📚 Year 7 CIE Biology: Core Concepts Summary | Year 7 CIE 生物：核心知识点梳理
This revision guide covers the most important topics in Year 7 Biology according to the CIE Lower Secondary curriculum. Understanding these core concepts is essential for building a strong foundation in life sciences, and each section below pairs the key definitions, examples and exam-style ideas that students are expected to know before moving on to IGCSE.
这份复习指南涵盖 CIE 初中课程七年级生物最重要的主题。理解这些核心概念对于打下坚实的生命科学基础至关重要。下面每一节都配有核心定义、例子以及考试常见思路，帮助学生在进入 IGCSE 之前把基础打牢。
1. Characteristics of Living Things | 生命特征
All organisms share seven life processes summarised by the acronym MRS GREN. A useful starting point is to ask whether an object carries out all seven processes, because only living things do.
所有生物都具有由首字母缩略词 MRS GREN 概括的七项生命过程。判断某物是否有生命，最实用的方法是问它是否同时具备全部七项过程，因为只有生物才会全部具备。
Movement: an action causing a change of position or place. Plants may not travel, but they still move - roots grow downwards and shoots bend towards the light.
运动：引起位置或地方改变的动作。植物虽然不会移动位置，但它们仍然会运动——根向下生长，芽向光弯曲。
Respiration: chemical reactions that release energy from nutrients. This is not the same as breathing; it happens inside every living cell, all the time.
呼吸作用：从营养物质中释放能量的化学反应。呼吸作用不等于呼吸运动，它发生在每一个活细胞内，并且持续进行。
Sensitivity: detecting and responding to changes in the environment, such as a plant growing towards light or a pupil shrinking in bright light.
感应：察觉环境变化并作出反应，例如植物向光生长，或瞳孔在强光下缩小。
Growth: a permanent increase in size and complexity. Temporary changes such as a balloon being blown up do not count as growth.
生长：尺寸和复杂性的永久增加。气球被吹大这类临时变化不算生长。
Reproduction: producing offspring to continue the species. It may be sexual, involving two parents, or asexual, involving one parent.
繁殖：产生后代以延续物种。繁殖可以是有性繁殖，涉及两个亲本；也可以是无性繁殖，只涉及一个亲本。
Excretion: removal of metabolic waste products from the body, for example carbon dioxide, urea and excess salts. Undigested food leaving the gut is egestion, not excretion.
排泄：从体内排出代谢废物，例如二氧化碳、尿素和多余的盐分。未消化的食物排出肠道属于排遗，而不是排泄。
Nutrition: intake of materials for energy, growth and repair. Plants make their own food by photosynthesis; animals must eat other organisms.
营养：摄入物质以获取能量、生长和修复。植物通过光合作用自己制造食物，动物则必须取食其他生物。
Non-living things may show some of these features but not all. A car moves and uses fuel but does not grow or reproduce, so it is non-living. Similarly, a crystal grows but does not respire or respond to stimuli in a biological way.
非生物可能表现出其中一些特征，但并非全部。汽车会移动并使用燃料，但它不会生长或繁殖，因此它是非生物。同样，晶体虽然会变大，但不进行呼吸作用，也不以生物学方式对刺激作出反应。
2. Cells | 细胞
All living organisms are made of cells. The cell is the basic structural and functional unit of life. Some organisms are unicellular, made of a single cell, while others are multicellular and may contain billions of cells.
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。有些生物是单细胞的，只由一个细胞组成；另一些是多细胞的，体内可能含有数十亿个细胞。
Animal cells contain a cell membrane, cytoplasm, nucleus, mitochondria and ribosomes. Plant cells have all these plus a cellulose cell wall, a large permanent vacuole and chloroplasts.
动物细胞含有细胞膜、细胞质、细胞核、线粒体和核糖体。植物细胞除了这些，还有纤维素细胞壁、一个大液泡和叶绿体。
Nucleus: stores genetic material and controls cell activities.
细胞核：储存遗传物质并控制细胞活动。
Cytoplasm: a jelly-like fluid where most chemical reactions of the cell take place.
细胞质：一种胶状液体，细胞内大部分化学反应在此进行。
Cell membrane: a thin partially permeable layer that controls what enters and leaves the cell.
细胞膜：一层薄的半透性结构，控制物质进出细胞。
Mitochondria: small structures where aerobic respiration occurs, releasing energy for the cell.
线粒体：进行有氧呼吸的小型结构，为细胞释放能量。
Ribosomes: tiny structures where proteins are made.
核糖体：制造蛋白质的微小结构。
Cell wall: a tough cellulose layer outside the cell membrane that gives the plant cell a fixed shape and support.
细胞壁：细胞膜外一层坚韧的纤维素结构，使植物细胞具有固定形状并提供支持。
Vacuole: a large space filled with cell sap that helps keep the cell firm and stores dissolved substances.
液泡：充满细胞液的大空间，有助于维持细胞的坚挺并储存溶解的物质。
Chloroplasts: green structures containing chlorophyll, which absorb light energy for photosynthesis.
叶绿体：含有叶绿素的绿色结构，吸收光能用于光合作用。
| Feature | Animal cell | Plant cell |
| Cell membrane | Yes | Yes |
| Nucleus | Yes | Yes |
| Cell wall | No | Yes (cellulose) |
| Chloroplasts | No | Yes, in green parts |
| Large vacuole | No (small ones may occur) | Yes |
Specialised cells have shapes suited to their jobs. A red blood cell has no nucleus and is packed with haemoglobin; a nerve cell is very long so it can carry impulses; a root hair cell has a long extension to absorb water; a palisade cell contains many chloroplasts for photosynthesis; a ciliated cell has tiny hairs that sweep mucus away from the lungs.
特化细胞的形状与其功能相适应。红细胞没有细胞核，并充满血红蛋白；神经细胞很长，便于传导冲动；根毛细胞有细长突起以吸收水分；栅栏组织细胞含有大量叶绿体进行光合作用；纤毛细胞表面有细小纤毛，可把黏液从肺部扫出。
3. Levels of Organisation | 组织层次
Multicellular organisms are organised in a clear hierarchy: cells, tissues, organs, organ systems and finally the whole organism. Understanding this order helps students explain how a simple cell can become part of a complex body.
多细胞生物按照清晰的层次组织：细胞、组织、器官、器官系统，最后是整个生物体。理解这一顺序有助于学生解释简单的细胞如何成为复杂身体的一部分。
Cell: the smallest unit of life, such as a muscle cell or a leaf cell.
细胞：生命的最小单位，例如肌细胞或叶细胞。
Tissue: a group of similar cells working together to carry out a shared function, such as muscle tissue or xylem tissue.
组织：一群相似的细胞共同完成某一功能，例如肌肉组织或木质部组织。
Organ: several tissues working together, such as the stomach, heart or leaf.
器官：多种组织共同协作，例如胃、心脏或叶片。
Organ system: a group of organs that work together, such as the digestive system, circulatory system or respiratory system.
器官系统：一组协同工作的器官，例如消化系统、循环系统或呼吸系统。
Organism: the complete living individual, able to carry out all seven life processes.
生物体：完整的生物个体，能够完成全部七项生命过程。
An example in humans runs from a muscle cell to muscle tissue, then to the stomach, then to the digestive system, and finally to the whole body. In plants, a palisade cell forms palisade tissue, which is part of a leaf, which belongs to the shoot system.
人体中的一个例子是：肌细胞构成肌肉组织，肌肉组织构成胃，胃属于消化系统，最终组成整个人体。在植物中，栅栏组织细胞构成栅栏组织，栅栏组织是叶的一部分，叶属于茎叶系统。
Unicellular organisms such as Amoeba and yeast carry out all life processes within one cell, so they do not form tissues or organs. This contrast is a common exam question.
变形虫和酵母等单细胞生物在一个细胞内完成所有生命过程，因此不会形成组织或器官。这一对比是常见的考试问题。
4. Classification and Variation | 分类与变异
Classification means grouping living things according to shared features. Scientists use a system of groups that becomes more specific: kingdom, phylum, class, order, family, genus and species.
分类就是根据共同特征对生物进行分组。科学家使用一套由大到小的分类等级：界、门、纲、目、科、属、种。
A species is a group of organisms that can breed together to produce fertile offspring. The scientific name of an organism is written in two parts, genus then species, for example Homo sapiens; the genus starts with a capital letter and the whole name is italicised or underlined.
物种是一群能够相互交配并产生可育后代的生物。生物的科学名称由两部分组成，先是属名后是种名，例如 Homo sapiens；属名首字母大写，整个名称用斜体或下划线表示。
Vertebrates have a backbone and are divided into five groups. Fish have scales, gills and external fertilisation; amphibians have moist skin and lay eggs in water; reptiles have dry scaly skin and lay shelled eggs on land; birds have feathers, beaks and hollow bones; mammals have fur or hair, lungs and produce milk for their young.
脊椎动物具有脊柱，可分为五类。鱼类有鳞片、鳃，进行体外受精；两栖动物皮肤湿润，在水中产卵；爬行动物皮肤干燥有鳞，在陆地上产有壳的卵；鸟类有羽毛、喙和中空骨骼；哺乳动物有毛或毛发、用肺呼吸，并用乳汁喂养幼崽。
Invertebrates lack a backbone and include insects, arachnids, molluscs, annelids and crustaceans. Insects have three body parts, six legs and often wings; arachnids have two body parts and eight legs.
无脊椎动物没有脊柱，包括昆虫、蛛形纲、软体动物、环节动物和甲壳动物。昆虫身体分三部分，有六条腿，通常有翅；蛛形纲身体分两部分，有八条腿。
Variation can be continuous, such as height or mass, which shows a smooth range of values, or discontinuous, such as blood group or eye colour, which falls into distinct categories. Variation may be inherited, caused by genes, or environmental, caused by diet, exercise, sunlight or lifestyle.
变异可分为连续变异和不连续变异。连续变异如身高或体重，数值呈连续变化；不连续变异如血型或眼睛颜色，分成明显类别。变异也可能来自遗传（由基因决定）或环境（由饮食、运动、阳光或生活方式造成）。
5. Nutrition in Plants | 植物的营养
Plants are autotrophs, meaning they make their own food by photosynthesis. Light energy is absorbed by chlorophyll in chloroplasts and used to convert carbon dioxide and water into glucose, releasing oxygen as a by-product.
植物是自养生物，通过光合作用自己制造食物。叶绿体中的叶绿素吸收光能，把二氧化碳和水转化为葡萄糖，并释放氧气作为副产物。
carbon dioxide + water → glucose + oxygen
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
The reaction needs light energy and chlorophyll, and it takes place mainly in the palisade cells of the leaf. Glucose produced is used for respiration, converted into starch for storage, or changed into cellulose, proteins and oils.
该反应需要光能和叶绿素，主要在叶片的栅栏组织细胞中进行。生成的葡萄糖可用于呼吸作用，也可转化为淀粉储存，或转变为纤维素、蛋白质和油脂。
Leaves are adapted for photosynthesis: they are broad and thin to absorb light and allow gases to diffuse quickly, they have many chloroplasts, a network of veins for transport, stomata for gas exchange and a waxy cuticle to reduce water loss.
叶片对光合作用有多项适应：宽而薄，便于吸收光并让气体快速扩散；含有大量叶绿体；有叶脉网络进行运输；有气孔进行气体交换；表面有蜡质角质层减少水分散失。
Plants also need mineral ions from the soil. Nitrates are needed for making proteins and healthy growth; phosphates for respiration and root growth; potassium for healthy leaves and flowers; magnesium for making chlorophyll.
植物还需要从土壤中获取矿质离子。硝酸盐用于制造蛋白质和健康生长；磷酸盐参与呼吸作用和根系生长；钾有助于叶片和花朵健康；镁用于合成叶绿素。
A common practical test is the starch test: boil the leaf in water to kill it, boil it in ethanol to remove chlorophyll, rinse it, then add iodine solution. A blue-black colour shows starch is present, proving photosynthesis has occurred.
常见的实验是淀粉检验：先把叶片放入水中煮沸以杀死细胞，再放入乙醇中煮沸脱去叶绿素，冲洗后滴加碘液。若呈蓝黑色，说明存在淀粉，证明光合作用已经发生。
6. Nutrition and Digestion in Humans | 人的营养与消化
Humans are heterotrophs and need a balanced diet containing carbohydrates, proteins, lipids, vitamins, minerals, fibre and water. Each nutrient has a specific role in the body.
人是异养生物，需要包含碳水化合物、蛋白质、脂质、维生素、矿物质、膳食纤维和水的均衡饮食。每种营养素在体内都有特定作用。
Carbohydrates are the main source of energy; proteins are used for growth and repair; lipids store energy and provide insulation; vitamins and minerals are needed in small amounts for health; fibre keeps the gut moving; water is a solvent for reactions and helps control temperature.
碳水化合物是主要能源；蛋白质用于生长和修复；脂质储存能量并提供保温；维生素和矿物质虽然需要量小，但对健康必不可少；膳食纤维促进肠道蠕动；水是反应的溶剂，并有助于调节体温。
Deficiency diseases are common exam material. Lack of vitamin C causes scurvy, with bleeding gums and poor healing. Lack of vitamin D or calcium causes rickets, with soft, bent bones. Lack of iron causes anaemia, with tiredness and pale skin. Lack of protein in children causes kwashiorkor, with a swollen abdomen.
缺乏症是常见的考试内容。缺乏维生素 C 会引起坏血病，表现为牙龈出血和伤口愈合差。缺乏维生素 D 或钙会引起佝偻病，骨骼变软弯曲。缺铁会引起贫血，表现为疲倦和面色苍白。儿童缺乏蛋白质会引起夸希奥科病，出现腹部肿胀。
Digestion breaks large insoluble molecules into small soluble ones that can be absorbed. Mechanical digestion happens in the mouth and stomach; chemical digestion uses enzymes.
消化把大分子不溶性物质分解为可吸收的小分子可溶性物质。物理消化发生在口腔和胃；化学消化依靠酶完成。
Carbohydrases break starch into simple sugars; proteases break proteins into amino acids; lipases break lipids into fatty acids and glycerol. Enzymes work best at a specific temperature and pH, and are denatured by high temperature or the wrong pH.
淀粉酶把淀粉分解为单糖；蛋白酶把蛋白质分解为氨基酸；脂肪酶把脂质分解为脂肪酸和甘油。酶在特定温度和 pH 下活性最佳，高温或 pH 不适宜会使其变性。
The digestive system includes the mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus, with the liver and pancreas adding juices. Peristalsis moves food along, and villi in the small intestine give a large surface area for absorption.
消化系统包括口腔、食道、胃、小肠、大肠、直肠和肛门，肝脏和胰腺提供消化液。蠕动推动食物前进，小肠中的绒毛提供巨大表面积以便吸收。
7. Respiration and Gas Exchange | 呼吸作用与气体交换
Respiration is the release of energy from food inside cells. It happens in all living cells, all the time, and should never be confused with breathing, which is simply the movement of air in and out of the lungs.
呼吸作用是在细胞内从食物中释放能量的过程。它发生在所有活细胞中，并且持续进行，绝不能与呼吸运动混淆——后者只是空气进出肺部的运动。
Aerobic respiration uses oxygen and releases a large amount of energy.
有氧呼吸需要氧气，并释放大量能量。
glucose + oxygen → carbon dioxide + water + energy
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
Anaerobic respiration happens without oxygen and releases less energy. In human muscle cells it produces lactic acid, which causes cramp and an oxygen debt; in yeast it produces ethanol and carbon dioxide, a process used in brewing and bread making.
无氧呼吸不需要氧气，释放的能量较少。在人体肌肉细胞中，它产生乳酸，导致抽筋和氧债；在酵母中，它产生乙醇和二氧化碳，这一过程用于酿酒和制作面包。
glucose → lactic acid (+ energy)
glucose → ethanol + carbon dioxide (+ energy)
Gas exchange in humans occurs in the alveoli of the lungs. Alveoli have a large surface area, a thin one-cell wall, a rich blood supply and a moist surface, all of which speed up diffusion. Oxygen moves into the blood and carbon dioxide moves out.
人体气体交换发生在肺泡中。肺泡具有巨大表面积、单层细胞的薄壁、丰富的血液供应和湿润表面，这些都加快了扩散速度。氧气进入血液，二氧化碳排出。
8. Transport Systems | 运输系统
Large multicellular organisms need a transport system because diffusion alone is too slow to supply every cell. In humans the circulatory system carries oxygen, nutrients, hormones and waste around the body.
大型多细胞生物需要运输系统，因为单靠扩散无法快速为每个细胞提供物质。在人体中，循环系统把氧气、营养物质、激素和废物运送到全身。
The heart is a muscular pump with four chambers: the right atrium and right ventricle send deoxygenated blood to the lungs, while the left atrium and left ventricle send oxygenated blood to the body. The left ventricle has the thickest wall because it pumps blood the furthest.
心脏是一个由肌肉构成的泵，有四个腔：右心房和右心室把缺氧血送往肺部，左心房和左心室把含氧血送往全身。左心室壁最厚，因为它把血液泵到最远的距离。
Arteries carry blood away from the heart and have thick elastic walls; veins carry blood back to the heart and contain valves to prevent backflow; capillaries are one cell thick, allowing rapid exchange of materials with tissues.
动脉把血液从心脏运出，管壁厚而有弹性；静脉把血液运回心脏，内有静脉瓣防止血液倒流；毛细血管壁仅一层细胞厚，便于与组织快速交换物质。
Blood contains red blood cells, which carry oxygen using haemoglobin; white blood cells, which defend against pathogens; platelets, which help clotting; and plasma, which transports dissolved substances.
血液含有红细胞，利用血红蛋白运输氧气；白细胞，抵抗病原体；血小板，帮助血液凝固；以及血浆，运输溶解的物质。
Plants have two transport tissues. Xylem carries water and mineral ions upwards from the roots and is made of dead, hollow cells. Phloem carries dissolved sugars up and down the plant and is made of living cells. Water loss through stomata is called transpiration, and it pulls water up the stem.
植物有两种运输组织。木质部把水分和矿质离子从根部向上运输，由死亡的中空细胞构成。韧皮部把溶解的糖类上下运输，由活细胞构成。水分通过气孔散失称为蒸腾作用，它把水向上拉入茎中。
9. Reproduction and Growth | 繁殖与生长
Reproduction may be sexual, involving the fusion of two gametes, or asexual, involving only one parent and producing genetically identical offspring. Sexual reproduction creates variation, which helps a species survive change.
繁殖可以是有性繁殖，涉及两个配子的融合；也可以是无性繁殖，只涉及一个亲本，产生遗传上相同的后代。有性繁殖产生变异，有助于物种在环境变化中生存。
In humans, the male gamete is the sperm, made in the testes
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