Utdöenden

Utdöenden Arter försvinner C:a 500,000,000 arter sedan livet uppstod 1,400,000 har beskrivits Arter idag: > 30,000,000 )

Utdöenden Inget att skämmas för – helt normalt Utdöendefrekvenser ej konstanta David Raup: (1991,1994) Analys av 543 Ma 1 Ma intervall % utdöendefrekvens under intervall Ett fåtal större massutdöenden Ultimate fate of all species Research into extinctions is still rudimentary…..however…..one thing is clear: Global extinction rate has not been constant thru time – Periods of intense extinction David Raup: (1991,1994) Examined Earth’s evolutionary history over past 543 million years Broke it down into 1 million year intervals Calculated the percent of species that went extinct during each interval NOTE: histogram has pronounced right skew which was created by a few large events

Mekanismer Konkurrens Miljön Mänsklig påverkan Naturligt urval Klimat, havsytenivå, oceanografiska förändringar Mänsklig påverkan Miljöförstöring, jakt etc. What types of mechanistic theories have been postulated to explain extinctions? Catastrophic: Rapid geoogic event or more commonly today – asteroid impact Competition: Extinction of an old group by a newly evolving superior group. Generally not accepted as primary cause Multituberculate - rodent Environmental: Climatic change (generally cooling events), sea level changes (usually declines), and other sea changes (salinity – nutrients) Over-Kill by humans

Massutdöenden Mest extrema Intervall där minst 60% av arterna dör ut Hur många? “BIG FIVE” Most extreme of these events referred to as MASS extinctions Represent intervals in which 60% of species that were alive at time went extinct within a 1 my period How many occurred during Phanerozoic? Benton (1995): Plotted plotted the percent of families that died out during each stage in the fossil record for last 510 million years Five prominent spikes were evident Traditionally recognized as the “BIG FIVE”

“Big 5” “Big Five” – Utdöenden som var: Snabba, globala & mängder av arter Slutet av Ordovicium (c:a. 440 Ma) Senare delen av Devon (c:a 365 Ma) Slutet Perm (c:a 250 Ma) Senare delen av Trias (c:a 215 Ma) K-T (c:a 65 Ma) IMPORTANT: The big Five Account for only 4% of species extinctions Geologically rapid Global in nature Wide diversity of taxa affected 1. End Ordovician: Loss of 12% families, 61% of genera, 85% of species 2. Late Devonian: Loss of 14% of families, 55% of genera, 85% of species 3. Late Permian: Loss of 52% of families, 85% genera, 96% of species 4. Late Triassic: Loss of 12% families, 47% genera, 76% species 5. K-T: 11% families, 47% genera, 76% species. Is a possible 6th event caused by humans underway???

Perm 290 – 245 Ma

Perm-Trias Utdöendet Största utdöendet 250 Ma 90-96% av alla arter Flesta träd och mindre växter 8 av 27 insektfamiljer 21 av 27 reptilfamiljer Alla revekosystem Många Ryggradslösa djur Most dramatic and mysterious extinction events > 50% all families of animals 90-96% all spp 8 of 27 insect orders 21 of 27 reptile families > 70% genera of marine invertebrates All reef-building corals (extant type appeared later

Permiska organismer som drabbas Armfotingar Trilobiter Ammoniter Koraller

Jordens största massutdöende varför? Pangaea bildas & istid? Havsytesänkning? Vulkanism? Meteoritnedslag? Syrehalt minskar? ”Naturlig” Ekologisk katastrof?

Perm

Gondwana - nedisning

Havsyteförändring Shelferna minskas från 34% av kontinenterna till 13% Orsakas av istid + platt-tektonik Förlust av habitat Large portions of continental shelf covered by shallow seas in early permian (~43%) Slow regression during Permian (down to 34%), with dramatic drop at end of period (to 13%) Massive loss of shallow-water shelf habitat Rapid increase in sea level in Triassic (80% recovery) Many possible causes: primarily due to movement of plates, collision of continents,uplift & possibly glaciation

Vulkanism Sibiriska flodbasalter Stänger ute solljus och kyler ned Djupa spricksystem (2900km) Ca 3,000m tjocka lavaflöden 1.5 million km2 Stänger ute solljus och kyler ned Siberian flood basalts (Renne et al, 1995) Came from deep underground (2900km or roughly 1800 mi – from between mantle and core) Churned out around a 1.6 km3 / year 400m to 3,000m thick and cover 1.5 million km2 northeast Asia Created uplift of continent Tremendous contribution of: Heat CO2 SO2 Rock particles to crust and atmosphere Blocked sunlight and rapidly cooled the earth Followed by a warming trend due to CO2 buildup & greenhouse effect. I, 2 punch could have wiped out much of life on earth.

Förändringar i oceanerna Lång djuphavs-anoxia: Syrefria havsbottnar Orsaker: Pangea Havsströmmar försvinner Pelagic Cherts (SiO2) available from P-T boundary Record a long term and worldwide deep-sea anoxia. Data from deep sea cherts Also appears in shallow seas High in pyrite (FeS2) resulting from sulfur-reducing bacteria—anoxic conditions Causes: Formation of Pangea Resulted in Stagnation of ocean currents Buildup of detritus and CO2 kill could occur with overturn of anoxic water

Mesozoikum

K/T-utdöendet Utdöende i havet: Utdöende på land: Diversitetsförlust Alla ammoniter + stora havsreptiler Utdöende på land: Dinosaurier, flygödlor Diversitetsförlust Planktonalger, djurplankton, musslor, sjöliljor, sjöborrar, fiskar 70% av alla arter 20-25% av familjer

K/T-utdöendet Men dessa klarar sig: Groddjur Däggdjur Hajar Vissa djurplankton Växter!

K/T-utdöendet Gradualistiska modeller Katastrofiska modeller Långsamma ekologiska förändringar Ekologisk kollaps Katastrofiska modeller Meteoriter Vulkanism

Krita (145 – 65 Ma)

Meteoritnedslag?

K/T-utdöendet Bevis för nedslag Iridium Chockad kvarts Tektiter “fern spikes”

Iridium - hittad av Alvarez et al. (1980 Science) Ir ovanlig på jorden Anrikas på jorden från rymdstoft

Chockad kvarts

Tektiter – vulkaniska glaspärlor mm

Ödelagda växtsamhällen efter mass utdöendet FSAA = Fern Spore Abundance Anomaly Växtlivet helt dominerat av ormbunkar

”Fern spike” & ”fungal spike”

Tsunami

10 km diameter 108 Teraton TNT (10,000 x alla kärnvapen)

MEN, Chicxulb nedslaget skedde kanske 300.000 år FÖRE massutdöendet! Keller et al., 2007

K/T-utdöendet Alternativa hypoteser - Vulkanism – Indiska flodbasalter

500,000 km3

Meteoritnedslag i perm också ? Meteor Impact: (Becker, 2001) A large meteor (5-11 km across) impacted earth around P-T Observed helium isotope within cavities of meteorite rocks These were similar to Murchison Meteor – indicating extraterrestrial origin Large impact would have set off an immense wave of superheated vapor Sent tons of dust into atmosphere Global cooling, glaciation May have coincided with SO2 output from Siberian flood basalts “volcanic winter” Uplift of continent, increase in altitude Global warming trend Long-term greenhouse effect from released CO2

Bedout-kratern

Kombination? Mot slutet av krita och mot slutet av perm: Vulkanism (flodbasalter) Upprepade meteornedslag? Stressad livsmiljö? Stegvis utdöende? Den sista avgörande faktorn?