📚 Year 7 CCEA Biology: Core Knowledge Revision | CCEA 七年级生物：核心知识点梳理
This article provides a comprehensive review of essential biology topics for Year 7 students following the CCEA curriculum. We cover cells, life processes, classification, ecosystems, human body systems, reproduction, variation, microbes and more, with paired English and Chinese explanations to support bilingual learners and help you prepare effectively for assessments.
本文为遵循 CCEA 课程大纲的七年级学生提供生物核心知识点的全面梳理，涵盖细胞、生命过程、分类、生态系统、人体系统、生殖、变异、微生物等内容，并配有中英双语解释，帮助双语学习者有效备考。
1. Cells - The Building Blocks of Life | 细胞——生命的基本单位
All living organisms are made of cells. Cells are the smallest units that can carry out life processes. Some organisms, like bacteria, are unicellular (single-celled), while most plants and animals are multicellular.
所有生物都由细胞构成。细胞是能进行生命活动的最小单位。有些生物，如细菌，是单细胞的，而大多数植物和动物是多细胞的。
Animal cells typically contain a nucleus, cytoplasm, cell membrane and mitochondria. The nucleus controls the cell's activities and contains genetic material. Cytoplasm is a jelly-like substance where chemical reactions occur. The cell membrane controls which substances enter and leave the cell. Mitochondria are the sites of respiration, releasing energy for the cell.
动物细胞通常包含细胞核、细胞质、细胞膜和线粒体。细胞核控制细胞的活动并含有遗传物质。细胞质是果冻状物质，化学反应在此发生。细胞膜控制物质进出细胞。线粒体是呼吸作用的场所，为细胞释放能量。
Plant cells have all the parts found in animal cells, plus a cell wall, a large permanent vacuole and often chloroplasts. The cell wall, made of cellulose, provides support and shape. The vacuole contains cell sap and helps maintain rigidity. Chloroplasts contain chlorophyll and are the sites of photosynthesis.
植物细胞具有动物细胞的所有部分，另外还有细胞壁、一个大液泡，通常还有叶绿体。由纤维素构成的细胞壁提供支撑和形状。液泡含有细胞液，有助于保持坚挺。叶绿体含有叶绿素，是光合作用的场所。
The table below compares the structures of animal and plant cells:
| Structure | Animal Cell | Plant Cell |
|---|---|---|
| Nucleus | Present | Present |
| Cytoplasm | Present | Present |
| Cell membrane | Present | Present |
| Mitochondria | Present | Present |
| Cell wall | Absent | Present |
| Large vacuole | Absent | Present |
| Chloroplasts | Absent | Present |
下表比较了动物细胞和植物细胞的结构：
| 结构 | 动物细胞 | 植物细胞 |
|---|---|---|
| 细胞核 | 有 | 有 |
| 细胞质 | 有 | 有 |
| 细胞膜 | 有 | 有 |
| 线粒体 | 有 | 有 |
| 细胞壁 | 无 | 有 |
| 大液泡 | 无 | 有 |
| 叶绿体 | 无 | 有 |
magnification. For example, an eyepiece of ×10 and an objective of ×40 give a total magnification of ×400. When preparing a specimen, a thin slice is placed on a slide, a drop of stain may be added to make structures visible, and a coverslip is lowered carefully to avoid air bubbles.
我们使用显微镜观察细胞。总放大倍数等于目镜放大倍数乘以物镜放大倍数。例如，目镜 10 倍、物镜 40 倍，总放大倍数为 400 倍。在制作标本时，将薄切片放在载玻片上，可加一滴染液使结构清晰可见，然后小心放下盖玻片以避免气泡。
2. The Seven Life Processes (MRS GREN) | 七大生命过程 (MRS GREN)
All living things share seven life processes, often remembered by the acronym MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition. An organism does not necessarily need to move from place to place, but all living things show some kind of movement.
所有生物共有七大生命过程，常用首字母缩写 MRS GREN 记忆：运动 (Movement)、呼吸作用 (Respiration)、感应 (Sensitivity)、生长 (Growth)、生殖 (Reproduction)、排泄 (Excretion) 和营养 (Nutrition)。生物不一定能四处移动，但所有生物都表现出某种形式的运动。
- Movement: Animals move using muscles; plants move slowly towards light.
- Respiration: The process of releasing energy from food, occurring in every living cell.
- Sensitivity: Detecting and responding to changes in the surroundings.
- Growth: A permanent increase in size and complexity.
- Reproduction: Producing offspring to ensure the survival of the species.
- Excretion: Removal of waste products from the body, such as carbon dioxide and urine.
- Nutrition: Obtaining food for energy, growth and repair.
- 运动：动物用肌肉运动；植物缓慢地向光移动。
- 呼吸作用：从食物中释放能量的过程，发生在每个活细胞中。
- 感应：探测并响应周围环境的变化。
- 生长：体积和复杂性的永久性增加。
- 生殖：产生后代以保证物种的延续。
- 排泄：将废物（如二氧化碳和尿液）排出体外。
- 营养：获取食物，用于能量、生长和修复。
3. Classification of Living Things | 生物的分类
Scientists classify organisms into groups based on shared characteristics. The five-kingdom system includes Animals, Plants, Fungi, Protoctists (Protists) and Prokaryotes (Bacteria). Animals are further divided into vertebrates (with a backbone) and invertebrates (without a backbone).
科学家根据共同特征将生物分类。五界系统包括动物界、植物界、真菌界、原生生物界和原核生物界（细菌）。动物又分为脊椎动物（有脊椎）和无脊椎动物（无脊椎）。
The main groups of vertebrates and their key features are:
- Fish: Live in water, have gills, scales and fins, lay eggs.
- Amphibians: Begin life in water with gills, later develop lungs, have moist skin, lay eggs in water.
- Reptiles: Have dry scaly skin, lay leathery eggs on land, breathe with lungs.
- Birds: Have feathers, beak, wings, lay hard-shelled eggs, are warm-blooded.
- Mammals: Have hair or fur, give birth to live young (mostly), produce milk, are warm-blooded.
脊椎动物的主要类别及其关键特征：
- 鱼类：生活在水里，有鳃、鳞和鳍，卵生。
- 两栖类：幼体在水里生活，用鳃呼吸，长大后用肺，皮肤湿润，在水中产卵。
- 爬行类：皮肤干燥有鳞，在陆地产革质卵，用肺呼吸。
- 鸟类：有羽毛、喙和翅膀，产硬壳卵，恒温动物。
- 哺乳类：有毛发，多数胎生哺乳，恒温动物。
Invertebrates include groups such as arthropods (insects, spiders, crustaceans), molluscs, annelids (segmented worms) and cnidarians (jellyfish). Arthropods have jointed legs and a hard exoskeleton.
无脊椎动物包括节肢动物（昆虫、蜘蛛、甲壳类）、软体动物、环节动物（分节蠕虫）和刺胞动物（水母）等。节肢动物具有分节的腿和坚硬的外骨骼。
4. Food Chains and Food Webs | 食物链与食物网
A food chain shows the feeding relationship between organisms, with arrows pointing in the direction of energy flow (from the eaten to the eater). Every chain begins with a producer, usually a green plant, that makes its own food by photosynthesis.
食物链展示生物之间的摄食关系，箭头指向能量流动的方向（从被吃者到吃者）。每条食物链都始于生产者，通常是能通过光合作用制造食物的绿色植物。
- Producer → Primary consumer (herbivore) → Secondary consumer (carnivore or omnivore) → Tertiary consumer
- 生产者 → 初级消费者（草食动物）→ 次级消费者（肉食或杂食动物）→ 三级消费者
Decomposers, such as bacteria and fungi, break down dead organisms and waste, returning nutrients to the soil. A food web is a network of several interconnected food chains, providing a more realistic picture of feeding relationships in a habitat.
分解者（如细菌和真菌）分解死去的生物和废弃物，使养分回归土壤。食物网是由多条食物链相互连接而成的网络，更真实地反映栖息地中的摄食关系。
Energy is lost at each level of a food chain, mainly as heat from respiration, which limits the length of food chains. The build-up of toxins in organisms along a food chain is called bioaccumulation.
能量在食物链每一级都会损失，主要以呼吸作用释放的热能形式散失，这限制了食物链的长度。有毒物质沿食物链在生物体内积累的现象称为生物累积。
5. Photosynthesis - How Plants Make Food | 光合作用——植物如何制造食物
Photosynthesis is the process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen. It takes place in chloroplasts, which contain the green pigment chlorophyll that absorbs sunlight.
光合作用是绿色植物利用光能将二氧化碳和水转化为葡萄糖和氧气的过程，发生在含有叶绿素的叶绿体中，叶绿素能吸收太阳光。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
The glucose produced can be used immediately for respiration, converted into starch for storage, or used to make other substances like cellulose for cell walls. Photosynthesis provides oxygen essential for the respiration of most living organisms.
产生的葡萄糖可立即用于呼吸作用，或转化为淀粉储存，也可用来制造其他物质，如构成细胞壁的纤维素。光合作用释放的氧气是大多数生物呼吸所必需的。
To test a leaf for starch, you can place it in boiling water to stop chemical reactions, then heat it in ethanol to remove chlorophyll, and finally add iodine solution. A blue-black colour indicates the presence of starch, proving photosynthesis has occurred.
要检验叶中的淀粉，可将其放入沸水中终止化学反应，然后在乙醇中加热除去叶绿素，最后滴加碘液。若呈现蓝黑色，则证明有淀粉存在，说明发生了光合作用。
6. Human Digestion | 人体的消化作用
The digestive system breaks down large insoluble food molecules into small soluble molecules that can be absorbed into the blood and carried to cells. Digestion involves both physical breakdown (e.g. chewing, churning) and chemical breakdown by enzymes.
消化系统将大而不溶的食物分子分解为可溶于水的小分子，使其能被吸收进入血液并输送到细胞。消化包括物理性消化（如咀嚼、搅拌）和酶的化学性消化。
The main organs and their roles in digestion are:
- Mouth: Chewing breaks food into pieces; saliva contains an enzyme that starts digesting starch.
- Oesophagus: A tube that pushes food down to the stomach by peristalsis.
- Stomach: Churns food and mixes it with acid and enzymes to digest proteins.
- Small intestine: Digestion is completed by enzymes; the soluble products are absorbed into the blood through the intestinal wall.
- Large intestine: Absorbs water from undigested food, forming faeces.
主要器官及其消化作用：
- 口腔：咀嚼将食物磨碎；唾液中的酶开始消化淀粉。
- 食道：通过蠕动将食物向下推送至胃的管道。
- 胃：搅拌食物，并将其与胃酸和酶混合以消化蛋白质。
- 小肠：消化酶完成消化过程；可溶性产物经肠壁吸收进入血液。
- 大肠：从无法消化的食物中吸收水分，形成粪便。
The liver produces bile, which is stored in the gall bladder and helps to break down fats into smaller droplets (emulsification). The pancreas produces digestive enzymes that are released into the small intestine.
肝脏分泌胆汁，胆汁储存在胆囊中，有助于将脂肪分解为更小的油滴（乳化作用）。胰腺产生消化酶，释放到小肠中。
7. Breathing and the Circulatory System | 呼吸与循环系统
Breathing (ventilation) is the physical process of moving air into and out of the lungs. When we inhale, the diaphragm contracts and moves down, while the intercostal muscles lift the rib cage, increasing the
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