📚 Year 8 CIE Biology: Core Knowledge Review | CIE Year 8 生物核心知识点梳理
This revision guide pulls together the key ideas from the Cambridge Lower Secondary Year 8 Biology syllabus. Understanding these concepts will help you build a strong foundation for IGCSE and beyond. Each section is presented with an English explanation followed by a matching Chinese version so you can learn the language of science in both directions.
本复习手册梳理了 Cambridge Lower Secondary Year 8 生物课程的核心知识点。掌握这些概念将为你打好 IGCSE 及后续学习的基础。每个部分都按英文说明后紧跟中文对照的方式呈现，帮助你用中英双语理解科学语言。
1. Characteristics of Living Organisms | 生物的基本特征
All living organisms share seven life processes, commonly remembered by the acronym MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition.
所有生物都具有七大生命活动，通常用首字母缩写 MRS GREN 记忆：运动、呼吸、感应、生长、生殖、排泄和营养。
Movement can be the ability to change position (animals) or slow growth responses (plants). Respiration is the chemical breakdown of nutrients to release energy in cells. Sensitivity means detecting and responding to changes in the surroundings.
运动可以是改变位置的能力（动物）或缓慢的生长反应（植物）。呼吸是细胞中营养物质化学分解以释放能量的过程。感应指探测并对外界环境变化做出反应。
Growth involves an increase in size and cell number. Reproduction is the production of offspring, either sexually or asexually. Excretion removes metabolic waste products, and Nutrition is the intake and use of nutrients for energy and building materials.
生长涉及体积增大和细胞数量增加。生殖是产生后代，分为有性生殖和无性生殖。排泄清除代谢废物，营养则是摄入和利用营养物质以提供能量和构建物质。
2. Cells: The Basic Units of Life | 细胞：生命的基本单位
All organisms are made of cells. Animal cells contain a nucleus, cytoplasm, cell membrane and mitochondria. Plant cells have the same organelles plus a cell wall, a large vacuole and chloroplasts.
所有生物体都由细胞构成。动物细胞包含细胞核、细胞质、细胞膜和线粒体。植物细胞拥有相同的细胞器，还多了细胞壁、大液泡和叶绿体。
The nucleus controls the cell's activities and contains genetic material. Cytoplasm is a jelly-like substance where most chemical reactions occur. The cell membrane controls what enters and leaves the cell.
细胞核控制细胞活动并含有遗传物质。细胞质是一种果冻状物质，大多数化学反应在其中发生。细胞膜控制物质的进出。
Mitochondria are the sites of aerobic respiration. The cell wall (made of cellulose) provides support and shape in plant cells. A large permanent vacuole stores sap and helps maintain turgor pressure. Chloroplasts absorb light energy for photosynthesis.
线粒体是有氧呼吸的场所。细胞壁（由纤维素构成）为植物细胞提供支撑和形状。大型永久液泡储存细胞液并帮助维持膨压。叶绿体吸收光能以进行光合作用。
3. Levels of Organisation | 生物组织的层次
Cells are organised into tissues, organs and organ systems. A tissue is a group of similar cells working together to carry out a specific function, such as muscle tissue or xylem.
细胞组织形成组织、器官和器官系统。组织是一群形态结构相似、共同完成特定功能的细胞，如肌肉组织或木质部。
An organ is made of different tissues working together, e.g. the stomach contains muscular tissue, glandular tissue and epithelial tissue. Organ systems are groups of organs that carry out a major body function, e.g. the digestive system.
器官由不同的组织协同工作构成，例如胃含有肌肉组织、腺体组织和上皮组织。器官系统是一组共同完成主要生理功能的器官，如消化系统。
In plants, leaves are organs made of epidermal, mesophyll and vascular tissues. The shoot system and root system form the main plant organ systems.
在植物中，叶是由表皮组织、叶肉组织和维管组织构成的器官。地上部分（茎叶）系统和根系构成植物的主要器官系统。
4. Movement of Substances: Diffusion and Osmosis | 物质的运动：扩散和渗透
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 a passive process that 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，沿浓度梯度进行。这是一种被动过程，不需要能量。
Everyday examples include oxygen diffusing into blood in the lungs and carbon dioxide diffusing out of cells. Osmosis is a special type of diffusion involving water molecules across a partially permeable membrane.
日常例子包括氧气在肺部扩散进入血液以及二氧化碳从细胞中扩散出来。渗透是扩散的一种特殊类型，涉及水分子通过半透膜的运动。
In osmosis, water moves from a dilute solution (more water, less solute) to a concentrated solution (less water, more solute). This process is crucial for water uptake in plant roots and maintaining animal cell shape.
在渗透过程中，水从稀溶液（水多、溶质少）向浓溶液（水少、溶质多）移动。这一过程对于植物根部吸水以及维持动物细胞形态至关重要。
5. Nutrition and a Balanced Diet | 营养与均衡膳食
A balanced diet provides all essential nutrients in the right proportions. The seven main nutrient groups are carbohydrates, proteins, lipids (fats), vitamins, minerals, dietary fibre and water.
均衡膳食以恰当的比例提供所有必需营养素。七大营养素类别为：碳水化合物、蛋白质、脂类（脂肪）、维生素、矿物质、膳食纤维和水。
Carbohydrates provide the main source of energy. Proteins are needed for growth and repair of tissues. Lipids supply a concentrated energy source and help with insulation and cell membrane structure.
碳水化合物是主要能量来源。蛋白质用于生长和组织修复。脂类提供浓缩的能量来源，有助于保温和构建细胞膜结构。
Vitamins and minerals are needed in small amounts for various functions, e.g. vitamin C for immune health, calcium for bones. Deficiency diseases arise when a nutrient is lacking, such as scurvy from lack of vitamin C.
维生素和矿物质需求量小但功能多样，如维生素C维持免疫力，钙元素促进骨骼健康。缺乏某种营养素会导致缺乏症，如缺乏维生素C引起坏血病。
6. The Human Digestive System | 人体消化系统
Digestion breaks down large insoluble food molecules into small soluble ones that can be absorbed into the blood. Mechanical digestion (e.g. chewing, stomach churning) increases surface area, while chemical digestion uses enzymes.
消化将大块不溶性食物分子分解为可被吸收进入血液的小分子可溶物质。物理消化（如咀嚼、胃蠕动）增大表面积，化学消化则依靠酶的作用。
Key organs include the mouth (salivary amylase starts starch breakdown), oesophagus, stomach (acid and proteases), small intestine (major site of digestion and absorption) and large intestine (water absorption).
关键器官包括口腔（唾液淀粉酶开始分解淀粉）、食道、胃（胃酸和蛋白酶）、小肠（消化与吸收的主要场所）和大肠（吸收水分）。
The small intestine contains villi which increase the surface area for absorption. Digested products such as glucose and amino acids are then transported by the blood to cells throughout the body.
小肠内壁有绒毛，增大了吸收表面积。消化产物如葡萄糖和氨基酸随后通过血液运输到全身细胞。
7. The Circulatory System | 循环系统
The circulatory system consists of the heart, blood vessels and blood. It transports oxygen, nutrients, hormones and waste products around the body. The heart is a double pump with four chambers: two atria and two ventricles.
循环系统由心脏、血管和血液组成。它运输氧气、营养物质、激素和废物到身体各处。心脏是一个双泵，有四个腔室：两个心房和两个心室。
Arteries carry blood away from the heart, usually oxygenated (except the pulmonary artery). Veins return blood to the heart, containing valves to prevent backflow. Capillaries are tiny, thin-walled vessels where exchange of substances occurs.
动脉将血液运离心脏，通常带氧（肺动脉除外）。静脉将血液送回心脏，内有瓣膜防止倒流。毛细血管是壁薄微小的血管，物质交换在此发生。
Blood contains red blood cells (carry oxygen using haemoglobin), white blood cells (defence), platelets (clotting) and plasma (liquid transport medium).
血液包含红细胞（利用血红蛋白运氧）、白细胞（防御）、血小板（凝血）和血浆（液态运输介质）。
8. Respiration and Gas Exchange | 呼吸与气体交换
es. Aerobic respiration uses oxygen: glucose + oxygen → carbon dioxide + water (+ energy).
呼吸作用不同于呼吸（换气）。它是从食物分子中释放能量的过程。有氧呼吸利用氧气：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。
Anaerobic respiration occurs without oxygen and produces less energy. In animal cells, glucose is converted to lactic acid; in yeast and some plants, ethanol and carbon dioxide are produced.
无氧呼吸在缺氧时发生，产能较少。在动物细胞中，葡萄糖转化为乳酸；在酵母和某些植物中，产生乙醇和二氧化碳。
Gas exchange in humans happens in the lungs. Air enters through the trachea, bronchi and bronchioles to reach the alveoli. Oxygen diffuses into the blood, and carbon dioxide diffuses out.
人体的气体交换在肺中进行。空气经气管、支气管和细支气管进入肺泡。氧气扩散进入血液，二氧化碳扩散排出。
During inhalation, the diaphragm contracts and flattens, and the ribcage moves up and out, increasing the volume of the chest cavity and drawing air in.
吸气时，膈肌收缩变平，肋骨上抬外移，胸腔容积增大，空气被吸入。
9. Photosynthesis and Plants | 光合作用与植物
word equation is: carbon dioxide + water → glucose + oxygen, using light and chlorophyll.
光合作用是植物利用光能制造自身养分的过程。文字方程式为：二氧化碳 + 水 → 葡萄糖 + 氧气，条件为光和叶绿素。
Leaves are adapted for photosynthesis: broad, flat shape for large surface area; thin for short diffusion distance; stomata for gas exchange; and chloroplasts containing chlorophyll to trap light energy.
叶的结构适应光合作用：宽而扁平的形状提供大的表面积；薄以缩短扩散距离；气孔进行气体交换；叶绿体中的叶绿素捕获光能。
Transport in plants occurs through xylem (water and minerals up from roots) and phloem (sugars and other products of photosynthesis to all parts). The loss of water vapour through stomata is called transpiration.
植物体内的运输通过木质部（水分和矿物质自根部向上运输）和韧皮部（糖类等光合产物运往各处）进行。水蒸气经气孔散失的过程称为蒸腾作用。
10. Reproduction in Humans | 人体生殖
Human reproduction is sexual, involving the fusion of male and female gametes (sperm and egg) during fertilisation to form a zygote. The male reproductive system produces sperm in the testes and delivers them through the sperm duct.
人类生殖为有性生殖，涉及受精过程中雄配子（精子）和雌配子（卵子）的结合形成受精卵。男性生殖系统在睾丸产生精子，并通过输精管输送精子。
The female reproductive system contains ovaries that release eggs (ovulation), oviducts where fertilisation usually occurs, a uterus where the embryo develops, and a vagina.
女性生殖系统包含释放卵子的卵巢（排卵），通常发生受精的输卵管，胚胎发育的子宫以及阴道。
The placenta allows exchange of oxygen, nutrients and waste between mother and fetus without mixing their blood. The amniotic fluid protects the developing fetus. Puberty involves physical changes driven by sex hormones.
胎盘允许母体和胎儿之间交换氧气、养分和废物，但双方的血液不相混合。羊水保护发育中的胎儿。青春期是由性激素驱动的身体变化过程。
11. Ecosystems and Food Chains | 生态系统与食物链
An ecosystem includes all the living organisms (community) and the non-living (abiotic) factors in an area. Producers (plants) convert light energy into chemical energy via photosynthesis.
生态系统包括某一区域内的所有生物（群落）和非生物（无机）环境因素。生产者（植物）通过光合作用将光能转化为化学能。
onsumers, and so on. A food chain shows the transfer of energy, e.g. grass → rabbit → fox.
消费者通过取食获得能量：初级消费者吃植物，次级消费者吃初级消费者，依此类推。食物链显示能量传递，如草 → 兔 → 狐狸。
Decomposers (bacteria and fungi) break down dead matter, recycling nutrients back into the soil. Energy is lost at each trophic level, so food chains rarely have more than five levels.
分解者（细菌和真菌）分解死物，将营养物质循环回土壤。能量在每一营养级都会损失，因此食物链很少超过五个营养级。
Feeding relationships can be displayed in food webs, which are networks of interconnected food chains. Changes in one population can affect many others in the web.
取食关系可用食物网表示，即相互连接的食物链网络。一个种群的变化可能影响网中许多其他生物。
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