📚 Year 8 CIE Biology: Formula & Theorem Quick Reference Handbook | Year 8 CIE 生物：公式定理速查手册
This quick-reference guide brings together the essential equations, formulas and key principles you will encounter in the Year 8 CIE Biology course. Keep it handy when revising topics such as photosynthesis, respiration, microscopy, ecology and human nutrition. Each entry is laid out with a clear statement or equation, followed by a worked-style explanation so you can check your understanding instantly.
这份速查手册汇集了你在 Year 8 CIE 生物课程中会遇到的核心方程式、公式和关键原理。复习光合作用、呼吸作用、显微镜使用、生态学以及人体营养等主题时，可以随时翻阅。每一条都先给出清晰的表述或方程式，再配上解释，让你能够立即检查自己的理解。
1. Photosynthesis Word Equation | 光合作用文字方程式
Photosynthesis is the process by which green plants make their own food using light energy. The overall word equation is fundamental.
光合作用是绿色植物利用光能制造自身食物的过程。总体文字方程式是基础。
carbon dioxide + water → glucose + oxygen
二氧化碳 + 水 → 葡萄糖 + 氧气
This reaction takes place in chloroplasts and requires chlorophyll and light energy. It is often written with the conditions above the arrow.
该反应发生在叶绿体中，需要叶绿素和光能。通常会把条件写在箭头上下。
If you prefer the balanced chemical equation, it can be written as:
如果你偏好平衡的化学方程式，可以写成：
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Remember that the glucose produced may be used immediately for respiration or converted into starch for storage.
记住，产生的葡萄糖可能立即用于呼吸作用，也可以转化成淀粉储存起来。
2. Aerobic Respiration Equation | 有氧呼吸方程式
Aerobic respiration releases energy from glucose in the presence of oxygen. The word equation describes the overall chemical change taking place in mitochondria.
有氧呼吸是在有氧条件下从葡萄糖中释放能量的过程。文字方程式描述了线粒体中发生的总体化学变化。
glucose + oxygen → carbon dioxide + water (+ energy)
葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）
Energy is released as ATP, which cells use for activities such as muscle contraction, active transport and keeping warm. The balanced chemical equation is exactly the reverse of photosynthesis.
能量以 ATP 形式释放，细胞将其用于肌肉收缩、主动运输和保温等活动。平衡的化学方程式正好是光合作用的逆反应。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ energy)
Make sure you learn both the word and chemical versions, as CIE questions often ask for one or the other.
务必同时学会文字版和化学版，因为 CIE 考试常会要求写出其中一种。
3. Anaerobic Respiration Equations | 无氧呼吸方程式
When oxygen is limited or absent, cells can respire anaerobically. The products differ between animals and yeast.
当氧气不足或缺氧时，细胞可以进行无氧呼吸。动物和酵母的产物有所不同。
In animals (muscle cells): glucose → lactic acid (+ energy)
在动物（肌细胞）中：葡萄糖 → 乳酸（+ 能量）
In yeast and some plants: glucose → ethanol + carbon dioxide (+ energy)
在酵母和某些植物中：葡萄糖 → 乙醇 + 二氧化碳（+ 能量）
Anaerobic respiration releases much less energy per glucose molecule than aerobic respiration. The accumulation of lactic acid causes muscle fatigue and cramps.
与有氧呼吸相比，无氧呼吸每分子葡萄糖释放的能量要少得多。乳酸的堆积会引起肌肉疲劳和抽筋。
The yeast equation is also important in baking and brewing, where carbon dioxide makes dough rise and ethanol is the alcohol in drinks.
酵母的无氧呼吸方程式在烘焙和酿造中也很重要，二氧化碳使面团膨胀，乙醇就是饮料中的酒精。
4. Microscope Magnification Formula | 显微镜放大倍数公式
When using a light microscope, the total magnification is not read directly off the instrument but must be calculated.
使用光学显微镜时，总放大倍数并不是直接从仪器上读出的，而是需要计算得出。
total magnification = eyepiece lens magnification × objective lens magnification
总放大倍数 = 目镜放大倍数 × 物镜放大倍数
eyepiece is ×10 and the objective lens is ×40, the total magnification is 10 × 40 = ×400.
例如，若目镜为 ×10，物镜为 ×40，则总放大倍数为 10 × 40 = ×400。
Knowing this formula also helps you convert between image size and actual size when you are given the magnification.
掌握这个公式也有助于在已知放大倍数时，在图像大小与实际大小之间进行换算。
5. Energy Transfer and the 10% Rule | 能量传递与“十分之一定律”
Energy flows through food chains, but only a small proportion is passed from one trophic level to the next. The rough guide is often called the 10% rule.
能量通过食物链流动，但只有一小部分从一个营养级传递到下一个营养级。这个粗略的规律常被称为“十分之一定律”。
energy available at next trophic level ≈ 10% of energy at current trophic level
下一营养级可利用的能量 ≈ 当前营养级能量的 10%
The rest of the energy is lost through movement, respiration, heat and uneaten parts. You can use this rule to draw pyramids of energy or to explain why food chains rarely have more than five trophic levels.
其余能量通过运动、呼吸、散热和未被取食的部分而散失。你可以运用这一定律绘制能量金字塔，或者解释为什么食物链很少超过五个营养级。
ciency is similar: percentage efficiency = (biomass transferred ÷ biomass available) × 100%.
生物量的传递效率也类似：效率百分比 =（传递的生物量 ÷ 可用的生物量）× 100%。
6. Estimating Population Size Using Quadrats | 利用样方估算种群大小
Ecologists often use quadrats to sample slow-moving or stationary organisms. The population size can be estimated using a simple formula.
生态学家常用样方对移动缓慢或固着生活的生物进行取样。种群大小可以用一个简单的公式来估算。
estimated population size = (mean number per quadrat × total area) ÷ area of one quadrat
估算的种群大小 =（每个样方的平均数 × 总面积）÷ 单个样方面积
ount per quadrat is 12, then the estimated total daisy population = (12 × 200) ÷ 1 = 2400.
计算示例：若用 1 平方米的样方在 200 平方米的草坪上取样，每个样方平均有 12 朵雏菊，则估算的雏菊总数量 =（12 × 200）÷ 1 = 2400。
Random placement of quadrats and a large sample size improve the accuracy of this estimation.
样方的随机放置和较大的样本量可以提高这一估算的准确性。
7. Rate of Enzyme-Catalysed Reactions | 酶促反应速率
The speed at which an enzyme works can be measured by how quickly a substrate disappears or a product appears. A useful formula is:
酶作用的速度可以通过底物消失或产物出现的快慢来衡量。一个实用的公式是：
rate of reaction = 1 ÷ time taken (or amount changed ÷ time)
反应速率 = 1 ÷ 所用时间（或变化量 ÷ 时间）
For instance, if you time how long it takes for starch to disappear using amylase and iodine solution, a shorter time indicates a faster rate. The rate is then calculated as 1/time.
例如，如果测定使用淀粉酶和碘液时淀粉消失所需的时间，时间越短表示速率越快。此时速率可按 1/时间 计算。
Factors such as temperature and pH affect this rate, and you may be asked to interpret graphs of 1/time against these variables.
温度和 pH 等因素会影响这一速率，你可能需要解读 1/时间 对这些变量的作图。
8. Key Digestion Equations (Enzyme Actions) | 关键消化反应方程式（酶的作用）
Digestion breaks large insoluble molecules into small soluble ones using specific enzymes. Learning the word equations for the main substrates is very helpful.
消化利用特定的酶将大分子不溶性物质分解为小分子可溶性物质。记住主要底物的文字方程式非常有帮助。
Starch → maltose (by amylase)
淀粉 → 麦芽糖（由淀粉酶催化）
Proteins → amino acids (by protease)
蛋白质 → 氨基酸（由蛋白酶催化）
Lipids (fats) → glycerol + fatty acids (by lipase)
脂质（脂肪）→ 甘油 + 脂肪酸（由脂肪酶催化）
These reactions occur in different parts of the digestive system: amylase works in the mouth and small intestine, protease in the stomach and small intestine, and lipase mainly in the small intestine.
这些反应发生在消化系统的不同部位：淀粉酶在口腔和小肠起作用，蛋白酶在胃和小肠起作用，脂肪酶主要在小肠起作用。
Knowing the substrate and product for each enzyme allows you to predict the effect of enzyme deficiencies or to interpret food tests.
了解每种酶的底物和产物，可以让你预测酶缺乏的影响，或解释食物检测的结果。
9. Body Mass Index (BMI) | 身体质量指数（BMI）
BMI is a simple formula used to assess whether a person has a healthy body weight for their height. It links nutrition and health in the CIE Year 8 course.
BMI 是一个简单的公式，用于评估一个人的体重相对于身高是否健康。它将营养与健康联系起来，出现在 CIE Year 8 课程中。
BMI = body mass (kg) ÷ [height (m)]²
BMI = 体重（kg）÷ 身高（m）的平方
s a BMI = 45 ÷ (1.50)² = 45 ÷ 2.25 = 20 kg/m². This falls within the normal healthy range.
例如，一名学生体重 45 kg，身高 1.50 m，其 BMI = 45 ÷ (1.50)² = 45 ÷ 2.25 = 20 kg/m²。这属于正常健康范围。
General guidelines: underweight <18.5, healthy weight 18.5–24.9, overweight 25– bese ≥30. Note that very muscular individuals may have a high BMI without excess body fat.
大致参考标准：偏瘦 <18.5，健康体重 18.5–24.9，超重 25–29.9，肥胖 ≥30。注意，肌肉非常发达的人可能 BMI 偏高但并没有多余的体脂。
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