Biodiversity: Species, Genetic Diversity and Conservation | 生物多样性：物种、遗传多样性与保护

📚 Biodiversity: Species, Genetic Diversity and Conservation | 生物多样性：物种、遗传多样性与保护

Biodiversity is the variety of life on Earth, from genes and individuals to species and whole ecosystems. In A-Level Biology, biodiversity is not just a list of organisms; it is a measurable property of a community that reflects its stability, productivity and resilience to environmental change.

生物多样性是地球上生命的多样性，涵盖基因、个体、物种以及整个生态系统。在 A-Level 生物课程中，生物多样性不仅仅是一份生物名录，更是群落的一项可测量属性，能够反映群落的稳定性、生产力以及抵御环境变化的能力。

1. What Is Biodiversity? | 什么是生物多样性？

Biodiversity can be defined as the variety of living organisms in an area. It includes species diversity (the number and abundance of different species), genetic diversity (the variety of alleles within a species) and ecosystem diversity (the range of habitats and ecological communities).

生物多样性可定义为一个区域内生物体的多样性。它包括物种多样性（不同物种的数量与多度）、遗传多样性（一个物种内部等位基因的多样性）以及生态系统多样性（栖息地与生态群落的范围）。

Exam questions often ask you to distinguish these three levels. Remember that species diversity is usually measured within a community, whereas genetic diversity focuses on variation within a single species.

考试题目常要求区分这三个层次。请记住，物种多样性通常在群落内部测量，而遗传多样性关注的是单一物种内部的变异。

2. Levels of Biodiversity | 生物多样性的层次

Species diversity has two components: species richness and species evenness. Species richness is simply the number of different species present. Species evenness is a measure of how similar the population sizes of each species are.

物种多样性包含两个组成部分：物种丰富度和物种均匀度。物种丰富度仅指存在的不同物种数目。物种均匀度衡量各物种种群大小的相似程度。

For example, two meadows may both contain 10 species (same richness), but if one meadow has 90% of individuals belonging to a single species, it has lower evenness and therefore lower species diversity than a meadow where the 10 species have similar abundances.

例如，两片草地可能都含有 10 个物种（丰富度相同），但如果一片草地中 90% 的个体属于同一物种，那么它的均匀度较低，因此物种多样性也低于 10 个物种多度相近的草地。

3. Species Richness and Species Evenness | 物种丰富度与物种均匀度

Measuring species richness alone can be misleading. A community with a high number of rare species can appear diverse, yet it may be dominated by a few abundant species. This is why ecologists use diversity indices that combine richness and evenness.

仅测量物种丰富度可能会产生误导。一个拥有大量稀有物种的群落看似多样，但可能被少数优势物种主导。因此生态学家使用兼顾丰富度和均匀度的多样性指数。

It is also important to define the sampling area and the taxonomic group being counted. For instance, plant species richness in a quadrat is not the same as total biodiversity because animals, fungi and microorganisms are often excluded.

同时还需要明确采样区域和被统计的分类群。例如，样方中的植物物种丰富度并不等于总生物多样性，因为动物、真菌和微生物通常未被纳入。

4. Simpson’s Index of Diversity | 辛普森多样性指数

Simpson’s Index of Diversity (D) is a commonly used measure that accounts for both species richness and evenness. It is calculated as:

辛普森多样性指数 (D) 是一种常用指标，同时考虑物种丰富度和均匀度。其计算公式为：

D = 1 − Σ (n ÷ N)²

Here, n is the total number of individuals of a particular species, N is the total number of individuals of all species, and Σ means ‘sum of’. The value of D ranges from 0 to 1. A value close to 1 indicates high diversity; a value close to 0 indicates low diversity.

其中，n 为某一特定物种的个体总数，N 为所有物种的个体总数，Σ 表示“求和”。D 的取值范围为 0 到 1。D 接近 1 表示多样性较高；D 接近 0 表示多样性较低。

Some specifications use an alternative form, D = N(N − 1) ÷ Σ n(n − 1). You must use whichever form is given in the question. The key skill is not memorising a single version but interpreting the result.

部分大纲也使用另一种形式：D = N(N − 1) ÷ Σ n(n − 1)。答题时必须使用题目给出的形式。核心技能不是死记某一个版本，而是能够解释计算结果。

5. Calculating Simpson’s Index: Worked Example | 辛普森指数计算示例

The table below shows counts of three tree species in a woodland sample. Species A: 20 individuals, Species B: 10 individuals, Species C: 10 individuals. The total N = 40.

下表显示了某林地样方中三种乔木的个体数量。物种 A：20 个个体，物种 B：10 个个体，物种 C：10 个个体。总数 N = 40。

更多咨询请联系16621398022（同微信）