📚 Year 10 Cambridge Biology: Formula & Principle Quick Reference Handbook | Year 10 Cambridge 生物：公式定理速查手册
Welcome to this essential quick-reference handbook for Year 10 Cambridge IGCSE Biology. Mastering key formulas and fundamental principles is crucial for success in the examination. This guide consolidates the most important equations, ratios, and laws you’ll encounter, from magnification and respiration to genetics and ecology. Each section presents the core formula or principle, followed by clear explanations to help you apply them correctly.
欢迎使用这本 Year 10 Cambridge IGCSE 生物必备公式定理速查手册。熟练掌握关键公式和基本原理是考试取得好成绩的关键。本指南汇集了从放大率、呼吸作用到遗传学和生态学中最关键的方程、比例和定律。每个部分都呈现核心公式或原理，并提供清晰的解释，帮助你正确应用它们。
1. Magnification Formula | 放大率公式
The magnification of a biological drawing or micrograph is calculated using the following equation. It is essential to ensure that both the image size and the actual size are in the same unit.
生物绘图或显微照片的放大率使用以下公式计算。必须确保图像大小和实际大小的单位一致。
Magnification = Image size ÷ Actual size
放大率 = 图像大小 ÷ 实际大小
es are measured in millimetres (mm) while actual specimen sizes are given in micrometres (µm). To convert, remember that 1 mm = 1000 µ to find the actual size, rearrange the formula: Actual size = Image size ÷ Magnification.
通常，图像大小以毫米（mm）为单位测量，而标本实际大小以微米（µm）给出。换算时请记住 1 mm = 1000 µm。如需计算实际大小，请变换公式：实际大小 = 图像大小 ÷ 放大率。
2. Photosynthesis Equation | 光合作用方程
Photosynthesis is the process by which green plants convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water. The balanced symbol equation is shown below. Chlorophyll and light energy are essential for this reaction.
光合作用是绿色植物将光能转化为化学能的过程，利用二氧化碳和水生成葡萄糖和氧气。平衡化学方程式如下所示。该反应必须依赖叶绿素和光能。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
as: carbon dioxide + water → glucose + oxygen (in the presence of light and chlorophyll).
文字方程式总结为：二氧化碳 + 水 → 葡萄糖 + 氧气（需要光能和叶绿素）。
3. Aerobic Respiration Equation | 有氧呼吸方程
Aerobic respiration releases energy from glucose using oxygen. It occurs in the mitochondria and produces a large yield of ATP. The overall balanced equation mirrors photosynthesis in reverse.
有氧呼吸利用氧气从葡萄糖中释放能量。该过程发生在线粒体中，产生大量的ATP。总平衡方程式可以说是光合作用的逆反应。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 能量（ATP）
4. Anaerobic Respiration Equations | 无氧呼吸方程
When oxygen is scarce, cells can respire anaerobically. In yeast and some plants, glucose is converted into ethanol and carbon dioxide. In animal muscles, it is converted into lactic acid. Both pathways release a small amount of energy.
当氧气不足时，细胞可进行无氧呼吸。在酵母和一些植物中，葡萄糖转化为乙醇和二氧化碳。在动物肌肉中，葡萄糖转化为乳酸。两者都只能释放少量能量。
Yeast: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (+ energy)
酵母：C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂（+能量）
Muscle: C₆H₁₂O₆ → 2C₃H₆O₃ (+ energy)
肌肉：C₆H₁₂O₆ → 2C₃H₆O₃（+能量）
Anaerobic respiration in muscles leads to an oxygen debt, which must be repaid by continued deep breathing to oxidise lactic acid.
肌肉无氧呼吸会导致氧债，需要通过持续深呼吸将乳酸氧化来偿还。
5. Surface Area to Volume Ratio (SA:V) | 表面积与体积比
The surface area to volume ratio is calculated by dividing the total surface area by the volume. As an organism grows larger, its volume increases much faster than its surface area, so the SA:V ratio decreases. This limits the rate of diffusion for substances like oxygen and nutrients.
表面积与体积比通过总表面积除以体积来计算。随着生物体长大，其体积增长远快于表面积，因此SA:V比率下降。这限制了氧气和营养物质等物质的扩散速率。
SA:V ratio = Surface area ÷ Volume
SA:V 比率 = 表面积 ÷ 体积
Small organisms such as amoeba have a large SA:V and can exchange materials directly through their surface. Large organisms require specialised exchange surfaces (e.g., lungs, gills) and a transport system (e.g., circulatory system).
像变形虫这样的小型生物拥有较大的SA:V，可以直接通过体表交换物质。大型生物则需要特化的交换面（如肺、鳃）和运输系统（如循环系统）。
6. Osmosis and Water Potential | 渗透与水势
Osmosis is the net movement of water through a partially permeable membrane from a region of higher water potential to a region of lower water potential. Water potential (Ψ) is measured in kilopascals (kPa) and determines the direction of water movement.
渗透是水通过半透膜从水势较高区域向水势较低区域的净移动。水势（Ψ）以千帕（kPa）为单位，决定了水分运动的方向。
Ψ = Ψs + Ψp
Ψ = Ψs + Ψp
Pure water at standard pressure has a water potential of zero. Adding solutes lowers the solute potential (Ψs) making it negative, while pressure potential (Ψp) can be positive or zero. Water always moves towards the more negative water potential.
标准压力下纯水的水势为零。加入溶质会降低溶质势（Ψs）使其变为负值，而压力势（Ψp）可为正值或零。水分总是向更负的水势方向移动。
7. Monohybrid Cross Ratios | 单基因杂交比率
In a monohybrid cross
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