📚 Core Knowledge Review for Year 8 CAIE Biology | Year 8 CAIE 生物核心知识点梳理
Welcome to the ultimate review of key topics in Year 8 CAIE Biology. This guide covers the essential concepts you need to master, from cell structure to health and disease. Each section is presented in both English and Chinese, helping you build a solid bilingual understanding of biology. Use it to revise, test yourself, and deepen your knowledge as you prepare for assessments.
欢迎来到 Year 8 CAIE 生物核心知识点的终极梳理。本指南涵盖从细胞结构到健康与疾病的关键概念。每一部分都以英文和中文呈现，帮助你建立扎实的双语生物学理解。你可以用它来复习、自测，并在准备测试的过程中加深理解。
1. Cell Structure and Function | 细胞结构与功能
Animal and plant cells: All living organisms are made of cells. Animal cells have a cell membrane, cytoplasm, nucleus, mitochondria and ribosomes. Plant cells have all those structures plus a rigid cell wall, chloroplasts and a large central vacuole.
动物细胞与植物细胞： 所有生物都由细胞构成。动物细胞具有细胞膜、细胞质、细胞核、线粒体和核糖体。植物细胞除了这些结构外，还有坚硬的细胞壁、叶绿体和一个大中央液泡。
Organelle functions: The nucleus controls the cell's activities and stores genetic information in the form of DNA. Mitochondria release energy through aerobic respiration. Ribosomes synthesise proteins. In plant cells, chloroplasts absorb light energy for photosynthesis, and the vacuole stores water and helps maintain turgor pressure.
细胞器的功能： 细胞核控制细胞活动，并以DNA形式储存遗传信息。线粒体通过有氧呼吸释放能量。核糖体合成蛋白质。在植物细胞中，叶绿体吸收光能以进行光合作用，液泡储存水分并有助于维持膨压。
Specialised cells: Many cells are adapted to perform specific functions. For example, red blood cells have no nucleus and a biconcave shape to carry more oxygen. Root hair cells have long extensions to increase surface area for water and mineral absorption. Sperm cells have a tail for movement and many mitochondria for energy.
特化细胞： 许多细胞适应于执行特定的功能。例如，红血细胞没有细胞核，呈双面凹陷的圆盘状，从而携带更多的氧气。根毛细胞有长长的突起以增加吸收水和矿物质的表面积。精子细胞有尾巴用于运动，并含有大量线粒体提供能量。
2. Classification of Living Organisms | 生物的分类
The five kingdoms: Scientists classify living things into five kingdoms: Animals, Plants, Fungi, Protists (Protoctista) and Prokaryotes (Bacteria). Animals are multicellular, feed on other organisms and usually move. Plants are multicellular and make their own food by photosynthesis. Fungi include moulds, mushrooms and yeast; they absorb nutrients from decaying matter. Protists are mostly unicellular organisms like Amoeba. Prokaryotes are single-celled organisms without a true nucleus.
五界系统： 科学家将生物分为五界：动物界、植物界、真菌界、原生生物界和原核生物界。动物是多细胞的，以其他生物为食，通常能够运动。植物是多细胞的，通过光合作用制造自己的食物。真菌包括霉菌、蘑菇和酵母；它们从腐烂的物质中吸收养分。原生生物主要是像变形虫那样的单细胞生物。原核生物是没有真正细胞核的单细胞生物。
Vertebrate classes: Vertebrates are animals with a backbone. They are divided into five classes: mammals, birds, reptiles, amphibians and fish. Mammals have hair or fur, give birth to live young and feed them with milk. Birds have feathers and lay hard-shelled eggs. Reptiles have dry, scaly skin and lay leathery eggs. Amphibians have moist skin and lay jelly-coated eggs in water. Fish have gills, fins and scales.
脊椎动物分类： 脊椎动物是有脊柱的动物，分为五纲：哺乳类、鸟类、爬行类、两栖类和鱼类。哺乳动物有毛发或毛皮，产下幼崽并用乳汁喂养。鸟类有羽毛并产下硬壳卵。爬行动物有干燥的鳞状皮肤并产皮革质卵。两栖动物有湿润的皮肤并在水中产下有胶状外壳的卵。鱼类有鳃、鳍和鳞片。
Binomial nomenclature: Every species is given a two-part scientific name in Latin, such as Homo sapiens for humans. The first part is the genus, and the second is the species. This system avoids confusion between common names in different languages.
双名法： 每个物种都有一个由两部分构成的拉丁学名，例如人类的学名是Homo sapiens。第一部分是属名，第二部分是种名。这个系统避免了不同语言中的俗名造成的混淆。
3. Ecosystems and Feeding Relationships | 生态系统与摄食关系
Key definitions: A habitat is the place where an organism lives. A population is a group of organisms of the same species living in the same area. A community is made up of all the populations of different species in a habitat. An ecosystem includes the community and the non-living (abiotic) factors such as temperature, water and light.
关键定义： 栖息地是生物居住的地方。种群是生活在同一地区的同一物种的所有个体。群落由栖息地中不同物种的所有种群组成。生态系统包括群落以及温度、水和光照等非生物因素。
Food chains and webs: A food chain shows the feeding relationship between organisms. It always starts with a producer, usually a green plant that makes its own food by photosynthesis. Primary consumers (herbivores) eat producers. Secondary consumers (carnivores) eat primary consumers. Decomposers such as bacteria and fungi break down dead matter and recycle nutrients. A food web is a network of interconnected food chains.
食物链和食物网： 食物链显示了生物之间的摄食关系。它总是从生产者开始，生产者通常是能通过光合作用制造食物的绿色植物。初级消费者（食草动物）吃生产者。次级消费者（食肉动物）吃初级消费者。分解者如细菌和真菌分解死去的生物，回收养分。食物网是由相互连接的食物链组成的网络。
Energy flow and pyramids: Energy passes along a food chain, but much of it is lost as heat at each level. A pyramid of numbers shows the number of organisms at each trophic level; it is not always pyramid-shaped. A pyramid of biomass is usually a better representation of the energy available.
能量流动与金字塔： 能量沿着食物链传递，但每一营养级都会有大量的能量以热的形式散失。数量金字塔显示各营养级生物的数量，它不总是金字塔形状。生物量金字塔通常能更好地表示可用的能量。
4. Photosynthesis | 光合作用
The process of photosynthesis: Photosynthesis is the process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen. It takes place in the chloroplasts, which contain the green pigment chlorophyll. Chlorophyll absorbs light energy, mainly from the blue and red parts of the spectrum.
光合作用的过程： 光合作用是绿色植物利用光能把二氧化碳和水转化为葡萄糖和氧气的过程。它发生在含有绿色色素叶绿素的叶绿体中。叶绿素主要吸收光谱中蓝光和红光区域的光能。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Uses of glucose: The glucose produced can be used immediately for respiration to release energy. It can be converted into starch for storage in leaves, stems or roots. Glucose can also be turned into cellulose to build cell walls, or combined with other nutrients to make amino acids and lipids.
葡萄糖的用途： 产生的葡萄糖可以立即用于呼吸作用以释放能量。它可以转化为淀粉储存在叶、茎或根中。葡萄糖也可以转化为纤维素用于构建细胞壁，或者与其他营养物质结合生成氨基酸和脂质。
Testing for starch: To test whether a leaf has carried out photosynthesis, we can use an iodine test. Boil the leaf in water to soften it, then place it in warm ethanol to remove chlorophyll. Rinse the leaf and add iodine solution. A blue-black colour indicates the presence of starch, confirming that photosynthesis occurred.
淀粉检测： 为了检验叶片是否进行了光合作用，我们可以用碘液测试。将叶片在水中煮沸软化，然后放入温热的酒精中脱去叶绿素。漂洗叶片后滴加碘液。蓝黑色表明有淀粉存在，证实了光合作用的发生。
5. Gas Exchange and Breathing | 气体交换与呼吸
The respiratory system: Air enters through the nose or mouth, passes down the trachea, and enters the bronchi that lead to each lung. The bronchi branch into smaller bronchioles and end in tiny air sacs called alveoli. The alveoli are surrounded by capillaries, allowing efficient gas exchange.
呼吸系统： 空气通过鼻或口进入，沿气管向下，进入通往两侧肺的支气管。支气管分支成更细的细支气管，末端是称为肺泡的微小气囊。肺泡被毛细血管包围，从而能够进行高效的气体交换。
Inhaled and exhaled air: Inhaled air contains about 21% oxygen and 0.04% carbon dioxide. Exhaled air contains less oxygen (about 16%) and more carbon dioxide (about 4%). It is also warmer and contains more water vapour.
吸入气与呼出气： 吸入的空气约含21%的氧气和0.04%的二氧化碳。呼出的空气含氧量较低（约16%），而二氧化碳含量较高（约4%）。此外，呼出的空气更温暖且含有更多的水蒸气。
Aerobic respiration: Respiration is the process that releases energy from glucose in cells. Aerobic respiration uses oxygen and can be summarised by the equation:
有氧呼吸： 呼吸作用是细胞中从葡萄糖释放能量的过程。有氧呼吸需要氧气，可用以下方程式概括：
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
Breathing during exercise: During exercise, muscles respire faster and need more oxygen. The breathing rate and depth increase to take in more oxygen and remove extra carbon dioxide. The heart rate also increases to deliver oxygen to muscles more quickly.
运动时的呼吸： 运动时，肌肉的呼吸作用加快，需要更多氧气。呼吸频率和深度增加，以吸入更多氧气并排出多余的二氧化碳。心率也会加快，从而更快地将氧气输送到肌肉。
6. The Human Digestive System | 人体消化系统
Organs of the digestive system: The digestive system breaks down large, insoluble food molecules into small, soluble ones that can be absorbed into the blood. Food passes through the mouth, oesophagus, stomach, small intestine, large intestine and rectum. The liver and pancreas are accessory organs that produce enzymes and other digestive juices.
消化系统器官： 消化系统将大的、不溶的食物分子分解为小的、可溶性分子，以便被吸收进血液。食物依次经过口腔、食道、胃、小肠、大肠和直肠。肝脏和胰腺是辅助器官，产生酶和其他消化液。
Digestive enzymes: Amylase breaks down starch into maltose; it is found in saliva and pancreatic juice. Protease breaks down proteins into amino acids; it works in the stomach and small intestine. Lipase breaks down fats into fatty acids and glycerol; it is active in the small intestine. Bile, produced by the liver and stored in the gall bladder, emulsifies fats to increase their surface area for lipase action.
消化酶： 淀粉酶将淀粉分解为麦芽糖，存在于唾液和胰液中。蛋白酶将蛋白质分解为氨基酸，在胃和小肠中起作用。脂肪酶将脂肪分解为脂肪酸和甘油，在小肠中活跃。胆汁由肝脏产生并储存在胆囊中，能将脂肪乳化成小油滴，增大表面积以利于脂肪酶发挥作用。
Absorption: The small intestine is lined with millions of tiny finger-like projections called villi. Villi have a thin wall, a good blood supply and a large surface area, making them ideal for absorbing digested food molecules into the bloodstream.
吸收： 小肠内壁有数百万个称为绒毛的指状突起。绒毛具有单层薄壁、丰富的血液供应和巨大的表面积，因此非常适合将消化后的食物分子吸收进入血液。
7. The Circulatory System | 循环系统
Structure of the heart: The human heart has four chambers: two upper atria and two lower ventricles. The right side pumps deoxygenated blood to the lungs, while the left side pumps oxygenated blood to the rest of the body. The left ventricle has a thicker muscular wall because it must pump blood around the whole body.
心脏结构： 人类心脏有四个腔室：两个上部的心房和两个下部的心室。右侧将缺氧血泵向肺部，左侧将富氧血泵向全身。左心室具有更厚的肌肉壁，因为它需要将血液泵送至全身各处。
Blood vessels: Arteries carry blood away from the heart; they have thick, elastic muscular walls to withstand high pressure. Veins carry blood back to the heart and have valves to prevent backflow. Capillaries are tiny, thin-walled vessels where substances are exchanged between blood and body cells.
血管： 动脉将血液从心脏运出；它们有厚而富有弹性的肌肉壁以承受高压。静脉将血液送回心脏，并具有防止回流的瓣膜。毛细血管是微小且壁薄的血管，是血液与体细胞之间进行物质交换的场所。
Components of blood: Red blood cells transport oxygen using the protein haemoglobin. White blood cells defend the body against pathogens by producing antibodies or engulfing microbes. Platelets help blood clot to seal wounds. Plasma is the liquid part that transports dissolved nutrients, hormones and waste products.
血液成分： 红血细胞利用血红蛋白运输氧气。白血细胞通过产生抗体或吞噬微生物来保卫身体。血小板帮助血液凝结以封闭伤口。血浆是液体部分，运输溶解的营养物质、激素和废物。
8. Transport in Plants | 植物体内的运输
Xylem and phloem: Xylem vessels transport water and dissolved minerals from the roots up to the leaves. The movement is one-way. Phloem tubes transport sugars and other organic nutrients from the leaves to growing and storage parts of the plant. This movement can be in any direction.
木质部和韧皮部： 木质部导管将水和溶解的矿物质从根部向上运输到叶片。这种运输是单向的。韧皮部管将糖和其他有机养分从叶片运输到植物生长和储存的部位。这种运输可以是双向的。
Transpiration: Transpiration is the loss of water vapour from the leaves through stomata. It creates a pulling force that draws water up the xylem from the roots. This continuous movement of water is called the transpiration stream. Higher temperature, increased light intensity and wind speed can all increase the rate of transpiration.
蒸腾作用： 蒸腾作用是水分以水蒸气形式通过气孔从叶片散失的过程。它产生一个拉力，将水从根部沿木质部向上拉。这种持续的水流叫做蒸腾流。较高的温度、较强的光照和风速都能加快蒸腾速率。
Root hair cells: Water and minerals enter the plant through root hair cells. These cells have a large surface area and thin walls to absorb water by osmosis. Minerals are taken up by active transport, which requires energy.
根毛细胞： 水和矿物质通过根毛
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