📚 Experimental and Practical Assessment Essentials for Year 7 Cambridge Biology | Year 7 剑桥生物实验与实操考核要点
Practical work is at the heart of Year 7 Cambridge Biology. It is not just about following instructions — you are expected to develop the skills of a young scientist: asking questions, making careful observations, handling equipment safely and drawing conclusions from real data. This guide covers the essential experimental and practical assessment points you will encounter throughout the year. By mastering these, you will feel confident both in the laboratory and in any practical‑based test or checkpoint.
实验操作是 Year 7 剑桥生物课程的核心。这不仅要求你按步骤操作，更要像一位小科学家那样：提出问题、细心观察、安全使用器材并从真实数据中得出结论。本指南涵盖了你将在这一年中遇到的全部实验与实操考核要点。掌握这些技能，你在实验室和任何以实践为基础的测评中都将充满信心。
1. Scientific Enquiry Skills | 科学探究技能
Scientific enquiry is the process of investigating the natural world. In Year 7, you learn to ask testable questions, make predictions and decide what to change, what to measure and what to keep the same in an experiment.
科学探究是研究自然世界的过程。在 Year 7，你将学习提出可检验的问题、作出预测，并决定在实验中需要改变什么、测量什么以及保持什么不变。
The variable you deliberately change is called the independent variable. The variable you measure or observe is the dependent variable. All other factors that could affect the results must be kept constant — these are control variables. Thinking about variables helps you design a fair test.
你有意改变的那个变量称为自变量（独立变量）。你测量或观察的变量称为因变量（依赖变量）。所有其他可能影响结果的因素都必须保持不变——这些就是控制变量。思考变量能帮助你设计一个公平的测试。
A hypothesis is a clear statement that predicts how the independent variable will affect the dependent variable. For example: ‘If light intensity increases, then the rate of photosynthesis will increase, because more light energy is available.’ Always write your hypothesis before starting the practical work.
假设是一个清晰的陈述，用于预测自变量将如何影响因变量。例如：“如果光照强度增加，那么光合作用速率就会增加，因为可获得的光能更多了。” 务必在开始实验操作前写下你的假设。
2. Safety in the Biology Laboratory | 生物实验室安全须知
Safety is the number one priority in any practical lesson. You must know the hazard symbols on chemicals and biological materials, wear appropriate protective equipment and follow your teacher’s instructions at all times.
在任何实验课上，安全都是第一要务。你必须认识化学药品和生物材料上的危险标志，穿戴适当的防护装备，并始终听从老师的指导。
Common safety rules include: tie back long hair, tuck in loose clothing, never eat or drink in the lab, and wash your hands after handling living organisms or chemicals. If you break glassware, report it immediately and do not pick up pieces with bare hands.
常见的安全规则包括：扎好长发、将宽松的衣物塞好、绝不在实验室吃喝，以及在接触活体生物或化学药品后洗手。如果打碎了玻璃器皿，要立即报告，不要徒手捡碎片。
The table below shows some hazard symbols you may see in a biology laboratory and their meanings.
下表展示了你在生物实验室可能会见到的一些危险标志及其含义。
| Symbol | Meaning | 中文含义 |
|---|---|---|
| ⚠️ Exclamation mark | General warning / irritant | 一般警告 / 刺激物 |
| 🔥 Flame | Flammable | 易燃 |
| 💀 Skull and crossbones | Toxic / poisonous | 有毒 |
| ☣️ Biohazard | Biological risk | 生物危害 |
| 🧪 Corrosion | Corrosive | 腐蚀性 |
Always check the label on any bottle before using it. If you are unsure, ask your teacher. A safe scientist is a successful scientist.
在使用任何瓶子前，务必先检查标签。如果不确定，就去问老师。安全的科学家才是成功的科学家。
3. Using a Hand Lens and Microscope | 使用放大镜和显微镜
Many biological specimens are too small to see with the naked eye. A hand lens (magnifying glass) can help you observe details such as the veins on a leaf or the tiny hairs on a stem. Hold the lens close to your eye and bring the specimen towards you until it comes into sharp focus.
许多生物标本小到肉眼无法看清。放大镜可以帮助你观察诸如叶片上的叶脉或茎上的细小茸毛等细节。将放大镜贴近眼睛，再将标本靠近，直到影像变得清晰。
The compound light microscope is a more powerful tool. You must be able to name its main parts: eyepiece, objective lenses, stage, clips, coarse focus knob, fine focus knob, diaphragm and mirror or built‑in light source. Proper handling is essential — always carry a microscope with one hand under the base and the other holding the arm.
复式光学显微镜是更强大的工具。你必须能说出它的主要部件名称：目镜、物镜、载物台、压片夹、粗准焦螺旋、细准焦螺旋、光圈，以及反光镜或内置光源。正确取放至关重要——始终一手托住镜座，另一手握住镜臂来搬运显微镜。
When focusing, start with the lowest‑power objective lens. Use the coarse focus knob first to bring the stage close to the lens (watching from the side to avoid cracking the slide), then look through the eyepiece and turn the coarse knob to move the stage down until the image appears. Use the fine focus knob for a sharp picture. Never use the coarse focus knob with a high‑power objective lens.
调焦时，应从低倍物镜开始。先使用粗准焦螺旋，从侧面看着将载物台靠近镜头（避免压碎玻片），然后通过目镜观察，转动粗准焦螺旋使载物台向下移动，直到出现图像。最后用细准焦螺旋调出清晰画面。在高倍物镜下绝不要使用粗准焦螺旋。
Total magnification is calculated using this simple formula:
总放大倍数可通过以下简单公式计算：
Total Magnification = Eyepiece magnification × Objective lens magnification
总放大倍数 = 目镜放大倍数 × 物镜放大倍数
For example, a 10× eyepiece and a 40× objective give a total magnification of 400×.
例如，10倍目镜和40倍物镜给出的总放大倍数为400倍。
4. Preparing a Temporary Slide | 制作临时装片
Making a wet mount slide is a fundamental skill. You will often use onion epidermis, cheek cells or pond water. The key steps are: place a thin, transparent specimen flat on a clean glass slide, add a drop of water or stain, and lower a coverslip at an angle to avoid trapping air bubbles.
制作临时装片是一项基本技能。你常会用到洋葱表皮、口腔上皮细胞或池塘水。关键步骤是：将薄而透明的标本平放在洁净的载玻片上，滴一滴水或染色剂，然后倾斜着放下盖玻片，以避免产生气泡。
Stains such as iodine solution (for plant cells) or methylene blue (for animal cells) are used to make cell structures more visible. Always add the stain at the edge of the coverslip and let it diffuse across, or add it before placing the coverslip. Too much liquid can cause the coverslip to float and the specimen to move around.
为了更清晰地显示细胞结构，会使用染色剂，如碘液（用于植物细胞）或亚甲蓝（用于动物细胞）。染色时可以将染液滴在盖玻片边缘让其渗入，也可在放盖玻片前染色。液体过多会导致盖玻片漂浮，标本也会跟着移动。
If you see dark‑ringed circles under the microscope, those are air bubbles. To avoid them, touch the coverslip with a mounted needle and lower it gradually. A well‑prepared slide shows a single layer of cells, clearly stained and free from large bubbles.
如果在显微镜下看到带黑圈的圆形，那就是气泡。避免气泡的方法是用解剖针抵住盖玻片，再缓缓放下。一张制作良好的装片应显示单层细胞、染色清晰且没有大气泡。
5. Drawing Accurate Biological Diagrams | 绘制精确的生物图
Biological drawing is not art — it is a scientific record of what you see. Your diagram should be clear, drawn with a sharp pencil, and include only what you actually observe, not what you think should be there.
生物绘图不是艺术，而是对所见事物的科学记录。你的图应清晰、用削尖的铅笔绘制，并且只画你实际观察到的内容，而不是你认为该有的内容。
Rules for a good biological drawing: use plain white paper, draw a large diagram in the centre, make firm continuous lines without shading or colouring, label structures with straight ruled lines that point exactly to the part, and write labels in pencil horizontally. Always include a title that says what the specimen is and the magnification used.
优质生物图的绘制规则：使用白纸，在中央画大图，线条连续流畅、不打阴影不涂色，用直尺画出标线精确指向结构，标号一律用铅笔水平书写。同时必须写上标题，说明标本是什么以及所用放大倍数。
For example, when drawing a typical plant cell from an onion epidermis, you should show and label: cell wall, cell membrane, cytoplasm, nucleus and a large vacuole. Do not include chloroplasts unless you actually see them in the onion peel – onion epidermis cells lack chloroplasts.
例如，在绘制洋葱表皮典型植物细胞时，你应画出并标出：细胞壁、细胞膜、细胞质、细胞核以及大液泡。除非在洋葱表皮中确实看到叶绿体，否则不要画上——洋葱表皮细胞不含叶绿体。
6. Measuring and Observing Specimens | 测量与观察标本
Accurate measurement is crucial in biology experiments. You will use rulers, measuring cylinders, stopwatches, thermometers and digital balances. Always read the scale at eye level to avoid parallax error, and record the unit next to each measurement.
准确测量在生物实验中至关重要。你将用到直尺、量筒、秒表、温度计和电子天平。读数时视线要与刻度保持水平以避免视差，并在每个测量值旁记录单位。
When observing, use all your senses appropriately – look for colour changes, listen for sounds, smell cautiously if allowed, but never taste anything in the lab. Record observations in a table immediately, noting dates, times and any unexpected occurrences.
观察时要恰当地使用所有感官——留意颜色变化、倾听声音、在允许的情况下谨慎地闻气味，但绝对不要在实验室品尝任何东西。立即将观察结果记录在表格中，并注明日期、时间和任何意外情况。
Estimating size under a microscope can be practised using a clear ruler or a stage micrometer. If you know the field of view diameter, you can estimate how many cells fit across it and roughly calculate the size of one cell.
可使用透明直尺或镜台测微尺练习显微镜下估计大小。如果你知道视野直径，就能估算出横跨视野的细胞数目，从而粗略计算一个细胞的大小。
For example, if the low‑power field diameter is 4000 µm and you count 8 cells across, then the approximate cell length is 4000 ÷ 8 = 500 µm. Such calculations are often part of practical assessments.
例如，如果低倍视野直径为4000微米，而你数出横跨有8个细胞，那么细胞的近似长度就是 4000 ÷ 8 = 500 微米。这类计算经常是实操考评的一部分。
7. Planning a Fair Test Investigation | 设计公平测试调查
A fair test is one in which only the independent variable is changed, while all other variables are kept controlled. This ensures that any change in the dependent variable is truly caused by the independent variable. Designing a fair test is a key assessment skill.
公平测试是指只改变自变量，而保持其他所有变量不变。这样才能确保因变量的任何变化确实由自变量引起。设计公平测试是一项关键的考核技能。
Start by writing a plan that includes: the aim, the hypothesis, a list of apparatus, a detailed method, a risk assessment and a results table. The method should be written in numbered steps and use clear imperative language, e.g. ‘Place 5 seeds in each petri dish’ not ‘We will put seeds in dishes’.
先写一份计划，内容包括：目的、假设、器材清单、详细的实验步骤、风险评估和结果表格。实验步骤应用编号列出，并使用清晰的祈使句，如“每个培养皿中放入5粒种子”，而不是“我们会把种子放进培养皿”。
Controlling variables is often tested. For example, in an experiment on how temperature affects seed germination, you must keep the type of seed, amount of water, light intensity and oxygen availability the same. Only temperature should vary.
控制变量常常是考查点。例如，在研究温度如何影响种子萌发的实验中，你必须保持种子种类、水量、光照强度和氧气供应相同。只有温度是变化的。
Always include a range of values for the independent variable and, where possible, repeat each measurement three times to calculate a mean. This improves reliability and helps identify anomalous results.
自变量要设置一系列数值，并在可能的情况下，每个测量重复三次以计算平均值。这能提高可靠性，也有助于识别异常结果。
8. Recording Data and Presenting Results | 记录数据与展示结果
Data must be recorded in clear tables with headings that include the quantity and unit, e.g. ‘Temperature (°C)’ or ‘Number of bubbles per minute’. The independent variable goes in the first column, and the dependent variable (or repeated trials) in the following columns.
数据必须记录在清晰的表格中，表头应包含物理量和单位，例如“温度 (°C)”或“每分钟气泡数”。自变量放在第一列，因变量（或重复试验）放在后续各列。
When constructing a graph, use graph paper or software, label both axes with the variable and unit, and choose a sensible scale that makes the plotted points fill at least half of the grid. For a bar chart, the bars should be of equal width and separated; for a line graph, plot points carefully and draw a line of best fit.
绘制图表时，使用坐标纸或软件，为两轴标明变量和单位，并选择合适的刻度让所画点至少占据一半网格。柱状图的柱子应宽度相等且分开；折线图需仔细描点并画出最佳拟合线。
Do not connect the dots with a ruler from point to point unless instructed — a smooth curve or straight line that represents the trend is usually correct. Also, never colour in the plotted points or bars; keep the presentation neat and scientific.
除非特别要求，不要用直尺把点逐个连起来——通常应画一条代表趋势的光滑曲线或直线。而且，绝不要给描点或柱子涂色；保持展示整洁、科学。
When you have numerical data, calculate the mean by adding up all the values and dividing by the number of values. Ignore obvious outliers when explaining the trend, but mention them in your evaluation.
如果有数字数据，计算平均值的方法是把所有数值加起来再除以数值的个数。解释趋势时可忽略明显的异常值，但要在评价中提及它们。
9. Interpreting Observations and Drawing Conclusions | 分析观察结果并得出结论
Interpretation means explaining what your results show. Do they support your hypothesis? Describe the pattern, e.g. ‘As temperature increased, the number of bubbles produced each minute increased up to 35°C, then decreased’. Use data values to back up your statements.
分析结果意味着解释你的结果说明了什么。它们是否支持你的假设？描述出规律，例如“随着温度升高，每分钟产生的气泡数量不断增加，直到35°C后又开始减少”。要用数据来支持你的陈述。
A valid conclusion answers the aim and refers directly to the data gathered. It uses scientific knowledge to explain the findings. For example: ‘Photosynthesis rate increased with light intensity up to a point because light is a limiting factor; beyond that, another factor such as carbon dioxide became limiting.’
一个有效的结论能回答实验目的，并直接引用所收集的数据。它还会运用科学知识来解释发现。例如：“光合作用速率随着光照强度增加到一定程度而上升，因为光是限制因子；超过这一点，另一个因子如二氧化碳就成为限制因子。”
Always use scientific vocabulary correctly. In Year 7, you should be comfortable with terms like ‘cell respiration’, ‘photosynthesis’, ‘diffusion’, ‘enzyme’, ‘habitat’ and ‘biodiversity’ when they are relevant to the experiment.
始终正确地使用科学词汇。在 Year 7，你应能熟练使用与实验相关的术语，如“细胞呼吸”、“光合作用”、“扩散”、“酶”、“栖息地”和“生物多样性”。
If your results do not agree with the prediction, that is not a failure. Identify possible reasons and suggest how the experiment could be improved. A good scientist learns from unexpected outcomes.
如果你的结果与预测不符，那并不是失败。要找出可能的原因，并提出改进实验的建议。优秀的科学家会从意外的结果中学习。
10. Evaluating an Experiment | 实验评价
Evaluation is about looking back at the method and results to judge how trustworthy they are. You need to comment on accuracy, reliability and validity. Were the measurements precise? Were there enough repeats? Was it a fair test?
评价就是回顾实验方法和结果，判断它们的可信程度。你需要对准确性、可靠性和有效性作出评论。测量是否精确？重复次数是否足够？这算不算一个公平测试？
Suggest specific improvements, not just ‘do it more carefully’. For example: ‘Use a water bath to control temperature more accurately instead of a beaker of hot water that cools down’, or ‘Use a data logger with a light sensor instead of counting bubbles by eye, to reduce human error’.
提出具体的改进建议，而不是仅仅说“更小心地操作”。例如：“使用水浴锅更精确地控制温度，而不是用一烧杯会变凉的热水”，或“使用带光传感器的数据记录器代替肉眼数气泡，以减少人为误差”。
Also consider the source of biological material. Living organisms show variation; using a larger sample size or clones would make the results more reliable. Mention any safety issues that could be better managed in a repeat investigation.
还要考虑生物材料的来源。活体生物存在变异；使用更大的样本量或克隆体可以使结果更可靠。同时，要指出在重复实验中哪些安全问题可以更好地管理。
Finally, link your evaluation back to the original hypothesis and the real‑world application. This shows deeper understanding and is often rewarded in Cambridge practical assessments.
最后，将你的评价与最初的假设和现实应用联系起来。这能体现出更深刻的理解，在剑桥实操评估中通常能得到加分。
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