https://en.wikipedia.org/wiki/Extinction_event
Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty,
下列是五大生物集群滅絕事件，最早由大衛·勞普和傑克·塞科斯基1982年發佈的論文所認定。[2][3]
- 奧陶紀-志留紀滅絕事件：發生在奧陶紀晚期或奧陶紀與志留紀過渡時期，4.45億年前至4.43億年前，約27%的科與57%的屬滅種。[4]從滅種的生物分類的屬的數量，被評為五次大滅絕事件的第二位。直接原因是當時一顆極超新星釋出的伽馬射線暴摧毀了地球一半的臭氧層，使得太陽釋出的紫外線襲擊地球，導致地面及近海面的大量生物死亡，從而破壞食物鏈。
- 泥盆紀後期滅絕事件：3.75億年前至3.60億年前，接近泥盆紀-石炭紀過渡時期。這次主要是海洋生物的滅絕，陸地生物受影響不顯著。約19%的科、50%的屬滅絕。[4]這次大滅絕事件持續了近2000萬年，期間有多次滅絕高峰期。造礁生物消失，竹節石類、腕足動物的3個目、四射珊瑚10多個科滅亡，稱凱勒瓦瑟爾事件，也稱弗朗斯-法門事件。由於滅絕事件持續時間很長，其根源很難辨識。可能的生物學原因是在此前的泥盆紀陸生植物大量繁育，導致地球大氣中氧含量的增加、二氧化碳的大幅減少，地球進入卡魯冰河時期所致。陸生植物進化出發達的根系深入地表土之下數米，加速了陸地岩石土壤的風化，大量鐵等元素釋放進入地表水，造成了水系的富營養化大爆發，導致了海底缺氧事件。海洋表層繁盛的有機物的沉降，使得全球碳循環中大氣層的二氧化碳大量進入海底沉積層，也加強了地球冷化。泥盆紀也是陸地上生成大煤田的時期，這也加劇了二氧化碳固化入岩石圈。
- 二疊紀-三疊紀滅絕事件：發生在2.5億年前的二疊紀-三疊紀過渡時期。這是已知的地質歷史上最大規模的物種滅絕事件。許多動物門類整個目或亞目在此次滅絕事件中全部滅亡。曾普遍分布的舌羊齒植物群幾乎全部絕滅。早古生代繁盛的三葉蟲全部消失。䗴類原有40多個屬，該世結束時完全消失。菊石有10個科絕滅；腕足類之前有140個屬，在該事件後所剩無幾。總共約57%的科、83%的屬[4]（53%的海洋生物的科、84%的海洋生物的屬、大約96%的海洋生物的種），估計有70%的陸地生物包括昆蟲的物種滅絕了。[5]對於植物的影響較不明確，但新植物類群在此次滅絕後開始占優勢。[6]全世界幾乎沒有三疊紀早期形成的煤田。這次大滅絕事件的可能成因包括西伯利亞大規模玄武岩噴發造成的附近淺海區可燃冰融化大量釋放溫室氣體甲烷，盤古大陸形成後改變了地球環流與洋流系統等等。
- 三疊紀-侏羅紀滅絕事件：2.0億年前的三疊紀-侏羅紀過渡時期。約23%的科與48%的屬（20%的海生生物科別與55%的海生生物屬別）共 70-75% 的生物滅絕[4]。包括當時大多數非恐龍的主龍類、大多數的獸孔目以及幾乎所有大型兩棲類，其原因尚無定論。這次大滅絕事件使得恐龍失去了許多陸地上的競爭者，而非恐龍的主龍類與雙孔亞綱則繼續主宰海洋。離片椎目的大部分物種雖然都滅絕了，但有一支（酷拉龍）一直在澳洲存活到白堊紀後才滅絕。
- 白堊紀-古近紀滅絕事件（縮寫為K-T滅絕或K-T事件）,俗稱「恐龍大滅絕」：6千6百萬年前[7]，約17%的科、50%的屬[4]滅絕。雖然其滅絕程度在地球的五次大滅絕中只能排到第四，但由於完全毀滅了非鳥恐龍而異常令人所熟知。其成因一般認為是墨西哥尤卡坦半島的隕石撞擊。（參見希克蘇魯伯隕石坑）
The "Big Five" mass extinctions
In a landmark paper published in 1982, Jack Sepkoski and David M. Raupidentified five particular geological intervals with excessive diversity loss.[2]They were originally identified as outliers on a general trend of decreasing extinction rates during the Phanerozoic,[3] but as more stringent statistical tests have been applied to the accumulating data, it has been established that in the current, Phanerozoic Eon, multicellular animal life has experienced at least five major and many minor mass extinctions.[4] The "Big Five" cannot be so clearly defined, but rather appear to represent the largest (or some of the largest) of a relatively smooth continuum of extinction events.[3] An earlier (first?) event at the end of the Ediacaran is speculated, and all are preceded by the presumed far more extensive mass extinction of microbial life during the Oxygen Catastrophe early in the Proterozoic Eon.[5]
1. Ordovician–Silurian extinction events (End Ordovician or O–S): 445–444 Ma, just prior to and at the Ordovician–Silurian transition. Two events occurred that killed off 27% of all families, 57% of all genera and 85% of all species.[6] Together they are ranked by many scientists as the second-largest of the five major extinctions in Earth's history in terms of percentage of genera that became extinct. In May 2020, studies suggested that the causes of the mass extinction were global warming, related to volcanism, and anoxia, and not, as considered earlier, cooling and glaciation.[7][8] However, this is at odds with numerous previous studies, which have indicated global cooling as the primary driver.[9] Most recently, the deposition of volcanic ash has been suggested to be the trigger for reductions in atmospheric carbon dioxide leading to the glaciation and anoxia observed in the geological record.[10]
2. Late Devonian extinctions: 372–359 Ma, occupying much of the Late Devonian up to the Devonian–Carboniferous transition. The Late Devonian was an interval of high diversity loss, concentrated into two extinction events. The largest extinction was the Kellwasser Event (Frasnian-Famennian, or F-F, 372 Ma), an extinction event at the end of the Frasnian, about midway through the Late Devonian. This extinction annihilated coral reefs and numerous tropical benthic (seabed-living) animals such as jawless fish, brachiopods, and trilobites. Another major extinction was the Hangenberg Event (Devonian-Carboniferous, or D-C, 359 Ma), which brought an end to the Devonian as a whole. This extinction wiped out the armored placoderm fish and nearly led to the extinction of the newly evolved ammonoids. These two closely-spaced extinction events collectively eliminated about 19% of all families, 50% of all genera[6] and at least 70% of all species.[11] Sepkoski and Raup (1982)[2] did not initially consider the Late Devonian extinction interval (Givetian, Frasnian, and Famennian stages) to be statistically significant.[2] Regardless, later studies have affirmed the strong ecological impacts of the Kellwasser and Hangenberg Events.[12]
3. Permian–Triassic extinction event (End Permian): 252 Ma, at the Permian–Triassictransition.[13] Phanerozoic Eon's largest extinction killed 53% of marine families, 84% of marine genera, about 81% of all marine species[14] and an estimated 70% of terrestrial vertebrate species.[15] This is also the largest known extinction event for insects.[16] The highly successful marine arthropod, the trilobite, became extinct. The evidence regarding plants is less clear, but new taxa became dominant after the extinction.[17] The "Great Dying" had enormous evolutionary significance: On land, it ended the primacy of early synapsids. The recovery of vertebrates took 30 million years,[18] but the vacant niches created the opportunity for archosaurs to become ascendant. In the seas, the percentage of animals that were sessile (unable to move about) dropped from 67% to 50%. The whole late Permian was a difficult time, at least for marine life, even before the P–T boundary extinction. More recent research has indicated that the End-Capitanian extinction event that preceded the "Great Dying" likely constitutes a separate event from the P–T extinction; if so, it would be larger than some of the "Big Five" extinction events and perhaps merit a separate place in this list immediately before this one.
4. Triassic–Jurassic extinction event (End Triassic): 201.3 Ma, at the Triassic–Jurassic transition. About 23% of all families, 48% of all genera (20% of marine families and 55% of marine genera) and 70% to 75% of all species became extinct.[6] Most non-dinosaurian archosaurs, most therapsids, and most of the large amphibians were eliminated, leaving dinosaurs with little terrestrial competition. Non-dinosaurian archosaurs continued to dominate aquatic environments, while non-archosaurian diapsids continued to dominate marine environments. The Temnospondyl lineage of large amphibians also survived until the Cretaceous in Australia (e.g., Koolasuchus).
5. Cretaceous–Paleogene extinction event (End Cretaceous, K–Pg extinction, or formerly K–T extinction): 66 Ma, at the Cretaceous (Maastrichtian) – Paleogene(Danian) transition.[19] The event was formerly called the Cretaceous-Tertiary or K–T extinction or K–T boundary; it is now officially named the Cretaceous–Paleogene (or K–Pg) extinction event. About 17% of all families, 50% of all genera[6] and 75% of all species became extinct.[2] In the seas all the ammonites, plesiosaurs and mosasaursdisappeared and the percentage of sessile animals was reduced to about 33%. All non-avian dinosaurs became extinct during that time.[20] The boundary event was severe with a significant amount of variability in the rate of extinction between and among different clades. Mammals and birds, the former descended from the synapsids and the latter from theropod dinosaurs, emerged as dominant terrestrial animals.
Sixth mass extinction
Research completed after the seminal 1982 paper (Sepkoski and Raup) has concluded that a sixth mass extinction event is ongoing due to human activities:
6. Holocene extinction currently ongoing. Extinctions have occurred at over 1,000 times the background extinction rate since 1900, and the rate is increasing.[25][26][a] The mass extinction is a result of human activity (an ecocide)[28][29][30][31] driven by population growth and overconsumption of the earth's natural resources.[b] The 2019 global biodiversity assessment by IPBESasserts that out of an estimated 8 million species, 1 million plant and animal species are currently threatened with extinction.[33][34][35][36] In late 2021, WWF Germany suggested that over a million species could go extinct within a decade in the "largest mass extinction event since the end of the dinosaur age."[37] A 2023 study published in PNAS concluded that at least 73 genera of animals have gone extinct since 1500. If humans had never existed, it would have taken 18,000 years for the same genera to have disappeared naturally, the report states.[38][39][40]
