接种将死或弱化形式的病原体引入体内，刺激抗体产生和记忆细胞形成而不会致病，从而提供免疫力。抗生素可以杀死细菌，但对病毒无效。抗生素的过度使用导致耐药菌株产生。卫生习惯、洗手和清洁用水有助于防止疾病传播。

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Core Knowledge Revision for KS3 CCEA Biology | KS3 CCEA 生物核心知识点梳理