📚 Year 8 SQA Biology: Core Knowledge Review | Year 8 SQA 生物：核心知识点梳理
This article summarises the core topics covered in Year 8 SQA Biology, from the tiny building blocks of life to whole ecosystems. Understanding these key concepts will help you build a solid foundation for future science learning.
本文总结了 Year 8 SQA 生物课程涵盖的核心主题，从微小的生命基本单位到整个生态系统。掌握这些关键概念将为你未来的科学学习奠定坚实的基础。
1. Cells – The Building Blocks of Life | 细胞——生命的基本单位
All living things are made up of cells. Cells are the smallest units that can carry out life processes. Some organisms, like bacteria, are single-celled, while others, like humans, are multicellular. Both animal and plant cells share several common structures, but plant cells have extra features that allow them to make their own food and stay rigid.
所有生物都由细胞构成。细胞是能够进行生命活动的最小单位。有些生物（如细菌）是单细胞的，而另一些（如人类）则是多细胞的。动物细胞和植物细胞共享多种结构，但植物细胞具有额外的特征，使它们能够自己制造食物并保持坚挺。
| Organelle | Function | Animal Cell | Plant Cell |
|---|---|---|---|
| Cell membrane | Controls what enters and leaves the cell | ✔ | ✔ |
| Cytoplasm | Gel-like substance where chemical reactions occur | ✔ | ✔ |
| Nucleus | Contains DNA and controls cell activities | ✔ | ✔ |
| Mitochondria | Site of aerobic respiration, releasing energy | ✔ | ✔ |
| Ribosomes | Make proteins | ✔ | ✔ |
| Cell wall | Provides support and structure (made of cellulose) | ✘ | ✔ |
| Chloroplasts | Contain chlorophyll for photosynthesis | ✘ | ✔ |
| Permanent vacuole | Filled with cell sap, helps keep the plant firm | ✘ | ✔ |
The table above lists the main organelles and shows which are present in animal and plant cells. Using a light microscope, you can observe many of these structures, such as the nucleus and cell wall. Staining with iodine or methylene blue makes them easier to see.
上表列出了主要的细胞器，并显示了它们在动物细胞和植物细胞中的存在情况。使用光学显微镜，你可以观察到其中的许多结构，例如细胞核和细胞壁。用碘液或亚甲基蓝染色可以使它们更容易被观察到。
2. Digestive System and Enzymes | 消化系统与酶
The digestive system breaks down large, insoluble food molecules into small, soluble ones that can be absorbed into the blood. Digestion begins in the mouth, where teeth mechanically break food and saliva contains amylase to start starch digestion. The stomach produces acid and protease, while the small intestine is where most digestion and absorption happen.
消化系统将大的、不溶解的食物分子分解为小的、可溶解的分子，以便被血液吸收。消化从口腔开始，牙齿机械地磨碎食物，唾液中含有淀粉酶，开始消化淀粉。胃产生胃酸和蛋白酶，而大部分消化和吸收则发生在小肠。
| Enzyme | Produced in | Breaks down | Products |
|---|---|---|---|
| Amylase | Salivary glands, pancreas | Starch | Maltose (then glucose) |
| Protease | Stomach, pancreas | Protein | Amino acids |
| Lipase | Pancreas | Fats (lipids) | Fatty acids and glycerol |
Enzymes are biological catalysts made of protein. They speed up reactions without being used up. Each enzyme has an active site that fits a specific substrate, a bit like a lock and key. Temperature and pH affect enzyme activity; very high temperatures can denature them, changing the active site shape permanently.
酶是由蛋白质构成的生物催化剂。它们加速反应，但自身不被消耗。每种酶都有一个活性位点，能与特定的底物结合，有点像锁和钥匙。温度和 pH 会影响酶的活性；极高的温度会使酶变性，永久性地改变活性位点的形状。
3. Respiratory System – Gas Exchange | 呼吸系统——气体交换
Respiration releases energy from food, and the respiratory system supplies the oxygen needed and removes carbon dioxide. Air enters through the nose or mouth, passes down the trachea (windpipe), through the bronchi, and into the lungs. Inside the lungs, tiny air sacs called alveoli provide a huge surface area for gas exchange.
呼吸作用从食物中释放能量，呼吸系统则提供所需的氧气并排出二氧化碳。空气通过鼻或口进入，沿气管下行，经过支气管，进入肺部。在肺内部，称为肺泡的微小气囊为气体交换提供了巨大的表面积。
Oxygen diffuses from the alveoli into the blood in the surrounding capillaries, while carbon dioxide diffuses from the blood into the alveoli to be breathed out. Breathing in (inhalation) is caused by the diaphragm contracting and moving down, and the ribcage moving up and out. Breathing out (exhalation) is largely passive, with the diaphragm relaxing.
氧气从肺泡扩散到周围毛细血管的血液中，而二氧化碳则从血液扩散到肺泡中被呼出。吸气是由膈肌收缩并下移，以及肋骨向上向外移动引起的。呼气在很大程度上是被动的，膈肌舒张即可。
Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
This equation shows that glucose and oxygen react to produce carbon dioxide, water and energy. The energy is used for muscle contraction, maintaining body temperature and building new molecules.
这个方程式表明，葡萄糖和氧气反应生成二氧化碳、水和能量。这些能量用于肌肉收缩、维持体温以及构建新的分子。
4. Circulatory System – Heart and Blood | 循环系统——心脏与血液
The circulatory system transports oxygen, nutrients, hormones and waste products around the body. The heart is a muscular pump with four chambers: two atria and two ventricles. The right side pumps deoxygenated blood to the lungs; the left side pumps oxygenated blood to the rest of the body.
循环系统将氧气、营养物质、激素和废物运送到全身。心脏是一个肌肉泵，拥有四个腔室：两个心房和两个心室。右侧将缺氧血泵入肺部；左侧将富氧血泵入身体其他部位。
- Arteries carry blood away from the heart; they have thick, muscular walls to withstand high pressure. 动脉将血液从心脏运出；它们的管壁厚而富有肌肉，以承受高压。
- Veins return blood to the heart; they have valves to prevent backflow. 静脉将血液送回心脏；它们有瓣膜以防止回流。
- Capillaries are tiny, thin-walled vessels where exchange of gases and nutrients occurs. 毛细血管是微小、薄壁的血管，是气体和营养物质交换的场所。
Blood consists of four main components: red blood cells (carry oxygen using haemoglobin), white blood cells (defend against infection), platelets (help blood clot) and plasma (the liquid part that transports dissolved substances).
血液由四种主要成分组成：红细胞（利用血红蛋白携带氧气）、白细胞（抵御感染）、血小板（帮助血液凝固）和血浆（运输溶解物质的液体部分）。
5. Reproductive System and Puberty | 生殖系统与青春期
The male reproductive system includes the testes (produce sperm and testosterone), sperm ducts, and penis. The female system includes the ovaries (produce eggs and oestrogen), oviducts (fallopian tubes), uterus (womb), and vagina. Fertilisation occurs when a sperm cell fuses with an egg cell in the oviduct.
男性生殖系统包括睾丸（产生精子和睾酮）、输精管和阴茎。女性生殖系统包括卵巢（产生卵子和雌激素）、输卵管、子宫和阴道。当精子与卵子在输卵管内融合时，就发生了受精。
Puberty is the stage when the body becomes capable of reproduction. In boys, the voice deepens, muscles develop, and facial hair grows. In girls, the hips widen, breasts develop, and menstruation begins. The menstrual cycle typically lasts about 28 days and involves the release of an egg (ovulation) and the thickening of the uterus lining.
青春期是身体具备生殖能力的阶段。在男孩身上，声音变得低沉，肌肉发育，面部毛发生长。在女孩身上，髋部变宽，乳房发育，月经开始。月经周期通常持续约 28 天，包括卵子的释放（排卵）和子宫内膜的增厚。
6. Photosynthesis – How Plants Make Food | 光合作用——植物如何制造食物
Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesise nutrients from carbon dioxide and water. It takes place in the chloroplasts, where the green pigment chlorophyll captures light energy.
光合作用是绿色植物和某些其他生物利用阳光，由二氧化碳和水合成营养物质的过程。它发生在叶绿体中，绿色色素叶绿素在那里捕获光能。
Photosynthesis equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
The glucose produced can be used immediately for respiration, stored as starch, or converted into cellulose for cell walls. Plants also need mineral ions, such as nitrates for protein synthesis and magnesium for making chlorophyll. A simple starch test with iodine can show whether photosynthesis has occurred in a leaf.
产生的葡萄糖可以立即用于呼吸作用，以淀粉形式储存，或转化为纤维素用于构建细胞壁。植物还需要矿物质离子，例如硝酸盐用于合成蛋白质，镁用于制造叶绿素。用碘液进行简单的淀粉测试，可以显示叶片中是否进行了光合作用。
7. Ecosystems and Food Chains | 生态系统与食物链
An ecosystem is a community of living organisms interacting with each other and their non-living environment. A habitat is the place where an organism lives. A population is all the organisms of one species in a habitat, and a community is made up of all the populations of different species living together.
生态系统是由生物群落与非生物环境相互作用形成的整体。栖息地是生物居住的地方。一个栖息地中同一物种的所有个体构成一个种群，而不同物种所有种群共同生活就构成一个群落。
- Producers: plants and algae that make their own food by photosynthesis. 生产者：通过光合作用自养食物的植物和藻类。
- Consumers: animals that eat other organisms; primary consumers eat producers, secondary consumers eat primary consumers. 消费者：吃其他生物的动物；初级消费者吃生产者，二级消费者吃初级消费者。
- Decomposers: bacteria and fungi that break down dead material, recycling nutrients. 分解者：分解死亡物质的细菌和真菌，循环利用营养物质。
how the direction of energy transfer. In reality, feeding relationships form a food web, showing many interconnected chains. Energy is lost at each trophic level, mostly as heat from respiration.
食物链显示了能量从一个生物传递到下一个生物的流向。例如：草 → 兔 → 狐。箭头表示能量传递的方向。实际上，捕食关系构成了食物网，展示许多相互关联的链条。每一个营养级都会损失能量，主要以呼吸作用散热的形式。
8. Microorganisms and Disease | 微生物与疾病
Microorganisms (microbes) are tiny living things that can only be seen with a microscope. They include bacteria, viruses, fungi and some protoctists. Many are harmless or even helpful – for example, gut bacteria help digest food, and yeast is used in baking. However, some cause infectious diseases.
微生物（微生物）是只能用显微镜才能看到的微小生物。它们包括细菌、病毒、真菌和一些原生生物。许多微生物是无害甚至有益的——例如，肠道细菌帮助消化食物，酵母用于烘焙。但是，有些微生物会引起传染病。
| Pathogen Type | Examples of Diseases | How They Spread |
|---|---|---|
| Bacteria | Tuberculosis, food poisoning | Airborne droplets, contaminated food/water |
| Viruses | Flu, COVID-19, measles | Coughs, sneezes, direct contact |
| Fungi | Athlete's foot, ringworm | Direct contact with spores or infected surfaces |
The body defends itself with physical barriers like skin, chemical barriers like stomach acid, and the immune system. White blood cells can engulf pathogens or produce antibodies. Vaccination helps the body develop immunity without becoming ill. Good hygiene – hand washing, cooking food properly and covering coughs – reduces spread.
身体通过皮肤等物理屏障、胃酸等化学屏障以及免疫系统进行防御。白细胞可以吞噬病原体或产生抗体。疫苗接种有助于身体在不生病的情况下产生免疫力。良好的卫生习惯——洗手、彻底煮熟食物以及咳嗽时遮挡——可以减少传播。
9. Inheritance and Variation | 遗传与变异
Inheritance is the passing of characteristics from parents to offspring through genes. Genes are sections of DNA on chromosomes, found in the nucleus of almost every cell. Humans have 46 chromosomes arranged in 23 pairs. One chromosome of each pair comes from the mother and one from the father.
遗传是指通过基因将特征从父母传递给后代。基因是染色体上的一段 DNA，存在于几乎所有细胞的细胞核中。人类有 46 条染色体，排列成 23 对。每对染色体中的一条来自母亲，一条来自父亲。
Variation means differences between individuals of the same species. Some variation is genetic (inherited), such as eye colour or natural hair shape. Other variation is caused by the environment, such as scars or muscle development. Most characteristics, like height, are influenced by both genes and environment.
变异意味着同一物种个体之间的差异。有些变异是遗传的，例如眼睛颜色或天然的头发形状。其他变异是由环境引起的，例如伤疤或肌肉发育。像身高这样的大多数特征都受到基因和环境的共同影响。
10. Health and Lifestyle Choices | 健康与生活方式选择
A balanced diet provides all the nutrients needed for growth, repair and energy. The main food groups are carbohydrates (energy), proteins (growth and repair), lipids (energy store and insulation), vitamins and minerals (essential for body processes), fibre (aids digestion) and water.
均衡饮食提供生长、修复和能量所需的所有营养素。主要的食物类别包括：碳水化合物（提供能量）、蛋白质（生长和修复）、脂质（能量储存和保温）、维生素和矿物质（身体过程必需）、纤维（帮助消化）和水。
Lifestyle choices greatly affect health. Regular exercise strengthens the heart and lungs and reduces the risk of obesity. Smoking damages the lungs and can cause cancer, while alcohol can harm the liver and brain. Drugs alter body chemistry and can lead to addiction. Making informed choices helps maintain a healthy body and mind.
生活方式的选择对健康影响极大。定期锻炼可以增强心脏和肺部功能，降低肥胖风险。吸烟损害肺部并可能致癌，而酒精会损害肝脏和大脑。药物会改变身体化学性质并可能导致成瘾。做出明智的选择有助于保持身心健康。
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