📚 Year 7 OCR Biology: Core Concepts Review | Year 7 OCR 生物：核心知识点梳理
Biology helps us understand the living world, from the tiniest cells to entire ecosystems. In Year 7, OCR science introduces fundamental ideas that form the foundation for GCSE study. This guide covers the key topics you'll meet: cell structure, body systems, reproduction, variation, and ecology.
生物学帮助我们认识生命世界——从最小的细胞到完整的生态系统。Year 7 OCR 科学课程引入了为 GCSE 学习打基础的核心概念。本文梳理了你会遇到的关键主题：细胞结构、身体系统、生殖、变异和生态学。
1. Cells – The Building Blocks of Life | 细胞——生命的基本单位
All living organisms are made up of cells. Some organisms, like bacteria and amoeba, consist of a single cell, while larger organisms like humans contain trillions of cells working together.
所有生物都由细胞构成。像细菌和变形虫这样的生物只由一个细胞组成，而人类这样的大型生物则包含数万亿个协同工作的细胞。
Cells carry out all the processes needed for life, including taking in nutrients, releasing energy, growing, and reproducing. The cell is the smallest unit that can perform these functions independently.
细胞执行生命所需的所有过程，包括摄入营养、释放能量、生长和繁殖。细胞是能独立完成这些功能的最小单位。
Most cells are too small to see with the naked eye. We use microscopes to observe them and learn about their structures. A typical microscope magnifies objects by 100 to 400 times.
大多数细胞小到肉眼无法看见。我们使用显微镜来观察它们并了解其结构。典型的显微镜能将物体放大 100 到 400 倍。
2. Animal and Plant Cells | 动植物细胞
Animal cells and plant cells share three main parts: a nucleus that controls the cell and contains DNA, cytoplasm where chemical reactions happen, and a cell membrane that controls what enters and leaves.
动物细胞和植物细胞共有三个主要部分：控制细胞并含 DNA 的细胞核、发生化学反应的细胞质，以及控制物质进出的细胞膜。
Plant cells have additional structures that animal cells lack. They have a rigid cell wall made of cellulose for support, a large permanent vacuole filled with cell sap that helps maintain shape, and chloroplasts containing chlorophyll for photosynthesis.
植物细胞还有一些动物细胞没有的结构。它们有由纤维素组成的坚硬的细胞壁起支撑作用，一个充满细胞液的大液泡帮助维持形状，以及含叶绿素的叶绿体用于进行光合作用。
| Structure 结构 | Animal Cell 动物细胞 | Plant Cell 植物细胞 |
|---|---|---|
| Nucleus 细胞核 | Present 有 | Present 有 |
| Cytoplasm 细胞质 | Present 有 | Present 有 |
| Cell membrane 细胞膜 | Present 有 | Present 有 |
| Cell wall 细胞壁 | Absent 无 | Present (cellulose) 有（纤维素） |
| Chloroplasts 叶绿体 | Absent 无 | Present 有 |
| Large vacuole 大液泡 | Absent 无 | Present 有 |
3. Specialised Cells | 特化细胞
Many cells become specialised to perform a particular function. Their shape and internal structure adapt to their job. For example, a sperm cell has a long tail, or flagellum, to swim towards an egg cell, and contains many mitochondria to provide energy for movement.
许多细胞特化以执行特定功能。它们的形状和内部结构适应其职责。例如，精子细胞有一条长长的尾巴（鞭毛）用于游向卵细胞，并含有许多线粒体为运动提供能量。
Root hair cells in plants have a long, thin extension that increases the surface area for absorbing water and minerals from the soil. They lack chloroplasts because they are underground and do not photosynthesise.
植物的根毛细胞有一个细长的突起，增加了从土壤中吸收水分和矿物质的表面积。它们没有叶绿体，因为它们位于地下，不进行光合作用。
Red blood cells have a biconcave disc shape and no nucleus, which creates more space for haemoglobin to carry oxygen around the body. Ciliated epithelial cells in the airways have tiny hair-like cilia that sweep mucus and trapped particles out of the lungs.
红细胞呈双凹圆盘状且没有细胞核，这为血红蛋白携带氧气创造了更多空间。呼吸道中的纤毛上皮细胞有微小的毛发状纤毛，能将黏液和截留的颗粒扫出肺部。
4. Levels of Organisation | 组织层次
Cells work together in a structured hierarchy. Similar cells group together to form a tissue. For example, muscle tissue is made of many muscle cells working together to contract.
细胞在一个结构化的层次中协同工作。相似的细胞聚集形成组织。例如，肌肉组织由许多协同收缩的肌细胞组成。
Different tissues combine to form an organ. The stomach is an organ that contains muscle tissue to churn food, glandular tissue to produce digestive juices, and epithelial tissue to cover its surface.
不同的组织结合形成器官。胃是一个器官，它包含搅动食物的肌肉组织、产生消化液的腺体组织以及覆盖其表面的上皮组织。
Organs that work together to perform a major function make up an organ system. The digestive system includes the stomach, intestines, liver, and pancreas. Multiple organ systems together form an organism.
协同工作以完成主要功能的器官构成器官系统。消化系统包括胃、肠、肝和胰腺。多个器官系统共同构成一个生物体。
Cells → Tissues → Organs → Organ Systems → Organism
细胞 → 组织 → 器官 → 器官系统 → 生物体
5. The Skeletal and Muscular Systems | 骨骼与肌肉系统
The skeleton provides support, protects vital organs, and allows movement. Bones also store minerals and produce blood cells in the bone marrow. The human skeleton is made of over 200 bones joined at joints.
骨骼提供支撑、保护重要器官并允许运动。骨骼还储存矿物质，并在骨髓中产生血细胞。人类骨骼由 200 多块骨头组成，通过关节连接。
Muscles work by contracting – they can only pull, never push. Pairs of muscles, called antagonistic pairs, work opposite each other. For instance, when the biceps contracts to bend the arm, the triceps relaxes; to straighten the arm, the triceps contracts and the biceps relaxes.
肌肉通过收缩工作——它们只能拉，不能推。成对的肌肉称为拮抗肌对，彼此反向工作。例如，当肱二头肌收缩弯曲手臂时，肱三头肌放松；要伸直手臂，肱三头肌收缩，肱二头肌放松。
Tendons attach muscles to bones, and ligaments connect bones to other bones at joints. Synovial joints, such as the knee and elbow, contain synovial fluid that reduces friction, and cartilage that cushions the ends of bones.
肌腱将肌肉附着到骨骼上，韧带将骨骼与骨骼在关节处连接。滑膜关节如膝关节和肘关节，含有减少摩擦的滑液和缓冲骨端的软骨。
6. The Digestive System | 消化系统
Digestion breaks down large, insoluble food molecules into small, soluble substances that can be absorbed into the blood. The process involves both physical breakdown, like chewing in the mouth, and chemical breakdown by enzymes.
消化将大而不溶的食物分子分解成可溶于水、能被吸收进入血液的小分子物质。这个过程既包括物理分解（如口腔中的咀嚼），也包括酶的化学分解。
Food travels through the mouth, oesophagus, stomach, small intestine, large intestine, and rectum. The stomach churns food and releases protease enzymes. In the small intestine, nutrients are absorbed through the walls into the bloodstream. The large intestine absorbs water, leaving faeces to be egested.
食物依次经过口腔、食道、胃、小肠、大肠和直肠。胃搅拌食物并释放蛋白酶。在小肠中，营养物质通过肠壁被吸收进入血液。大肠吸收水分，剩余粪便被排出。
The liver produces bile, which is stored in the gall bladder and released into the small intestine to help digest fats. The pancreas produces several digestive enzymes that break down carbohydrates, proteins, and lipids.
肝脏产生胆汁，储存在胆囊中并释放到小肠以帮助消化脂肪。胰腺产生多种消化酶，分解碳水化合物、蛋白质和脂类。
7. The Respiratory System | 呼吸系统
The respiratory system brings oxygen into the body and removes carbon dioxide. Air enters through the nose or mouth, passes down the trachea, and into two bronchi that lead to each lung. Inside the lungs, the bronchi branch into smaller bronchioles ending in tiny air sacs called alveoli.
呼吸系统将氧气带入体内并移除二氧化碳。空气通过鼻子或嘴进入，沿气管向下，进入通向双侧肺的支气管。在肺内，支气管分支成更小的细支气管，末端是称为肺泡的微小气囊。
Gas exchange happens at the alveoli. They are surrounded by capillaries. Oxygen diffuses from the air in the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli to be breathed out. The alveoli are adapted for this: they have very thin walls, a large surface area, and a rich blood supply.
气体交换在肺泡进行。它们被毛细血管包围。氧气从肺泡内的空气中扩散进入血液，二氧化碳从血液扩散到肺泡中被呼出。肺泡对此有适应性：它们壁非常薄，表面积大，且有丰富的血液供应。
Breathing involves the diaphragm and intercostal muscles. During inhalation, the diaphragm contracts and flattens, and the rib cage moves up and out, increasing the chest volume and drawing air in. Exhalation is usually passive as these muscles relax.
呼吸涉及膈肌和肋间肌。吸气时，膈肌收缩变平，肋骨向上向外移动，增加胸腔容积并吸入空气。呼气通常是这些肌肉放松时的被动过程。
glucose + oxygen → carbon dioxide + water (+ energy)
葡萄糖 + 氧气 → 二氧化碳 + 水 (+ 能量)
This word equation summarises aerobic respiration, which happens constantly in cells to release energy from food.
这个文字方程式总结了有氧呼吸，它在细胞中持续发生，从食物中释放能量。
8. The Circulatory System | 循环系统
The circulatory system transports substances around the body. The heart acts as a pump, sending blood through arteries, capillaries, and veins. Arteries carry blood away from the heart; veins return blood to the heart; capillaries connect them and allow exchange of materials with tissues.
循环系统运输物质到全身。心脏充当泵，推动血液流经动脉、毛细血管和静脉。动脉将血液运离心脏；静脉将血液送回心脏；毛细血管连接两者并允许与组织交换物质。
The heart has four chambers: the right atrium and right ventricle pump deoxygenated blood to the lungs; the left atrium and left ventricle pump oxygenated blood to the rest of the body. The left ventricle has a thicker muscle wall because it must generate higher pressure.
心脏有四个腔室：右心房和右心室将缺氧血泵入肺；左心房和左心室将富氧血泵到全身。左心室的肌肉壁更厚，因为它必须产生更高的压力。
Blood is composed of plasma, red blood cells, white blood cells, and platelets. Plasma transports dissolved nutrients, hormones, and waste. Red blood cells carry oxygen, white blood cells fight infection, and platelets help clotting.
血液由血浆、红细胞、白细胞和血小板组成。血浆运输溶解的营养物质、激素和废物。红细胞携带氧气，白细胞抵抗感染，血小板帮助凝血。
9. Reproduction in Humans | 人类的生殖
Sexual reproduction involves the fusion of male and female gametes (sperm and egg) to form a zygote, which develops into a new individual. In humans, the male reproductive system produces sperm in the testes, and the female system produces eggs in the ovaries.
有性生殖涉及雄性和雌性配子（精子和卵子）的结合，形成受精卵，然后发育成新个体。在人类中，男性生殖系统在睾丸中产生精子，女性系统在卵巢中产生卵子。
Fertilisation typically occurs in the oviduct (fallopian tube). The fertilised egg implants in the uterus lining, where it grows into an embryo. The placenta develops to exchange nutrients, oxygen, and waste between the mother's blood and the embryo without the blood mixing.
受精通常发生在输卵管中。受精卵植入子宫内膜，在那里发育成胚胎。胎盘形成，以便在母体血液和胚胎之间交换营养、氧气和废物，而血液不混合。
Puberty causes physical changes as the body becomes capable of reproduction. Hormones trigger growth of reproductive organs and secondary sexual characteristics, such as deepening of the voice in males and breast development in females. The menstrual cycle begins, preparing the uterus for possible pregnancy each month.
青春期使身体发生变化，具备生殖能力。激素触发生殖器官和第二性征的发育，例如男性变声和女性乳房发育。月经周期开始，每月为可能的怀孕准备子宫。
10. Plant Reproduction | 植物生殖
Flowering plants reproduce sexually through pollination and fertilisation. Pollination is the transfer of pollen from the anther of a stamen to the stigma of a carpel. This can be carried out by wind, insects, or other animals.
开花植物通过授粉和受精进行有性繁殖。授粉是花粉从雄蕊的花药转移到雌蕊的柱头上的过程。这可以通过风、昆虫或其他动物完成。
After pollination, a pollen tube grows from the pollen grain down through the style to the ovary, where the male gamete fuses with the female ovule. The fertilised ovule becomes a seed, and the ovary wall develops into a fruit. The fruit protects seeds and aids in dispersal.
授粉后，花粉管从花粉粒长出，穿过花柱到达子房，在那里雄配子与雌胚珠结合。受精的胚珠发育成种子，子房壁发育成果实。果实保护种子并帮助传播。
Seeds need warmth, water, and oxygen to germinate. The young root (radicle) and shoot (plumule) emerge, and the seedling begins photosynthesis once the leaves reach light. Dispersal methods include wind, animal attachment, explosive pods, and water.
种子需要温暖、水和氧气才能萌发。幼根（胚根）和幼芽（胚芽）长出，一旦叶子见光，幼苗就开始光合作用。传播方式包括风、动物附着、爆裂的豆荚和水。
11. Ecosystems and Food Chains | 生态系统与食物链
An ecosystem includes all the living organisms in a habitat and the non-living factors they interact with. Energy enters most ecosystems through sunlight and is captured by producers – green plants and algae – during photosynthesis.
生态系统包括栖息地中的所有生物以及它们与之相互作用的非生物因素。能量大多通过阳光进入生态系统，由生产者——绿色植物和藻类——在光合作用中捕获。
Consumers obtain energy by eating other organisms. Primary consumers eat plants, secondary consumers eat primary consumers, and so on. Decomposers like bacteria and fungi break down dead material, returning nutrients to the soil.
消费者通过取食其他生物获得能量。初级消费者吃植物，次级消费者吃初级消费者，依此类推。分解者如细菌和真菌分解死亡的生物体，将养分归还土壤。
g relationships in a simple sequence: grass → rabbit → fox. In this chain, the arrow means 'is eaten by' s predators at the top of the chain may contain high concentrations of harmful substances.
食物链以简单序列展示摄食关系：草 → 兔子 → 狐狸。在这个链条中，箭头意为“被……吃”。毒素可以沿食物链积累；这个过程称为生物富集，意味着食物链顶端的捕食者可能含有高浓度的有害物质。
12. Variation and Classification | 变异与分类
Variation is the differences between individuals of the same species. Some variation is inherited through genes, like eye colour or blood group. Other variation is caused by the environment, such as scar tissue or language spoken. Many traits are influenced by both.
变异是同一物种个体间的差异。有些变异通过基因遗传，如眼睛颜色或血型。其他变异由环境引起，如疤痕组织或所说的语言。许多特征受两者共同影响。
Continuous variation shows a range of values and can be measured, like height or hand span. Discontinuous variation falls into distinct categories, like being able to roll your tongue or having a particular blood group.
连续变异显示一个范围内的数值，可以测量，如身高或手间距。不连续变异则分属截然不同的类别，如能否卷舌或具有特定血型。
Classification organises living things into groups based on shared characteristics. The main ranks are kingdom, phylum, class, order, family, genus, and species. The largest groups are the five kingdoms: animals, plants, fungi, bacteria (prokaryotes), and protists. Each species has a unique two-part scientific name, such as Homo sapiens for humans.
分类根据共同特征将生物分成不同类别。主要等级是界、门、纲、目、科、属、种。最大的类别是五个界：动物、植物、真菌、细菌（原核生物）和原生生物。每个物种都有独特的双名学名，例如人类为 Homo sapiens。
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