📚 Year 11 CIE Biology: Core Knowledge Review | Year 11 CIE 生物：核心知识点梳理
This article provides a focused review of the essential topics for Year 11 CIE IGCSE Biology. From the characteristics of life to ecosystems and genetics, each section delivers key facts and explanations in both English and Chinese to support your revision.
本文为 Year 11 CIE IGCSE 生物提供一份核心知识梳理。从生命特征到生态系统和遗传学，每部分都以中英双语呈现关键事实与解释，帮助巩固复习。
1. Characteristics and Classification | 生物的特征与分类
All living organisms carry out seven life processes summarized by the acronym MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition. Movement is an action by the organism causing a change of position; respiration is the chemical breakdown of food molecules to release energy; sensitivity is the ability to detect and respond to changes in the environment; growth is a permanent increase in size and dry mass; reproduction produces offspring of the same kind; excretion is the removal of toxic metabolic waste products; and nutrition is the intake of materials for energy, growth and development.
所有生物都进行七个生命过程，用缩写 MRS GREN 概括：运动、呼吸、感应、生长、繁殖、排泄和营养。运动是生物体引起位置改变的动作；呼吸是分解食物分子以释放能量的化学过程；感应是检测并响应环境变化的能力；生长是体积和干质量的永久增加；繁殖产生相同类型的后代；排泄是去除代谢产生的有毒废物；营养是摄取用于能量、生长和发育的物质。
Organisms are classified into five kingdoms: Prokaryotes (bacteria), Protoctists (unicellular eukaryotes such as amoeba), Fungi, Plants, and Animals. Viruses are not placed in any kingdom because they lack cellular structure and cannot carry out life processes independently.
生物被分为五个界：原核生物（细菌）、原生生物（如变形虫等单细胞真核生物）、真菌、植物和动物。病毒不被归入任何一界，因为它们没有细胞结构，且无法独立完成生命过程。
2. Cell Structure and Function | 细胞结构与功能
Typical plant and animal cells share a cell membrane, cytoplasm, nucleus, mitochondria, and ribosomes. Plant cells also possess a cellulose cell wall, a large permanent vacuole, and chloroplasts for photosynthesis. The nucleus contains DNA and controls cell activities; mitochondria are the site of aerobic respiration; ribosomes synthesise proteins; chloroplasts absorb light energy to make carbohydrates; the vacuole stores cell sap and maintains turgor pressure.
典型的植物和动物细胞都具有细胞膜、细胞质、细胞核、线粒体和核糖体。植物细胞还具有纤维素细胞壁、一个大型中央液泡以及用于光合作用的叶绿体。细胞核含有 DNA 并控制细胞活动；线粒体是有氧呼吸的场所；核糖体合成蛋白质；叶绿体吸收光能以制造碳水化合物；液泡储存细胞液并维持膨压。
m. Specialised cells such as root hair cells, ciliated cells, and red blood cells have adaptations that make them suited to their functions.
组织层次：细胞 → 组织 → 器官 → 器官系统 → 生物体。特化细胞如根毛细胞、纤毛细胞和红细胞具有适应其功能的特殊结构。
3. Movement Across Membranes | 跨膜运输
Substances move across cell membranes by diffusion, osmosis, and active transport. 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 requiring no energy. Osmosis is the net movement of water molecules through a partially permeable membrane from a dilute solution to a more concentrated solution. Active transport moves substances against a concentration gradient using energy from respiration and carrier proteins.
物质通过扩散、渗透和主动运输穿过细胞膜。扩散是粒子从较高浓度区域沿浓度梯度向较低浓度区域的净移动；这是一个无需能量的被动过程。渗透是水分子通过部分透膜从稀溶液向较浓溶液的净移动。主动运输利用呼吸作用提供的能量和载体蛋白逆浓度梯度移动物质。
Plant cells gain support from turgor pressure when water enters by osmosis. In animal cells, too much water entry may cause lysis, while water loss makes them shrink (crenation).
植物细胞通过渗透吸水产生的膨压获得支撑。在动物细胞中，过多水分进入可能导致细胞破裂（裂解），而失水则使细胞皱缩。
4. Biological Molecules and Enzymes | 生物分子与酶
Carbohydrates, proteins, and lipids are the main biological molecules. Carbohydrates are made of simple sugars (glucose) and are used as a primary energy source. Proteins, composed of amino acids, build tissues and act as enzymes. Lipids (fats and oils) store energy and provide insulation.
碳水化合物、蛋白质和脂质是主要的生物分子。碳水化合物由单糖（葡萄糖）组成，是主要的能量来源。蛋白质由氨基酸构成，用于构建组织并作为酶发挥作用。脂质（脂肪和油脂）储存能量并提供保温作用。
Enzymes are biological catalysts that speed up reactions without being used up. They are proteins with an active site complementary to a specific substrate. Enzyme activity is affected by temperature and pH: high temperatures cause denaturation, and extreme pH changes alter the shape of the active site.
酶是生物催化剂，能加速反应而自身不被消耗。它们是一种蛋白质，具有与特定底物互补的活性位点。酶活性受温度和 pH 影响：高温导致变性，极端的 pH 变化会改变活性位点的形状。
5. Plant Nutrition: Photosynthesis | 植物营养：光合作用
bon dioxide + water → glucose + oxygen, in the presence of light and chlorophyll. The balanced chemical equation is:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
光合作用是植物利用光能将原料转化为碳水化合物的过程。文字方程式为：二氧化碳 + 水 → 葡萄糖 + 氧气，需要光照和叶绿素。平衡化学方程式如上。
Chlorophyll in chloroplasts absorbs sunlight, which is converted into chemical energy. Limiting factors include light intensity, carbon dioxide concentration, and temperature. Leaves are adapted for photosynthesis by having a broad, flat surface, stomata for gas exchange, and a transparent epidermis.
叶绿体中的叶绿素吸收阳光，将光能转化为化学能。限制因素包括光照强度、二氧化碳浓度和温度。叶片通过宽阔扁平的表面、气孔气体交换以及透明的表皮等结构适应光合作用。
6. Human Nutrition: Digestive System | 人类营养：消化系统
Digestion is the breakdown of large, insoluble food molecules into small, soluble molecules that can be absorbed. Mechanical digestion (chewing, churning) increases surface area. Chemical digestion is carried out by enzymes. Amylase breaks down starch into maltose; protease breaks down proteins into amino acids; lipase breaks down fats into fatty acids and glycerol.
消化是将大而不溶的食物分子分解成小的可吸收分子的过程。物理性消化（咀嚼、搅拌）增加表面积。化学消化由酶完成。淀粉酶将淀粉分解为麦芽糖；蛋白酶将蛋白质分解为氨基酸；脂肪酶将脂肪分解为脂肪酸和甘油。
Absorption occurs mainly in the small intestine, where villi provide a large surface area, thin epithelium, and a good blood supply to absorb products into the bloodstream. The liver processes absorbed nutrients and detoxifies harmful substances.
吸收主要发生在小肠，小肠绒毛提供了极大的表面积、薄的上皮层和良好的血液供应，将消化产物吸收入血。肝脏处理吸收的营养物质，并清除有害物质。
7. Circulatory System | 循环系统
The human circulatory system consists of the heart, blood vessels, and blood. The heart is a four-chambered organ: right atrium and right ventricle pump deoxygenated blood to the lungs; left atrium and left ventricle pump oxygenated blood to the body. Valves prevent backflow of blood.
人体循环系统由心脏、血管和血液组成。心脏是一个四室器官：右心房和右心室将缺氧血泵入肺部；左心房和左心室将富氧血泵送到全身。瓣膜防止血液倒流。
Arteries carry blood away from the heart under high pressure; veins carry blood back to the heart; capillaries form networks for exchange of materials. Blood contains red blood cells (transport oxygen via haemoglobin), white blood cells (defence), platelets (clotting), and plasma (transport nutrients, hormones, waste).
动脉将血液从心脏高压输送出去；静脉将血液送回心脏；毛细血管形成网络进行物质交换。血液含有红细胞（通过血红蛋白运输氧气）、白细胞（防御）、血小板（凝血）以及血浆（运输营养、激素、废物）。
8. Respiration | 呼吸作用
Respiration is the release of energy from food molecules such as glucose. Aerobic respiration uses oxygen and produces a large amount of energy:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
呼吸作用是释放食物分子（如葡萄糖）中能量的过程。有氧呼吸利用氧气并产生大量能量，方程式如上。
Anaerobic respiration occurs without oxygen: in human muscles, glucose is converted to lactic acid; in yeast, glucose is fermented to ethanol and carbon dioxide. Anaerobic respiration releases much less energy per glucose molecule.
无氧呼吸在缺氧时发生：在人体肌肉中，葡萄糖转化为乳酸；在酵母中，葡萄糖发酵生成乙醇和二氧化碳。无氧呼吸每分子葡萄糖释放的能量少得多。
9. Excretion and Homeostasis | 排泄与稳态
Excretion is the removal of metabolic waste products from the body. The kidneys filter blood to produce urine, removing urea (from excess amino acids), excess water, and salts. The nephron is the functional unit: ultrafiltration in the glomerulus produces a filtrate; useful substances are reabsorbed in the tubule; secretion adds further wastes.
排泄是体内代谢废物的清除。肾脏过滤血液产生尿液，排出尿素（来自过量氨基酸）、多余水分和盐类。肾单位是功能单位：肾小球进行超滤产生滤液；有用物质在肾小管中被重吸收；分泌作用加入更多废物。
Homeostasis maintains a constant internal environment. Control of blood glucose by insulin and glucagon, and temperature regulation through sweating, vasodilation, and shivering are key examples.
稳态维持恒定的内环境。通过胰岛素和胰高血糖素对血糖的调控，以及通过出汗、血管扩张和颤抖进行的体温调节是重要实例。
10. Coordination and Response | 协调与反应
Animals respond to stimuli via nervous and hormonal systems. The nervous system uses electrical impulses along neurones, providing rapid short-lived responses. A reflex arc includes a receptor, sensory neurone, relay neurone in the CNS, motor neurone, and effector, enabling fast protective actions.
动物通过神经系统和激素系统对刺激作出反应。神经系统沿神经元传导电信号，产生快速而短暂的响应。反射弧包括感受器、感觉神经元、中枢内的中间神经元、运动神经元和效应器，实现快速保护性动作。
Hormones are chemical messengers transported in the blood, bringing about slower but longer-lasting changes. Adrenaline triggers the 'fight or flight' response; insulin lowers blood glucose by stimulating cells to absorb glucose and converting it to glycogen.
激素是经血液运输的化学信使，引起较慢但持久的变化。肾上腺素触发“战斗或逃跑”反应；胰岛素通过促进细胞吸收葡萄糖并将其转化为糖原来降低血糖。
Plants respond to light (phototropism) and gravity (gravitropism) via the hormone auxin, which regulates cell elongation.
植物通过激素生长素对光（向光性）和重力（向地性）作出反应，生长素调控细胞伸长。
11. Reproduction and Genetics | 繁殖与遗传
Asexual reproduction produces genetically identical offspring from one parent, while sexual reproduction involves the fusion of gametes, introducing variation. Flower structure includes carpels (female) and stamens (male); pollination transfers pollen to stigma, followed by fertilisation and seed development.
无性生殖由单一亲本产生遗传相同的后代，而有性生殖通过配子融合引入变异。花的结构包括心皮（雌性）和雄蕊（雄性）；传粉将花粉传至柱头，随后发生受精和种子发育。
In humans, sperm are produced in the testes and travel through the sperm duct; eggs are released from the ovaries into the oviduct, where fertilisation may occur. The fertilised egg implants in the uterus and develops into a foetus, nourished via the placenta.
在人类中，精子在睾丸中产生并通过输精管运输；卵子从卵巢释放进入输卵管，受精可在那里发生。受精卵植入子宫并发育成胎儿，通过胎盘获得营养。
Genes are sections of DNA that code for proteins. Alleles are alternative forms of a gene. Monohybrid inheritance follows simple dominant/recessive patterns. A cross between heterozygous parents (Tt x Tt) produces a 3:1 phenotype ratio.
基因是编码蛋白质的 DNA 片段。等位基因是基因的不同形式。单基因遗传遵循简单的显性/隐性模式。杂合亲本杂交（Tt x Tt）产生 3:1 的表现型比例。
12. Ecology and Human Impact | 生态与人类影响
Ecosystems are made up of communities of organisms interacting with their environment. Energy flows through food chains and webs, starting with producers (plants) that capture sunlight. Energy is lost at each trophic level as heat, faeces, and uneaten parts, so food chains rarely exceed five levels.
生态系统由生物群落与其环境相互作用构成。能量通过食物链和食物网流动，始于捕捉阳光的生产者（植物）。每一营养级能量以热、粪便和未食用部分的形式损失，因此食物链很少超过五级。
Key nutrient cycles include the carbon cycle, where carbon dioxide is fixed by photosynthesis, released by respiration and combustion, and cycled through decomposition. Human activities such as burning fossil fuels, deforestation, and intensive farming increase atmospheric carbon dioxide, contributing to the greenhouse effect.
关键的养分循环包括碳循环，二氧化碳通过光合作用固定，通过呼吸作用和燃烧释放，并经由分解循环。人类活动如燃烧化石燃料、森林砍伐和集约农业增加了大气中的二氧化碳，导致温室效应。
Conservation and sustainable practices aim to protect biodiversity and reduce pollution. Biological control, recycling, and renewable energy sources are important strategies to minimise ecological damage.
保护与可持续实践旨在保护生物多样性并减少污染。生物防治、回收利用和可再生能源是减少生态破坏的重要策略。
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