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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Cambrian explosion | 11/11 | https://en.wikipedia.org/wiki/Cambrian_explosion | reference | science, encyclopedia | 2026-05-05T11:01:41.804996+00:00 | kb-cron |
== Uniqueness of the early Cambrian biodiversification == The "Cambrian explosion" can be viewed as two waves of metazoan expansion into empty niches: first, a coevolutionary rise in diversity as animals explored niches on the Ediacaran sea floor, followed by a second expansion in the early Cambrian as they became established in the water column. The rate of diversification seen in the Cambrian phase of the explosion is unparalleled among marine animals: it affected all metazoan clades of which Cambrian fossils have been found. Later radiations, such as those of fish in the Silurian and Devonian periods, involved fewer taxa, mainly with very similar body plans. Although the recovery from the Permian-Triassic extinction started with about as few animal species as the Cambrian explosion, the recovery produced far fewer significantly new types of animals. Whatever triggered the early Cambrian diversification opened up an exceptionally wide range of previously unavailable ecological niches. When these were all occupied, limited space existed for such wide-ranging diversifications to occur again, because strong competition existed in all niches and incumbents usually had the advantage. If a wide range of empty niches had continued, clades would be able to continue diversifying and become disparate enough for us to recognise them as different phyla; when niches are filled, lineages will continue to resemble one another long after they diverge, as limited opportunity exists for them to change their life-styles and forms. There were two similar explosions in the evolution of land plants: after a cryptic history beginning about 450 million years ago, land plants underwent a uniquely rapid adaptive radiation during the Devonian period, about 400 million years ago. Furthermore, angiosperms (flowering plants) originated and rapidly diversified during the Cretaceous period.
== See also == Avalon explosion, a similar biodiversity of life that occurred 33 million years prior.
== Footnotes ==
== References ==
== Further reading == Budd, G. E.; Jensen, J. (2000). "A critical reappraisal of the fossil record of the bilaterian phyla". Biological Reviews. 75 (2): 253–295. Bibcode:2000BioRv..75..253B. doi:10.1111/j.1469-185X.1999.tb00046.x. PMID 10881389. S2CID 39772232. Collins, Allen G. "Metazoa: Fossil record". Retrieved 14 December 2005. Conway Morris, S. (1997). The Crucible of Creation: the Burgess Shale and the rise of animals. Oxford University Press. ISBN 0-19-286202-2. Conway Morris, S. (June 2006). "Darwin's dilemma: the realities of the Cambrian 'explosion'". Philosophical Transactions of the Royal Society B: Biological Sciences. 361 (1470): 1069–1083. doi:10.1098/rstb.2006.1846. ISSN 0962-8436. PMC 1578734. PMID 16754615. An enjoyable account. Gould, S.J. (1989). Wonderful Life: The Burgess Shale and the Nature of History. W.W. Norton & Company. Bibcode:1989wlbs.book.....G. Kennedy, M.; M. Droser; L. Mayer.; D. Pevear & D. Mrofka (2006). "Clay and Atmospheric Oxygen". Science. 311 (5766): 1341. doi:10.1126/science.311.5766.1341c. S2CID 220101640. Knoll, A.H.; Carroll, S.B. (25 June 1999). "Early Animal Evolution: Emerging Views from Comparative Biology and Geology". Science. 284 (5423): 2129–37. doi:10.1126/science.284.5423.2129. PMID 10381872. S2CID 8908451. Markov, Alexander V.; Korotayev, Andrey V. (2007). "Phanerozoic marine biodiversity follows a hyperbolic trend". Palaeoworld. 16 (4): 311–318. Bibcode:2007Palae..16..311M. doi:10.1016/j.palwor.2007.01.002. Montenari, M.; Leppig, U. (2003). "The Acritarcha: their classification morphology, ultrastructure and palaeoecological/palaeogeographical distribution". Paläontologische Zeitschrift. 77 (1): 173–194. Bibcode:2003PalZ...77..173M. doi:10.1007/bf03004567. S2CID 127238427. Wang, D. Y.-C.; S. Kumar; S. B. Hedges (January 1999). "Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi". Proceedings of the Royal Society B. 266 (1415): 163–71. doi:10.1098/rspb.1999.0617. ISSN 0962-8452. PMC 1689654. PMID 10097391. Wood, Rachel A., "The Rise of Animals: New fossils and analyses of ancient ocean chemistry reveal the surprisingly deep roots of the Cambrian explosion", Scientific American, vol. 320, no. 6 (June 2019), pp. 24–31. Xiao, S.; Y. Zhang & A. Knoll (January 1998). "Three-dimensional preservation of algae and animal embryos in a Neoproterozoic phosphorite". Nature. 391 (1): 553–58. Bibcode:1998Natur.391..553X. doi:10.1038/35318. ISSN 0090-9556. S2CID 4350507. Timeline References:
Martin, M.W; Grazhdankin, D.V; Bowring, S.A; Evans, D.A.D; Fedonkin, M.A; Kirschvink, J.L (2000). "Age of Neoproterozoic Bilaterian Body and Trace Fossils, White Sea, Russia: Implications for Metazoan Evolution". Science. 288 (5467): 841–845. Bibcode:2000Sci...288..841M. doi:10.1126/science.288.5467.841. PMID 10797002.
== External links == The Cambrian "explosion" of metazoans and molecular biology: would Darwin be satisfied? On embryos and ancestors by Stephen Jay Gould Conway Morris, S. (April 2000). "The Cambrian "explosion": Slow-fuse or megatonnage?". Proceedings of the National Academy of Sciences. 97 (9): 4426–4429. Bibcode:2000PNAS...97.4426C. doi:10.1073/pnas.97.9.4426. PMC 34314. PMID 10781036. The Cambrian Explosion – In Our Time, BBC Radio 4 broadcast, 17 February 2005 "Burgess Shale". Virtual Museum of Canada. 2011., exhaustive details about the Burgess Shale, its fossils and its significance for the Cambrian explosion Utah's Cambrian life Archived 23 July 2012 at the Wayback Machine – new (2008) website with good images of a range of Burgess-shale-type and other Cambrian fossils Smithsonian National Museum