📚 6.6 Populations and Sustainability: Exam Practice | 6.6 种群与可持续性真题精练
This article provides focused exam practice on the topic of populations and sustainability, covering key concepts from population growth models to ecosystem management and conservation. Each section includes a typical exam-style question with a model answer, helping you to check your understanding and improve your exam technique.
本文针对“种群与可持续性”这一主题进行真题精练，涵盖种群增长模型、生态系统管理与保护等核心概念。每个小节提供一道典型的考试风格题目及标准答案，帮助您检验理解并提高应试技巧。
1. Exponential and Logistic Growth | 指数增长与逻辑斯谛增长
Concept: Populations can grow exponentially under ideal conditions, described by the equation Nt = N0 × 2n, where Nt is the population size at time t, N0 is the initial size, and n is the number of generations. In reality, resources become limiting, so growth follows a logistic curve and levels off at the carrying capacity (K). Question: Explain why exponential population growth cannot be sustained indefinitely in nature. Answer: Exponential growth requires unlimited resources and no competition, predation, or disease. In nature, limiting factors such as food availability, space, accumulation of waste, and increased disease transmission cause the growth rate to slow and the population to stabilise at the carrying capacity.
概念：在理想条件下，种群呈指数增长，可用方程 Nt = N0 × 2n 描述，其中 Nt 为 t 时种群大小，N0 为初始大小，n 为世代数。实际上，资源会变得有限，因此增长遵循逻辑斯谛曲线并在承载能力（K）附近趋于平稳。问题：解释为什么指数增长在自然界中不能无限持续。答案：指数增长需要无限资源且无竞争、捕食或疾病。在自然界中，食物供应、空间、废物积累和疾病传播增加等限制因素会使增长率下降，种群数量稳定在承载能力附近。
2. Carrying Capacity and Limiting Factors | 承载能力与限制因素
Concept: Carrying capacity (K) is the maximum stable population size that an ecosystem can support. It is determined by limiting factors, which can be density-dependent (e.g. competition for food, disease) or density-independent (e.g. flood, fire). Question: Describe how density-dependent factors regulate the size of a population. Answer: Density-dependent factors have a greater effect as the population density increases. For example, competition for food intensifies, leading to starvation and lower birth rates; disease spreads more easily in dense populations, increasing death rates; and the build-up of toxic waste products can also raise mortality. These negative feedback mechanisms bring the population down towards carrying capacity.
概念：承载能力（K）是生态系统能够长期维持的最大种群数量。它由限制因素决定，这些因素可以是密度制约的（例如食物竞争、疾病）或非密度制约的（例如洪水、火灾）。问题：描述密度制约因素如何调节种群大小。答案：密度制约因素的作用随种群密度增加而增强。例如，食物竞争加剧导致饥饿和出生率降低；疾病在密集种群中更易传播，增加死亡率；有毒废物的累积也会提高死亡率。这些负反馈机制使种群数量回落至承载能力附近。
3. Estimating Population Size: Mark-Release-Recapture | 估计种群大小：标记重捕法
Concept: The Lincoln index is used to estimate population size of mobile organisms: N = (M × C) / R, where M is the number initially captured and marked, C is the number captured in the second sample, and R is the number of marked individuals recaptured. Question: In a survey of a beetle population, a student catches and marks 80 beetles. Two days later, she catches 60 beetles, of which 15 are marked. Calculate the estimated population size and state two assumptions of this method. Answer: N = (80 × 60) / 15 = 320 beetles. Assumptions include: marked individuals mix randomly with the unmarked population; no migration, births, or deaths between samples; marks do not affect survival or catchability; and marks are not lost.
概念：林肯指数用于估算移动生物的种群大小：N = (M × C) / R，其中 M 是首次捕获并标记的个体数，C 是第二次样本中的捕获数，R 是第二次捕获中带有标记的个体数。问题：在一次甲虫种群调查中，一名学生捕获并标记了 80 只甲虫。两天后，她捕获了 60 只甲虫，其中 15 只带有标记。计算估计的种群大小，并说明该方法的两个假设。答案：N = (80 × 60) / 15 = 320 只甲虫。假设包括：标记个体与未标记个体随机混合；两次取样之间无迁移、出生或死亡；标记不影响生存或被捕获的概率；标记不会脱落。
4. Sampling Using Quadrats and Transects | 使用样方和样线取样
Concept: Quadrats and transects are used to sample sessile or slow-moving organisms. Random quadrat placement avoids bias, while systematic transects can reveal zonation. Question: Describe how you would estimate the percentage cover of a plant species, such as clover, in a meadow using a 0.5 m × 0.5 m quadrat divided into 100 small squares. Answer: Place the quadrat randomly within the study area, e.g. using random coordinates. Count the number of small squares in which clover covers at least half of the square. This number is the percentage cover for that quadrat. Repeat at least 10 times and calculate the mean percentage cover to improve reliability.
概念：样方和样线用于取样固着或缓慢移动的生物。随机放置样方可避免偏差，而系统样线则可揭示带状分布。问题：描述如何使用一个划分为 100 个小格的 0.5 m × 0.5 m 样方估算草地中三叶草的覆盖率。答案：在样地内随机放置样方，例如使用随机坐标。计数三叶草覆盖至少一半小格的数量。该数字即为该样方的覆盖率百分比。至少重复 10 次，计算平均覆盖率以提高可靠性。
5. Predator-Prey Relationships | 捕食者-猎物关系
Concept: Predator and prey populations often exhibit cyclic fluctuations. When prey numbers increase, predator numbers rise after a time lag; predators then reduce the prey population, leading to a decline in predators, allowing the prey to recover. Question: Explain why the peaks in predator population often lag behind those of the prey. Answer: A lag occurs because it takes time for predators to reproduce and increase in response to greater food availability. Initially, more prey survive longer, providing more food for predators, but the predator population grows more slowly. By the time predator numbers peak, prey population is already declining, which eventually causes the predator population to fall.
概念：捕食者与猎物种群常呈现周期性波动。猎物数量增加后，捕食者数量会经过一段时滞后上升；捕食者随后减少猎物种群，导致捕食者数量下降，使得猎物得以恢复。问题：解释为什么捕食者种群的峰值通常滞后于猎物的峰值。答案：存在滞后是因为捕食者需要时间来繁殖并响应增加的食物供应。最初，更多的猎物存活更久，为捕食者提供了更多食物，但捕食者种群增长较慢。到捕食者数量达到峰值时，猎物种群已经开始下降，这最终导致捕食者种群下降。
6. Interspecific and Intraspecific Competition | 种间与种内竞争
Concept: Intraspecific competition occurs between members of the same species for resources such as food and mates. Interspecific competition occurs between different species, and can lead to competitive exclusion, where one species outcompetes the other. Question: State the competitive exclusion principle and explain its outcome using an example. Answer: The competitive exclusion principle states that two species competing for exactly the same resources cannot coexist indefinitely; one will outcompete the other. For example, in laboratory experiments with Paramecium caudatum and Paramecium aurelia, when grown together, P. aurelia always drove P. caudatum to extinction because it utilised food more efficiently.
概念：种内竞争发生在同一物种个体之间，争夺食物和配偶等资源。种间竞争发生在不同物种之间，可能导致竞争排斥，即一个物种战胜另一个物种。问题：陈述竞争排斥原理，并用一个例子解释其结果。答案：竞争排斥原理指出，两个争夺完全相同资源的物种不能长期共存；一个物种会战胜另一个。例如，在实验室中培养的草履虫 (Paramecium caudatum) 和双小核草履虫 (Paramecium aurelia)，当共同培养时，P. aurelia 总是将 P. caudatum 驱至灭绝，因为它更有效地利用食物。
7. Energy Transfer and Ecological Pyramids | 能量传递与生态金字塔
Concept: Energy is transferred between trophic levels, but only about 10% is converted into new biomass; the rest is lost as heat through respiration. Question: In a food chain, 25 000 kJ of solar energy enters the producer level. The net production of the producers is 1 500 kJ, and that of the primary consumers is 200 kJ. Calculate the percentage efficiency of energy transfer from producers to primary consumers. Answer: First calculate the transfer: efficiency = (energy in primary consumers / energy in producers) × 100 = (200 / 1500) × 100 = 13.3%. Note that ecological efficiency is based on the energy available at each trophic level, not the original solar input.
概念：能量在营养级之间传递，但只有约 10% 转化为新的生物量；其余以热的形式通过呼吸散失。问题：在某食物链中，25000 kJ 的太阳能进入生产者营养级。生产者的净生产量为 1500 kJ，初级消费者的净生产量为 200 kJ。计算从生产者到初级消费者的能量传递效率百分比。答案：首先计算传递效率：效率 =（初级消费者的能量 / 生产者的能量）× 100 =（200 / 1500）× 100 = 13.3%。请注意，生态效率是基于每个营养级可利用的能量，而非原始太阳能输入。
8. Sustainable Timber Production | 可持续木材生产
Concept: Sustainable forestry aims to meet current wood demands without compromising the ability of future generations to meet theirs. Techniques include selective logging, replanting native species, and maintaining habitat corridors. Question: Describe how strip felling and selective cutting can make timber production more sustainable. Answer: Strip felling involves cutting trees in narrow strips, leaving adjacent strips intact to act as seed sources and to protect the soil from erosion. Selective cutting removes only mature trees of economically valuable species, leaving the forest structure largely intact. Both methods allow regeneration, maintain biodiversity, and reduce soil degradation, ensuring a continuous supply of timber.
概念：可持续林业旨在满足当前木材需求，同时不损害后代满足其需求的能力。技术包括选择性砍伐、重新种植本地物种和维持栖息地廊道。问题：描述条状砍伐和选择性砍伐如何使木材生产更具可持续性。答案：条状砍伐指将树木切成狭窄的条状，保留相邻条带作为种子来源并保护土壤免受侵蚀。选择性砍伐仅移除成熟且具经济价值的树木，基本保持森林结构完整。这两种方法都能使森林再生、维持生物多样性并减少土壤退化，从而确保持续的木材供应。
9. Conservation: In Situ vs Ex Situ | 保护：就地保护与迁地保护
Concept: In situ conservation protects species in their natural habitats (e.g. nature reserves), while ex situ conservation involves removing organisms from their habitat (e.g. zoos, seed banks). Question: Compare the advantages of in situ and ex situ conservation for protecting a critically endangered species. Answer: In situ conservation allows natural selection to continue and maintains co-evolved interactions with other species. However, if the habitat is severely degraded, the species may not survive. Ex situ conservation can provide a controlled environment for breeding and genetic management, but individuals may lose behaviours needed for survival in the wild, and reintroduction can fail. Combining both approaches often yields the best results.
概念：就地保护是在自然栖息地中保护物种（例如自然保护区），而迁地保护涉及将生物从栖息地移出（例如动物园、种子库）。问题：比较就地保护和迁地保护对于保护一种极度濒危物种的优势。答案：就地保护使自然选择得以继续，并维持与其他物种共同进化的关系。然而，如果栖息地严重退化，物种可能无法存活。迁地保护可为繁殖和遗传管理提供受控环境，但个体可能丧失在野外生存所需的行为，且再引入可能失败。通常结合两种方法可取得最佳效果。
10. Human Impact: Deforestation and Global Warming | 人类影响：森林砍伐与全球变暖
Concept: Deforestation reduces the number of trees available to absorb CO2 for photosynthesis, and burning of trees releases stored carbon into the atmosphere. This contributes to the enhanced greenhouse effect and global warming, which can alter climate patterns and raise sea levels. Question: Explain how tropical deforestation contributes to both global warming and biodiversity loss. Answer: Trees act as carbon sinks; when cut down and often burned, the stored carbon is released as CO2, a greenhouse gas. Fewer trees also mean less CO2 is removed from the atmosphere. This intensifies the greenhouse effect. Biodiversity loss occurs because tropical forests have very high species richness; habitat destruction leads to extinction of many specialist species that cannot adapt to other environments.
概念：森林砍伐减少了可用于光合作用吸收 CO2 的树木数量，而燃烧树木会将储存的碳释放到大气中。这加剧了温室效应和全球变暖，从而改变气候模式并导致海平面上升。问题：解释热带森林砍伐如何同时导致全球变暖和生物多样性丧失。答案：树木充当碳汇；当树木被砍伐并往往被焚烧时，储存的碳以 CO2（一种温室气体）的形式释放出来。树木减少也意味着从大气中去除的 CO2 更少。这加剧了温室效应。生物多样性丧失的原因是热带森林具有极高的物种丰富度；栖息地破坏导致许多无法适应其他环境的特有物种灭绝。
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