📚 Year 7 OCR Biology: Formula & Theorem Quick Reference Handbook | Year 7 OCR 生物：公式定理速查手册
This handbook collects the essential formulas, key equations, and fundamental theorems you will encounter in Year 7 OCR Biology. Understanding these will help you calculate magnification, work out rates of biological processes, and master core concepts like cell theory and energy transfer. Use this as a quick revision guide before tests and exams.
本手册汇集了 Year 7 OCR 生物课程中会遇到的必备公式、关键方程和基本定理。掌握这些内容将帮助你计算放大倍率、求出生物过程的速率，并掌握细胞学说和能量传递等核心概念。在测验和考试前，可将其用作快速复习指南。
1. Magnification Formula | 放大倍率公式
Magnification tells you how many times larger an image is compared to the real object. The formula is:
放大倍率告诉你图像比实际物体大多少倍。公式为：
Magnification = Image size ÷ Actual size
You can rearrange this to find image size or actual size using the triangle method: cover the quantity you want, and the remaining two show the calculation.
你可以通过三角法重新排列，求解图像大小或实际大小：遮住你想求的量，剩下的两个就显示了计算方法。
- Image size = Magnification × Actual size
- Actual size = Image size ÷ Magnification
- 图像大小 = 放大倍率 × 实际大小
- 实际大小 = 图像大小 ÷ 放大倍率
l diagram is 50 mm long and the real cell is 0.1 mm, the magnification is 50 ÷ 0.1 = 500×.
始终使用相同单位（例如毫米或微米）。如果细胞示意图长 50 mm，而真实细胞长 0.1 mm，则放大倍率为 50 ÷ 0.1 = 500 倍。
2. Total Magnification of a Microscope | 显微镜总放大倍率
When using a compound light microscope, the total magnification is the product of the eyepiece lens magnification and the objective lens magnification.
使用复合光学显微镜时，总放大倍率是目镜放大倍率与物镜放大倍率的乘积。
Total magnification = Eyepiece magnification × Objective magnification
le, if the eyepiece is 10× and the objective is 40×, total magnification = 10 × 40 = 400×.
例如，如果目镜为 10×，物镜为 40×，则总放大倍率 = 10 × 40 = 400×。
3. Rate of a Biological Process | 生物过程速率
Rate describes how quickly something happens. It is often measured as the change in a quantity divided by the time taken.
速率描述某事发生的快慢。通常用量的变化除以所用时间来表示。
Rate = Change in quantity ÷ Time
Common examples: heart rate (beats per minute), breathing rate (breaths per minute), reaction rate (e.g., volume of gas produced per minute).
常见例子：心率（次/分钟）、呼吸频率（次/分钟）、反应速率（例如每分钟产生的气体体积）。
If a plant produces 12 cm³ of oxygen in 60 seconds, the rate = 12 ÷ 60 = 0.2 cm³/s.
如果一株植物在 60 秒内产生 12 cm³ 氧气，则速率 = 12 ÷ 60 = 0.2 cm³/s。
4. Calculating the Mean | 计算平均值
The mean (average) is used to increase reliability. Add all the values and divide by the number of values.
平均值用于提高可靠性。将所有数值相加，再除以数值的个数。
Mean = Sum of values ÷ Number of values
lse rate readings: 72, 68, 74, 71, 70 bpm. Mean = (72+68+74+71+70) ÷ 5 = 355 ÷ 5 = 71 bpm.
例子：五次脉搏读数：72、68、74、71、70 次/分钟。平均值 = (72+68+74+71+70) ÷ 5 = 355 ÷ 5 = 71 次/分钟。
5. Percentage Change | 百分比变化
Percentage change is useful when comparing start and end values, for example in osmosis experiments with potato strips.
百分比变化在比较起始值和最终值时很有用，例如在土豆条渗透实验中。
Percentage change = (Final value − Start value) ÷ Start value × 100%
A positive value means an increase; a negative value means a decrease. If a potato strip's mass changes from 5.0 g to 5.4 g, the percentage change is (5.4 − 5.0) ÷ 5.0 × 100% = 8.0% increase.
正值表示增加；负值表示减少。如果土豆条的质量从 5.0 g 变化到 5.4 g，百分比变化为 (5.4 − 5.0) ÷ 5.0 × 100% = 增加 8.0%。
6. Surface Area to Volume Ratio | 表面积与体积之比
Small organisms have a large surface area compared to their volume, which helps efficient exchange of substances without a complex transport system.
小型生物的表面积相对于体积较大，这有助于在没有复杂运输系统的情况下高效交换物质。
Surface area : Volume ratio
rface area = 54 cm², volume = 27 cm³, ratio = 2:1. As size increases, the ratio decreases.
对于边长为 1 cm 的立方体：表面积 = 6 cm²，体积 = 1 cm³，比值 = 6:1。对于边长为 3 cm 的立方体：表面积 = 54 cm²，体积 = 27 cm³，比值 = 2:1。随着尺寸增大，比值减小。
7. Cell Theory | 细胞学说定理
Cell theory is a fundamental concept in biology. It states:
细胞学说是生物学的基本概念。它指出：
- All living organisms are composed of one or more cells.
- The cell is the basic unit of structure and function in living things.
- All cells arise from pre-existing cells by cell division.
- 所有生物体都由一个或多个细胞组成。
- 细胞是生物体结构和功能的基本单位。
- 所有细胞都来自已存在的细胞，通过细胞分裂产生。
This theorem unifies our understanding of life at the microscopic level.
这个定理统一了我们在微观层面对生命的理解。
8. MRS GREN – Life Processes | MRS GREN – 生命过程
Living organisms carry out seven life processes, remembered by the acronym MRS GREN:
生物体执行七种生命过程，可用缩写 MRS GREN 记忆：
| Letter | Process | 中文过程 |
|---|---|---|
| M | Movement | 运动 |
| R | Respiration | 呼吸作用 |
| S | Sensitivity | 感应 |
| G | Growth | 生长 |
| R | Reproduction | 繁殖 |
| E | Excretion | 排泄 |
| N | Nutrition | 营养 |
These processes define life and are used to distinguish living from non-living things.
这些过程定义了生命，并用于区分生物与非生物。
9. Photosynthesis Word Equation | 光合作用文字方程
Photosynthesis is the process by which green plants make glucose using light energy.
光合作用是绿色植物利用光能制造葡萄糖的过程。
Carbon dioxide + Water → Glucose + Oxygen
Light energy is absorbed by chlorophyll in chloroplasts. This formula shows the reactants (left) and products (right).
光能被叶绿体中的叶绿素吸收。此式显示反应物（左侧）和产物（右侧）。
10. Aerobic Respiration Word Equation | 有氧呼吸文字方程
Aerobic respiration releases energy from glucose using oxygen. It occurs continuously in most living cells.
有氧呼吸利用氧气从葡萄糖中释放能量。它在大多数活细胞中持续进行。
Glucose + Oxygen → Carbon dioxide + Water (+ energy)
The energy is used for processes such as muscle contraction, cell division, and maintaining body temperature in mammals.
能量用于肌肉收缩、细胞分裂以及哺乳动物维持体温等过程。
11. Energy Transfer in Food Chains | 食物链中的能量传递
In an ecosystem, energy is passed along food chains. Only about 10% of the energy at one trophic level is transferred to the next level.
在生态系统中，能量沿食物链传递。大约只有 10% 的能量从一个营养级传递至下一个营养级。
The remaining 90% is lost as heat from respiration, uneaten parts, and waste. This 10% rule explains why food chains rarely have more than four or five trophic levels.
剩下的 90% 以呼吸散热、未被取食的部分和排泄物的形式损失。这个 10% 定律解释了为什么食物链很少超过四到五个营养级。
12. Classification Hierarchy | 分类层级定理
Living things are organised into groups based on shared features. The main taxonomic ranks, from largest to smallest, are:
生物根据共同特征被归入不同类群。主要分类等级从大到小为：
Kingdom → Phylum → Class → Order → Family → Genus → Species
This hierarchical system helps scientists identify and study biodiversity. The binomial naming system uses Genus and Species, e.g., Homo sapiens.
这个层级系统帮助科学家识别和研究生物多样性。双名命名法使用属名和种名，例如 Homo sapiens。
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