📚 KS3 Cambridge Biology: Core Knowledge Summary | KS3 Cambridge 生物：核心知识点梳理
Cambridge Lower Secondary Science Stage 7-9 lays the foundation for IGCSE Biology. This article brings together the most essential biology topics you will cover during KS3. You will explore cells, life processes, human body systems, reproduction, photosynthesis, ecosystems, genetics, and health. A strong grasp of these ideas will make your transition to IGCSE much smoother.
剑桥初中科学（7 至 9 年级）为 IGCSE 生物打下基础。本文梳理了你将在 KS3 阶段学习的最核心生物知识点。你将探索细胞、生命活动、人体各大系统、生殖、光合作用、生态系统、遗传以及健康。扎实掌握这些知识，能让你更顺利地过渡到 IGCSE 课程。
1. Cells and Organisation | 细胞与组织
All living organisms are made up of cells, the basic structural and functional units of life. Some organisms, such as bacteria and amoeba, are unicellular, while plants and animals are multicellular.
所有生物体都由细胞构成，细胞是生命的基本结构和功能单位。有些生物，如细菌和变形虫，是单细胞的，而植物和动物则是多细胞的。
Animal cells typically contain a cell membrane, cytoplasm, nucleus, and mitochondria. Plant cells have these structures plus a rigid cell wall, chloroplasts for photosynthesis, and a large permanent vacuole filled with cell sap.
动物细胞通常含有细胞膜、细胞质、细胞核和线粒体。植物细胞除了这些结构，还有坚硬的细胞壁、进行光合作用的叶绿体，以及充满细胞液的大液泡。
In multicellular organisms, similar cells group together to form tissues. Tissues work together to form organs, and organs are organised into organ systems. For example, muscle tissue and nervous tissue coordinate to form the stomach, which is part of the digestive system.
在多细胞生物体内，相似的细胞组合形成组织。组织协同工作形成器官，器官再构成器官系统。例如，肌肉组织和神经组织相互配合构成胃，而胃是消化系统的一部分。
2. Life Processes and Classification | 生命活动与分类
All living things carry out seven life processes. These can be remembered using MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition.
所有生物都进行七个生命活动，可以用 MRS GREN 来记忆：运动、呼吸、感应、生长、生殖、排泄和营养。
Scientists classify organisms into five kingdoms: Animals, Plants, Fungi, Protists, and Prokaryotes. Vertebrates are further divided into mammals, birds, reptiles, amphibians, and fish. Invertebrates include arthropods (insects, arachnids, crustaceans, myriapods), molluscs, and annelids.
科学家将生物分为五个界：动物界、植物界、真菌界、原生生物界和原核生物界。脊椎动物进一步分为哺乳类、鸟类、爬行类、两栖类和鱼类。无脊椎动物包括节肢动物（昆虫、蛛形纲、甲壳纲、多足纲）、软体动物和环节动物。
The binomial naming system uses a genus and species name, e.g., Homo sapiens for humans. Classification keys help us identify organisms by asking a series of yes/no questions about their characteristics.
双名法使用属名和种名，例如人类被命名为 Homo sapiens。分类检索表通过一系列关于特征的是否问题帮助我们鉴定生物。
3. Nutrition and Digestion | 营养与消化
A balanced diet includes carbohydrates, proteins, lipids, vitamins, minerals, dietary fibre, and water. Each nutrient has a specific role: carbohydrates provide energy, proteins support growth and repair, and fats supply long-term energy and insulation.
均衡膳食包含碳水化合物、蛋白质、脂类、维生素、矿物质、膳食纤维和水。每种营养素都有特定作用：碳水化合物提供能量，蛋白质用于生长和修复，脂肪提供长期能量并维持体温。
The digestive system breaks down large insoluble food molecules into small soluble ones that can be absorbed into the bloodstream. Mechanical digestion begins in the mouth with chewing, while chemical digestion involves enzymes.
消化系统将大的不溶性食物分子分解为小的可溶性分子，以便吸收进入血液。物理性消化从口腔咀嚼开始，化学性消化则需要酶的参与。
The main digestive organs are the mouth, oesophagus, stomach, small intestine, large intestine, and anus. Accessory organs like the liver and pancreas produce bile and digestive enzymes. Villi in the small intestine increase the surface area for absorption.
主要的消化器官有口腔、食道、胃、小肠、大肠和肛门。肝脏和胰腺等辅助器官产生胆汁和消化酶。小肠中的绒毛增大了吸收的表面积。
4. The Respiratory System | 呼吸系统
Respiration is the process that releases energy from glucose. It is not the same as breathing. Aerobic respiration uses oxygen and produces carbon dioxide and water, releasing a large amount of energy.
呼吸作用是从葡萄糖中释放能量的过程，与日常所说的呼吸（通气）不同。有氧呼吸利用氧气，产生二氧化碳和水，并释放大量能量。
Glucose + Oxygen → Carbon Dioxide + Water (+ Energy)
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ Energy)
Anaerobic respiration occurs when oxygen is limited, producing lactic acid in muscles and much less energy. In yeast, anaerobic respiration produces ethanol and carbon dioxide (fermentation).
在氧气不足时会发生无氧呼吸，肌肉中产生乳酸并释放较少能量。在酵母中，无氧呼吸产生乙醇和二氧化碳（发酵）。
The respiratory system includes the trachea, bronchi, bronchioles, and alveoli. Gas exchange happens in the alveoli: oxygen diffuses into the blood, and carbon dioxide diffuses out. The diaphragm and intercostal muscles control breathing movements.
呼吸系统包括气管、支气管、细支气管和肺泡。气体交换在肺泡中进行：氧气扩散进入血液，二氧化碳扩散出来。膈肌和肋间肌控制呼吸运动。
5. The Circulatory System | 循环系统
The circulatory system transports oxygen, nutrients, hormones, and waste products around the body. It consists of the heart, blood vessels, and blood.
循环系统负责将氧气、营养物质、激素和废物运输到全身各处，由心脏、血管和血液组成。
The heart is a double pump with four chambers: two atria and two ventricles. The right side pumps deoxygenated blood to the lungs, while the left side pumps oxygenated blood to the rest of the body. Valves prevent backflow.
心脏是一个双泵，有四个腔室：两个心房和两个心室。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; veins return blood to the heart and contain valves. Capillaries are tiny vessels where substances are exchanged with tissues. Blood is composed of red blood cells, white blood cells, platelets, and plasma.
动脉在高压下将血液送出心脏；静脉将血液送回心脏并含有瓣膜。毛细血管是进行物质交换的微小血管。血液由红细胞、白细胞、血小板和血浆组成。
6. Reproduction | 生殖
Reproduction can be sexual or asexual. Sexual reproduction involves the fusion of male and female gametes, producing genetically varied offspring. Asexual reproduction requires only one parent and produces genetically identical clones.
生殖可分为有性生殖和无性生殖。有性生殖涉及雄配子和雌配子的融合，产生遗传上多样的后代。无性生殖只需一个亲本，产生遗传相同的克隆。
In humans, the male reproductive system produces sperm in the testes. The female reproductive system releases eggs from the ovaries and, if fertilised, the embryo implants in the uterus. The menstrual cycle prepares the uterus for pregnancy each month.
在人体中，男性生殖系统在睾丸产生精子。女性生殖系统从卵巢排出卵子，若受精，胚胎将在子宫着床。月经周期每个月为子宫受孕做准备。
In flowering plants, pollen grains contain male gametes. Pollination transfers pollen to the stigma; fertilisation occurs when the pollen tube grows down to the ovule. The fertilised ovule develops into a seed, and the ovary becomes a fruit.
在开花植物中，花粉粒含有雄配子。传粉将花粉传递到柱头；花粉管向下生长到达胚珠完成受精。受精后的胚珠发育成种子，子房发育成果实。
7. Photosynthesis and Plant Transport | 光合作用与植物运输
Photosynthesis is the process by which green plants and some other organisms use light energy to convert carbon dioxide and water into glucose and oxygen. It takes place in chloroplasts containing chlorophyll.
光合作用是绿色植物等生物利用光能，将二氧化碳和水转化为葡萄糖和氧气的过程。该过程发生在含有叶绿素的叶绿体内。
Carbon Dioxide + Water → Glucose + Oxygen
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Glucose produced in photosynthesis is used for respiration, converted into starch for storage, or used to make cellulose, proteins, and oils. Light intensity, carbon dioxide concentration, and temperature all affect the rate of photosynthesis.
光合作用产生的葡萄糖用于呼吸作用，也可转化为淀粉储存，或用来制造纤维素、蛋白质和油脂。光照强度、二氧化碳浓度和温度都会影响光合作用的速率。
Xylem vessels transport water and dissolved minerals from the roots to the leaves. Phloem tubes carry sugars and other nutrients from the leaves to the rest of the plant (translocation). Transpiration is the loss of water vapour from leaves, which pulls water up the xylem.
木质部导管将水和溶解的矿物质从根部输送到叶片。韧皮部管将糖等营养物质从叶片运送到植物其他部位（转运）。蒸腾作用是叶片散失水蒸气的过程，这会产生拉力使水沿木质部上移。
8. Ecosystems and Feeding Relationships | 生态系统与摄食关系
An ecosystem is made up of a community of living organisms interacting with the non-living environment. Habitats provide organisms with food, shelter, and a place to reproduce. Populations within a habitat depend on each other and on resources.
生态系统由生物群落及其相互作用的环境组成。栖息地为生物提供食物、庇护所和繁殖场所。同一栖息地内的种群相互依赖，并依赖各种资源。
Feeding relationships can be shown using food chains and food webs. Producers are green plants and algae that make their own food via photosynthesis. Consumers are organisms that eat other organisms. Decomposers break down dead matter and return nutrients to the soil.
摄食关系可用食物链和食物网表示。生产者是通过光合作用制造食物的绿色植物和藻类。消费者是捕食其他生物的生物。分解者分解死去的生物，把养分归还给土壤。
Pyramids of number show the population size at each trophic level. Energy is lost at each step, mainly as heat through respiration, which limits the length of food chains. Bioaccumulation occurs when toxins build up in organisms higher up the food chain.
数量金字塔显示每个营养级的种群数量。能量在每一级都会损失，主要以热能形式通过呼吸作用散失，这限制了食物链的长度。毒素在食物链高端的生物体内积累，称为生物富集作用。
9. Inheritance and Variation | 遗传与变异
Information is passed from parents to offspring in the form of genes located on chromosomes inside the nucleus. DNA is the molecule that carries the genetic code. Humans have 23 pairs of chromosomes, including one pair of sex chromosomes (XX or XY).
亲代的遗传信息以基因的形式传递给子代，基因位于细胞核内的染色体上。DNA 是携带遗传密码的分子。人类有 23 对染色体，其中包括一对性染色体（XX 或 XY）。
Variation between individuals can be continuous (height, weight) or discontinuous (blood group, tongue rolling). Some variation is inherited through genes, and some is caused by the environment, such as diet or exposure to sunlight.
个体间的变异可以是连续的（如身高、体重），也可以是不连续的（如血型、卷舌能力）。有些变异是由基因遗传的，有些则由环境引起，如饮食或日照。
Selective breeding is when humans choose organisms with desired characteristics to reproduce. Natural selection is the process by which organisms better adapted to their environment survive and produce more offspring. Darwin’s theory of evolution explains how species change over time.
人工选择是指人类选择具有理想性状的生物进行繁殖。自然选择则是适应环境能力更强的个体存活并产生更多后代的过程。达尔文进化论解释了物种如何随时间发生变化。
10. Health and Disease | 健康与疾病
Health is the state of physical, mental, and social well-being. Diseases can be communicable (caused by pathogens such as viruses, bacteria, fungi, and protists) or non-communicable (such as cancer, diabetes, and heart disease).
健康是身体、心理和社会适应的完好状态。疾病可分为传染性疾病（由病原体如病毒、细菌、真菌和原生生物引起）和非传染性疾病（如癌症、糖尿病和心脏病）。
The body has several defence mechanisms: skin forms a physical barrier, mucus traps pathogens, and stomach acid kills many microbes. The immune system produces white blood cells that engulf pathogens or produce antibodies to neutralise toxins.
人体有多道防御机制：皮肤形成物理屏障，黏液粘住病原体，胃酸杀死许多微生物。免疫系统产生白细胞，吞噬病原体或产生抗体来中和毒素。
Vaccination introduces a harmless form of a pathogen to stimulate the immune system, creating memory cells that respond quickly upon future infection. Antibiotics can kill bacteria but are ineffective against viruses. Maintaining a healthy lifestyle with exercise, a balanced diet, and good hygiene reduces the risk of many diseases.
疫苗接种将一种无害的病原体形式引入体内，刺激免疫系统产生记忆细胞，在未来感染时迅速反应。抗生素能杀死细菌，但对病毒无效。保持健康的生活方式，如锻炼、均衡饮食和良好卫生习惯，可以降低许多疾病的风险。
Published by TutorHao | Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图