Experimental Design for Populations and Sustainability | 种群与可持续性实验设计

📚 Experimental Design for Populations and Sustainability | 种群与可持续性实验设计

In A-level Biology, understanding how populations change over time and how they can be managed sustainably is fundamental. This article explores the key experimental designs used to investigate population size, growth and sustainable resource use. You will learn about classic field techniques like capture-mark-recapture and quadrat sampling, as well as laboratory models using yeast. We also examine how to design experiments that test sustainable harvesting strategies, always considering the assumptions and ethics behind each method.

在A-level生物学中，理解种群如何随时间变化以及如何可持续地管理种群是基础。本文探讨用于研究种群大小、增长和可持续资源利用的关键实验设计。你将学习经典的野外技术，如标记重捕法和样方法，以及使用酵母的实验室模型。我们还研究如何设计测试可持续收获策略的实验，始终考虑每种方法背后的假设与伦理。

1. Introduction to Population Ecology and Sustainability | 种群生态学与可持续性导论

Population ecology is the study of how groups of organisms of the same species interact with their environment. Key factors include birth rate, death rate, immigration and emigration. Sustainability means using biological resources in ways that do not deplete them for future generations. Designing experiments in this field requires both precision and an awareness of ecological limits.

种群生态学研究同一物种群体如何与环境相互作用。关键因素包括出生率、死亡率、迁入与迁出。可持续性意味着以不耗尽未来世代资源的方式利用生物资源。设计该领域的实验既需要精确性，也需要对生态限制的认识。

2. The Lincoln Index: Capture-Mark-Recapture Method | 林肯指数：标记重捕法

The Lincoln Index is a classic method for estimating population size of motile animals. It involves capturing a sample of individuals, marking them harmlessly, releasing them back, and then capturing a second sample later. The proportion of marked individuals in the second sample is used to estimate the total population. The formula is:

林肯指数是一种估计能运动动物种群数量的经典方法。它包括捕获一群个体、无伤害地标记、释放回去，然后一段时间后再次取样。根据第二样本中标记个体的比例来估计总种群数量。公式如下：

N = (M × C) ÷ R

Where N = estimated total population, M = number of individuals captured and marked in the first sample, C = total number of individuals captured in the second sample, R = number of marked individuals recaptured in the second sample.

其中N = 估计的种群总数，M = 第一次捕获并标记的个体数，C = 第二次捕获的总个体数，R = 第二次捕获中已标记的个体数。

Important assumptions include: marks do not affect survival or behaviour, marks are not lost, the population is closed (no births, deaths, immigration or emigration between samples), and mixing is random. Violating these assumptions can lead to inaccurate estimates.

重要假设包括：标记不影响生存或行为；标记不会丢失；种群是封闭的（两次取样之间没有出生、死亡、迁入或迁出）；混合是随机的。违反这些假设会导致估计不准确。

3. Experimental Procedure for Estimating a Woodlouse Population | 估算潮虫种群的实验步骤

Woodlice are excellent subjects for a school-based Lincoln Index experiment. Follow this procedure: choose a defined area, such as a 5 m × 5 m plot of leaf litter. In session one, capture as many woodlice as possible by hand or using pitfall traps over a set time. Count them (M), mark them on their dorsal surface using a small dot of non-toxic, waterproof paint, and release immediately. In session two, about 24 hours later, recapture woodlice in the same area using the same effort. Count the total caught (C) and the number that are marked (R). Calculate N using the formula.

潮虫是学校进行林肯指数实验的极好对象。请遵循以下步骤：选择一个确定的区域，如5米×5米的落叶层。在第一次采样中，在规定时间内尽可能多地捕捉潮虫，用手或陷阱。计数（M），用防水无毒的颜料在其背甲点一个小点标记，立即释放。约24小时后进行第二次采样，在同一区域用同样的努力捕捉潮虫。计数总捕获数（C）以及其中已标记的个数（R）。使用公式计算N。

Control variables: temperature, humidity, time of day, and search effort. A risk assessment must be completed before fieldwork. Always handle organisms gently and return them promptly.

控制变量：温度、湿度、一天中的时间和搜寻努力。野外工作前必须完成风险评估。务必轻取轻放生物，并尽快送回。

4. Using Quadrats to Study Plant Populations | 使用样方研究植物种群

For sessile organisms like plants, quadrat sampling is used to estimate population density and frequency. A quadrat is a square frame of known area, often 0.5 m × 0.5 m or 1 m × 1 m. Random sampling is achieved by laying out two tape measures as axes and generating random coordinates. At each coordinate, place the quadrat and count the number of individuals of the target species, or estimate percentage cover.

对于固着生物如植物，样方取样用于估计种群密度与频度。样方是已知面积的正方形框，常用0.5米×0.5米或1米×1米。随机抽样通过铺设两条卷尺作为坐标轴、生成随机坐标来实现。在每个坐标处放置样方，计数目标物种的个体数，或估计覆盖百分率。

Systematic sampling using a transect line is helpful when studying how a population changes along an environmental gradient, for example from a path’s edge into a woodland. Place quadrats at regular intervals along the line and record abundance.

当研究种群沿环境梯度如何变化时，使用样线的系统抽样很有帮助，例如从小路边缘到林地内部。沿线以规则间隔放置样方，记录多度。

5. Investigating Abiotic Factors and Distribution | 研究非生物因素与分布

Populations are influenced by abiotic factors such as light intensity, soil pH, moisture and temperature. In a quadrat study, you can measure these variables at each sampling point using a light meter, pH probe, soil moisture meter and thermometer. Then plot species abundance against the abiotic factor to identify patterns. Correlation does not imply causation, but such data can suggest hypotheses for controlled experiments.

种群受非生物因素影响，如光照强度、土壤pH、水分和温度。在样方研究中，可以使用照度计、pH探头、土壤水分计和温度计在每个取样点测量这些变量。然后绘制物种多度与非生物因素的关系图以识别模式。相关性不意味因果关系，但此类数据可以为受控实验提供假说。

6. Laboratory Model: Yeast Population Growth | 实验室模型：酵母种群增长

Saccharomyces cerevisiae (yeast) is a simple unicellular fungus that reproduces rapidly under suitable conditions. A population growth experiment can be set up using a sterile glucose broth inoculated with a small volume of yeast culture. Incubate at a constant temperature (typically 25–30 °C). Measure population size indirectly using a colorimeter to monitor turbidity, or directly using a haemocytometer to count cells. Plot a growth curve of cell number against time; it typically shows lag, exponential, stationary and death phases.

啤酒酵母是一种简单的单细胞真菌，在适宜条件下迅速繁殖。可设置种群增长实验，使用无菌葡萄糖肉汤接种少量酵母培养物。在恒温下（通常25–30°C）培养。使用比色计监测浊度间接测量种群大小，或使用血球计数板直接计数细胞。绘制细胞数对时间的生长曲线；通常显示延滞期、指数期、稳定期和衰亡期。

Carrying capacity can be demonstrated by limiting nutrients or allowing waste products to accumulate. This models the concept of environmental resistance. Aseptic technique must be used throughout to prevent contamination.

通过限制营养物或让废物积累，可以展示环境容纳量。这模拟了环境阻力的概念。整个过程必须使用无菌操作防止污染。

7. Designing an Experiment on Sustainable Harvesting | 设计可持续收获实验

Sustainability experiments often model fishing or forestry. A simple classroom model uses a container of dried beans or counters representing a fish population. Students can simulate harvesting by removing a fixed number or a fixed proportion each ‘year’ and then allowing the remaining population to ‘reproduce’ by adding a number of new individuals according to a recruitment rule (e.g., 20% increase). By varying harvest effort, they can find the maximum sustainable yield without causing population collapse.

可持续性实验通常模拟渔业或林业。一个简单的课堂模型使用装有干豆或计数器的容器代表鱼类种群。学生每年移除固定数量或固定比例的’鱼’来模拟收获，然后根据补充规则（如增长20%）让剩余种群’繁殖’，添加新个体。通过改变收获努力，可以找到最大可持续产量，而不至于使种群崩溃。

This experiment can be extended by introducing ‘bycatch’ or changing environmental conditions. Record population size after each cycle and plot a time series. A sustainable strategy keeps the population near the carrying capacity or at a level where growth is maximal.

可以通过引入’兼捕’或改变环境条件来扩展此实验。记录每个周期后的种群大小，绘制时间序列。可持续策略将使种群维持在接近环境容纳量或最大增长的水平。

8. Data Analysis and the Lincoln Index Assumptions | 数据分析与林肯指数假设

After obtaining R, M and C, calculate N and discuss confidence limits. The Lincoln Index gives only an estimate; it is more reliable with large samples and when R is not too small. A statistical variation of the formula, the Bailey correction, can be used when R < 20: N = [M × (C+1)] ÷ (R+1). In a report, always state the assumptions and discuss how any violation might affect the estimate.

获得R、M和C后，计算N并讨论置信限。林肯指数仅给出估计值；当样本量大且R不太小时更可靠。当R < 20时，可以使用该公式的统计变体贝利修正：N = [M × (C+1)] ÷ (R+1)。在报告中，务必陈述假设并讨论任何违反如何影响估计。

For quadrat data, calculate mean density per quadrat and then multiply by the total area. Standard deviation and standard error help assess precision. Present data using bar charts or scatter graphs with best-fit lines.

对于样方数据，计算每个样方的平均密度，然后乘以总面积。标准差和标准误有助于评估精确度。用条形图或散点图配合最佳拟合线展示数据。

9. Ethical Considerations in Population Experiments | 种群实验中的伦理考量

Field experiments involving live animals require ethical justification. Minimise handling time, avoid harmful markings, and release animals exactly where they were found. For plant studies, avoid trampling sensitive habitats. Replacement, reduction and refinement (the 3Rs) should be considered when designing any animal-based investigation. In the UK, experiments with vertebrates are strictly regulated; however, invertebrates like woodlice are more commonly used in schools.

涉及活体动物的野外实验需要伦理上的合理性。尽量减少处理时间，避免有害标记，并将动物放回原发现地。对于植物研究，避免践踏敏感生境。设计任何基于动物的调查时，应考虑替代、减少和优化（3R原则）。在英国，脊椎动物实验受到严格监管；不过，像潮虫这样的无脊椎动物在学校中更常用。

10. Designing Your Own Investigation on Sustainability | 设计你自己的可持续性调查

To synthesise your learning, design a novel experiment that addresses a sustainability question. For example, ‘Does selective harvesting (taking only large individuals) lead to a more stable population size than random harvesting?’ Use a model system (e.g., beans representing a short-lived plant). State your hypothesis, independent variable (harvest method), dependent variable (population size over time), and at least five control variables (e.g., starting population, reproduction rate, duration of experiment, container size, environmental conditions). Include a risk assessment and ethical statement.

为综合所学，设计一个新颖的实验来解决一个可持续性问题。例如，’选择性收获（仅取大型个体）是否比随机收获导致更稳定的种群大小？’使用模型系统（如豆子代表短命植物）。陈述你的假说、自变量（收获方法）、因变量（随时间变化的种群大小），以及至少五个控制变量（如起始种群、繁殖率、实验持续时间、容器大小、环境条件）。包含风险评估与伦理声明。

This process mirrors the work of ecologists who must balance resource extraction with conservation. Good experimental design should be repeatable, produce reliable data, and allow meaningful conclusions to be drawn.

这一过程反映了生态学家的工作，他们必须平衡资源开采与保护。好的实验设计应可重复、产生可靠数据，并能得出有意义的结论。

11. Common Pitfalls and How to Avoid Them | 常见误区与避免方法

One common mistake in mark-recapture is assuming the population is closed when it is not. Always perform the two samples as close together in time as practical, while allowing enough time for mixing. Another pitfall is using marks that may attract predators or cause sickness; test marks on a small group first. In quadrat work, a biased placement (e.g., deliberately placing quadrats in dense patches) can invalidate random sampling; use true random coordinates.

标记重捕法中一个常见错误是假设种群是封闭的，而实际上并不封闭。务必在两次取样之间保持尽可能短的时间间隔，同时留出足够的混合时间。另一个误区是使用可能吸引捕食者或导致生病的标记；应先在小组上测试标记。在样方工作中，有偏的样方放置（如故意将样方放在密集斑块）会使随机抽样失效；务必使用真正的随机坐标。

For laboratory yeast experiments, contamination can confound results. Work near a Bunsen burner, flaming necks of containers, and ensure all equipment is sterile. Record temperature consistently as even small fluctuations can alter growth rates.

对于实验室酵母实验，污染会混淆结果。应在本生灯附近操作，灼烧容器颈部，并确保所有设备无菌。持续记录温度，因为即使小的波动也可能改变生长速率。

12. Conclusion: Linking Experiments to Real-World Sustainability | 结论：将实验与真实世界可持续性联系起来

Experimental design in population ecology bridges classroom concepts and global environmental challenges. By mastering techniques such as mark-recapture, quadrat sampling and model harvesting simulations, you gain skills that are directly applicable to conservation biology and resource management. Always question your assumptions, refine your methods, and consider the ethical implications of your work. These habits will serve you well not only in examinations but also in contributing to a more sustainable future.

种群生态学中的实验设计将课堂概念与全球环境挑战联系起来。通过掌握标记重捕法、样方取样和模型收获模拟等技术，你将获得直接应用于保护生物学和资源管理的技能。始终质疑你的假设，改进方法，并考虑工作的伦理影响。这些习惯不仅在考试中对你有利，也有助于为更可持续的未来作出贡献。

Published by TutorHao | Biology Revision Series | aleveler.com

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