📚 GCSE WJEC Biology: Calculation Practice | GCSE WJEC 生物：计算题专项训练
Mastering numerical questions is essential for GCSE WJEC Biology. This article covers key calculation types, from microscopy and magnification to cardiac output, respiration quotients, genetic probability, bacterial growth, and biomass transfer. Each section provides step‑by‑step methods and practice tips to boost your confidence and marks.
掌握计算题是 GCSE WJEC 生物考试的关键。本文涵盖主要计算类型，包括显微镜与放大倍数、心输出量、呼吸商、遗传概率、细菌数量和生物量传递。每个部分都提供分步方法和练习技巧，帮助你提升信心和分数。
1. Magnification & Actual Size | 放大倍数与实际尺寸
Magnification is defined as the number of times larger an image is compared to the real object. The formula used in GCSE Biology is: Magnification = Image size ÷ Actual size. All measurements must be in the same units, typically millimetres (mm) or micrometres (µm).
放大倍数的定义是图像大小与实物大小的比值。GCSE 生物学中使用的公式为：放大倍数 = 图像尺寸 ÷ 实际尺寸。所有测量值必须使用相同单位，通常是毫米（mm）或微米（µm）。
To calculate actual size, rearrange the formula to: Actual size = Image size ÷ Magnification. You may need to convert between units: 1 mm = 1000 µm. In WJEC questions, images are often drawn with a scale bar, or the magnification is given directly. Measure the image with a ruler in mm, then convert to appropriate units.
计算实际尺寸时，将公式变形为：实际尺寸 = 图像尺寸 ÷ 放大倍数。你通常需要进行单位转换：1 mm = 1000 µm。WJEC 考题中，图像往往带有比例尺，或直接给出放大倍数。用直尺测量图像尺寸（以 mm 为单位），再转换为合适单位。
For example, if an image of a cell measures 45 mm across and the magnification is ×600, the actual size = 45 mm ÷ 600 = 0.075 mm = 75 µm. Always show your working and state the final unit.
例如，一个细胞图像宽度为 45 mm，放大倍数为 ×600，则实际尺寸 = 45 mm ÷ 600 = 0.075 mm = 75 µm。务必展示运算过程并注明最终单位。
| Quantity | Formula |
| Magnification | Image size ÷ Actual size |
| Actual size | Image size ÷ Magnification |
| Unit conversion | × 1000 from mm to μm; ÷ 1000 from μm to mm |
M = I ÷ A
2. Scale Bar Interpretation | 比例尺解读
WJEC often supplies a scale bar on micrographs. A scale bar is a line labelled with its actual length, e.g. ’10 µm’. Measure the length of the scale bar in mm, then calculate the magnification: Magnification = Measured length of scale bar (in mm, converted to µm) ÷ Indicated length (in µm).
WJEC 常会在显微照片上提供比例尺。比例尺是一条标注了实际长度的线段，例如“10 µm”。用直尺测量比例尺的长度（单位 mm），然后计算放大倍数：放大倍数 = 比例尺测量长度（换算成 µm）÷ 所标长度（µm）。
Once you have the magnification, you can find the actual size of any structure in the same image by measuring its length and applying Actual size = Image size ÷ Magnification. This avoids errors from directly converting scale bar measurements.
得到放大倍数后，就可以通过测量图像中任意结构的长度，应用公式实际尺寸 = 图像尺寸 ÷ 放大倍数来求它的实际大小。这能避免直接通过比例尺推算时产生的误差。
If a scale bar of 20 µm measures 25 mm, then magnification = 25 000 µm ÷ 20 µm = ×1250. Then a cell measured at 15 mm has actual size = 15 000 µm ÷ 1250 = 12 µm.
如果标注为 20 µm 的比例尺长度测得为 25 mm，则放大倍数 = 25 000 µm ÷ 20 µm = ×1250。那么一个测得长度为 15 mm 的细胞，其实际尺寸 = 15 000 µm ÷ 1250 = 12 µm。
3. Cardiac Output Calculations | 心输出量计算
Cardiac output is the volume of blood pumped by the heart per minute. It is the product of heart rate (beats per minute) and stroke volume (volume of blood pumped per beat). Cardiac output (CO) = Heart rate (HR) × Stroke volume (SV).
心输出量是心脏每分钟泵出的血液体积。它等于心率（每分钟搏动次数）与每搏输出量（每次搏动泵出的血量）的乘积。心输出量（CO）= 心率（HR）× 每搏输出量（SV）。
Units are typically litres per minute (L/min) or millilitres per minute (mL/min). In WJEC, you may be asked to calculate any one of the three variables if the other two are provided. Rearrange as: HR = CO ÷ SV; SV = CO ÷ HR.
单位通常为升每分钟（L/min）或毫升每分钟（mL/min）。在 WJEC 考题中，可能会给出其中两个变量，要求计算第三个。变形公式为：HR = CO ÷ SV；SV = CO ÷ HR。
For example, if a person’s heart rate is 70 bpm and stroke volume is 75 mL/beat, CO = 70 × 75 = 5250 mL/min, or 5.25 L/min. Be careful with unit conversions when comparing answers.
例如，一个人的心率为 70 bpm，每搏输出量为 75 mL/次，则 CO = 70 × 75 = 5250 mL/min，即 5.25 L/min。比较答案时要注意单位转换。
CO = HR × SV
4. Percentage Change & Rate Calculations | 百分比变化与速率计算
Percentage change questions appear when comparing an initial value with a final value. The formula is: Percentage change = (Final value − Initial value) ÷ Initial value × 100%. Negative values indicate a decrease.
百分比变化题出现于比较初始值和最终值时。公式为：百分比变化 = （最终值 − 初始值）÷ 初始值 × 100%。负值表示减少。
Rates are often required in enzyme activity or osmosis practicals. Rate = Change in quantity ÷ Time taken. For example, rate of oxygen production = Volume of oxygen produced ÷ Time. Units depend on what is measured, e.g. cm³/min, g/s.
速率计算常见于酶活性或渗透作用实验中。速率 = 量的变化 ÷ 所用时间。例如，氧气生成速率 = 产生的氧气体积 ÷ 时间。单位取决于测量对象，如 cm³/min、g/s。
In a photosynthesis experiment, if 24 cm³ of oxygen is collected in 8 minutes, the rate = 24 ÷ 8 = 3 cm³/min. Always state units and show the calculation line clearly.
在光合作用实验中，若 8 分钟内收集了 24 cm³ 氧气，则速率 = 24 ÷ 8 = 3 cm³/min。务必写明单位，清楚展示计算过程。
5. Respiratory Quotient (RQ) | 呼吸商（RQ）
The respiratory quotient indicates which substrate is being respired. RQ = Volume of CO₂ produced ÷ Volume of O₂ consumed. Measurements are usually in cm³ or arbitrary units from a respirometer.
呼吸商用于判断呼吸作用中利用了哪种底物。RQ = 产生的 CO₂ 体积 ÷ 消耗的 O₂ 体积。测量通常以 cm³ 或来自呼吸计的任意单位表示。
Typical RQ values: carbohydrates = 1.0; lipids ∼ 0.7; proteins ∼ 0.9. In WJEC, you might be given gas volume changes in a respirometer and asked to calculate RQ. Remember that if CO₂ is absorbed by soda lime, you will only measure O₂ uptake directly; you may need to infer CO₂ production from a control tube.
典型的 RQ 值：碳水化合物 = 1.0；脂质约为 0.7；蛋白质约为 0.9。WJEC 考试中，可能会提供呼吸计内的气体体积变化数据，要求计算 RQ。要记住，如果 CO₂ 被碱石灰吸收，则只能直接测得 O₂ 吸收量；你可能需要借助对照组推断 CO₂ 产生量。
For instance, in a respirometer with germinating peas, O₂ uptake is 0.8 cm³ without soda lime the net change is +0.2 cm³, showing that CO₂ production = 0.2 + 0.8 = 1.0 cm³. RQ = 1.0 ÷ 0.8 = 1.25. This might indicate a mixture of substrates.
例如，在含有萌发豌豆的呼吸计中，吸氧量为 0.8 cm³，没有碱石灰时净变化为 +0.2 cm³，表明 CO₂ 产量 = 0.2 + 0.8 = 1.0 cm³。RQ = 1.0 ÷ 0.8 = 1.25，这可能意味着混合底物的呼吸。
RQ = CO₂ produced ÷ O₂ used
6. Genetic Probability & Ratios | 遗传概率与比值
Monohybrid crosses are a common calculation topic. Probability is expressed as a fraction, decimal, or percentage. For a single gene with dominant and recessive alleles, a Punnett square gives the expected ratio among offspring.
单基因杂交是常见的计算主题。概率可以用分数、小数或百分比表示。对于一对显性和隐性等位基因，使用旁氏表（Punnett square）可以得到子代预期的比例。
If two heterozygous parents (Aa × Aa) are crossed, the genotypic ratio is 1 AA : 2 Aa : 1 aa. The phenotypic ratio for a dominant‑recessive trait is 3 : 1. The probability of producing a homozygous recessive offspring is 1/4 or 25%.
如果两个杂合子亲本（Aa × Aa）杂交，基因型比例为 1 AA : 2 Aa : 1 aa。对显隐性性状而言，表现型比例为 3 : 1。产生纯合隐性后代的概率是 1/4 或 25%。
WJEC may ask you to calculate the probability of a specific outcome across multiple offspring. Each fertilisation is an independent event, so you multiply probabilities. For two heterozygous parents, the chance of having two children both with the recessive condition is 1/4 × 1/4 = 1/16.
WJEC 可能要求计算多个后代出现特定结果的概率。每个受精事件都是独立事件，所以概率相乘。对于两个杂合子亲本，生两个孩子都表现出隐性性状的概率为 1/4 × 1/4 = 1/16。
Sex determination: the chance of a child being male is always 1/2, as males produce X and Y sperm in equal numbers. A family with four daughters still has a 1/2 probability of the next child being a boy.
性别决定：生男孩的概率始终是 1/2，因为男性产生等量的 X 和 Y 精子。一个已有四个女儿的家庭，再生一个男孩的概率依然是 1/2。
| Parental genotypes | Phenotypic ratio |
| AA × aa | All dominant (100%) |
| Aa × Aa | 3 dominant : 1 recessive |
| Aa × aa | 1 dominant : 1 recessive |
7. Bacterial Growth Calculations | 细菌生长计算
Bacteria reproduce by binary fission, doubling in number every division. Under ideal conditions, the population growth can be calculated using the formula: Number of bacteria at time t = Starting number × 2ⁿ, where n is the number of divisions that have occurred.
细菌通过二分裂繁殖，每次分裂数量翻倍。在理想条件下，种群数量可用公式计算：某时刻细菌数量 = 起始数量 × 2ⁿ，其中 n 是已经发生分裂的次数。
You must first work out how many divisions occur in the given time. If the mean division time is 20 minutes, in 2 hours (120 minutes), n = 120 ÷ 20 = 6 divisions. Starting with 1 bacterium, after 2 hours there are 1 × 2⁶ = 64 bacteria.
首先需要算出给定时间内发生了多少次分裂。如果平均分裂时间为 20 分钟，在 2 小时（120 分钟）内，n = 120 ÷ 20 = 6 次分裂。起始为 1 个细菌，2 小时后数量为 1 × 2⁶ = 64 个。
WJEC might present data on a graph of log numbers against time, or ask you to predict numbers given a starting population. Always state the formula and show the exponent calculation clearly. Use your calculator’s power function to find 2ⁿ.
WJEC 可能会在图上给出细菌对数数目随时间的变化，或要求根据起始数量预测种群数。务必写出公式，展示指数运算过程。使用计算器的幂函数求 2ⁿ。
N = N₀ × 2ⁿ
8. Percentile Charts & Growth Data | 百分位图与生长发育数据
Pediatric growth charts use percentiles to compare a child’s growth to a reference population. The 50th percentile represents the median. Calculations may involve interpreting which percentile a given measurement falls into, based on provided tables.
儿科生长发育图使用百分位来比较儿童的生长情况与参照人群。第 50 百分位代表中位数。计算题可能要求根据给出的表格，判断某个测量值对应的百分位。
You might also need to calculate the percentage of a population above or below a certain threshold. For instance, if a child’s mass is at the 85th percentile, 85% of the reference population has a lower or equal mass, while 15% have a higher mass.
可能还需要计算某一阈值以上或以下的人口百分比。例如，如果一个孩子的体重处于第 85 百分位，意味着参照人群中有 85% 的人体重在他之下或相同，而 15% 的人体重更高。
BMI calculations may also appear: BMI = Mass (kg) ÷ (Height in m)². Practice rearranging the formula to find mass or height if the other values are given.
BMI 计算也可能出现：BMI = 体重（kg）÷ （身高以米计）²。练习变形公式，在已知其他值时求体重或身高。
BMI = m ÷ h²
9. Biomass Transfer & Efficiency | 生物量传递与效率
In food chains, only a fraction of biomass is transferred from one trophic level to the next. Efficiency of biomass transfer is calculated as: Efficiency (%) = (Biomass at higher trophic level ÷ Biomass at lower trophic level) × 100.
在食物链中，只有一小部分生物量传递到下一营养级。生物量传递效率的计算公式为：效率（%）=（较高营养级的生物量 ÷ 较低营养级的生物量）× 100。
Typical numbers are around 10%, but WJEC questions may require you to calculate this from data tables showing biomass (often in g/m² or kg). Always show the formula, substitute values, and give the answer as a percentage.
典型数值约为 10%，但 WJEC 考题可能要求根据数据表（生物量单位常为 g/m² 或 kg）来计算。务必写出公式，代入数值，并将结果以百分比呈现。
You may also calculate the percentage of biomass lost. Biomass lost = Lower level biomass − Higher level biomass. Percentage loss = (Biomass lost ÷ Lower level biomass) × 100. Losses occur due to respiration, egestion, and uneaten parts.
也可能需要计算生物量损失百分比。生物量损失 = 低营养级生物量 − 高营养级生物量。损失百分比 =（生物量损失 ÷ 低营养级生物量）× 100。损失源自呼吸作用、排遗和未被捕食的部分。
Efficiency = (Biomass in higher level ÷ Biomass in lower level) × 100%
10. Osmosis & Water Potential Trends | 渗透与水势变化趋势
Although quantitative water potential values are not calculated directly, WJEC expects you to calculate percentage change in mass or length from osmosis experiments. Initial mass and final mass are recorded, then percentage change = (Final mass − Initial mass) ÷ Initial mass × 100%.
虽然不需要直接计算水势值，但 WJEC 期望你能根据渗透实验数据计算质量或长度的百分比变化。记录初始质量和最终质量后，百分比变化 =（最终质量 − 初始质量）÷ 初始质量 × 100%。
Plotting percentage change against sucrose concentration enables you to find the isotonic point where the curve crosses the zero‑change line. This involves reading values from your graph and performing simple interpolation.
以蔗糖浓度为横轴、百分比变化为纵轴作图，可以找到曲线与零变化线相交的等渗点。这需要从图表上读取数值并进行简单的插值计算。
Be precise with decimal places and use negative signs for mass loss. An example: initial mass 5.2 g, final mass 4.8 g, percentage change = (4.8 − 5.2) ÷ 5.2 × 100 = −7.7%.
注意小数位数的精度，质量减少时使用负号。例如：初始质量 5.2 g，最终质量 4.8 g，则百分比变化 = (4.8 − 5.2) ÷ 5.2 × 100 = −7.7%。
11. Quadrat & Transect Sampling Calculations | 样方与样带取样计算
Sampling techniques generate data that require calculation of population estimates. Using quadrats, you can estimate the population size of a species in an area: Total population estimate = (Number of organisms counted in all quadrats ÷ Number of quadrats) × Total area ÷ Area of one quadrat.
取样技术会产生需要估算种群数量的数据。使用样方法，你可以估算某一区域内物种种群大小：种群总数估计值 =（所有样方计数的生物总数 ÷ 样方数）× 研究总面积 ÷ 单个样方面积。
Alternatively, for percentage cover, you calculate the mean percentage cover from all quadrat readings. Use the mean to compare two habitats. WJEC may also ask for the median or mode from a set of quadrat data.
另一种情况，对于百分比覆盖度，你需要计算所有样方读数的平均覆盖度百分比。使用平均值来比较两个栖息地。WJEC 也可能要求从一组样方数据中找出中位数或众数。
In belt transects, you record species occurrence at intervals. Calculating frequency: Frequency (%) = (Number of quadrats containing the species ÷ Total number of quadrats placed) × 100. This yields a percentage frequency for each species along the gradient.
在样带（belt transect）中，你按一定间隔记录物种出现情况。计算频率：频率（%）=（出现该物种的样方数 ÷ 放置的总样方数）× 100。这给出沿环境梯度每个物种的出现频率百分比。
Population estimate = (mean per quadrat) × (total area ÷ quadrat area)
12. Tips for Success in WJEC Calculation Questions | WJEC 计算题高分技巧
Always write down the formula before you substitute any numbers. This guarantees method marks even if the final answer is wrong. Convert all units to a common system early – mixing mm and µm is a common error. In the WJEC exam, if you are not given a formula, recall it from memory and write it plainly.
务必先写出公式再代入数字。这样即使最终答案错误也能获得方法分。尽早将所有单位统一——混淆 mm 和 µm 是常见错误。在 WJEC 考试中，如果没有给出公式，则需自己回忆并清楚写出。
Show every step of your working. For multi‑step problems, break them down: calculate one variable, then use it to find another. Check the sense of your answer – can a cell really be 100 mm wide? If not, you may have made a unit error. Leave yourself time to proofread calculations.
展示每一步运算过程。对于多步题，进行分解：先计算一个变量，再用它求出另一个。检查答案的合理性——一个细胞真的能宽达 100 mm 吗？如果不能，你可能犯了单位错误。给自己留出检查计算的时间。
Use your calculator effectively: know how to enter powers (for bacterial growth), square and square root (for BMI), and convert between fractions and decimals for genetic probability. Finally, always state the unit in your final answer.
熟练使用计算器：知道如何输入指数（用于细菌生长）、平方与开方（用于 BMI），以及分数和小数的转换（用于遗传概率）。最后，务必在最终答案中注明单位。
Published by TutorHao | Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导Cancel reply