Chapter 1: Classifying species

Biological species concept

A definition of species as groups of actual, or potentially, interbreeding natural populations that are reproductively isolated from other such populations

Gene pool

The range of genes and all their alleles present in a population

Hybrid

An organism resulting from the interbreeding of two different species

Morphological species concept

A definition of species that is based on physical characteristics

Phylogenetic species concept

A definition of species that is based on the smallest group of individuals having a common ancestor, often determined through genetic analysis

Ecological species concept

A definition of species that is based on occupying the same ecological niche and similar interactions with the environment

Taxonomy

System of classification, particularly biological; or the study of these systems

Hierarchy

System categorised by the specific arrangement of information into layers

Binomial nomenclature

Naming system in which each individual is given a two

Taxon

Level of a hierarchical classification system,e.g. kingdom, family or species

Domain

The highest taxon in Linnaean classification, e.g. Eukarya.

Kingdom

Second-highest taxon in Linnaean classification, e.g. Animalia

Phylum

Third-highest taxon in Linnaean classification of animals, e.g. Chordata

Division

Third-highest taxon in Linnaean classification, e.g. Tracheophyta (vascular plants).

Class

Fourth-highest taxon in Linnaean classification, e.g. Mammalia.

Order

Fifth-highest taxon in Linnaean classification,e.g. Carnivora

Family

Sixth-highest (third lowest) taxon inLinnaean classification, e.g. Felidae

Genus

Seventh-highest (second lowest) taxon in Linnaean classification; it is always italicised, e.g. Felis.

Species

Lowest taxon in Linnaean classification; it is always italicised and combined with genus, e.g. catus in Felis catus

Organelle

A cellular structure that performs a specific function in a partitioned space within the cell

Dichotomous key

A series of choices between two options that results in the classification of an organism