espece

Espece, the French term for species, denotes the basic unit of biological classification and a fundamental concept in biology. In general usage, species refer to groups of organisms that share common ancestry and are distinct from other such groups. In practice, scientists describe species as populations or lineages that are relatively consistent in their genetic makeup, morphology, and ecological role, and that can be separated from other groups by diagnostic traits.

Multiple definitions of species coexist in science. The biological species concept emphasizes reproductive isolation and the potential to interbreed under natural conditions. The morphological species concept relies on distinct physical characteristics. The phylogenetic species concept defines species as the smallest diagnosable lineages with a unique evolutionary history, and the ecological species concept focuses on adaptation to a particular niche. Cryptic species—distinct lineages that appear very similar morphologically—are increasingly identified through genetic analysis, highlighting the limits of single-definition approaches.

Nomenclature and taxonomy organize species through binomial names: a genus name followed by a specific epithet, such as Homo sapiens. This system, developed by Carl Linnaeus, is governed by codes that regulate naming across different groups of organisms (for example, the ICZN for animals and the ICN for plants, fungi, and algae).

Speciation, the process by which new species arise, occurs via mechanisms such as geographic isolation or genetic differentiation within a shared region. Species are central to studies of evolution, ecology, and conservation. Accurate identification and delimitation of species inform biodiversity assessments, conservation priorities, and ecological research, while the total global number of species remains uncertain, with millions described and many more yet to be described.