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An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity.
Biodiversity is the variability of life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Earth. It is greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than one-fifth of Earth's terrestrial area and contain about 50% of the world's species. There are latitudinal gradients in species diversity for both marine and terrestrial taxa.
Extinction is the termination of a taxon by the death of its last member. A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" after a period of apparent absence.
Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, isolation and habitat area. Phytogeography is the branch of biogeography that studies the distribution of plants. Zoogeography is the branch that studies distribution of animals. Mycogeography is the branch that studies distribution of fungi, such as mushrooms.
Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an interdisciplinary subject drawing on natural and social sciences, and the practice of natural resource management.
The Anthropocene is a now rejected proposal for the name of a geological epoch that would follow the Holocene, dating from the commencement of significant human impact on Earth up to the present day. It was rejected in 2024 by the International Commission on Stratigraphy in terms of being a defined geologic period. The impacts of humans affect Earth's oceans, geology, geomorphology, landscape, limnology, hydrology, ecosystems and climate. The effects of human activities on Earth can be seen for example in biodiversity loss and climate change. Various start dates for the Anthropocene have been proposed, ranging from the beginning of the Neolithic Revolution, to as recently as the 1960s. The biologist Eugene F. Stoermer is credited with first coining and using the term anthropocene informally in the 1980s; Paul J. Crutzen re-invented and popularized the term. However, in 2024 the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS) rejected the Anthropocene Epoch proposal for inclusion in the Geologic Time Scale.
Paleoecology is the study of interactions between organisms and/or interactions between organisms and their environments across geologic timescales. As a discipline, paleoecology interacts with, depends on and informs a variety of fields including paleontology, ecology, climatology and biology.
Coextinction and cothreatened refer to the phenomenon of the loss or decline of a host species resulting in the loss or endangerment of another species that depends on it, potentially leading to cascading effects across trophic levels. The term was originated by the authors Stork and Lyal (1993) and was originally used to explain the extinction of parasitic insects following the loss of their specific hosts. The term is now used to describe the loss of any interacting species, including competition with their counterpart, and specialist herbivores with their food source. Coextinction is especially common when a keystone species goes extinct.
Joseph John Sepkoski Jr. was a University of Chicago paleontologist. Sepkoski studied the fossil record and the diversity of life on Earth. Sepkoski and David Raup produced a new understanding of extinction events, by developing a statistical approach to the study of taxonomic diversification. He suggested that the extinction of dinosaurs 66 mya was part of a cycle of mass extinctions that may have occurred every 26 million years. But his most important contribution was the identification of the "Big 5" mass extinctions, events that have shaped the evolution of life on earth.
Peter Douglas Ward is an American paleontologist and professor at the University of Washington, Seattle, and Sprigg Institute of Geobiology at the University of Adelaide. He has written numerous popular science works for a general audience and is also an adviser to the Microbes Mind Forum. In 2000, along with his co-author Donald E. Brownlee, he co-originated the term Rare Earth and developed the Medea hypothesis alleging that multicellular life is ultimately self-destructive.
Species richness, or biodiversity, increases from the poles to the tropics for a wide variety of terrestrial and marine organisms, often referred to as the latitudinal diversity gradient. The latitudinal diversity gradient is one of the most widely recognized patterns in ecology. It has been observed to varying degrees in Earth's past. A parallel trend has been found with elevation, though this is less well-studied.
Paleobiology is an interdisciplinary field that combines the methods and findings found in both the earth sciences and the life sciences. Paleobiology is not to be confused with geobiology, which focuses more on the interactions between the biosphere and the physical Earth.
Anne Elizabeth Magurran is a British Professor of ecology at University of St Andrews in Scotland. She is the author of several books on measuring biological diversity, and the importance for quantifying biodiversity for conservation. She has won numerous awards and honors, is regularly consulted for global assessments and analyses of biodiversity and conservation and her research is often highlighted by journalists.
John Alroy is a paleobiologist born in New York in 1966 and now residing in Sydney, Australia.
Stephen C. Stearns is an American biologist, and the Edward P. Bass Professor of Ecology and Evolutionary Biology Emeritus at Yale University. He is known for his work in life history theory and evolutionary medicine.
Jeffrey Alexander Hutchings FRSC was a Canadian fisheries scientist. He was a professor of biology, and the Izaak Walton Killam Memorial Chair in Fish, Fisheries, and Oceans at Dalhousie University.
The Mesozoic–Cenozoic Radiation is the third major extended increase of biodiversity in the Phanerozoic, after the Cambrian Explosion and the Great Ordovician Biodiversification Event, which appeared to exceeded the equilibrium reached after the Ordovician radiation. Made known by its identification in marine invertebrates, this evolutionary radiation began in the Mesozoic, after the Permian extinctions, and continues to this date. This spectacular radiation affected both terrestrial and marine flora and fauna, during which the "modern" fauna came to replace much of the Paleozoic fauna. Notably, this radiation event was marked by the rise of angiosperms during the mid-Cretaceous, and the K-Pg extinction, which initiated the rapid increase in mammalian biodiversity.
Katherine Jane Willis, Baroness Willis of Summertown, is a British biologist, academic and life peer, who studies the relationship between long-term ecosystem dynamics and environmental change. She is Professor of Biodiversity in the Department of Biology and Pro-Vice-Chancellor at the University of Oxford, and an adjunct professor in biology at the University of Bergen. In 2018 she was elected Principal of St Edmund Hall, and took up the position from 1 October. She held the Tasso Leventis Chair of Biodiversity at Oxford and was founding Director, now Associate Director, of the Biodiversity Institute Oxford. Willis was Director of Science at the Royal Botanic Gardens, Kew from 2013 to 2018. Her nomination by the House of Lords Appointments Commission as a crossbench life peer was announced on 17 May 2022.
Mark C. Urban is a biologist and associate professor in ecology and evolutionary biology at the University of Connecticut. His work focuses on the ecological and evolutionary mechanisms that shape natural communities across multiple spatial scales.
Andrew Benjamin Smith is a British palaeontologist, known for his research on the palaeontology of echinoderms. His cladistic classification of the phylum Echinodermata has become standard.
References
- 1 2 Mayhew, Peter J (2006). Discovering Evolutionary Ecology. Oxford: Oxford University Press. ISBN 978-0-19-857060-8. OCLC: 62133413 .
- ↑ Mayhew, P. J.; Jenkins, G. B.; Benton, T. M. (7 January 2008). "A long term association between global temperature and biodiversity, origination and extinction in the fossil record". Proceedings of the Royal Society B. 275 (1630). London: Royal Society: 47–53. doi:10.1098/rspb.2007.1302. PMC 2562410 . PMID 17956842.
- ↑ Borenstein, Seth (24 October 2007). "Warmer seas spark extinction worries". Toronto Star. Retrieved 1 January 2008.
- ↑ "Great Britons". Archived from the original on 2 November 2007. Retrieved 1 January 2007.