📚 KS3 CAIE Biology Core Knowledge Summary | KS3 CAIE 生物核心知识点梳理
Biology is the study of living organisms, from the tiniest cells to complex ecosystems. In KS3 CAIE Biology, you build a foundation by exploring how life works, how organisms are built, and how they interact with each other and their environment. This article brings together the key concepts you need to know, explained in clear, bite‑sized sections.
生物学是研究生命有机体的学科，从最微小的细胞到复杂的生态系统。在 KS3 CAIE 生物课程中，你将通过探索生命如何运作、生物体如何构建以及它们如何彼此及与环境相互作用来建立基础。本文汇总了需要掌握的核心概念，并用清晰、简洁的小节进行说明。
1. Cells and Organisation | 细胞与组织
All living organisms are made of cells. Some, like bacteria and amoeba, are unicellular, while plants and animals are multicellular. Cells are the basic building blocks of life and each one carries out the processes needed for survival.
所有生物都由细胞构成。有些生物如细菌和变形虫是单细胞的，而植物和动物是多细胞的。细胞是生命的基本结构单位，每个细胞都执行维持生存所需的过程。
A typical animal cell has a cell membrane, cytoplasm, and a nucleus containing genetic material. It also contains mitochondria where respiration happens. Plant cells have all these plus a rigid cell wall made of cellulose, a large permanent vacuole filled with cell sap, and chloroplasts for photosynthesis.
典型的动物细胞有细胞膜、细胞质和含有遗传物质的细胞核。它还含有发生呼吸作用的线粒体。植物细胞除了这些，还有由纤维素构成的坚硬的细胞壁、一个充满细胞液的大液泡以及进行光合作用的叶绿体。
In multicellular organisms, similar cells group together to form tissues. Different tissues work together to form organs, such as the heart or leaf. Organs are organised into organ systems, like the digestive system or the shoot system of a plant.
在多细胞生物中，相似的细胞聚集形成组织。不同的组织共同工作形成器官，例如心脏或叶。器官再组织成器官系统，如消化系统或植物的地上枝系统。
2. Life Processes | 生命过程
All living things share certain characteristics that distinguish them from non‑living matter. These are often remembered by the acronym MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition.
所有生物都具有某些共同特征，以区别于非生命物质。这些特征通常用缩写 MRS GREN 来记忆：运动、呼吸、感应、生长、生殖、排泄和营养。
Movement can be locomotion of the whole organism or movement of substances inside, such as cytoplasm streaming. Respiration is the chemical reaction that releases energy from food in all cells. Sensitivity means detecting and responding to changes in the environment, like plants bending toward light.
运动可以是整个生物体的移动，也可以是体内物质的运动，如细胞质流动。呼吸是发生在所有细胞中、从食物释放能量的化学反应。感应是指探测环境变化并作出反应，例如植物向光弯曲。
Growth is the permanent increase in size and complexity, often involving cell division and enlargement. Reproduction is the ability to produce offspring, either sexually or asexually. Excretion is removal of waste products like carbon dioxide and urea. Nutrition is the intake and use of materials for energy and growth.
生长是体积和复杂性的永久增大，通常涉及细胞分裂和扩展。生殖是产生后代的能力，分为有性生殖和无性生殖。排泄是去除二氧化碳和尿素等代谢废物。营养是获取和利用物质以提供能量和支持生长的过程。
3. Nutrition and Digestion | 营养与消化
Humans need a balanced diet containing carbohydrates, proteins, lipids (fats), vitamins, minerals, water and dietary fibre. Each nutrient has specific roles: carbohydrates provide energy, proteins are for growth and repair, and lipids provide energy storage and insulation.
人类需要包含碳水化合物、蛋白质、脂类（脂肪）、维生素、矿物质、水和膳食纤维的均衡饮食。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，脂类提供能量储存和保温。
Digestion breaks down large, insoluble food molecules into small, soluble ones that can be absorbed into the blood. Mechanical digestion, such as chewing in the mouth, increases surface area. Chemical digestion uses enzymes like amylase, protease and lipase.
消化将大而不可溶的食物分子分解成可被吸收进入血液的小而可溶的分子。机械性消化，例如口腔中的咀嚼，增加了表面积。化学性消化则利用淀粉酶、蛋白酶和脂肪酶等酶来完成。
The digestive system is a continuous tube from the mouth to the anus. Key organs include the stomach, where protein digestion begins, and the small intestine, where most digestion and absorption occur. The liver produces bile, which emulsifies fats, and the large intestine absorbs water.
消化系统是从口腔到肛门的连续管道。关键器官包括胃（蛋白质消化开始的地方）和小肠（大部分消化和吸收发生的部位）。肝脏产生胆汁，能乳化脂肪；大肠则吸收水分。
4. Plant Nutrition and Photosynthesis | 植物营养与光合作用
Plants make their own food through photosynthesis, a process that converts light energy into chemical energy stored in glucose. The word equation is:
植物通过光合作用自己制造食物，该过程将光能转化为储存在葡萄糖中的化学能。文字方程式为：
carbon dioxide + water → glucose + oxygen
二氧化碳 + 水 → 葡萄糖 + 氧气
Photosynthesis takes place in chloroplasts, which contain chlorophyll, the green pigment that captures light energy. The reaction requires light and occurs mainly in the leaves. The glucose produced is used for respiration, stored as starch, or used to build cellulose and proteins.
光合作用发生在含有叶绿素的叶绿体中，叶绿素是捕获光能的绿色色素。该反应需要光，主要在叶片中进行。产生的葡萄糖用于呼吸作用，以淀粉形式储存，或用于构建纤维素和蛋白质。
Plants also need mineral ions absorbed from the soil through their roots. Nitrates are needed for making amino acids and proteins, while magnesium is required to produce chlorophyll. A deficiency in nitrates causes stunted growth, and lack of magnesium results in yellowing leaves.
植物还需要通过根部从土壤中吸收矿质离子。硝酸盐用于合成氨基酸和蛋白质，而镁是制造叶绿素所必需的。缺乏硝酸盐会导致植株矮小，而缺镁则会使叶片发黄。
5. Respiration and Gas Exchange | 呼吸与气体交换
Respiration is not the same as breathing. It is a chemical reaction that happens inside cells, releasing energy from glucose. Aerobic respiration uses oxygen and produces carbon dioxide and water, summarised as:
呼吸作用不同于呼吸动作。它是发生在细胞内部、从葡萄糖释放能量的化学反应。有氧呼吸利用氧气，产生二氧化碳和水，概括方程式为：
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
Anaerobic respiration takes place when oxygen is limited. In animal cells, it produces lactic acid, while in yeast and some plants it produces ethanol and carbon dioxide. Anaerobic respiration releases less energy than aerobic respiration.
无氧呼吸在氧气有限时发生。在动物细胞中，它产生乳酸；而在酵母和一些植物中则产生乙醇和二氧化碳。无氧呼吸释放的能量比有氧呼吸少。
In humans, gas exchange happens in the lungs. Air enters through the trachea, passes into bronchi and bronchioles, and reaches tiny air sacs called alveoli. Oxygen diffuses from the alveoli into the blood in surrounding capillaries, and carbon dioxide diffuses in the opposite direction.
人类的气体交换在肺中进行。空气通过气管进入，经过支气管和细支气管，到达称为肺泡的微小气囊。氧气从肺泡扩散到周围毛细血管的血液中，二氧化碳则从相反方向扩散。
6. Transport Systems | 运输系统
The human circulatory system transports substances around the body. It consists of the heart, blood vessels and blood. The heart is a muscular pump with four chambers: two atria and two ventricles. Valves prevent backflow of blood.
人体循环系统在全身运输物质。它由心脏、血管和血液组成。心脏是一个有四个腔室的肌肉泵：两个心房和两个心室。瓣膜防止血液倒流。
Arteries carry blood away from the heart under high pressure and have thick, elastic walls. Veins return blood to the heart and contain valves. Capillaries are tiny, thin‑walled vessels where exchange of gases and nutrients occurs with tissues.
动脉在高压下将血液从心脏送走，具有厚而富有弹性的壁。静脉将血液送回心脏，内有瓣膜。毛细血管是微小、壁薄的血管，在那里与组织进行气体和营养物质的交换。
In plants, xylem vessels transport water and dissolved minerals from roots to leaves. This movement is driven by transpiration, the evaporation of water from the leaf surface. Phloem tubes carry sucrose and amino acids from photosynthetic areas to other parts of the plant.
在植物中，木质部导管将水和溶解的矿物质从根部运输到叶片。这种运动由蒸腾作用驱动，即水分从叶片表面蒸发。韧皮部管则将蔗糖和氨基酸从光合作用区域运送到植物的其他部分。
7. Health and Disease | 健康与疾病
Health is a state of complete physical, mental and social well‑being, not just the absence of disease. Diseases can be communicable (infectious) or non‑communicable. Pathogens such as bacteria, viruses, fungi and protists cause infectious diseases.
健康是身体、精神和社会全面完好的状态，而不仅仅是没有疾病。疾病可分为传染性（感染性）和非传染性。病原体如细菌、病毒、真菌和原生生物引起感染性疾病。
The body has several defence mechanisms against pathogens. Physical barriers include the skin and mucus in airways. White blood cells can engulf pathogens and produce antibodies that neutralise specific microbes. Vaccination trains the immune system to recognise and destroy a pathogen before it causes illness.
身体有多种抵御病原体的防御机制。物理屏障包括皮肤和气道中的黏液。白细胞能够吞噬病原体，并产生可中和特定微生物的抗体。疫苗接种训练免疫系统在病原体致病之前识别并消灭它。
Non‑communicable diseases, such as heart disease and type 2 diabetes, are often linked to lifestyle factors like poor diet, lack of exercise, smoking and excessive alcohol intake. Eating a balanced diet and staying active can reduce the risk of these diseases.
非传染性疾病，如心脏病和2型糖尿病，通常与生活方式因素有关，例如不良饮食、缺乏运动、吸烟和过量饮酒。均衡饮食和保持活跃可以降低患这些疾病的风险。
8. Reproduction | 生殖
Reproduction ensures the continuation of a species. In sexual reproduction, genetic material from two parents fuses to produce genetically varied offspring. In asexual reproduction, a single parent produces genetically identical clones.
生殖确保物种的延续。在有性生殖中，两个亲本的遗传物质融合，产生基因变异的子代。在无性生殖中，单个亲本产生基因完全相同的克隆。
Human reproductive systems differ between sexes. In males, testes produce sperm cells and the hormone testosterone. In females, ovaries produce egg cells and hormones oestrogen and progesterone. Fertilisation occurs when a sperm nucleus fuses with an egg nucleus, normally in the oviduct.
人类生殖系统因性别而异。男性睾丸产生精子和睾酮激素。女性卵巢产生卵细胞以及雌激素和孕激素。当精子核与卵细胞核融合时，发生受精，通常发生在输卵管中。
Flowering plants reproduce sexually too. Pollen grains, produced by anthers, are transferred to the stigma during pollination. Fertilisation happens when a pollen tube carries the male nucleus to the ovule. The fertilised ovule becomes a seed; the ovary develops into a fruit.
开花植物也进行有性生殖。由花药产生的花粉粒在授粉过程中被传递到柱头。当花粉管将雄核运送到胚珠时发生受精。受精的胚珠发育成种子，子房发育成果实。
9. Ecosystems and Food Chains | 生态系统与食物链
An ecosystem includes all the living organisms in a particular area, together with their non‑living environment. Organisms in an ecosystem are interdependent — they rely on one another for food, shelter and other resources.
生态系统包括特定区域的所有生物以及它们所处的非生物环境。生态系统中的生物是相互依赖的——它们依靠彼此获取食物、庇护所和其他资源。
In an ecosystem, energy flows through feeding relationships. A food chain shows how energy and matter pass from one organism to the next. Typically, it starts with a producer, such as a green plant or alga, which is eaten by a primary consumer, which in turn may be eaten by a secondary consumer.
在生态系统中，能量通过摄食关系流动。食物链显示能量和物质如何从一个生物体传递到下一个。通常，它以生产者（如绿色植物或藻类）开始，被初级消费者吃掉，后者又可能被次级消费者吃掉。
Food webs are made of many interconnected food chains and give a more realistic picture of feeding relationships. Predators are animals that kill and eat other animals; prey are the animals they eat. Changes in the numbers of one organism can affect others in the web.
食物网由许多相互连接的食物链组成，能更真实地反映摄食关系。捕食者是杀死并吃掉其他动物的动物，猎物则是被吃掉的动物。一个生物体数量的变化会影响食物网中的其他生物。
10. Inheritance and Variation | 遗传与变异
Inheritance is the passing of characteristics from parents to offspring through their genes. Genes are sections of DNA found on chromosomes in the nucleus. Offspring inherit one set of chromosomes from each parent, so they are genetically unique, except for identical twins.
遗传是特征通过基因从父母传递给后代的过程。基因是位于细胞核染色体上的 DNA 片段。子代从每个亲本中获得一套染色体，因此除了同卵双胞胎外，他们在遗传上是独一无二的。
Variation refers to the differences between individuals of the same species. It can be caused by genetic factors, environmental factors, or a combination of both. For example, eye colour is determined by genes, while body mass can be influenced by diet and exercise.
变异是指同一物种个体之间的差异。它可能由遗传因素、环境因素或两者共同引起。例如，眼睛颜色由基因决定，而体重可能受饮食和运动的影响。
Gregor Mendel’s experiments with pea plants revealed that traits are determined by discrete units, now called genes. Some alleles are dominant, and others are recessive. A characteristic may skip a generation if a recessive allele is masked by a dominant one in a heterozygous individual.
格雷戈尔·孟德尔的豌豆实验揭示，性状是由离散的、现在被称为基因的单位决定的。有些等位基因是显性的，有些是隐性的。如果一个隐性等位基因在杂合个体中被一个显性等位基因掩盖，特征可能隔代出现。
11. Adaptation and Evolution | 适应与进化
Organisms have adaptations — special features that help them survive in their environment. These can be structural (like the thick fur of an arctic fox), behavioural (like migration), or physiological (like producing venom).
生物体具有适应性特征——帮助它们在环境中生存的特殊功能。这些可以是结构性的（如北极狐的厚毛皮）、行为性的（如迁徙）或生理性的（如产生毒液）。
Adaptations arise through the process of natural selection. Charles Darwin’s theory states that in any population, individuals show variation. Those with traits better suited to the environment are more likely to survive, reproduce and pass on those advantageous traits to their offspring.
适应性通过自然选择过程产生。查尔斯·达尔文的学说指出，在任何种群中，个体都存在变异。那些具有更适应环境特征的个体更有可能存活、繁殖并将这些有利特征传递给后代。
Over many generations, this can lead to the evolution of new species. Fossils provide evidence for evolution, showing how organisms have changed over time. The fossil record indicates that life on Earth began over 3.5 billion years ago and has become increasingly complex.
经过许多代之后，这可能导致新物种的进化。化石为进化提供了证据，显示了生物体如何随时间变化。化石记录表明，地球上的生命起源于 35 亿多年前，并且已变得越来越复杂。
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