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species
References & Edit History Related Topics
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A nautilus mollusk with a spiral, brown-and-white striped shell and numerous white tentacles extending from its soft body, set against a dark background. A diagram showing the hierarchy of animal classification in taxonomy, with colored boxes arranged from broadest to most specific: domain, kingdom, phylum, class, order, family, genus, and species. gray wolf coyote Adaptive radiation in Galapagos finches A diagram illustrating speciation, showing how a parent species splits into isolated populations due to physical or climatic barriers, eventually evolving into two distinct new species labeled A and B. Text explains each stage of population separation and genetic divergence. A branching phylogenetic tree diagram shows evolutionary relationships among various organisms, from Neurospora mold to humans, based on differences in cytochrome c gene sequences. Each branch is labeled with nucleotide substitution values and illustrated with animal or organism icons along the tree.
Close-up of a king cobra overlaid with question marks, a drawn crown, and an arrow pointing to the snake
A circular chart illustrates the estimated number of known living species, divided into segments for plants, monerans, protists, fungi, animals excluding insects, and animals that are insects only, with insects occupying the largest portion.
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greylag. Flock of Greylag geese during their winter migration at Bosque del Apache National Refugee, New Mexico. greylag goose (Anser anser)
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species: References & Edit History

Additional Reading

Good introductions to species are included in M.F. Claridge, H.A. Dawah, and M.R. Wilson (eds.), Species: The Units of Biodiversity (1997); and Peter R. Grant, Ecology and Evolution of Darwin’s Finches (2017). More advanced works related to species, speciation, and taxonomy include Jerry A. Coyne and H. Allen Orr, Speciation (2004); Frank E. Zachos, Species Concepts in Biology: Historical Development, Theoretical Foundations and Practical Relevance (2016); and Robert Snedden, The Diversity of Life: From Single Cells to Multicellular Organisms, 2nd ed. (2007).

Article History

Type Description Contributor Date
Add new Web site: Biology LibreTexts - Species Defined. Aug 11, 2026
Add new Web site: Rotel Project - Understanding Organisms: An Evolutionary, Ecological and Comparative Approach - Defining Species. Jul 04, 2026
Add new Web site: Indian Academy of Sciences - What is a Species? An Endless Debate (PDF). Feb 14, 2026
Add new Web site: Natural History Museum - What is a species, and how many species are there? Nov 21, 2025
Add new Web site: PNAS - Acknowledging more biodiversity without more species. Jul 19, 2025
Media added. Apr 02, 2025
Add new Web site: Live Science - What is a species? Feb 14, 2025
Add new Web site: Academia - What is a Species? An endless debate (PDF). Dec 21, 2024
Add new Web site: The New York Times - What Is a Species, Anyway? Sep 20, 2024
Add new Web site: OpenStax - Biology for AP® Courses - Formation of New Species. Jun 21, 2024
Add new Web site: Khan Academy - Species and speciation. Feb 27, 2024
Add new Web site: Raider Digital Publishing - Introductory Biology 2 - Species Concepts. Dec 08, 2023
Add new Web site: Nature - Scitable - Why Should We Care about Species? Oct 10, 2023
Add new Web site: National Center for Biotechnology Information - PubMed Central - So what is a species anyway? A primatological perspective. Apr 29, 2023
Add new Web site: Biology LibreTexts - The Origin of Species. Dec 09, 2022
Removed species count illustration. Nov 06, 2019
Add new Web site: Mexican biodiversity - Species. Sep 23, 2019
Add new Web site: University College, London - Biodiversity and Species. Sep 23, 2019
Fixed typo. Dec 04, 2018
Added a photograph of a nautilus (Nautilus) and a diagram of taxonomic nomenclature. Aug 24, 2018
Article revised and updated. Aug 24, 2018
Bibliography thoroughly revised. Apr 19, 2018
Add new Web site: ARKive - Species. Mar 06, 2014
Added diagram depicting how new species may arise. Nov 15, 2010
Added text noting that 1.9 million species have been described. Aug 17, 2010
New bibliography added. Apr 03, 2009
Article thoroughly revised and updated. Apr 03, 2009
Added new Web site: Wyoming Bioinformation Node's Species Atlas. Jun 28, 2006
Added new Web site: Wyoming Bioinformation Node's Species Atlas. Jun 28, 2006
Article added to new online database. Jul 20, 1998
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