📚 Year 11 SQA Biology: Core Key Points Summary | Year 11 SQA 生物：核心知识点梳理
This revision guide summarises the essential topics for the SQA National 5 Biology course, covering cell biology, multicellular organisms, and life on Earth. Each concept is explained clearly to support your exam preparation and build a strong foundation in biological principles.
本复习指南梳理了 SQA National 5 生物课程的核心主题，涵盖细胞生物学、多细胞生物以及地球上的生命。每个概念都解释得清晰明了，以助你备考并打下坚实的生物学基础。
1. Cell Structure and Function | 细胞结构与功能
All living organisms are composed of cells. Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells have all of these plus a rigid cell wall, a permanent vacuole and chloroplasts. Fungal and bacterial cells also show key differences, such as bacterial cells lacking a true nucleus.
所有生物体都由细胞构成。动物细胞含有细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞除此之外还有坚硬的细胞壁、永久液泡和叶绿体。真菌和细菌细胞也有关键区别，例如细菌细胞没有真正的细胞核。
The cell membrane is selectively permeable, controlling the movement of substances in and out of the cell by diffusion, osmosis and active transport. Diffusion is the net movement of particles from a high concentration to a low concentration down a concentration gradient.
细胞膜具有选择透过性，通过扩散、渗透和主动运输控制物质进出细胞。扩散是粒子沿浓度梯度从高浓度区域向低浓度区域的净移动。
| Organelle | Function | 细胞器 | 功能 |
|---|---|---|---|
| Nucleus | Contains genetic material and controls cell activities | 细胞核 | 含有遗传物质，控制细胞活动 |
| Mitochondria | Site of aerobic respiration, releasing energy | 线粒体 | 有氧呼吸的场所，释放能量 |
| Ribosomes | Protein synthesis | 核糖体 | 蛋白质合成 |
| Chloroplasts | Site of photosynthesis in plant cells | 叶绿体 | 植物细胞中光合作用的场所 |
2. Cell Division – Mitosis and Its Importance | 细胞分裂——有丝分裂及其重要性
Mitosis is the process by which a cell divides to produce two genetically identical daughter cells. It is essential for growth, repair of damaged tissues and asexual reproduction. The genetic information is replicated beforehand, ensuring each new cell receives a full set of chromosomes.
有丝分裂是细胞分裂产生两个基因相同的子细胞的过程。它对生长、受损组织的修复以及无性繁殖至关重要。遗传信息预先进行复制，确保每个新细胞获得一整套染色体。
Stages of mitosis are prophase, metaphase, anaphase and telophase, followed by cytokinesis. In prophase, chromosomes condense and the nuclear membrane breaks down. During metaphase, chromosomes line up at the equator of the cell. Anaphase sees the chromatids pulled apart to opposite poles, and in telophase new nuclear membranes form around each set.
有丝分裂的阶段包括前期、中期、后期和末期，随后是胞质分裂。在前期，染色体浓缩，核膜解体。中期时，染色体排列在细胞的赤道板上。后期染色单体被拉向细胞两极，末期间围绕每一组染色体形成新的核膜。
Cancer can result from uncontrolled cell division, leading to a mass of abnormal cells called a tumour. Understanding mitosis helps scientists develop treatments that target rapidly dividing cells.
癌症可能源于不受控制的细胞分裂，形成一团异常细胞，称为肿瘤。了解有丝分裂有助于科学家开发针对快速分裂细胞的治疗方法。
3. DNA, Genes and Chromosomes | DNA、基因与染色体
Deoxyribonucleic acid (DNA) is a double-stranded helix that carries the genetic instructions for the development and functioning of living organisms. The two strands are held together by complementary base pairs: adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).
脱氧核糖核酸（DNA）是一种双链螺旋结构，携带着生物体发育和功能的遗传指令。两条链通过互补碱基对连接在一起：腺嘌呤（A）与胸腺嘧啶（T）配对，胞嘧啶（C）与鸟嘌呤（G）配对。
A gene is a section of DNA that codes for a particular protein. Genes are located on chromosomes, which are found in the nucleus of the cell. Human body cells contain 23 pairs of chromosomes, making a total of 46.
基因是编码特定蛋白质的一段DNA。基因位于染色体上，染色体存在于细胞核中。人体细胞含有23对染色体，总共46条。
Genetic information is passed from parent to offspring through gametes (sperm and egg cells), which contain half the number of chromosomes. This halving occurs during meiosis, ensuring variation in sexually reproducing organisms.
遗传信息通过配子（精子和卵细胞）从亲代传递给后代，配子含有染色体数目的一半。这种减半发生在减数分裂过程中，确保了有性生殖生物的变异。
4. Protein Synthesis and Enzymes | 蛋白质合成与酶
Proteins are made up of long chains of amino acids. The sequence of amino acids determines the shape and function of the protein. Protein synthesis occurs in two main stages: transcription (DNA is used to make mRNA in the nucleus) and translation (mRNA is read by ribosomes to assemble amino acids into a protein).
蛋白质由长链氨基酸组成。氨基酸的序列决定了蛋白质的形状和功能。蛋白质合成主要分为两个阶段：转录（在细胞核中利用DNA合成mRNA）和翻译（核糖体读取mRNA将氨基酸组装成蛋白质）。
Enzymes are biological catalysts that speed up chemical reactions without being used up. They are specific to their substrate due to the complementary shape of the active site. The 'lock and key' model explains how a substrate fits into the enzyme's active site to form an enzyme-substrate complex.
酶是生物催化剂，能在不被消耗的情况下加速化学反应。酶的活性部位具有与底物互补的形状，因此具有特异性。"锁钥"模型解释了底物如何嵌入酶的活性部位形成酶-底物复合物。
Enzyme activity is affected by temperature and pH. Each enzyme has an optimum temperature and pH at which it works fastest. Denaturation occurs when the shape of the active site is permanently changed, so the substrate can no longer bind.
酶的活性受温度和pH值影响。每种酶都有其作用最快的最适温度和pH值。当活性部位形状发生永久性改变时，酶就会变性，底物便无法再与之结合。
Substrate + Enzyme → Enzyme-Substrate Complex → Product + Enzyme
5. Photosynthesis and Respiration | 光合作用与呼吸作用
Photosynthesis is the process by which green plants make their own food using light energy, carbon dioxide and water. It occurs in the chloroplasts and produces glucose and oxygen. The chemical equation for photosynthesis can be written as:
光合作用是绿色植物利用光能、二氧化碳和水制造自身养料的过程。该过程发生在叶绿体中，产生葡萄糖和氧气。光合作用的化学方程式为：
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Light energy is absorbed by chlorophyll, a green pigment found in chloroplasts. The rate of photosynthesis is limited by factors such as light intensity, carbon dioxide concentration and temperature.
光能被叶绿素（叶绿体中的绿色色素）吸收。光合作用的速率受光照强度、二氧化碳浓度和温度等因素的限制。
Aerobic respiration releases energy from glucose using oxygen. It takes place in the mitochondria and provides the energy needed for cellular activities. The overall equation is:
有氧呼吸使用氧气从葡萄糖中释放能量。它发生在线粒体中，提供细胞活动所需的能量。总反应式为：
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
When oxygen is scarce, cells may carry out anaerobic respiration (fermentation). In animal cells, glucose is broken down into lactic acid, while in yeast, it is converted to ethanol and carbon dioxide. Anaerobic respiration releases much less energy than aerobic.
当氧气不足时，细胞可能进行无氧呼吸（发酵）。在动物细胞中，葡萄糖被分解为乳酸；在酵母中，则转化为乙醇和二氧化碳。无氧呼吸释放的能量远少于有氧呼吸。
6. Hormones and Blood Glucose Regulation | 激素与血糖调节
Hormones are chemical messengers produced by endocrine glands and carried in the blood to target organs. They help coordinate many body functions, including metabolism, growth and reproduction. Hormonal responses are usually slower but longer-lasting than nervous responses.
激素是由内分泌腺产生、经血液运输到靶器官的化学信使。它们协助协调许多身体功能，包括新陈代谢、生长和生殖。激素反应通常比神经反应慢，但持续时间更长。
Blood glucose concentration must be kept within a narrow range. The pancreas detects changes and releases insulin or glucagon. Insulin lowers blood glucose by promoting the conversion of glucose to glycogen in the liver. Glucagon raises blood glucose by triggering the breakdown of glycogen back into glucose.
血糖浓度必须保持在较窄的范围内。胰腺检测到血糖变化，释放胰岛素或胰高血糖素。胰岛素通过促进肝脏将葡萄糖转化为糖原来降低血糖。胰高血糖素则通过促使糖原分解回葡萄糖来提高血糖。
This is an example of negative feedback, where a change in a condition triggers a response that counteracts the change, restoring the body to its set point. Diabetes is a condition in which blood glucose regulation fails, often due to insufficient insulin production or insulin resistance.
这是负反馈的一个例子，即某一条件的变化触发一种抵制该变化的反应，使身体恢复到设定点。糖尿病是血糖调节失常的一种疾病，通常由于胰岛素分泌不足或胰岛素抵抗所致。
7. The Nervous System and Reflex Arc | 神经系统与反射弧
The nervous system enables rapid communication between different parts of the body. It consists of the central nervous system (brain and spinal cord) and peripheral nerves. Electrical impulses travel along neurons to transmit information quickly.
神经系统使身体各部分之间能快速交流。它由中枢神经系统（脑和脊髓）以及周围神经组成。电脉冲沿着神经元传导，快速传递信息。
ry neuron → relay neuron in the spinal cord → motor neuron → effector. The effector is usually a muscle or gland.
反射动作是对刺激作出的自动、非自主的反应，用以保护身体免受伤害。反射弧的通路为：感受器→感觉神经元→脊髓中的中间神经元→运动神经元→效应器。效应器通常是肌肉或腺体。
At a synapse, the electrical impulse triggers the release of neurotransmitter chemicals, which diffuse across the gap and bind to receptors on the next neuron, starting a new impulse. This ensures impulses travel in one direction only.
在突触处，电脉冲触发神经递质化学物质的释放，这些递质扩散通过间隙，与下一个神经元上的受体结合，启动新的脉冲。这确保了脉冲只沿一个方向传播。
8. Reproduction and Variation | 生殖与变异
Reproduction can be sexual or asexual. Asexual reproduction involves one parent and produces offspring that are genetically identical clones. Sexual reproduction involves two parents and produces offspring that show variation due to the mixing of genes during meiosis and fertilisation.
生殖可分为有性生殖和无性生殖。无性生殖只涉及一个亲本，产生基因相同的克隆后代。有性生殖涉及两个亲本，后代由于减数分裂和受精过程中基因的混合而表现出变异。
Variation within a species can be continuous (e.g., height) or discrete (e.g., blood type). Continuous variation is influenced by many genes and the environment, while discrete variation is controlled by a small number of genes with distinct categories.
同一物种内的变异可以是连续的（如身高）或离散的（如血型）。连续变异受多基因和环境共同影响，而离散变异由少数几个基因控制，具有明显分类。
Mutations are random changes to the genetic material. They can be neutral, harmful or occasionally beneficial. Mutations are the ultimate source of new alleles, providing the raw material for evolution.
突变是遗传物质的随机变化。它们可能是中性的、有害的，或偶尔有益的。突变是新等位基因的最终来源，为进化提供了原材料。
9. Evolution and Natural Selection | 进化与自然选择
Evolution is the gradual change in the inherited characteristics of a population over many generations. Charles Darwin's theory of natural selection explains how evolution occurs. Individuals with traits better suited to their environment are more likely to survive, reproduce and pass on those advantageous alleles.
进化是种群遗传特征在多个世代中逐渐变化的过程。查尔斯·达尔文的自然选择学说解释了进化如何发生。那些性状更适应环境的个体更可能生存、繁殖并将那些有利等位基因传递给后代。
Over time, the frequency of advantageous alleles increases in the population, leading to adaptation. Natural selection can lead to the formation of new species if populations become isolated and diverge so much that they can no longer interbreed to produce fertile offspring.
随着时间推移，有利等位基因的频率在种群中升高，导致适应。如果种群被隔离并分化到无法再交配产生可育后代的程庹，自然选择可以导致新物种的形成。
Evidence for evolution comes from fossils, comparative anatomy, and DNA analysis. Antibiotic resistance in bacteria is a modern example of natural selection observable in a short time frame.
进化的证据来自化石、比较解剖学和DNA分析。细菌的抗生素耐药性是一个可在短时间内观察到的自然选择的现代实例。
10. Ecosystems and Energy Transfer | 生态系统与能量传递
An ecosystem contains living organisms (biotic factors) and non-living components (abiotic factors) such as temperature, light and water. Organisms in an ecosystem can be grouped into producers, consumers and decomposers based on how they obtain energy.
生态系统包含生物（生物因素）和非生物组成（非生物因素），如温度、光照和水。生态系统中可以根据获取能量的方式将生物分为生产者、消费者和分解者。
Energy enters ecosystems through producers (plants) capturing sunlight during photosynthesis. This energy is then transferred along food chains and food webs when consumers eat other organisms. At each trophic level, some energy is lost as heat, movement and waste, so the amount of energy available decreases up the chain.
能量通过生产者（植物）在光合作用中捕获阳光而进入生态系统。当消费者取食其他生物时，能量沿着食物链和食物网传递。在每一个营养级上，部分能量以热、运动和废物的形式散失，因此沿链条向上的可用能量逐渐减少。
Pyramids of number and pyramids of energy can be used to represent feeding relationships. A pyramid of energy is always a triangular shape because the loss of energy limits the length of food chains.
数量金字塔和能量金字塔可用来表示取食关系。能量金字塔总是呈三角形的，因为能量的损失限制了食物链的长度。
Decomposers, such as bacteria and fungi, break down dead material and waste, recycling nutrients back into the soil for producers to use. This maintains the balance of the ecosystem.
分解者（如细菌和真菌）分解死去的生物体和排泄物，将营养物质循环回土壤中供生产者使用，从而维持生态系统的平衡。
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