📚 Core Knowledge Review for Year 9 WJEC Biology | Year 9 WJEC 生物核心知识点梳理
This article provides a thorough recap of the key topics covered in Year 9 WJEC Biology. You will revisit cell structures, transport processes, body systems, reproduction, genetics, ecology and more. Each section is written in both English and Chinese to help you master the essential concepts with confidence.
本文全面梳理了 Year 9 WJEC 生物课程的核心知识点。你将重温细胞结构、物质运输、人体系统、生殖、遗传、生态等重要主题。每个小节都用中英双语撰写，帮助你自信地掌握关键概念。
1. Cell Structure and Function | 细胞结构与功能
All living organisms are built from cells. Animal cells contain a nucleus that stores DNA, cytoplasm where chemical reactions occur, a cell membrane controlling what enters and leaves, mitochondria for energy release and ribosomes for protein synthesis.
所有生物都由细胞构成。动物细胞含有储存DNA的细胞核、发生化学反应的细胞质、控制物质进出的细胞膜、释放能量的线粒体以及合成蛋白质的核糖体。
Plant cells share these structures but also possess a rigid cell wall made of cellulose, a large permanent vacuole filled with cell sap, and chloroplasts that capture light energy for photosynthesis. Fungal cells have a cell wall made of chitin and may be multinucleate, while bacterial cells lack a true nucleus and have a circular chromosome.
植物细胞同样有这些结构，但还有由纤维素组成的坚韧细胞壁、充满细胞液的大液泡，以及捕获光能进行光合作用的叶绿体。真菌细胞有由几丁质组成的细胞壁且可能多核，细菌细胞则没有真正的细胞核并含有环状染色体。
| Organelle (细胞器) | Function (功能) |
| Nucleus | Contains genetic material; controls cell activities |
| Mitochondria | Site of aerobic respiration; release energy |
| Ribosomes | Protein synthesis |
| Chloroplasts | Absorb light for photosynthesis; contain chlorophyll |
| Cell wall | Provides support and protection |
| Vacuole | Stores water, nutrients and waste; maintains turgor |
显微镜让我们观察到这些微小结构。放大率和分辨率是两个重要概念，放大倍数 = 目镜放大倍数 × 物镜放大倍数。
2. Diffusion, Osmosis and Active Transport | 扩散、渗透和主动运输
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 that does not require energy. Oxygen and carbon dioxide enter and leave cells by diffusion.
扩散是粒子从高浓度区域向低浓度区域的净移动，顺着浓度梯度进行，是被动过程，不需消耗能量。氧气和二氧化碳通过扩散进出细胞。
Osmosis is a special case of diffusion involving water molecules moving across a partially permeable membrane from a dilute solution to a more concentrated solution. In plant cells, osmosis can cause turgor or plasmolysis depending on the surrounding solution.
渗透是扩散的一种特殊情况，指水分子通过半透膜从稀溶液向浓溶液移动。在植物细胞中，渗透会引起质壁分离或保持紧张状态，取决于外界溶液的浓度。
Active transport moves substances against the concentration gradient using energy from respiration. Root hair cells absorb mineral ions from the soil by active transport even when the mineral concentration is lower in the soil than inside the cell.
主动运输利用呼吸作用提供的能量，将物质逆浓度梯度移动。根毛细胞通过主动运输从土壤吸收矿物质离子，即使土壤中的离子浓度低于细胞内。
3. Enzymes and Digestion | 酶与消化
Enzymes are biological catalysts that speed up chemical reactions without being used up. They are proteins with a specific active site where substrates bind. The lock-and-key model explains this specificity. Enzymes work best at their optimum temperature and pH; high temperatures or extreme pH can denature them.
酶是生物催化剂，能加快化学反应速度而自身不被消耗。它们是蛋白质，具有特定的活性位点，底物与之结合。锁钥假说解释了这种专一性。酶在其最适温度和pH下活性最高；高温或极端pH会使酶变性。
The human digestive system breaks large food molecules into smaller soluble ones that can be absorbed. Carbohydrases like amylase break down starch into maltose and glucose. Proteases digest proteins into amino acids, and lipases convert fats into fatty acids and glycerol. Bile, produced by the liver, emulsifies fats and provides an alkaline pH for enzymes in the small intestine.
人体消化系统将大食物分子分解成可吸收的小分子。淀粉酶等碳水化合物酶将淀粉分解为麦芽糖和葡萄糖。蛋白酶将蛋白质消化为氨基酸，脂肪酶将脂肪转化为脂肪酸和甘油。肝脏产生的胆汁乳化脂肪，并为小肠中的酶提供碱性环境。
4. The Respiratory System and Gas Exchange | 呼吸系统与气体交换
Breathing involves the movement of air into and out of the lungs. Inhaling occurs when the diaphragm contracts and flattens while the intercostal muscles raise the ribcage, increasing the volume of the thorax and lowering pressure. Exhaling is largely passive as these muscles relax.
呼吸运动使空气进出肺部。吸气时膈肌收缩变平，肋间肌上提肋骨，胸腔体积增大、压力降低。呼气时这些肌肉放松，过程大多是被动的。
Gas exchange takes place in the alveoli, tiny air sacs surrounded by capillaries. Oxygen diffuses from the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli to be exhaled. Alveoli have thin walls, a large surface area and a moist lining to maximise diffusion efficiency.
气体交换发生在肺泡——毛细血管包围的微小气囊。氧气从肺泡扩散进入血液，二氧化碳从血液扩散进入肺泡被呼出。肺泡壁薄、表面积大并保持湿润，最大程度提高扩散效率。
Aerobic respiration uses oxygen to release energy from glucose, producing carbon dioxide and water:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ energy)
有氧呼吸利用氧气从葡萄糖释放能量，产生二氧化碳和水。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ 能量)
Anaerobic respiration in animals produces lactic acid and releases less energy. In yeast, it produces ethanol and carbon dioxide.
无氧呼吸在动物体内产生乳酸，释放较少能量；在酵母中则产生乙醇和二氧化碳。
Glucose → Lactic acid (+ energy)
葡萄糖 → 乳酸 (+ 能量)
5. The Circulatory System | 循环系统
The 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, while the left ventricle pumps oxygenated blood to the rest of the body. The left ventricle has a thicker muscular wall because it must generate higher pressure.
循环系统由心脏、血管和血液组成。心脏是双泵：右心室将缺氧血泵至肺部，左心室将富氧血泵至全身。左心室肌肉壁较厚，因为它需要产生更高的压力。
Arteries carry blood away from the heart under high pressure and have thick elastic walls. Veins return blood to the heart, have valves to prevent backflow and a wider lumen. Capillaries are microscopic vessels where exchange of substances occurs; their walls are only one cell thick.
动脉将血液从心脏送出，壁厚而有弹性，承受高压。静脉将血液送回心脏，管腔较宽且有瓣膜防止倒流。毛细血管是微细血管，是物质交换的场所，管壁仅有一层细胞厚。
Blood transports oxygen, carbon dioxide, nutrients, hormones and waste. Red blood cells contain haemoglobin to carry oxygen. White blood cells defend against pathogens, and platelets help clot the blood.
血液运输氧气、二氧化碳、养分、激素和废物。红细胞含血红蛋白携带氧气。白细胞抵御病原体，血小板帮助血液凝固。
6. Plant Transport and Photosynthesis | 植物运输与光合作用
Xylem vessels transport water and dissolved minerals from the roots to the leaves in an upward flow. Xylem cells are dead and hollow, strengthened by lignin, forming continuous tubes. Phloem transports sugars and amino acids up and down the plant; this process is called translocation.
木质部导管将水和溶解的矿物质从根部向上运输至叶片。木质部细胞死而无原生质，由木质素强化，形成连续管道。韧皮部将糖类和氨基酸上下运输，这一过程称为输导。
Water is lost from leaves through stomata by transpiration. The transpiration stream pulls water up the xylem, driven by evaporation from mesophyll cells. Guard cells control the opening and closing of stomata to balance water loss and gas exchange.
水分通过气孔的蒸腾作用从叶片散失。蒸腾流拉动水分沿木质部上升，由叶肉细胞蒸发驱动。保卫细胞控制气孔开闭，以平衡水分丢失和气体交换。
Photosynthesis uses light energy to convert carbon dioxide and water into glucose and oxygen:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
光合作用利用光能将二氧化碳和水转化为葡萄糖和氧气：
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Factors affecting the rate include light intensity, carbon dioxide concentration and temperature. The glucose produced may be used for respiration, stored as starch or converted into cellulose for growth.
影响光合作用速率的因素包括光照强度、二氧化碳浓度和温度。生成的葡萄糖可用于呼吸、以淀粉形式储存或转化为纤维素供生长。
7. Reproduction in Plants and Humans | 植物与人类的生殖
Flowering plants reproduce sexually. The male gamete (pollen) is produced in anthers, while the female gamete (ovule) develops in the ovary. Pollination is the transfer of pollen from anther to stigma; fertilisation occurs when the pollen tube reaches the ovule. After fertilisation, the ovary develops into a fruit.
开花植物进行有性生殖。雄配子（花粉）在花药中产生，雌配子（胚珠）在子房中发育。传粉是花粉从花药传到柱头的过程；花粉管到达胚珠时发生受精。受精后子房发育成果实。
Human reproduction involves the fusion of a sperm cell and an egg cell. The male reproductive system produces sperm in the testes and delivers them through the penis. The female system releases an egg from an ovary about every 28 days; if fertilised, the zygote implants in the uterus where it develops into a foetus.
人类生殖涉及精子与卵细胞结合。男性生殖系统在睾丸中产生精子并通过阴茎输送。女性生殖系统大约每28天从卵巢排出一个卵子；如果受精，受精卵植入子宫，发育成胎儿。
The placenta allows exchange of nutrients, oxygen and waste between mother and foetus without mixing their blood. Hormones such as oestrogen and testosterone control secondary sexual characteristics during puberty.
胎盘允许母体和胎儿之间交换营养、氧气和废物而不混合血液。雌激素和睾酮等激素在青春期调控第二性征的发育。
8. DNA, Genes and Chromosomes | DNA、基因和染色体
Deoxyribonucleic acid (DNA) is a double-helix polymer made of nucleotides. Each nucleotide consists of a sugar, a phosphate group and a base (A, T, C or G). The sequence of bases forms the genetic code that determines protein structure.
脱氧核糖核酸(DNA)是双螺旋结构的聚合物，由核苷酸组成。每个核苷酸由糖、磷酸基团和碱基(A、T、C或G)构成。碱基序列构成遗传密码，决定蛋白质结构。
A gene is a section of DNA that codes for a particular protein. Alleles are different versions of the same gene. Chromosomes are long coiled molecules of DNA found in the nucleus; humans have 46 chromosomes arranged in 23 pairs. Gametes contain half this number (23) so that fertilisation restores the diploid number.
基因是编码特定蛋白质的DNA片段。等位基因是同一基因的不同形式。染色体是细胞核内长链螺旋状的DNA分子；人类有46条染色体，组成23对。配子只含半数染色体(23条)，受精后恢复二倍体数目。
9. Inheritance and Variation | 遗传与变异
Inheritance can be studied using monohybrid crosses. A dominant allele (capital letter) masks the effect of a recessive allele (lower case) when present. The genotype describes the alleles an organism carries, while the phenotype is the observable characteristic. A homozygous individual has two identical alleles; a heterozygous individual has two different alleles.
遗传可通过单基因杂交研究。显性等位基因（大写字母）存在时会掩盖隐性等位基因（小写字母）的效应。基因型描述生物携带的等位基因，表现型是可观察的特征。纯合子有两个相同等位基因，杂合子有两个不同等位基因。
Variation can be continuous, showing a range (e.g., height), or discontinuous, with distinct categories (e.g., blood group). Variation arises from genetic differences, environmental factors, or a combination of both. Mutations are random changes in DNA that can create new alleles.
变异可以是连续的，呈现范围分布（如身高），也可以是不连续的，分为明显类别（如血型）。变异源自遗传差异、环境因素或两者共同作用。突变是DNA的随机改变，可产生新等位基因。
10. Ecosystems and Food Chains | 生态系统与食物链
hotosynthesis. Food chains show linear feeding relationships: producer → primary consumer → secondary consumer → tertiary consumer.
生态系统由生物群落与其非生物环境相互作用组成。能量通过光合作用进入大多数生态系统。食物链表示线性捕食关系：生产者 → 初级消费者 → 次级消费者 → 三级消费者。
Food webs are more realistic networks of interconnected chains. Energy is lost at each trophic level through respiration, heat, movement and undigested materials, which is why food chains are usually short. Pyramids of number and biomass represent the structure of feeding levels.
食物网是更真实的互连食物链网络。每一个营养级都会因呼吸、散热、运动和未消化物质而损失能量，所以食物链通常较短。数量金字塔和生物量金字塔表示营养级结构。
Decomposers such as bacteria and fungi break down dead material, recycling nutrients back into the soil. Carbon and nitrogen cycles are central to ecosystem stability.
分解者如细菌和真菌分解死物，将营养循环回土壤。碳循环和氮循环对生态系统稳定至关重要。
11. Adaptation and Evolution | 适应与进化
Organisms are adapted to their environment through structural, behavioural and functional features. Polar bears have thick fur and blubber for insulation; cacti have spines to reduce water loss and stems that store water. These adaptations increase the chances of survival and reproduction.
生物通过结构、行为和生理特征适应环境。北极熊有厚皮毛和脂肪层保温；仙人掌的刺减少水分流失，茎储水。这些适应提高了生存和繁殖的机会。
Evolution by natural selection occurs when individuals with advantageous traits are more likely to survive and pass on their genes. Over generations, the frequency of those traits increases. Evidence includes the fossil record, antibiotic resistance in bacteria and comparative anatomy.
自然选择驱动的进化发生：具有有利性状的个体更易生存并传递其基因。经过多代，这些性状的频率增加。证据包括化石记录、细菌抗药性和比较解剖学。
12. Human Impact on the Environment | 人类对环境的影响
Human activities such as deforestation, burning fossil fuels and intensive farming can upset the balance of ecosystems. Deforestation reduces biodiversity and contributes to climate change by releasing stored carbon dioxide. Sulphur dioxide and nitrogen oxides from burning fuels cause acid rain, which damages habitats.
人类活动如砍伐森林、燃烧化石燃料和集约化农业会破坏生态平衡。砍伐森林减少生物多样性，并释放储存的二氧化碳，导致气候变化。燃烧燃料产生的二氧化硫和氮氧化物引起酸雨，破坏栖息地。
Conservation efforts include protecting habitats, breeding programmes for endangered species and sustainable practices such as replanting trees and using renewable energy. Understanding our impact allows us to make informed choices to preserve biodiversity for future generations.
保护措施包括保护栖息地、濒危物种繁殖计划以及植树、使用可再生能源等可持续做法。了解我们的影响使我们能做出明智选择，为后代保护生物多样性。
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