📚 Year 11 AQA Biology: Key Concepts Summary | Year 11 AQA 生物：核心知识点梳理
Year 11 AQA Biology brings together the fundamental principles that explain how living organisms function, from the microscopic machinery inside cells to the vast interactions within ecosystems. This article summarises the key concepts you need to master, organised into clear topic areas that align with the AQA specification. Use this guide to consolidate your understanding and identify any gaps before your exams.
Year 11 AQA 生物学汇集了能够解释生物体如何运作的基本原理，从细胞内的微观机制到生态系统中广泛的相互作用。本文总结了需要掌握的核心概念，按照与 AQA 考试大纲相对应的清晰主题进行组织。在考前，请利用这份指南来巩固理解并找出知识漏洞。
1. Cell Structure | 细胞结构
Eukaryotic cells, such as those in animals and plants, contain a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes. Plant cells additionally have a permanent vacuole, chloroplasts, and a cell wall made of cellulose. Prokaryotic cells, like bacteria, are much smaller and lack a true nucleus; their genetic material is a single DNA loop and may include small rings of DNA called plasmids.
动物和植物等真核细胞含有细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞还多了一个中央液泡、叶绿体以及由纤维素构成的细胞壁。原核细胞（例如细菌）要小得多，没有真正的细胞核；它们的遗传物质是一条DNA环，并可能包含称为质粒的小型DNA环。
ize of image / size of real object. When using a light microscope, you may need to prepare slides and apply stains to make organelles visible. Electron microscopes offer much higher resolution and can reveal the fine details of subcellular structures.
显微镜技术使我们能够观察这些结构。放大倍数的计算公式为：放大倍数 = 图像大小 / 实物大小。使用光学显微镜时，你可能需要制作玻片标本并染色，以便看清细胞器。电子显微镜则提供更高的分辨率，能够展现亚细胞结构的精细细节。
2. Cell Division | 细胞分裂
Mitosis is the process by which body cells divide to produce two genetically identical daughter cells. It is essential for growth, repair, and asexual reproduction. The cell cycle consists of interphase (where DNA is replicated and subcellular structures are copied), followed by mitosis (nucleus divides), and cytokinesis (cytoplasm and cell membrane separate).
有丝分裂是体细胞分裂产生两个遗传上完全相同的子细胞的过程。它对生长、修复和无性生殖至关重要。细胞周期包括间期（DNA复制、亚细胞结构拷贝），随后是有丝分裂（细胞核分裂）和胞质分裂（细胞质和细胞膜分离）。
Stem cells are undifferentiated cells that can develop into specialised cell types. Embryonic stem cells can differentiate into any cell type, while adult stem cells are more limited. In plants, meristems contain stem cells that allow the plant to grow throughout its life. The use of stem cells in medicine raises ethical concerns, particularly when embryos are destroyed to harvest them.
干细胞是能够分化成特定细胞类型的未分化细胞。胚胎干细胞可以分化成任何细胞类型，而成体干细胞的分化能力则较为有限。在植物中，分生组织中的干细胞使植物能够终生生长。干细胞在医学中的应用引发了伦理问题，尤其是当需要通过破坏胚胎来获取干细胞时。
3. Organisation and the Digestive System | 组织与消化系统
Tissues are groups of similar cells working together to perform a specific function. Organs are made of different tissues, and organ systems are groups of organs that perform major functions. The digestive system breaks down large insoluble molecules into small soluble ones that can be absorbed into the blood.
组织是一群相似细胞共同协作以完成特定功能的结构。器官由不同的组织构成，而器官系统则是共同执行主要功能的器官群。消化系统能将大分子、不溶性物质分解成可被血液吸收的小分子可溶性物质。
Key digestive enzymes include amylase (breaks down starch into maltose), proteases (break down proteins into amino acids), and lipases (break down lipids into glycerol and fatty acids). Bile, produced by the liver and stored in the gall bladder, emulsifies fats and neutralises stomach acid. The products of digestion are absorbed mainly in the small intestine, which has villi to increase surface area.
关键的消化酶包括淀粉酶（将淀粉分解为麦芽糖）、蛋白酶（将蛋白质分解为氨基酸）和脂肪酶（将脂质分解为甘油和脂肪酸）。由肝脏产生并储存于胆囊的胆汁能乳化脂肪并中和胃酸。消化产物主要在小肠被吸收，小肠壁上的绒毛增大了吸收表面积。
4. The Circulatory System | 循环系统
The human circulatory system consists of the heart, blood vessels, and blood. The heart is a double pump: the right ventricle pumps deoxygenated blood to the lungs, and the left ventricle pumps oxygenated blood to the rest of the body. The heart has four chambers: right atrium, right ventricle, left atrium, and left ventricle. Valves prevent backflow.
人体循环系统由心脏、血管和血液组成。心脏是一个双泵：右心室将缺氧血泵入肺部，左心室将富氧血泵送至全身。心脏有四个腔室：右心房、右心室、左心房和左心室。瓣膜可防止血液倒流。
Arteries carry blood away from the heart and have thick muscular walls to withstand high pressure. Veins carry blood back to the heart and contain valves. Capillaries are tiny vessels with walls one cell thick for efficient exchange of substances. Blood is a tissue containing red blood cells (which transport oxygen), white blood cells (defence), platelets (clotting), and plasma (liquid transport medium).
动脉将血液带离心脏，其管壁厚实且富有肌肉层，以承受高压。静脉将血液送回心脏，内有瓣膜。毛细血管管壁极薄，仅有一层细胞，利于物质交换。血液是一种组织，其中含有红细胞（运输氧气）、白细胞（防御）、血小板（凝血）和血浆（液态运输介质）。
5. Infection and Response | 感染与免疫反应
Pathogens are microorganisms that cause infectious diseases. They include bacteria, viruses, fungi, and protists. Bacteria reproduce rapidly and produce toxins that damage tissues. Viruses live inside host cells and use the cell's machinery to replicate, often destroying the cell in the process. Diseases such as measles and HIV are viral, while Salmonella and gonorrhoea are bacterial. Malaria is caused by a protist.
病原体是引起传染病的微生物，包括细菌、病毒、真菌和原生生物。细菌繁殖迅速并产生损伤组织的毒素。病毒生活在宿主细胞内，利用细胞机制进行复制，此过程常常会破坏细胞。麻疹和艾滋病是由病毒引起的疾病，而沙门氏菌感染和淋病则是细菌性疾病。疟疾由一种原生生物引起。
The body's first line of defence includes physical barriers like the skin and chemical barriers like stomach acid. The immune system uses white blood cells to defend against pathogens. Phagocytes engulf and digest foreign cells, while lymphocytes produce antibodies specific to the antigens on the pathogen. Antitoxins neutralise toxins. Vaccination introduces a harmless form of the pathogen to stimulate antibody production and create memory cells, providing future immunity.
人体的第一道防线包括皮肤等物理屏障和胃酸等化学屏障。免疫系统利用白细胞防御病原体。吞噬细胞吞噬并消化外来细胞，而淋巴细胞则产生针对病原体抗原的特异性抗体。抗毒素能中和毒素。疫苗接种通过引入无害的病原体形态来刺激抗体产生并生成记忆细胞，从而提供未来的免疫力。
6. Bioenergetics: Photosynthesis | 生物能学：光合作用
Photosynthesis takes place inside chloroplasts and uses energy from sunlight to convert carbon dioxide and water into glucose and oxygen. The word equation is:
光合作用发生在叶绿体内，利用光能将二氧化碳和水转化为葡萄糖和氧气。其文字方程式为：
carbon dioxide + water → glucose + oxygen
二氧化碳 + 水 → 葡萄糖 + 氧气
The rate of photosynthesis is affected by light intensity, carbon dioxide concentration, and temperature. A limiting factor is the one that is in shortest supply and restricts the rate when other factors are not limiting. With enough light and CO₂, the rate increases until it is limited by temperature, as enzymes involved in the light-independent reactions have an optimum temperature.
光合作用速率受光照强度、二氧化碳浓度和温度的影响。限制因子是指供应量最少、在其他因素不限制时所制约反应速率的那个因素。当有足够的光和 CO₂ 时，速率会上升，直到受温度限制，因为光不依赖反应中的酶有最适温度。
Glucose produced in photosynthesis can be used for respiration, converted into insoluble starch for storage, or used to make cellulose, amino acids (with nitrate ions from the soil), and lipids. This makes photosynthesis the foundation of food chains and essential for biomass production.
光合作用产生的葡萄糖可用于呼吸作用，转化为不溶性淀粉储存起来，或用于制造纤维素、氨基酸（需从土壤中吸收硝酸根离子）和脂质。这使得光合作用成为食物链的基础，对生物量生产至关重要。
7. Bioenergetics: Respiration | 生物能学：呼吸作用
Respiration is the process by which cells release energy from glucose. It is an exothermic reaction that takes place continuously in all living cells. Aerobic respiration requires oxygen and produces a large amount of energy:
呼吸作用是细胞从葡萄糖中释放能量的过程。这是一个在所有活细胞中持续发生的放热反应。有氧呼吸需要氧气，并产生大量能量：
glucose + oxygen → carbon dioxide + water ( + energy )
葡萄糖 + 氧气 → 二氧化碳 + 水 ( + 能量 )
Anaerobic respiration occurs when oxygen is absent. In muscles, glucose is converted to lactic acid, releasing less energy. In yeast, fermentation produces ethanol and carbon dioxide. Anaerobic respiration in yeast is used to make bread and alcoholic drinks, while in animals it provides a short burst of energy but causes oxygen debt.
当缺乏氧气时，会发生无氧呼吸。在肌肉中，葡萄糖被转化为乳酸，释放的能量较少。在酵母中，发酵会产生乙醇和二氧化碳。酵母的无氧呼吸被用来制作面包和酒精饮料，而在动物体内，它提供短时间的能量爆发，但会导致氧债。
Metabolism is the sum of all chemical reactions in the body, including conversions of glucose to glycogen, formation of lipid molecules from glycerol and fatty acids, and use of amino acids to build proteins. Respiration is central to metabolism because it provides the ATP required for these synthetic reactions.
新陈代谢是体内所有化学反应的总和，包括葡萄糖转化为糖原、甘油与脂肪酸形成脂质分子以及利用氨基酸构建蛋白质。呼吸作用对新陈代谢至关重要，因为它为这些合成反应提供了所需的 ATP。
8. Homeostasis and the Nervous System | 稳态与神经系统
Homeostasis is the maintenance of a stable internal environment in the body. Key regulated conditions include blood glucose concentration, body temperature, and water balance. Automatic control systems use receptors, coordination centres (like the brain), and effectors to keep internal conditions within narrow limits.
稳态是指维持身体内环境稳定的状态。受调节的关键条件包括血糖浓度、体温和水分平衡。自动控制系统通过感受器、协调中枢（如大脑）和效应器将内环境维持在狭窄的范围内。
uence is: stimulus → receptor → sensory neurone → relay neurone (in spinal cord) → motor neurone → effector → response. Synapses between neurones use chemical transmitters to pass the signal across the gap.
神经系统通过沿神经元传递的电脉冲进行通信。反射弧提供了一种快速、不自主的反应。其顺序为：刺激 → 感受器 → 感觉神经元 → 联络神经元（在脊髓中） → 运动神经元 → 效应器 → 反应。神经元之间的突触利用化学递质在间隙间传递信号。
9. Hormonal Coordination | 激素协调
Hormones are chemical messengers produced by endocrine glands and carried in the bloodstream to target organs, where they trigger a specific effect. Compared to the nervous system, hormonal responses are slower but longer-lasting. For example, adrenaline released from the adrenal glands prepares the body for 'fight or flight' by increasing heart rate and blood flow to muscles.
激素是由内分泌腺产生的化学信使，通过血液运输至靶器官，引发特定效应的化学物质。与神经系统相比，激素反应速度较慢，但持续时间更长。例如，肾上腺释放的肾上腺素通过增加心率和肌肉的血流量，使身体做好“战斗或逃跑”的准备。
Blood glucose regulation involves insulin and glucagon. When blood glucose is too high, the pancreas releases insulin, which causes cells to take up more glucose and the liver to convert glucose into glycogen. When too low, glucagon is released, signalling the liver to convert glycogen back to glucose. Diabetes occurs when this control is disrupted. Type 1 diabetes involves insufficient insulin production, while Type 2 involves cells becoming resistant to insulin.
血糖调节涉及胰岛素和胰高血糖素。当血糖过高时，胰腺释放胰岛素，促使细胞吸收更多葡萄糖，肝脏将葡萄糖转化为糖原。当血糖过低时，胰高血糖素分泌，指示肝脏将糖原重新转化为葡萄糖。当这种控制机制失灵时就会发生糖尿病。1 型糖尿病是因为胰岛素分泌不足，2 型糖尿病则是由于细胞对胰岛素产生抵抗。
In human reproduction, hormones control puberty, the menstrual cycle, and fertility. Several hormones interact to maintain the cycle, and fertility can be controlled through hormonal contraceptives or assisted reproductive technologies like IVF.
在人类生殖过程中，激素控制青春期、月经周期和生育能力。多种激素相互作用以维持周期运转，生育能力可通过激素避孕法或体外受精（IVF）等辅助生殖技术进行控制。
10. Reproduction and Inheritance | 生殖与遗传
Sexual reproduction involves the fusion of male and female gametes, producing genetically varied offspring. In humans, gametes are sperm and egg cells, each carrying half the genetic material (haploid). During meiosis, the number of chromosomes is halved, and genetic variation is introduced through independent assortment and crossing over. Asexual reproduction produces genetically identical clones by mitosis, which is faster but offers no genetic variation.
有性生殖涉及雌雄配子的融合，产生遗传上多样的后代。在人类中，配子是精子和卵细胞，各携带一半的遗传物质（单倍体）。在减数分裂过程中，染色体数目减半，并通过独立分配和交叉互换引入遗传变异。无性生殖通过有丝分裂产生遗传上完全相同的克隆体，速度快但没有遗传变异。
DNA is a polymer made up of nucleotides. A gene is a small section of DNA that codes for a specific protein. The structure of DNA is a double helix, with complementary base pairing (A with T, G with C). Proteins are synthesised through transcription (DNA to mRNA) and translation (mRNA to a sequence of amino acids). Mutations in DNA can alter the amino acid sequence and change the shape and function of the protein.
DNA 是由核苷酸组成的聚合物。基因是编码特定蛋白质的一小段 DNA。DNA 的结构是双螺旋，遵循碱基互补配对（A 与 T 配对，G 与 C 配对）。蛋白质通过转录（DNA 生成 mRNA）和翻译（mRNA 控制氨基酸序列）合成。DNA 发生突变可能会改变氨基酸序列，进而改变蛋白质的形状与功能。
Inherited disorders can be caused by dominant or recessive alleles. Punnett squares and family pedigree charts are used to predict the probability of inheriting certain traits. Cystic fibrosis is an example of a recessive disorder, while polydactyly is caused by a dominant allele. Genetic screening can identify carriers or affected embryos, raising ethical and social debates.
遗传病可由显性或隐性等位基因引起。旁氏表和家族谱系图用于预测遗传某种性状的概率。囊性纤维化是一种隐性遗传病，而多指畸形则由显性等位基因导致。基因筛查能识别携带者或受影响的胚胎，这引发了伦理和社会层面的讨论。
11. Variation and Evolution | 变异与进化
Variation between individuals can be genetic, environmental, or a combination of both. Mutations are the original source of genetic variation. Evolution is the gradual change in the inherited characteristics of a population over time. Natural selection, proposed by Charles Darwin, explains how organisms with advantageous traits are more likely to survive and reproduce, passing those traits to the next generation.
个体之间的变异可能源自遗传、环境或两者的组合。突变是遗传变异的原始来源。进化是指一个种群的可遗传性状随时间逐渐发生变化的过程。查尔斯·达尔文提出的自然选择学说解释了具有有利性状的个体更有可能存活、繁殖，并将这些性状传递给下一代。
A classic example is antibiotic-resistant bacteria. Random mutations produce some resistant individuals; when antibiotics are used, non-resistant bacteria die, leaving resistant ones to multiply. This is why completing a full course of antibiotics and reducing unnecessary use is crucial. Similarly, peppered moths show how environmental change (pollution) can shift the frequency of colour variants.
一个经典的例子是抗生素耐药菌。随机突变产生了一些具有耐药性的个体；当使用抗生素时，不耐药的细菌死亡，留下耐药菌大量繁殖。这就是为什么完成整个抗生素疗程、减少非必要使用如此重要的原因。同样，桦尺蛾展示了环境的变化（污染）如何使颜色变种的频率发生转移。
Fossils provide evidence for evolution, showing how organisms have changed over millions of years. The theory can also be supported by comparative anatomy, DNA analysis, and the observation of rapid evolution in species with short life cycles. Selective breeding is an artificial form of evolution where humans choose desired characteristics and breed individuals accordingly.
化石为进化提供了证据，显示出生物体在数百万年间的变化。该理论还得到比较解剖学、DNA 分析以及对生命周期较短的物种快速进化的观察结果的支持。选择性育种是进化的一种人工形式，人类通过选择具有理想特征的个体进行繁殖以强化这些特征。
12. Ecology | 生态学
Ecology is the study of interactions between organisms and their environment. Individuals form populations, which together with other species form a community. The community plus the non-living components (habitat) make up an ecosystem. Organisms compete for resources such as food, water, light, and mates; and they are interdependent, meaning a change in one population can affect others.
生态学是研究生物体与其环境之间相互作用的学科。个体组成种群，种群与其他物种共同形成群落。群落与非生物组分（生境）一起构成了生态系统。生物体会竞争食物、水、光照和配偶等资源；它们相互依存，意味着一个种群的变化可能影响其他种群。
Feeding relationships can be shown using food chains and food webs. Energy is transferred through trophic levels, but most is lost through respiration, movement, and waste. This explains why food chains rarely exceed four or five trophic levels. Biomass can be measured and pyramids of biomass constructed. The carbon cycle and water cycle describe how essential materials are recycled, with microorganisms playing a key role in decomposition and nutrient cycling.
取食关系可以用食物链和食物网表示。能量通过营养级传递，但大部分能量通过呼吸作用、运动和排泄而散失。这就解释了食物链为什么很少超过四到五个营养级。可以测量生物量并构建生物量金字塔。碳循环和水循环描述了基本物质的循环再利用，其中微生物在分解和养分循环中起着关键作用。
Biodiversity refers to the variety of all species on Earth. Human activities such as deforestation, pollution, and climate change are threatening biodiversity. Conservation programmes, sustainable food production, and reforestation aim to reduce these impacts. Sampling techniques like quadrats and transects are used to measure species distribution and abundance in a habitat.
生物多样性指地球上所有物种的多样性。森林砍伐、污染和气候变化等人类活动正威胁着生物多样性。保护计划、可持续食品生产和植树造林旨在减少这些影响。样方法和样带等取样技术用于测量栖息地中物种的分布和丰度。
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