Classification | 分类

📚 Classification | 分类

In biology, classification is the process of organising living organisms into groups based on shared features and evolutionary relationships. It helps scientists identify species, communicate clearly across languages, and understand how life on Earth is connected.

在生物学中，分类是根据共同特征和进化关系将生物体归类的过程。它帮助科学家鉴定物种、在不同语言之间清晰交流，并理解地球上的生命是如何相互联系的。

1. What Is Classification? | 什么是分类？

Classification, or taxonomy, is the science of naming, describing and grouping organisms. The groups, called taxa, are arranged in a hierarchy from large, inclusive categories to small, specific ones.

分类（或分类学）是对生物进行命名、描述和归类的科学。这些称为分类单元（taxa）的类群按等级排列，从包含范围大的类别到范围小、更具体的类别。

Classification systems aim to reflect evolutionary relationships, not just superficial appearance. A natural classification is based on phylogeny, while an artificial classification may group organisms only by convenient visible features.

分类系统旨在反映进化关系，而不仅仅是表面相似性。自然分类以系统发育为依据，而人为分类可能只根据便于观察的外部特征将生物归类。

For example, grouping whales with fish because both live in water is artificial; grouping whales with mammals because they share mammary glands, a four-chambered heart and a common ancestor is natural.

例如，鲸和鱼都生活在水中而将鲸归为鱼类是人为分类；而将鲸归为哺乳动物则是自然分类，因为它们都有乳腺、四室心脏和共同祖先。

2. The Species Concept | 物种概念

A species is often defined as a group of organisms that can interbreed in natural conditions to produce fertile offspring. For example, all domestic dogs belong to the species Canis familiaris because they can mate and have fertile puppies.

物种通常被定义为在自然条件下能够相互交配并产生可育后代的一组生物。例如，所有家犬都属于物种 Canis familiaris，因为它们可以交配并生育可育的后代。

The biological species concept has limitations. It does not work well for asexual organisms, fossils, or populations that are geographically separated but could theoretically interbreed.

生物学物种概念有局限性。它不适用于无性生殖生物、化石，或地理隔离但理论上可交配的种群。

In practice, taxonomists also use morphological, ecological and molecular criteria to define species. For example, bacterial species are usually distinguished by DNA similarity rather than by interbreeding.

在实践中，分类学家还会使用形态学、生态学和分子标准来定义物种。例如，细菌物种通常通过 DNA 相似性来区分，而不是通过交配。

3. Binomial Nomenclature | 双名法

Carl Linnaeus introduced binomial nomenclature, in which each species has a two-part Latin name: the genus and the species. The genus starts with a capital letter, and the species is lower-case. Both parts are italicised when printed or underlined when handwritten.

林奈引入了双名法：每个物种有一个由两个拉丁词组成的名称——属名和种加词。属名首字母大写，种加词小写。印刷时两部分用斜体，手写时用下划线。

For instance, humans are Homo sapiens, where Homo is the genus and sapiens is the specific epithet. The system avoids confusion caused by common names such as ‘robin’ or ‘lily’, which can refer to different species in different regions.

例如，人类是 Homo sapiens，其中 Homo 是属名，sapiens 是种加词

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