📚 IB CCEA Biology: A Guide to Experimental Techniques | IB CCEA 生物：实验操作指南
Practical work forms the backbone of both IB and CCEA Biology courses, allowing you to develop the investigative skills essential for success in internal assessments and written examinations. From mastering the microscope to designing a controlled enzyme assay, this guide walks you through the core experimental techniques, data handling methods, and evaluative practices required. Building confidence in the lab is not only about following a protocol—it is about understanding why each step matters and how to adapt when things do not go as planned.
实验操作是 IB 和 CCEA 生物课程的支柱，帮助你培养内部评估和笔试所必需的探究能力。从熟练掌握显微镜到设计一个对照严谨的酶活性测定，本指南将带你走过核心实验技术、数据处理方法和评估实践。在实验室中建立自信不仅仅是按步骤操作——更是理解每一步为何重要，以及在实验不如预期时如何灵活调整。
1. Microscopy and Biological Drawing | 显微镜使用与生物绘图
Begin by carrying the microscope with two hands, one supporting the base and the other holding the arm. Place it on a stable bench, plug it in, and switch on the light source. Rotate the nosepiece to the lowest power objective lens (usually ×4 or ×10) and raise the stage using the coarse adjustment knob until the objective is just above the slide. While looking through the eyepiece, use the coarse knob to lower the stage slowly until the specimen comes into focus. Fine-tune with the fine adjustment knob and adjust the condenser and iris diaphragm to optimise contrast.
首先用双手搬运显微镜，一只手托住底座，另一只手握住镜臂。将其放置在平稳的台面上，插上电源并打开光源。转动物镜转换器至最低倍物镜（通常为 ×4 或 ×10），使用粗调焦旋钮升高载物台，直至物镜刚好位于载玻片上方。通过目镜观察，慢慢使用粗调降下载物台，直到标本清晰。用细调焦旋钮微调，并调节聚光器和虹彩光圈以获得最佳对比度。
A high-quality biological drawing should be in sharp pencil, with smooth continuous lines and no shading. Label structures using straight ruled lines that do not cross, and write the label in pencil horizontally. Include a title (e.g., ‘Transverse section of a buttercup root’) and state the magnification. For low‑power plans, draw only the outlines of tissues; for high‑power detail, include representative cells with clear cell walls, nuclei, and any visible organelles.
高质量的生物绘图应使用尖细的铅笔，线条流畅连续，不加阴影。用直尺画线标注结构，线条不能交叉，并用铅笔水平书写标注文字。图中要包含标题（例如“毛茛根横切面”），并注明放大倍数。低倍镜下的平面图只需画出组织轮廓；高倍镜下的细节图则要画出有代表性的细胞，清晰地标明细胞壁、细胞核以及可见的细胞器。
When measuring or drawing, always note the scale. For example, if a chloroplast measures 5 μm under a ×400 magnification, the actual size is 5 μm, which you can calculate by dividing the measured size by magnification if necessary. Use a graticule calibrated with a stage micrometer for precise measurements.
测量或绘图时，务必注明比例尺。比如，一个叶绿体在 ×400 放大下测量为 5 μm，实际大小就是 5 μm；必要时可通过将测量尺寸除以放大倍数来求得实际大小。使用目镜测微尺配合镜台测微尺校准，可以进行精确测量。
2. Preparing Temporary Mounts | 临时装片的制作
A wet mount is the simplest way to view living specimens. Place a small drop of water or stain in the centre of a clean glass slide. Using forceps or a mounted needle, gently place the specimen—such as an onion epidermal peel or a strand of pondweed—into the drop. Hold a coverslip at a 45° angle near the drop, and lower it slowly with a needle to push out air bubbles. Blot excess liquid with filter paper.
湿装片是观察活体标本的最简单方法。在洁净载玻片中央滴一小滴水或染液。用镊子或解剖针轻轻将标本——如洋葱内表皮或水绵——放入液滴中。将盖玻片以 45° 角靠近液滴，用解剖针缓缓放下，以驱赶气泡。用滤纸吸去多余液体。
For thicker specimens like a thin section of plant stem, a squash mount may be needed. Place the tissue on a slide, add a drop of stain, and tease it apart with needles. Then lower a coverslip and press gently but firmly with the flat handle of a mounting needle to spread the cells into a monolayer, taking care not to crack the glass.
对于较厚的标本，如植物茎的薄切片，可能需要挤压装片法。将组织放在载玻片上，加一滴染液，用针将其撕散开。然后盖上盖玻片，用解剖针的钝柄平稳而有力地按压，使细胞铺成单层，注意不要压碎玻片。
Common stains include iodine solution (for starch and nuclei), methylene blue (for animal cells and nuclei), and acetocarmine (for chromosomes during cell division). Always add the stain away from the coverslip and draw it underneath by placing a piece of filter paper on the opposite side, a technique known as irrigation.
常用染液包括碘液（用于淀粉和细胞核）、亚甲蓝（用于动物细胞和细胞核）和醋酸洋红（用于分裂中的染色体）。染液要加在盖玻片外侧，通过在对面一侧放一小片滤纸将染液引流下去，这种方法称为置换加液法。
3. Measuring Cell Size and Magnification | 测量细胞大小与放大率
Magnification is calculated as image size ÷ actual size. To find the actual size of a cell in a photomicrograph, measure the cell’s length in millimetres, convert to micrometres (1 mm = 1000 μm), and divide by the stated magnification. For example, if a red blood cell appears 8 mm in a ×2000 image, its actual diameter = 8 × 1000 ÷ 2000 = 4 μm.
放大率 = 图像大小 ÷ 实际大小。要计算显微照片中细胞的实际大小，先测量细胞长度（毫米），转换为微米（1 毫米 = 1000 微米），再除以标明的放大倍数。例如，一个红细胞在 ×2000 照片中长度为 8 毫米，则实际直径 = 8 × 1000 ÷ 2000 = 4 μm。
Always calibrate the eyepiece graticule at each magnification. Place a stage micrometer (which has a precisely known scale, typically 1 mm divided into 100 divisions of 10 μm each) on the stage, and align it with the graticule. Count how many graticule divisions coincide with a known number of micrometer divisions, then calculate the value of one eyepiece unit. Record the calibration factor and use it on the same microscope at that magnification.
每次更换放大倍数都要校准目镜测微尺。将镜台测微尺（具有精确刻度，通常 1 毫米等分为 100 小格，每格 10 微米）放在载物台上，与目镜测微尺对齐。计数多少个目镜格数与多少个测微尺格数对齐，然后计算一个目镜单位的值。记录校准因子，并在同台显微镜相同放大倍数下使用。
When estimating field of view, use a clear ruler at low power or the stage micrometer. The area visible at low power (e.g., ×40) can then be used to calculate the proportional reduction at high power, because magnification and field diameter are inversely proportional.
估算视野大小时，可在低倍镜下使用透明直尺或镜台测微尺。低倍（如 ×40）下的可见面积可用于计算高倍下的比例缩减，因为放大倍数与视野直径成反比。
4. Constructing and Interpreting Tables and Graphs | 表格与图表的构建和解读
A well‑constructed results table includes an informative title, clearly labelled columns with units in brackets (e.g., Temperature / °C), and consistent decimal places. Record raw data to the precision of the measuring instrument. Do not include any calculations in the raw‑data columns; create separate columns for processed data like rates or percentages.
一个构建良好的结果表格包括信息明确的标题、带单位说明的清晰列标题（如 温度 / °C）和一致的小数位数。原始数据要记录到测量仪器的精度。不要在原始数据列中进行计算；为处理过的数据（如速率或百分比）单独设置列。
| Temperature / °C | Time for starch to disappear / s | Rate / s⁻¹ |
|---|---|---|
| 10 | 145 | 0.0069 |
| 20 | 80 | 0.0125 |
| 30 | 42 | 0.0238 |
Graphs should have the independent variable on the x‑axis and the dependent variable on the y‑axis. Use linear scales wherever possible, label axes with physical quantity and unit, and plot data points precisely with small ‘×’ or encircled dots. Draw either a line of best fit or a smooth curve that passes through as many points as possible. Never connect dot‑to‑dot by default unless measuring a discrete variable.
图表应将自变量放在 x 轴，因变量放在 y 轴。尽可能使用线性刻度，用物理量和单位标注坐标轴，精确地用小的“×”或圆圈点标出数据点。画出最佳拟合直线或光滑曲线，使线条尽量通过更多的点。除非测量离散变量，否则切勿默认逐点连线。
Use the slope or intercept to determine biologically meaningful values. For example, in a photosynthesis light‑intensity experiment, the initial slope of O₂ evolution vs. light intensity can indicate the quantum yield of the reaction.
利用斜率和截距可以得出有生物学意义的值。例如，在光合作用光照强度实验中，氧气释放量对光照强度曲线的初始斜率可反映反应的光量子产率。
5. Enzyme Activity Experiments | 酶活性实验
Enzyme‑based practicals often investigate the effect of temperature, pH, substrate concentration, or inhibitors on the rate of reaction. Always state the reaction being catalysed, such as catalase breaking down hydrogen peroxide into water and oxygen, or amylase hydrolysing starch into maltose. Control all other variables—buffer at constant pH, thermostatic water bath, and identical volumes and concentrations—so that only the independent variable changes.
基于酶学的实验通常探究温度、pH、底物浓度或抑制剂对反应速率的影响。要明确说明所催化的反应，例如过氧化氢酶催化过氧化氢分解为水和氧气，或淀粉酶水解淀粉为麦芽糖。控制所有其他变量——用缓冲液维持恒定 pH、恒温水浴、相同体积和浓度——确保只有自变量发生变化。
For catalase, measure the volume of oxygen evolved with a gas syringe or the time taken for a paper disc soaked in enzyme solution to rise through a column of hydrogen peroxide. For amylase, use iodine solution to test for starch at timed intervals until the blue‑black colour no longer appears, recording the time for complete breakdown.
对于过氧化氢酶实验，可用集气注射器测量氧气释放体积，或者记录浸泡过酶液的圆形滤纸片在过氧化氢溶液柱中上浮到水面所需的时间。淀粉酶实验则用碘液每隔一段时间检测淀粉，直到蓝黑色不再出现，记录完全分解所用的时间。
Rate can be expressed as 1 / time (s⁻¹) or as volume of product per unit time (cm³ min⁻¹). Plot rate against the independent variable. For temperature, the graph typically shows a peak at the optimum temperature, followed by a sharp decline due to denaturation. Explain the increase using kinetic theory and the decrease via disruption of tertiary structure and the active site.
速率可表示为 1 / 时间（s⁻¹），或单位时间内产物的体积（cm³ min⁻¹）。将速率作为因变量对自变量作图。对于温度，曲线通常在最适温度处出现峰值，随后因变性而急剧下降。用分子碰撞理论解释升高部分，用三级结构和活性位点被破坏解释下降部分。
Use the rate data to calculate the temperature coefficient Q₁₀ between two temperatures 10 °C apart: Q₁₀ = rate at T+10 / rate at T. A Q₁₀ of about 2 suggests the reaction is largely controlled by diffusion and collision frequency; a value much lower suggests limiting factors or approaching denaturation.
利用速率数据计算相差10°C之间的温度系数 Q₁₀：Q₁₀ = (在 T+10°C 的速率) / (在 T°C 的速率)。Q₁₀ 约为 2 提示反应主要受扩散和碰撞频率控制；该值显著偏低则表明存在限制因子或正在接近变性。
6. Diffusion and Osmosis | 扩散与渗透
Investigate diffusion rate using agar cubes containing phenolphthalein and dilute sodium hydroxide. Cut cubes of identical volume (e.g., 1 cm³, 2 cm³, 3 cm³) and immerse them in hydrochloric acid. The pink colour fades as the acid diffuses in. Record the time taken for each cube to turn colourless. Plot time against surface‑area‑to‑volume ratio to illustrate that a larger ratio promotes faster diffusion, supporting why cells are microscopic.
使用含酚酞和稀氢氧化钠的琼脂块探究扩散速率。切成相同体积的立方体（如 1 cm³、2 cm³、3 cm³），浸入盐酸中。随酸扩散进入，粉红色逐渐褪去。记录每个立方体褪色所需时间。以时间对表面积与体积之比作图，说明较大的比值促进更快的扩散，从而解释细胞为什么非常微小。
Osmosis can be demonstrated with potato cylinders or dialysis tubing. Prepare a series of sucrose solutions (e.g., 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 mol dm⁻³). Record the initial mass and length of potato cylinders, immerse them for a set time (e.g., 30 minutes), then blot dry and re‑measure. Calculate percentage change in mass: (final − initial) / initial × 100%. Plot % change against concentration; the x‑intercept indicates the approximate water potential of the potato tissue.
渗透实验可用马铃薯圆柱体或透析袋展示。配制一系列蔗糖溶液（如 0.0、0.2、0.4、0.6、0.8、1.0 mol dm⁻³）。记录马铃薯圆柱体的初始质量和长度，浸泡固定时间（如 30 分钟），取出吸干表面水分后重新测量。计算质量变化百分比：(最终质量 – 初始质量) / 初始质量 × 100%。以变化百分比对浓度作图；x 轴截距指示马铃薯组织的水势近似值。
For dialysis tubing, fill a bag with starch or glucose solution, tie it, and immerse in distilled water or iodine solution. Periodically test the external solution for the presence of solute to demonstrate selective permeability. This models the behaviour of a partially permeable membrane.
使用透析袋时，向袋内装入淀粉或葡萄糖溶液，扎紧后浸入蒸馏水或碘液中。定期检测外部溶液中是否出现溶质，以演示选择透过性。这一过程模拟了部分通透膜的行为。
7. Photosynthesis Rate Investigation | 光合作用速率探究
The pondweed (Elodea or Cabomba) experiment is a classic bioassay for measuring the rate of photosynthesis. Place a fresh shoot of pondweed upside down in a large beaker of water containing a balanced source of carbon dioxide, such as 0.2% sodium hydrogen carbonate solution. Place the beaker at a measured distance from a bright white lamp and allow the plant to equilibrate for 5 minutes. Count the number of gas bubbles released from the cut stem per minute, or collect the evolved gas in a graduated syringe to measure volume.
水草（伊乐藻或蜈蚣草）实验是测量光合作用速率的经典生物测定方法。将新鲜水草嫩枝倒置在含有足量二氧化碳源（如 0.2% 碳酸氢钠溶液）的大烧杯中。烧杯置于距离明亮白光灯一定距离的位置，让植物适应 5 分钟。计数每分钟从切口茎杆处释放的气泡数，或用刻度注射器收集释放的气体测量体积。
Vary the light intensity by altering the lamp distance. Light intensity obeys the inverse‑square law: intensity ∝ 1/d², where d is the distance. Calculate 1/d² as a proxy for intensity. Plot bubble rate against 1/d². The curve typically rises then plateaus, where another factor (usually CO₂ concentration or temperature) becomes limiting. You can also use coloured filters to investigate the action spectrum and compare absorption of different chlorophyll pigments.
通过改变灯距来调节光强度。光强度遵循平方反比定律：强度 ∝ 1/d²，其中 d 为距离。计算 1/d² 作为光强度指标。将气泡速率对 1/d² 作图，曲线通常先上升后趋于平台，表明此时其他因子（通常是 CO₂ 浓度或温度）成为限制因素。也可使用有色滤光片研究作用光谱，比较不同叶绿素色素的吸收情况。
A more quantitative method uses a photosynthometer or a oxygen sensor with datalogging. Measure the dissolved oxygen concentration over time under different conditions. Ensure that any heat from the lamp is filtered by a transparent heat shield (a glass tank of water) to avoid temperature confounding the results.
更定量的方法使用光合作用仪或连接数据采集器的氧传感器。测量不同条件下溶解氧浓度随时间的变化。务必用透明隔热屏（水族缸）过滤灯的热量，以免温度干扰实验结果。
8. Respiration and Fermentation | 呼吸作用与发酵
Respirometers measure oxygen uptake or carbon dioxide output to determine respiration rates in small organisms like germinating seeds, woodlice, or yeast. Assemble a U‑tube respirometer with a test tube containing living tissue, a manometer containing coloured fluid, and a soda‑lime pellet in a separate compartment to absorb CO₂, so that any pressure decrease is due solely to oxygen consumption. Submerge the apparatus in a thermostatic water bath. Record the movement of the manometer fluid at regular intervals.
呼吸计通过测量氧吸收量或二氧化碳释放量来测定小型生物（如萌发种子、潮虫或酵母）的呼吸速率。组装一个 U 形管呼吸计，包括盛有活组织的试管、含有有色液体的测压管，以及在隔室中放入碱石灰颗粒吸收二氧化碳，这样任何压强下降都仅来自氧气消耗。将整套装置浸入恒温水浴，定期记录测压管液柱的移动。
Calculate the volume of O₂ consumed using the manometer scale and the calibration of the capillary tube. Express the rate as mm³ O₂ per gram of tissue per minute. Compare respiration rates at different temperatures, or before and after exercise simulation. For plants, use boiled seeds as a control to prove that gas exchange is due to metabolism, not physical processes.
利用测压计刻度和毛细管校准值计算消耗的氧气体积。以 mm³ O₂ / 克组织 / 分钟表示呼吸速率。比较不同温度下的呼吸速率，或模拟运动前后的差异。对于植物，用煮过的种子作为对照，以证明气体交换来自代谢作用而非物理过程。
Anaerobic fermentation in yeast can be demonstrated by trapping the CO₂ produced in a fermentation tube or by measuring the ethanol concentration using a simple distillation and dichromate test. Mix yeast suspension with glucose solution, layer with liquid paraffin to exclude oxygen, and collect gas over time. Measure the volume of CO₂ or change in pH as the yeast produces organic acids and ethanol.
无氧发酵可用酵母进行，通过发酵管收集产生的 CO₂，或用简易蒸馏和重铬酸盐测试测定乙醇浓度。将酵母悬液与葡萄糖溶液混合，用液体石蜡覆盖以排氧气，并随时间收集气体。测量 CO₂ 体积或 pH 变化，因为酵母产生有机酸和乙醇。
9. DNA Extraction and Gel Electrophoresis | DNA 提取与凝胶电泳
Extract DNA from plant tissue (e.g., kiwi fruit or onion) by mashing the tissue with a salt‑detergent solution and incubating at 60 °C for 15 minutes. The detergent disrupts cell and nuclear membranes; salt neutralises the negative charges on DNA, allowing it to aggregate. Filter, then carefully layer ice‑cold ethanol (or isopropanol) over the filtrate. DNA precipitates as a white, thread‑like mass at the interface. Spool it onto a glass rod.
可从植物组织（如猕猴桃或洋葱）中提取 DNA：将组织与食盐-洗涤剂溶液一起捣碎，在 60 °C 下温育 15 分钟。洗涤剂破坏细胞膜和核膜；盐中和 DNA 的负电荷，使其聚集。过滤，然后将冰冷的乙醇（或异丙醇）沿管壁轻轻铺在滤液上。DNA 在界面处以白色丝状物质析出。用玻璃棒将其卷出。
Gel electrophoresis separates DNA fragments by size. Pour an agarose gel, set a comb to create wells, and submerge the gel in a buffer tank. Mix DNA samples with loading dye, load into wells, and apply a voltage. Negatively charged DNA migrates towards the positive anode. Smaller fragments move faster through the gel mesh. After staining (e.g., with SafeView or methylene blue), bands become visible under UV or white light. Compare band positions with a DNA ladder to estimate fragment size.
凝胶电泳按大小分离 DNA 片段。灌制琼脂糖凝胶，插入梳子形成加样孔，将凝胶浸入缓冲液槽中。DNA 样品与加样缓冲液混合，加入孔内，并施加电压。带负电荷的 DNA 向正极迁移。较小的片段在凝胶网中移动更快。染色（如 SafeView 或亚甲蓝）后，条带在紫外或白光下可见。与 DNA 分子量标准对比，可估算片段大小。
Always include restriction enzyme digests when mapping restriction sites. This technique is widely used in the IB biology syllabus, notably in the context of forensic analysis and genetic engineering. Calculate the sizes using a standard curve generated from the marker lane.
绘制限制性酶切图谱时总是要包含限制酶酶切。这一技术在 IB 生物课纲中广泛应用，尤其是法医分析和基因工程背景。利用标准分子量泳道生成的标准曲线计算片段大小。
10. Observing Mitosis and Meiosis | 有丝分裂与减数分裂的观察
Meristematic tissue from root tips of garlic or onion provides excellent mitotic figures. Grow roots in water, cut off the terminal 2–3 mm, and place in 1 M hydrochloric acid at 60 °C for 5–10 minutes to macerate the middle lamella. Rinse in distilled water, then stain with toluidine blue O or aceto‑orcein for several minutes. Transfer the tip to a clean slide, add a drop of 45% acetic acid, and gently squash under a coverslip. Search for cells in prophase, metaphase, anaphase, and telophase under ×400 magnification.
大蒜或洋葱根尖的分生组织提供了极好的有丝分裂图像。在水中培养根，切下顶端 2–3 毫米，放入 60 °C 的 1 mol dm⁻³ 盐酸中 5–10 分钟以解离中胶层。蒸馏水漂洗后用甲苯胺蓝 O 或醋酸洋红染色数分钟。将根尖移至洁净载玻片，加一滴 45% 醋酸，轻轻盖上盖玻片挤压。在 ×400 倍下寻找前期、中期、后期和末期的细胞。
Calculate the mitotic index: (number of cells in mitosis ÷ total number of cells counted) × 100%. This is used as a rough indicator of growth rate in plants or to compare cancerous vs. healthy tissues. Record observations with clear labeled diagrams.
计算有丝分裂指数：(处于分裂期的细胞数 ÷ 计数的细胞总数) × 100%。这常被用作植物生长速率的粗略指标，或比较癌组织与健康组织的差异。用清晰的标注图记录观察结果。
Though harder to prepare, meiotic stages can be seen in anther squashes of young flower buds. Locate cells undergoing meiosis I and II, identifying bivalents, chiasmata, and haploid products. Compare the chromosome number at different stages—this links karyotype diagrams to actual cellular images.
尽管制片难度更大，减数分裂阶段可从幼小花朵的药室挤压片中观察到。找到正在进行减数第一次与第二次分裂的细胞，辨认出二价体、交叉和单倍体产物。比较不同阶段的染色体数目，这将核型图与实际细胞图像联系起来。
11. Fieldwork and Sampling Techniques | 野外调查与取样技术
Ecological investigations rely on quadrat and transect sampling to estimate population sizes and community composition. A random number generator determines coordinates to place a 0.5 m × 0.5 m quadrat in a field, avoiding investigator bias. Record percentage cover using a point frame or visual estimation, and count each species present. Calculate species frequency and density.
生态调查依赖样方和样线取样来估算种群大小和群落组成。用随机数生成器确定坐标，在野外放置 0.5 m × 0.5 m 的样方，避免调查者主观偏差。使用点触框或视觉估算记录覆盖百分比，并计数每个物种的个体数。计算物种频度和密度。
For mobile organisms, use mark‑release‑recapture (Lincoln index). Capture a sample of animals (e.g., woodlice or snails), mark them harmlessly with a dot of non‑toxic paint, and release. After a day, capture a second sample. If M = number marked initially, C = total in second capture, and R = recaptures marked, then population size N = (M × C) / R. Discuss assumptions: closed population, marks not lost, marking does not affect survival or recapture probability.
对于移动动物，使用标志重捕法（Lincoln 指数）。捕获一组动物（如潮虫或蜗牛），用无毒颜料无害地标记后释放。一天后再捕获第二组。若 M = 初始标记数，C = 第二次捕获总数，R = 第二次捕获中有标记的个体数，则种群数量 N = (M × C) / R。讨论假设条件：封闭种群、标记不脱落、标记不影响存活率和重捕概率。
Use a line transect to examine zonation along an environmental gradient (e.g., from a woodland edge into the interior). Place a tape measure and record every plant touching the line at regular intervals. Plot kite diagrams to visually represent changes in species abundance with distance.
使用样线研究沿环境梯度的分带现象（例如从林地边缘到内部）。铺设卷尺，每隔固定距离记录所有与线接触的植物。用风筝图将物种丰富度随距离的变化可视化。
12. Evaluation and Error Analysis | 评估与误差分析
Every practical write‑up must include a thorough evaluation. Identify the main sources of systematic error (e.g., thermometer consistently reading 0.5 °C low) and random error (e.g., variation in reaction time when starting a stopwatch). Suggest realistic improvements: use a digital thermometer, control room temperature, or automate recording with data loggers. Distinguish between accuracy (how close a measurement is to the true value) and precision (the consistency of repeated measurements).
每份实验报告都必须包含彻底的评估。找出主要的系统误差来源（如温度计长期读数偏低 0.5 °C）和随机误差（如启动秒表时的反应时间差异）。提出切实可行的改进建议：使用数字温度计、控制室温，或使用数据采集器自动记录。区分准确度（测量值与真值的接近程度）和精确度（重复测量结果的一致性）。
For graphs showing a scatter of points, draw error bars where appropriate. If SD has been calculated for each mean, show ±1 SD above and below the mean. If error bars of two means do not overlap, it suggests a significant difference, but statistical tests like the t‑test should confirm this. For IB IA and CCEA assessed tasks, always compare results with literature values or accepted biological theory, explaining any deviations.
对于点分散的图表，适当时应添加误差线。若已为每个平均值计算了标准偏差（SD），则在平均值上下标出 ±1 SD。如果两个平均值的误差线不重叠，提示差异显著，但仍需借助 t 检验等统计方法确认。对于 IB 内部评估和 CCEA 评测任务，务必与文献值或公认的生物学理论进行比较，并解释任何偏差。
Always discuss ethical considerations if animals or human participants were involved. State that minimal handling was used, approval was obtained, and data are anonymised when necessary.
如果实验涉及动物或人类参与者，一定要讨论伦理考量。说明已尽量减少了对动物的干扰，获得了许可，并在必要时对数据进行匿名处理。
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