Biology: 1.1 Practical Skills Written Assessment – Experimental Design | 生物：1.1 实验技能书面评估——实验设计

📚 Biology: 1.1 Practical Skills Written Assessment – Experimental Design | 生物：1.1 实验技能书面评估——实验设计

Practical skills are central to biology, and written examination papers frequently assess your understanding of experimental design, data handling, and evaluation. Whether you are tackling a dedicated practical paper or integrated questions, a structured approach is vital. This article provides a comprehensive revision guide to help you think like a scientist and maximise your marks.

实验技能是生物学的核心，笔试常考查你对实验设计、数据处理和评价的理解。无论是专门的实验卷还是融合在其他题目中的考点，系统化的思维方式都至关重要。本文将为你提供一份全面的复习指南，帮助建立科学思维，争取高分。

1. Identifying Variables | 识别变量

Every experiment begins with variables. The independent variable (IV) is the factor you deliberately change. The dependent variable (DV) is what you measure. Control variables are all other factors that must be kept constant to ensure a fair test. In written assessments, you may be asked to identify these from a scenario or to suggest suitable ones.

每个实验都从变量开始。自变量是你有意改变的因素。因变量是你测量的结果。控制变量是所有其他必须保持不变的因素，以确保公平测试。在书面评估中，你可能会被要求从情景中识别它们，或给出合适的变量。

For example, an investigation into the effect of temperature on enzyme activity: IV = temperature, DV = rate of reaction (measured by product formation per unit time), controls = pH, enzyme concentration, substrate concentration, and incubation time.

例如，研究温度对酶活性影响的实验：自变量=温度，因变量=反应速率（单位时间内产物的生成量），控制变量=pH、酶浓度、底物浓度、孵育时间。

Tip: Use the phrase ‘to investigate the effect of… on…’ to frame your variables. State clearly: ‘The independent variable is…’, ‘The dependent variable is…’, and list at least three controls with practical methods of keeping them constant.

提示：用”探究……对……的影响”来组织变量。清晰地写出：”自变量是……”，”因变量是……”，并列出至少三个控制变量以及如何保持不变的具体方法。

2. Formulating Testable Hypotheses | 提出可检验的假设

A hypothesis is a clear, predictive statement linking the independent and dependent variables. It often includes a direction and a scientific rationale. Avoid vague wording such as ‘I think the enzyme will work better.’ Instead, write: ‘As temperature increases from 10°C to 40°C, the rate of reaction will increase because enzyme molecules have more kinetic energy, leading to more frequent successful collisions. Beyond the optimum temperature, the rate will decline due to denaturation.’

假设是一个清晰、可预测的陈述，将自变量与因变量联系起来。它通常包含方向性和科学依据。避免模糊的表述，如”我认为酶会工作得更好”。应该写：”当温度从10°C升高到40°C时，反应速率将加快，因为酶分子获得更多动能，导致更多有效碰撞。超过最适温度后，速率将由于变性而下降。”

The hypothesis must be testable with the apparatus available. In the exam, you may need to formulate a null hypothesis for statistical testing, e.g., ‘There is no significant difference between the rate of reaction at 20°C and 30°C.’

假设必须能用现有仪器检验。考试中，你可能需要为统计检验提出零假设，如”20°C和30°C下的反应速率之间没有显著差异”。

Always link the hypothesis to biological principles: kinetic theory, lock-and-key model, diffusion gradients, etc.

务必将假设与生物学原理联系起来：动理论、锁钥模型、扩散梯度等。

3. Controlling Variables and Reliability | 控制变量与实验的可靠性

To ensure results are reliable, you must control extraneous variables meticulously. Describe exactly how each control variable will be maintained. Example: for pH, ‘use a buffer solution of pH 7.0 and measure with a pH meter before and after the experiment.’ For temperature (when not the IV), ‘place test tubes in a thermostatically controlled water bath at 25°C and allow 10 minutes for equilibration.’

为保证结果可靠，必须严格地控制额外变量。准确描述如何维持每一个控制变量。例如：对于pH，”使用pH 7.0的缓冲液，并在实验前后用pH计测量”。对于温度（当不是自变量时），”将试管放入25°C恒温水浴中，并留出10分钟平衡时间”。

Reliability is increased by repeating measurements and calculating a mean. State ‘repeat the experiment three times at each temperature and calculate the mean rate’. Replicates also allow you to identify anomalies.

通过重复测量并计算平均值来提高可靠性。说明”在每个温度下重复实验三次，并计算平均速率”。重复还可以帮助识别异常值。

Define reliability: results are reliable if similar values are obtained when the experiment is repeated under the same conditions. Contrast with validity: an experiment is valid if it measures what it intends to measure (all controls properly managed).

定义可靠性：如果在相同条件下重复实验能得到相近的值，则结果可靠。与有效性对比：实验如果测量的是其计划测量的内容（所有控制变量得到恰当管理），则有效。

4. Choosing Appropriate Apparatus and Measurements | 选择适宜的仪器与测量

Marks are awarded for selecting apparatus that gives an appropriate level of precision. For measuring volumes, choose a graduated pipette or syringe rather than a beaker. For temperature, use a digital thermometer reading to 0.1°C. Explain the resolution of each instrument. For a colorimetric assay, a colorimeter provides quantitative data instead of subjective colour charts.

选择能提供适当精确度的仪器可获得分数。测量体积时，选择刻度移液管或注射器而不是烧杯。温度测量使用可读至0.1°C的数字温度计。解释每台仪器的分辨率。对于比色测定，比色计可提供定量数据，而非主观的比色卡。

Also consider the range and intervals. When investigating light intensity on photosynthesis, use distances from a lamp at 10 cm, 20 cm, 30 cm, 40 cm, and 50 cm. The range should be wide enough to show a trend, and intervals should be manageable. Mention ‘at least five intervals’ and justify them.

同时考虑范围和间隔。研究光强对光合作用的影响时，使用灯距10cm、20cm、30cm、40cm、50cm。范围需足够宽以显示趋势，间隔应合理。提到”至少五个间隔”并给出理由。

Include details: ‘place the chloroplast suspension in a spectrophotometer cuvette’, ‘zero the balance before each measurement’, ‘use a stopwatch recording to ±0.01 s’. Such precision shows good practical understanding.

添加细节：”将叶绿体悬浮液放入分光光度计比色皿中”，”每次测量前将天平归零”，”使用可记录±0.01秒的秒表”。这样的精度展示出对实验操作的充分理解。

5. Risk Assessment and Ethical Considerations | 风险评估与伦理考量

All practical write-ups should include a brief risk assessment. Identify specific hazards: ‘hot water above 50°C can cause scalding; use a water bath with a lid and handle with tongs’, ‘enzymes may cause allergic reactions; wear gloves and goggles’. Link the risk to the hazard and state a control measure.

所有实验报告都应包括简短的风险评估。识别具体危害：”50°C以上的热水可能导致烫伤；使用带盖水浴并用钳子操作”，”酶可能引起过敏

Published by TutorHao | Biology Revision Series | aleveler.com

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