📚 Year 7 CAIE Biology: Quick Formula & Principle Reference Handbook | 七年级 CAIE 生物：公式定理速查手册
Welcome to your go-to quick reference for Year 7 CAIE Biology. This handbook collects the essential formulas, equations, and fundamental principles you need to master for your course. Each section is presented in paired English and Chinese explanations to support bilingual learning and quick revision.
欢迎使用这本七年级 CAIE 生物的快速参考手册。本书汇集了你需要掌握的所有重要公式、方程式和基本原理。每个部分都配有中英对照的解释，帮助你进行双语学习和快速复习。
1. The Seven Life Processes (MRS GREN) | 生命七大特征（MRS GREN）
All living organisms share seven essential life processes, often remembered by the acronym MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition. These processes define what it means to be alive and are used to distinguish living things from non-living matter.
所有生物都共享七种基本的生命过程，通常用缩写词 MRS GREN 来记忆：运动、呼吸、感应、生长、繁殖、排泄和营养。这些过程定义了什么是生命，并且用来区分生物与非生物。
Movement is an action by an organism causing a change of position or place. Respiration is the release of energy from food molecules. Sensitivity is the ability to detect and respond to changes in the environment. Growth involves a permanent increase in size. Reproduction is the production of new individuals. Excretion is the removal of metabolic waste products. Nutrition is the intake of materials for energy, growth and repair.
运动是生物体导致位置或地点变化的动作。呼吸是从食物分子中释放能量。感应是探测并响应环境变化的能力。生长涉及尺寸的永久性增加。繁殖是产生新个体。排泄是移除代谢废物的过程。营养是获取用于能量、生长和修复的物质。
2. Magnification Formula | 放大率公式
The magnification of a microscope tells us how much larger an object appears compared to its real size. The total magnification is obtained by multiplying the magnification of the eyepiece lens by that of the objective lens.
显微镜的放大率描述的是物体在镜下显得比真实尺寸大多少。总放大率由目镜放大倍数乘以物镜放大倍数得出。
Magnification = Eyepiece magnification x Objective magnification
For example, if the eyepiece lens has a magnification of 10x and the objective lens is 40x, then the total magnification equals 10 x 40 = 400x. This means the specimen appears 400 times larger than its actual size.
例如，如果目镜放大倍数为10倍，物镜为40倍，那么总放大率等于 10 x 40 = 400倍。这意味着标本看起来比实际尺寸大400倍。
3. Calculating Actual Size | 计算实际大小
To find the actual size of a specimen from a microscope image, we use the rearrangement of the magnification formula. The image size is what you measure on the paper or on the screen, and actual size is the true length of the specimen.
要从显微镜图像中求出标本的实际大小，我们需要使用放大率公式的变形。图像大小是你在纸上或屏幕上测量到的尺寸，而实际大小是标本的真实长度。
Actual size = Image size / Magnification
Always use the same units for both image size and actual size—usually millimetres (mm) or micrometres (µm). Remember that 1 mm = 1000 µm. For example, if the image size is 20 mm and the magnification is 400x, the actual size is 20 / 400 = 0.05 mm, which is 50 µm.
图像大小和实际大小必须使用相同的单位——通常为毫米（mm）或微米（µm）。记住 1 mm = 1000 µm。例如，如果图像大小为20 mm，放大率为400倍，则实际大小为 20 / 400 = 0.05 mm，即50 µm。
4. Photosynthesis Equation | 光合作用方程式
Photosynthesis is the process by which green plants make their own food using light energy. The simple word equation summarises the reactants and products.
光合作用是绿色植物利用光能制造自身食物的过程。简单的文字方程式概括了反应物和生成物。
Carbon dioxide + Water -> Glucose + Oxygen
The balanced chemical equation, showing the molecules involved, is:
平衡的化学方程式显示了所涉及的分子：
6CO₂ + 6H₂O -> C₆H₁₂O₆ + 6O₂
This reaction takes place in the chloroplasts of plant cells and requires light energy and chlorophyll. Glucose is used for energy, growth, and storage, while oxygen is released as a by-product.
该反应发生在植物细胞的叶绿体中，需要光能和叶绿素。葡萄糖用于提供能量、生长和储存，而氧气作为副产品被释放出来。
5. Aerobic Respiration Equation | 有氧呼吸方程式
Aerobic respiration is the process that releases energy from glucose in the presence of oxygen. This energy is used to fuel all life processes.
有氧呼吸是在有氧条件下从葡萄糖中释放能量的过程。这些能量用于驱动所有的生命活动。
Glucose + Oxygen -> Carbon dioxide + Water + Energy
The balanced chemical equation is:
平衡的化学方程式为：
C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O + energy
All living cells carry out respiration continuously, including plant cells. Notice that the equation for respiration is essentially the reverse of photosynthesis, highlighting the complementary relationship between these two vital processes.
所有活细胞（包括植物细胞）都持续进行呼吸作用。注意呼吸作用的方程式本质上是光合作用的逆过程，这体现了这两个重要过程之间的互补关系。
6. Food Tests and Their Principles | 食物测试及其原理
We can identify the presence of key nutrients in food using specific chemical reagents. Each test relies on a colour change that indicates a positive result.
我们可以使用特定的化学试剂来检测食物中关键营养素的存在。每种测试都依赖于显示阳性结果的颜色变化。
Testing for starch: A few drops of iodine solution are added to the food sample. If starch is present, the yellow-brown iodine turns blue-black.
测试淀粉：向食物样品中加入几滴碘液。如果含有淀粉，黄褐色的碘液会变成蓝黑色。
Testing for reducing sugars (such as glucose): Benedict’s solution is added and the mixture is heated in a water bath. A positive result shows a colour change from blue to green, yellow, or brick-red, depending on the amount of sugar.
测试还原糖（如葡萄糖）：加入本尼迪克特溶液并在水浴中加热混合物。阳性结果会显示颜色从蓝色变为绿色、黄色或砖红色，具体取决于糖的含量。
Testing for proteins: Biuret reagent is added to the sample. A positive test turns the solution from blue to purple or violet.
测试蛋白质：向样品中加入双缩脲试剂。阳性测试会使溶液从蓝色变为紫色或紫罗兰色。
Testing for lipids (fats): The ethanol emulsion test is used. The sample is mixed with ethanol and shaken, then poured into water. A cloudy white emulsion indicates the presence of lipids.
测试脂质（脂肪）：使用乙醇乳浊液测试。样品与乙醇混合摇匀，然后倒入水中。出现乳白色的混浊液表明含有脂质。
7. Digestive Enzymes and Their Actions | 消化酶及其作用
Enzymes are biological catalysts that speed up the breakdown of large food molecules into smaller, absorbable ones. Each enzyme is specific to a particular substrate.
酶是生物催化剂，可以加速大食物分子分解为更小的、可吸收的分子。每种酶只对特定的底物起作用。
Amylase is produced in the salivary glands and pancreas. It breaks down starch (a polysaccharide) into maltose (a disaccharide sugar). This action begins in the mouth and continues in the small intestine.
淀粉酶由唾液腺和胰腺分泌。它将淀粉（多糖）分解为麦芽糖（二糖）。这一作用从口腔开始，在小肠中继续。
Proteases are produced in the stomach (pepsin) and pancreas (trypsin). They digest proteins into shorter peptides and finally into amino acids, which can be absorbed into the blood.
蛋白酶在胃（胃蛋白酶）和胰腺（胰蛋白酶）中产生。它们将蛋白质消化为较短的肽段，最终成为可被吸收到血液中的氨基酸。
Lipase is produced in the pancreas and digests lipids (fats) into fatty acids and glycerol. Bile, produced by the liver and stored in the gall bladder, emulsifies fats to create a larger surface area for lipase to work on. Enzymes have optimum temperature and pH conditions.
脂肪酶由胰腺产生，将脂质（脂肪）消化为脂肪酸和甘油。由肝脏产生并储存在胆囊中的胆汁能乳化脂肪，增大脂肪酶作用的表面积。酶有最适合的温度和 pH 条件。
8. Gas Exchange in the Lungs | 肺部的气体交换
Gas exchange happens in the alveoli, which are tiny air sacs in the lungs. The principles of diffusion drive this vital process.
气体交换发生在肺部微小的气囊——肺泡中。扩散原理驱动着这一至关重要的过程。
Oxygen diffuses from the air inside the alveoli into the blood capillaries because the concentration of oxygen is higher in the alveoli. Carbon dioxide diffuses from the blood (where its concentration is higher) into the alveoli to be breathed out.
氧气从肺泡内的空气中扩散到毛细血管中，因为肺泡中的氧气浓度更高。二氧化碳则从血液（浓度较高）扩散到肺泡中，然后被呼出。
The overall rule of diffusion: Particles move from a region of higher concentration to a region of lower concentration, down a concentration gradient, without requiring energy.
扩散的总体规律：粒子从较高浓度区域沿浓度梯度向较低浓度区域运动，这一过程不需要能量。
9. Heart and Double Circulation | 心脏与双循环
Mammals, including humans, have a double circulatory system. This means blood passes through the heart twice on one complete circuit of the body.
哺乳动物，包括人类，拥有双循环系统。这意味着血液在全身完成一次完整循环时，会两次经过心脏。
The right side of the heart pumps deoxygenated blood to the lungs (pulmonary circulation) to pick up oxygen. The left side pumps oxygenated blood to all other organs of the body (systemic circulation).
心脏的右侧将缺氧血泵送到肺部（肺循环）以获取氧气。左侧则将富氧血泵送到身体的其他所有器官（体循环）。
A simplified path of blood flow is: Body (via vena cava) -> Right Atrium -> Right Ventricle -> Pulmonary artery -> Lungs -> Pulmonary veins -> Left Atrium -> Left Ventricle -> Aorta -> Body.
血流的简化路径为：身体（通过腔静脉）-> 右心房 -> 右心室 -> 肺动脉 -> 肺部 -> 肺静脉 -> 左心房 -> 左心室 -> 主动脉 -> 身体。
10. Energy Transfer in Food Chains | 食物链中的能量传递
In every ecosystem, energy flows from the Sun to producers (plants) and then to consumers. A key ecological principle governs the efficiency of this transfer.
在每一个生态系统中，能量从太阳流向生产者（植物），再流向消费者。一条关键的生态学原理支配着这种传递的效率。
Only about 10% of the energy at one trophic level is transferred to the next level. The remaining 90% is lost, mostly as heat through respiration, or used in movement and growth, or remains undigested.
每个营养级中只有大约 10% 的能量传递到下一级。其余 90% 的能量会散失，主要是通过呼吸作用以热的形式散失，或用于运动和生长，或作为未消化的部分保留下来。
This principle explains why food chains rarely have more than four or five trophic levels; there is simply not enough energy to support higher numbers of consumers.
这一原理解释了为什么食物链很少超过四到五个营养级：根本没有足够的能量来支撑更多的消费者。
11. Classification: The Five Kingdoms | 分类：五界系统
Biologists classify living organisms into five large groups, or kingdoms, based on fundamental features such as cell type and nutritional strategy.
生物学家根据细胞类型和营养方式等基本特征，将生物分为五大类群，即五界。
The five kingdoms are: Monera (bacteria, simple cells without a nucleus), Protista (single-celled eukaryotes like algae and protozoa), Fungi (moulds, mushrooms, yeast; they are saprotrophs), Plantae (multicellular plants that photosynthesise), and Animalia (multicellular animals that ingest food).
五界分别是：原核生物界（细菌，无细胞核的简单细胞）、原生生物界（单细胞真核生物，如藻类和原生动物）、真菌界（霉菌、蘑菇、酵母；它们是腐生生物）、植物界（进行光合作用的多细胞植物）和动物界（摄取食物的多细胞动物）。
Plants are autotrophs (make their own food), animals are heterotrophs (consume ready-made food), and fungi are saprotrophs (decompose dead organic matter externally).
植物是自养生物（自己制造食物），动物是异养生物（摄入现成的食物），真菌是腐生生物（在体外分解死亡有机质）。
12. Reproduction in Flowering Plants | 开花植物的生殖
Flowering plants reproduce sexually using structures within the flower. The male gamete is contained in pollen grains, while the female gamete is inside the ovule.
开花植物利用花内的结构进行有性生殖。雄配子包含在花粉粒中，雌配子则位于胚珠
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