Diversity of Life

Alessandro Minelli, University of Padova, Padova, Italy
Lucio Bonato, University of Padova, Padova, Italy

Published online: September 2012

DOI: 10.1002/9780470015902.a0001518.pub3

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. Habitat fragmentation and host specialisation are two of the major causes explaining the origin of the multiplication of living species in the course of evolutionary history. About 2 million 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, current estimates favouring figures in the range of 8–12 millions.

Key Concepts:

  • There are three major ranks of biological diversity on Earth, at the gene, species and ecosystem level respectively.
  • Species diversity is fostered mainly by geographical isolation and by strict interspecific relationships such as parasitism, food specialisation and plant pollination by insects.
  • All animal phyla are represented in the sea and several phyla including echinoderms, ctenophores and brachiopods are exclusively marine, but only 15% of all living species described to date inhabit the sea.
  • Insects represent more than one half of the total species-level biological diversity on Earth.
  • Key events in the history of life were the Cambrian ‘explosion’ and the invasion of land by plants (Middle Silurian), arthropods (Upper Silurian) and vertebrates (Upper Devonian).
  • 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.
  • Recent descriptions of previously unknown species include a few cetaceans and other large animals as well as small animals representing completely new classes or phyla, such as Loricifera, Cicliophora and Micrognathozoa.
  • A sensible approach to estimating the number of existing species is to compare the number of described and undescribed species collected by prolonged sampling efforts in biologically rich and hitherto less investigated areas.
  • Global estimates of existing biodiversity range from 5 to 130 million species, a figure of 8–12 millions being currently favoured.

Keywords: species; ecosystem; adaptation; classification; biodiversity

Figure 1. Inter-relationships among the major domains of life. The archaeobacteria (Archaea) are more closely related to the eukaryotes (Eukaryota: protozoans, algae, plants, fungi and animals) than to the true bacteria (Eubacteria) despite the fact that Eubacteria and Archaea share a common (prokaryotic, without a nucleus) level of cellular organisation.
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 References
    Dalebout ML, Mead JG, Baker CS, Baker AN and van Helden AL (2002) A new species of beaked whale, Mesoplodon perrini sp. n. (Cetacea: Ziphiidae), discovered through phylogenetic analysis of mitochondrial DNA sequences. Marine Mammal Science 18(3): 577–608.
    Davenport TRB, Stanley WT, Sargis EJ et al. (2006) A new genus of African monkey, Rungwecebus: morphology, ecology and molecular phylogenetics. Science 312(5778): 1378–1384.
    Fontaine B, van Achterberg K, Alonso-Zarazaga MA et al. (2012) New species in the Old World: Europe as a frontier in biodiversity exploration, a test bed for 21st century taxonomy. PLoS ONE 7(5): e36881.
    Funch P and Kristensen RM (1995) Cycliophora is a new phylum with affinities to Entoprocta and Ectoprocta. Nature 378(6558): 711–714.
    Geissmann T, Lwin G, Aung S et al. (2011) A new species of snub-nosed monkey, genus Rhinopithecus Milne-Edwards, 1872 (Primates, Colobinae), from Northern Kachin State, Northeastern Myanmar. American Journal of Primatology 73: 96–107.
    Jones T, Ehardt CL, Butynski TM et al. (2005) The highland mangabey Lophocebus kipunji: A new species of African monkey. Science 308(5725): 1161–1164.
    Kristensen RM (1983) Loricifera, a new phylum with Aschelminthes characters from the meiobenthos. Zeitschrift für Zoologische Systematik und Evolutionsforschung 21(3): 163–180.
    Kristensen RM and Funch P (2000) Micrognathozoa: a new class with complicated jaws like those of Rotifera and Gnathostomulida. Journal of Morphology 246(1): 1–49.
    Mora C, Tittensor DP, Adl S, Simpson AGB and Worm B (2011) How many species are there on Earth and in the Ocean? PLoS Biology 9(8): e1001127.
    Slipinski SA, Leschen RAB and Lawrence JF (2011) Order Coleoptera Linnaeus, 1758. In: Zhang, Z-Q (ed.) Animal biodiversity: an outline of higher-level classification and survey of taxonomic richness. Zootaxa 3148: 203–208.
    Spinney L (2010) Evolution dreampond revisited. Nature 466(7303): 174–175.
    Sun G, Ji Q, Dilcher DL et al. (2002) Archaefructaceae, a new basal angiosperm family. Science 296(5569): 899–904.
    Van Nieukerken EJ, Kaila L, Kitching IJ et al. (2011) Order Lepidoptera Linnaeus, 1758. In: Zhang, Z-Q (ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness. Zootaxa 3148: 212–221.
    Wang X (2010) Schmeissneria: an angiosperm from the Early Jurassic. Journal of Systematics and Evolution 48(5): 326–335.
    Wang X, Duan S, Geng B, Cui J and Yang Y (2007) Schmeissneria: a missing link to angiosperms? BMC Evolutionary Biology 7: 14.
 Further Reading
    book Briggs DEG and Crowther PR (eds) (2001) Paleobiology II. Oxford: Blackwell Scientific Publications.
    book Forey PL, Humphries CJ and Vane-Wright PJ (eds) (1997) Systematics and Conservation Evaluation. Oxford: Oxford University Press.
    book Gaston KJ and Spicer JI (2004) Biodiversity: An Introduction. Oxford: Blackwell.
    book Groombridge B (ed.) (1992) Biodiversity: Status of the Earth's Living Resources. London: Chapman & Hall.
    other Hawksworth DL (ed.) (1994) Biodiversity: measurement and estimation. Philosophical Transactions of the Royal Society of London B 345(1311): 1–136.
    book Heywood VH and Watson RT (eds) (1995) Global Biodiversity Assessment. Cambridge, UK: Cambridge University Press.
    book Maynard SJ and Szathmáry E (1995) The Major Transitions in Evolution. New York: Freeman.
    book Novacek MJ and Futter EV (eds) (2001) The Biodiversity Crisis: Losing What Counts. New York: The New Press.
    book Reaka-Kudla ML, Wilson DE and Wilson EO (eds) (1997) Biodiversity II. Washington DC: Joseph Henry Press.
    book Wilson EO (1999) The Diversity of Life. New York: W.W. Norton.
    other Zhang Z-Q (ed.) (2011) Animal biodiversity: An outline of higher level classification and survey of taxonomic richness. Zootaxa 3148: 1–237.

Related Sub-Topics:

Diversification of Plants and Animals | Diversity of Life | Fossils and Evolution | Evolutionary Ecology | Biogeography and Macroecology | Biodiversity
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Article Title: Diversity of Life
 
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Minelli, Alessandro, and Bonato, Lucio(Sep 2012) Diversity of Life. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001518.pub3]