📚 Core Knowledge Review: Year 11 Cambridge IGCSE Biology | Year 11 剑桥IGCSE生物核心知识点梳理
Cambridge IGCSE Biology covers a wide range of fundamental topics that build a strong understanding of life processes. This revision article consolidates the key concepts you need to master in Year 11, from cells and enzymes to genetics and ecology. Each section pairs important explanations with equivalent Chinese translations to strengthen bilingual comprehension.
剑桥IGCSE生物课程涵盖众多基础主题，帮助学生深入理解生命过程。本文梳理了Year 11阶段必须掌握的核心知识点，从细胞、酶到遗传和生态，每个部分都配有中英文对照解释，强化双语理解。
1. Cell Structure and Organisation | 细胞结构与组织
All living organisms are made of cells. Prokaryotic cells, like bacteria, lack a nucleus and membrane-bound organelles, while eukaryotic cells, found in plants, animals and fungi, have a true nucleus.
所有生物体都由细胞构成。原核细胞（如细菌）没有细胞核和膜结合的细胞器，而真核细胞（存在于植物、动物和真菌中）具有真正的细胞核。
Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells possess the same structures plus a rigid cell wall, a large permanent vacuole, and chloroplasts for photosynthesis.
动物细胞包含细胞核、细胞质、细胞膜、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、中央大液泡以及进行光合作用的叶绿体。
Specialised cells are adapted to their function: red blood cells have no nucleus and a biconcave shape to maximise oxygen transport; sperm cells have a tail for movement and many mitochondria; palisade mesophyll cells contain abundant chloroplasts.
特化细胞适应其功能：红细胞无核且呈双凹圆盘形，以最大程度运输氧气；精细胞带有尾部方便运动，并含有大量线粒体；栅栏叶肉细胞富含叶绿体。
Cells are organised into tissues, organs and organ systems. For example, muscle cells form muscle tissue, which makes up the heart, part of the circulatory system.
细胞构成了组织、器官和器官系统。例如，肌细胞构成肌肉组织，进而组成心脏，成为循环系统的一部分。
2. Biological Molecules and Enzymes | 生物分子与酶
Carbohydrates, proteins and lipids are essential biological molecules. Starch and glycogen are polysaccharides that store energy, while cellulose gives strength to plant cell walls.
碳水化合物、蛋白质和脂质是重要的生物分子。淀粉和糖原是多糖，储存能量；纤维素则为植物细胞壁提供强度。
Proteins are made of amino acids and have diverse roles, including structural support, enzyme catalysis, and transport. Lipids are composed of fatty acids and glycerol, providing long-term energy storage and insulation.
蛋白质由氨基酸构成，具有多种功能，如结构支持、酶催化和运输。脂质由脂肪酸和甘油组成，提供长期能量储存和隔热作用。
Enzymes are biological catalysts that speed up reactions without being used up. They have an active site with a specific shape complementary to their substrate, following the lock-and-key model.
酶是生物催化剂，能加速反应而自身不被消耗。酶的活性部位具有与底物形状互补的特定结构，符合锁钥模型。
Enzyme activity is affected by temperature and pH. At very high temperatures, enzymes denature, losing their shape and function. Each enzyme works best at an optimum pH.
酶的活性受温度和pH影响。高温会使酶变性，失去形状和功能。每种酶在最适pH下活性最高。
Substrate + Enzyme → Enzyme-substrate complex → Product + Enzyme
底物 + 酶 → 酶-底物复合物 → 产物 + 酶
3. Plant Nutrition and Photosynthesis | 植物营养与光合作用
Photosynthesis converts light energy into chemical energy, producing glucose and oxygen. The overall word equation is carbon dioxide + water → glucose + oxygen, using chlorophyll and light.
光合作用将光能转化为化学能，生成葡萄糖和氧气。文字方程式为二氧化碳 + 水 → 葡萄糖 + 氧，需要叶绿素和光能。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
The leaf is the main photosynthetic organ. Its structure includes a waxy cuticle, upper and lower epidermis, palisade mesophyll packed with chloroplasts, spongy mesophyll, and stomata for gas exchange.
叶片是主要的光合器官。叶片结构包括蜡质角质层、上表皮和下表皮、富含叶绿体的栅栏叶肉、海绵叶肉以及进行气体交换的气孔。
Limiting factors for photosynthesis include light intensity, carbon dioxide concentration and temperature. At a certain point, increasing one factor alone no longer boosts the rate if another factor is insufficient.
光合作用的限制因素包括光照强度、二氧化碳浓度和温度。当某个因素成为限制因子时，仅提高另一因素无法再加快光合速率。
The starch test, using iodine solution (blue-black colour indicates starch), confirms that photosynthesis has taken place. A variegated leaf can show that only green parts produce starch.
淀粉实验用碘液检测，呈蓝黑色表示存在淀粉，从而验证光合作用的发生。斑叶可证明只有绿色部分能制造淀粉。
4. Transport in Plants | 植物体内运输
Xylem vessels transport water and mineral ions upwards from the roots to the leaves. Xylem cells are dead, hollow tubes strengthened by lignin. Phloem transports sucrose and amino acids both up and down the plant.
木质部导管将水分和矿物质离子从根部向上运输至叶片。木质部细胞为死细胞，形成由木质素强化的中空管道。韧皮部则负责运输蔗糖和氨基酸，可在植物体内双向运输。
Transpiration is the evaporation of water from leaf surfaces via stomata, creating a pull that draws water up through the xylem — known as the transpiration stream.
蒸腾作用指水分通过气孔从叶片表面蒸发，产生拉力，将水沿木质部向上牵引，形成蒸腾流。
Factors that increase transpiration rate include high temperature, low humidity, wind and bright light. A potometer can be used to measure water uptake, indirectly estimating transpiration rate.
增加蒸腾速率的因素包括高温、低湿度、风和强光。气泡蒸腾计可用于测量水分吸收量，间接估测蒸腾速率。
5. Human Nutrition and Digestion | 人体营养与消化
A balanced diet includes carbohydrates, proteins, lipids, vitamins, minerals, fibre and water. Carbohydrates are the main energy source; proteins are needed for growth and repair; lipids provide insulation and energy storage.
均衡膳食包括碳水化合物、蛋白质、脂质、维生素、矿物质、纤维和水。碳水化合物为主要能量来源；蛋白质用于生长和修复；脂质提供保温和能量储存。
Digestion breaks large insoluble molecules into small soluble ones. Amylase breaks down starch into maltose, proteases convert proteins into amino acids, and lipases digest lipids into fatty acids and glycerol.
消化将大分子的不溶性物质分解为可溶的小分子。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，脂肪酶则将脂质分解为脂肪酸和甘油。
The small intestine is adapted for absorption: it is long, with villi and microvilli providing a large surface area, a thin epithelial lining, and a dense capillary network to carry away absorbed nutrients.
小肠适应吸收功能：肠管较长，肠壁上有绒毛和微绒毛，大幅增加表面积，上皮层很薄，并有密集的毛细血管网运走被吸收的营养物质。
Bile, produced by the liver and stored in the gall bladder, emulsifies fats into smaller droplets, increasing the surface area for lipase action. It also neutralises stomach acid, creating an alkaline pH for intestinal enzymes.
胆汁由肝脏产生并储存在胆囊中，能将脂肪乳化成小液滴，增大脂肪酶的作用面积。胆汁还能中和胃酸，为小肠酶提供碱性环境。
6. The Circulatory System | 循环系统
The mammalian circulatory system is a double circulation: the right side of the heart pumps deoxygenated blood to the lungs (pulmonary circulation), while the left side pumps oxygenated blood to the rest of the body (systemic circulation).
哺乳动物的循环系统属于双循环：心脏右侧将缺氧血泵至肺部（肺循环），心脏左侧将含氧血泵至全身（体循环）。
The heart has four chambers: right atrium, right ventricle, left atrium and left ventricle. Valves prevent backflow of blood. The muscular left ventricle has a thicker wall, as it must generate higher pressure to deliver blood around the whole body.
心脏有四个腔室：右心房、右心室、左心房和左心室。瓣膜防止血液倒流。左心室肌肉壁更厚，因为它需要产生更高的压力将血液输送到全身。
Arteries carry blood away from the heart under high pressure; they have thick, elastic walls. Veins return blood to the heart and contain valves. Capillaries are narrow, one-cell-thick vessels where exchange of substances occurs.
动脉将血液带离心脏，承受较高压力，管壁厚且富有弹性。静脉将血液送回心脏，内含瓣膜。毛细血管是极细的管道，管壁仅一层细胞厚，是物质交换的场所。
Blood consists of plasma, red blood cells, white blood cells and platelets. Red blood cells transport oxygen via haemoglobin; white blood cells defend against pathogens; platelets are involved in blood clotting.
血液由血浆、红细胞、白细胞和血小板组成。红细胞通过血红蛋白运输氧气；白细胞抵御病原体；血小板参与血液凝固。
7. Gas Exchange and Respiration | 气体交换与呼吸
The human respiratory system includes the trachea, bronchi, bronchioles and alveoli. Alveoli are tiny air sacs with thin walls, a large surface area, and a rich capillary network, allowing efficient gas exchange by diffusion.
人类呼吸系统包括气管、支气管、细支气管和肺泡。肺泡是微小的气囊，壁薄、表面积大，且围绕丰富的毛细血管，能够通过扩散高效进行气体交换。
Breathing involves inhalation and exhalation. During inhalation, the diaphragm contracts and flattens, and the intercostal muscles lift the ribcage, increasing the volume of the thorax and drawing air in.
呼吸包括吸气和呼气。吸气时，膈肌收缩并变平，肋间肌抬起肋骨，使胸腔容积增大，空气被吸入。
Aerobic respiration releases energy from glucose in the presence of oxygen. The word equation is glucose + oxygen → carbon dioxide + water (+ energy).
有氧呼吸在氧气充足的条件下将葡萄糖中的能量释放出来。文字方程式：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Anaerobic respiration occurs when oxygen is scarce. In animal cells, it produces lactic acid and a small amount of energy. In yeast, anaerobic respiration produces ethanol, carbon dioxide and some energy.
无氧呼吸在缺氧时发生。动物细胞中，无氧呼吸产生乳酸和少量能量。酵母的无氧呼吸则产生乙醇、二氧化碳和部分能量。
8. Disease and Immunity | 疾病与免疫
Pathogens are microorganisms that cause disease, including bacteria, viruses, fungi and protists. They can be transmitted through direct contact, airborne droplets, contaminated food or water, and vectors.
病原体是引起疾病的微生物，包括细菌、病毒、真菌和原生生物。它们可通过直接接触、空气飞沫、受污染的食物或水以及媒介生物传播。
The body has mechanical, chemical and cellular defences. The skin acts as a physical barrier; stomach acid destroys many pathogens; white blood cells engulf microbes by phagocytosis or produce antibodies.
人体具有机械、化学和细胞防御机制。皮肤是物理屏障；胃酸能杀灭多种病原体；白细胞通过吞噬作用吞噬微生物，或产生抗体。
Lymphocytes produce specific antibodies that bind to antigens on pathogens, leading to their destruction. Memory cells remain in the body after an infection, providing long-term immunity.
淋巴细胞产生特异性抗体，与病原体表面的抗原结合，使病原体被消灭。感染后体内会留下记忆细胞，提供长期免疫。
Vaccination introduces a harmless form of a pathogen, triggering an immune response and the production of memory cells without causing illness. Herd immunity protects the wider population when a high percentage is vaccinated.
疫苗接种引入无害形式的病原体，激发免疫应答并产生记忆细胞，而不引发疾病。当接种率足够高时，群体免疫可保护整个群体。
9. Coordination and Response | 协调与反应
The nervous system enables rapid communication. A reflex arc goes through a stimulus, receptor, sensory neurone, relay neurone, motor neurone and effector, allowing quick involuntary responses.
神经系统实现快速通信。反射弧的路径为：刺激 → 感受器 → 感觉神经元 → 中间神经元 → 运动神经元 → 效应器，形成快速的不随意反应。
The human eye adjusts to light intensity and distance. The iris changes pupil size; the ciliary muscles alter the shape of the lens for accommodation, allowing focusing on near or distant objects.
人眼能根据光强度和距离调节。虹膜调节瞳孔大小；睫状肌改变晶状体形状进行调节，使人能聚焦于近处或远处的物体。
Hormones are chemical messengers produced by endocrine glands and transported in the blood. They bring about slower, longer-lasting changes. Insulin, secreted by the pancreas, lowers blood glucose concentration by converting glucose into glycogen.
激素是由内分泌腺产生并通过血液运输的化学信使，引起较缓慢但持久的变化。胰岛素由胰腺分泌，通过将葡萄糖转化为糖原来降低血糖浓度。
Adrenaline, released in ‘fight or flight’ situations, increases heart rate, dilates pupils and boosts glucose delivery to muscles, preparing the body for action.
肾上腺素在“战斗或逃跑”情境中释放，使心率加快、瞳孔扩大，并增加肌肉的葡萄糖供应，让身体做好行动准备。
10. Reproduction | 生殖
Asexual reproduction requires only one parent and produces genetically identical offspring. Examples include binary fission in bacteria, budding in yeast, and runners in strawberry plants.
无性生殖只需要一个亲本，产生遗传上相同的后代。实例包括细菌的二分裂、酵母的出芽生殖和草莓的走茎繁殖。
Sexual reproduction involves two parents, producing genetically varied offspring. Gametes (sperm and egg) are produced by meiosis, which halves the chromosome number. Fertilisation restores the diploid number.
有性生殖涉及两个亲本，产生遗传变异的后代。配子（精子和卵子）通过减数分裂产生，染色体数目减半。受精后恢复二倍体数目。
In the male reproductive system, sperm are produced in the testes and travel through the sperm duct. The female system includes ovaries, oviducts, a uterus and a vagina. The menstrual cycle prepares the uterus lining for possible pregnancy.
男性生殖系统中，精子在睾丸产生并经输精管运输。女性系统包括卵巢、输卵管、子宫和阴道。月经周期为可能的妊娠准备子宫内膜。
During the menstrual cycle, oestrogen thickens the uterine lining and FSH stimulates follicle development. After ovulation, progesterone maintains the lining. If fertilisation occurs, the embryo implants and produces hCG to sustain the corpus luteum.
月经周期中，雌激素使子宫内膜增厚，FSH促进卵泡发育。排卵后，孕酮维持子宫内膜。若发生受精，胚胎植入并分泌hCG以维持黄体。
11. Genetics and Evolution | 遗传与进化
DNA is a double-stranded molecule twisted into a double helix. A gene is a section of DNA that codes for a protein. Alleles are different forms of a gene, and they can be dominant or recessive.
DNA是双股螺旋分子。基因是编码蛋白质的一段DNA。等位基因是基因的不同形式，可以是显性或隐性。
Monohybrid crosses use a Punnett square to predict the probability of offspring genotypes. For example, crossing a homozygous dominant (AA) with a homozygous recessive (aa) yields 100% heterozygous (Aa) offspring in F1.
单因子杂交采用庞纳特方格预测后代基因型的概率。例如，纯合显性(AA)与纯合隐性(aa)杂交，F1代100%为杂合子(Aa)。
Natural selection is the process by which organisms with advantageous traits survive and reproduce more successfully, passing those traits to the next generation. This leads to evolution over time.
自然选择是指具有有利性状的个体更易存活和繁殖，并将这些性状传递给下一代的过程，随着时间的推移导致进化。
Antibiotic-resistant bacteria evolve when a mutation gives some bacteria resistance. These survive antibiotic treatment, multiply, and the population shifts to resistant strains — an example of evolution observable today.
抗生素耐药细菌的进化：突变使部分细菌产生耐药性，在抗生素治疗中存活繁殖，种群逐渐变为耐药菌株，这是当代可观察的进化实例。
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