Diversity of Life


Diversity of life (also called biological diversity or biodiversity) is the variety of living systems. It may refer to extant organisms but also to their diversity in the past. It is usually meant to encompass multiple levels of biological systems, from the gene level, through the level of populations and species, up to the communities of organisms and the ecosystems to which they belong. Geographic separation and exclusive interspecific relations are two of the major causes explaining the origin of the multiplication of living species in the course of evolutionary history. About 2 million extant species have been described to date and some 17 000–19 000 new entries are added every year to this list. The number of living species existing on Earth is unknown, many current estimates favouring figures in the range of 8–12 millions, others expanding up to one or a few billions, 70–90% of which would be prokaryotes.

Key Concepts

  • The diversity of biological systems is usually described at different levels, including gene diversity, species diversity and ecosystem diversity.
  • The history of biological diversity was punctuated by major critical events (mass extinctions) of which the most severe marks the end of the Palaeozoic era.
  • Marine species represent a much broader phylogenetic diversity than terrestrial species, however, only 15% of all living species described to date inhabit the sea.
  • Insects represent more than one‐half of the known species on Earth.
  • Global estimates of existing biodiversity range from 5 to 130 million species, a figure of 8 to 9 millions being currently favoured.

Keywords: species; species flock; speciation; water‐to‐land transition; history of life


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Further Reading

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Foottit RG and Adler PH (eds) (2018) Insect Biodiversity: Science and Society, 2nd edn, vol. 2. Wiley Blackwell: Oxford.

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Zhang Z‐Q (ed.) (2011) Animal biodiversity: an outline of higher level classification and survey of taxonomic richness. Zootaxa 3148: 1–237.

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Minelli, Alessandro, and Bonato, Lucio(Sep 2020) Diversity of Life. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0029203]