On the declining extinction and origination rates of fossil taxa

Paleobiology ◽  
1992 ◽  
Vol 18 (1) ◽  
pp. 89-92 ◽  
Author(s):  
Craig M. Pease
Keyword(s):  
Present Model ◽  
Marine Invertebrate ◽  
Extinction Rate ◽  
Geologic Time ◽  
The Past ◽  
Extinction Rates ◽  
Rate Versus ◽  
Biological Explanation ◽  
Length Changes ◽  
Sampling Biases

The per-stage extinction rate is the product of the per-taxon extinction rate and stage length, and the per-stage origination rate is defined similarly. These rates decline from ancient to recent times because of the pull of the Recent, because there is more young than old fossiliferous rock, and because average stage length increases from the recent to the past. More specifically, the present model assumes that the graphs of ln(per-stage extinction rate) and ln(per-stage origination rate) versus geologic time have slope zero in the absence of sampling biases, and shows how sampling biases cause both these graphs to appear to have slope min(h,q) + s in the distant past, where h and q are the fossil loss and actual per-taxon extinction rates, and the stratigraphic constant, s, quantifies how stage length changes through time.Although the per-stage rates of bivalve families and marine invertebrate genera decline toward the recent, the magnitudes of these declines are entirely consistent with what the present model predicts sampling biases will produce. Hence there is no need to postulate a biological explanation for these patterns.

scholarly journals Southern Ocean phytoplankton turnover in response to stepwise Antarctic cooling over the past 15 million years

2016 ◽  
Vol 113 (25) ◽  
pp. 6868-6873 ◽  
Author(s):  
James S. Crampton ◽  
Rosie D. Cody ◽  
Richard Levy ◽  
David Harwood ◽  
Robert McKay ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Atmospheric Carbon Dioxide ◽  
Large Scale ◽  
Species Turnover ◽  
Polar Front ◽  
Extinction Rate ◽  
The Past ◽  
Extinction Rates ◽  
Phytoplankton Communities ◽  
Global Extinction

It is not clear how Southern Ocean phytoplankton communities, which form the base of the marine food web and are a crucial element of the carbon cycle, respond to major environmental disturbance. Here, we use a new model ensemble reconstruction of diatom speciation and extinction rates to examine phytoplankton response to climate change in the southern high latitudes over the past 15 My. We identify five major episodes of species turnover (origination rate plus extinction rate) that were coincident with times of cooling in southern high-latitude climate, Antarctic ice sheet growth across the continental shelves, and associated seasonal sea-ice expansion across the Southern Ocean. We infer that past plankton turnover occurred when a warmer-than-present climate was terminated by a major period of glaciation that resulted in loss of open-ocean habitat south of the polar front, driving non-ice adapted diatoms to regional or global extinction. These findings suggest, therefore, that Southern Ocean phytoplankton communities tolerate “baseline” variability on glacial–interglacial timescales but are sensitive to large-scale changes in mean climate state driven by a combination of long-period variations in orbital forcing and atmospheric carbon dioxide perturbations.

A more precise speciation and extinction rate estimator

Paleobiology ◽  
2015 ◽  
Vol 41 (4) ◽  
pp. 633-639 ◽  
Author(s):  
John Alroy
Keyword(s):  
Turnover Rate ◽  
Marine Invertebrate ◽  
Time Interval ◽  
Extinction Rate ◽  
Turnover Rates ◽  
Sample Sizes ◽  
Extinction Rates ◽  
Highly Correlated ◽  
The One

AbstractA new turnover rate metric is introduced that combines simplicity and precision. Like the related three-timer and gap-filler equations, it involves first identifying a cohort of taxa sampled in the time interval preceding the one of interest (call the intervalsi0andi1). Taxa sampled ini0andi1are two-timers (t2); those sampled ini0andi2but noti1are part-timers (p); and taxa sampled only in eitheri1,i2, ori3are newly notated here as eithers1,s2, ors3. The gap-filler extinction proportion can be reformulated as (s1−s3)/(t2+p). The method proposed here is to substitutes3with the second-highest of the three counts when the expected orderings1≥s2≥s3is violated. In simulation, this new estimator yields values that are highly correlated with those produced by the gap-filler equation but more precise. In particular, it rarely produces highly negative values even when sample sizes are quite small. It is mildly upwards biased when sampling is extremely poor and turnover rates are extremely low, but it is otherwise highly accurate. Examples of Phanerozoic extinction rates for four major marine invertebrate groups are given to illustrate the method’s improved precision. Based on the results, the procedure is recommended for general use.

The Geologic Time Spiral - A Path to the Past

10.3133/gip58 ◽  
2008 ◽  
Author(s):  
Joseph Graham ◽  
William Newman ◽  
John Stacy
Keyword(s):  
Geologic Time ◽  
The Past

scholarly journals Current extinction rate in European freshwater gastropods greatly exceeds that of the late Cretaceous mass extinction

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Thomas A. Neubauer ◽  
Torsten Hauffe ◽  
Daniele Silvestro ◽  
Jens Schauer ◽  
Dietrich Kadolsky ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Recovery Period ◽  
Freshwater Ecosystems ◽  
Extinction Rate ◽  
Freshwater Gastropods ◽  
Extinction Rates ◽  
Freshwater Biota ◽  
Order Of Magnitude ◽  
To Come ◽  
Mass Extinction Event

AbstractThe Cretaceous–Paleogene mass extinction event 66 million years ago eradicated three quarters of marine and terrestrial species globally. However, previous studies based on vertebrates suggest that freshwater biota were much less affected. Here we assemble a time series of European freshwater gastropod species occurrences and inferred extinction rates covering the past 200 million years. We find that extinction rates increased by more than one order of magnitude during the Cretaceous–Paleogene mass extinction, which resulted in the extinction of 92.5% of all species. The extinction phase lasted 5.4 million years and was followed by a recovery period of 6.9 million years. However, present extinction rates in European freshwater gastropods are three orders of magnitude higher than even these revised estimates for the Cretaceous–Paleogene mass extinction. Our results indicate that, unless substantial conservation effort is directed to freshwater ecosystems, the present extinction crisis will have a severe impact to freshwater biota for millions of years to come.

Did Ground Cover Change Over Geologic Time?

2000 ◽  
Vol 6 ◽  
pp. 171-182 ◽  
Author(s):  
Ben A. LePage ◽  
Hermann W. Pfefferkorn
Keyword(s):  
Fossil Record ◽  
Ground Cover ◽  
The Other ◽  
Detailed Account ◽  
Geologic Time ◽  
The Past ◽  
Other Hand ◽  
Plant Fossil

When one hears the term “ground cover,” one immediately thinks of “grasses.” This perception is so deep-seated that paleobotanists even have been overheard to proclaim that “there was no ground cover before grasses.” Today grasses are so predominant in many environments that this perception is perpetuated easily. On the other hand, it is difficult to imagine the absence or lack of ground cover prior to the mid-Tertiary. We tested the hypothesis that different forms of ground cover existed in the past against examples from the Recent and the fossil record (Table 1). The Recent data were obtained from a large number of sources including those in the ecological, horticultural, and microbiological literature. Other data were derived from our knowledge of Precambrian life, sedimentology and paleosols, and the plant fossil record, especially in situ floras and fossil “monocultures.” Some of the data are original observations, but many others are from the literature. A detailed account of these results will be presented elsewhere (Pfefferkorn and LePage, in preparation).

3. Extinction in the past

2019 ◽  
pp. 33-50
Author(s):  
Paul B. Wignall
Keyword(s):  
Fossil Record ◽  
The Past ◽  
Extinction Rates ◽  
History Of ◽  
Extinction Events

Despite the less-than-perfect nature of the fossil record, it still provides a unique window on the history of life, and reveals that there have been dramatic fluctuations in extinction intensities since complex life evolved around 600 million years ago. ‘Extinction in the past’ considers Jack Sepkoski’s database compiled in the 1980s, and his series of highly informative charts showing both diversity and extinction rates since the start of the Cambrian Period 541 million years ago. The calculation of extinction rates and the improved dating of extinction events are discussed, along with the extinction trends that can be observed. Fossils also provide valuable evidence on the nature of selection during extinction.

scholarly journals The dynamics underlying avian extinction trajectories forecast a wave of extinctions

2019 ◽  
Vol 15 (12) ◽  
pp. 20190633 ◽  
Author(s):  
Melanie J. Monroe ◽  
Stuart H. M. Butchart ◽  
Arne O. Mooers ◽  
Folmer Bokma
Keyword(s):  
Extinction Risk ◽  
Population Decline ◽  
Bird Species ◽  
Iucn Red List ◽  
Red List ◽  
Extinction Rate ◽  
Critically Endangered Species ◽  
Extinction Rates ◽  
Historical Times ◽  
Risk Categories

Population decline is a process, yet estimates of current extinction rates often consider just the final step of that process by counting numbers of species lost in historical times. This neglects the increased extinction risk that affects a large proportion of species, and consequently underestimates the effective extinction rate. Here, we model observed trajectories through IUCN Red List extinction risk categories for all bird species globally over 28 years, and estimate an overall effective extinction rate of 2.17 × 10 −4 /species/year. This is six times higher than the rate of outright extinction since 1500, as a consequence of the large number of species whose status is deteriorating. We very conservatively estimate that global conservation efforts have reduced the effective extinction rate by 40%, but mostly through preventing critically endangered species from going extinct rather than by preventing species at low risk from moving into higher-risk categories. Our findings suggest that extinction risk in birds is accumulating much more than previously appreciated, but would be even greater without conservation efforts.

Plutonium in Crystalline Ceramics and Glasses

MRS Bulletin ◽  
2001 ◽  
Vol 26 (9) ◽  
pp. 698-706 ◽  
Author(s):  
Isabelle Muller ◽  
William J. Weber
Keyword(s):  
Long Range ◽  
Nuclear Waste ◽  
Materials Science ◽  
Ceramic Matrix ◽  
Range Order ◽  
Long Range Order ◽  
Geologic Time ◽  
The Past ◽  
Geologic Time Scale ◽  
High Flexibility

The investigation of plutonium in glasses (amorphous ceramics lacking long-range order), in crystalline ceramics, and in composite materials composed of multiple crystalline or glass and crystalline phases, relieson multidisciplinary studies of physics, chemistry, and materials science. It involves the study of the plutonium atoms in materials with only short-range periodicity, as in glasses, to materials with long-range periodicity, as in crystals. The materials studied over the past 30 years include simple binary crystals, used to investigate the electronic structure of plutonium, to complex glasses and ceramics selected not only for the safety and durability that they provide for the immobilization of nuclear waste and plutonium, but also for the high flexibility they offer in composition. The lack of long-range order at the atomic level in glasses permits the inclusion of abroad range of waste elements, but it renders more difficult the interpretation of data from many commonly used experimental techniques. Regardless of the challenge, much of the research conducted in this field over the past few decades has been motivated by the use of plutonium as a surrogate for all nuclear-waste actinides or on its own in immobilization studies, in order to develop a durable glass or ceramic matrix that can resist leaching and mobilization of the plutonium on a geologic time scale.

Harecxs Measurements of Elemental Disordering

2001 ◽  
Vol 7 (S2) ◽  
pp. 354-355
Author(s):  
Nestor J. Zaluzec ◽  
Katherine L. Smith
Keyword(s):  
Angular Resolution ◽  
Alpha Decay ◽  
High Angular Resolution ◽  
Crystalline Materials ◽  
X Ray ◽  
Geologic Time ◽  
The Past ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
High Level

It has been long known that orientation effects in crystalline materials can influence characteristic x-ray emission and microanalysis1-7. High Angular Resolution Electron Channeling X-ray Spectroscopy (HARECXS)6-7. a variation of ALCHEMI4-5, has been used at ANL for the last few years to investigate the effects of channeling on quantitative XEDS analysis of materials. More recently we have also been using HARECXS to carefully measure elemental disordering in a number of systems and have found that it can be used very successfully to elucidate the various stages of disorder.Perovskite (nominally CaTiO3) is a host phase for actinides in various wasteforms for the immobilization of high level radioactive nuclear waste. Over geologic time, alpha decay damage of the actinides in perovskite will cause displacive effects that influence the dimensional and chemical stability of the wasteform. in the past, the progression of damage has been studied by monitoring changes in selected area electron diffraction (SAED) patterns with increasing dose (e.g. 11).

Extinction, the Causes of Extinction and the Conservation of Biodiversity

2008 ◽  
Vol 3 (3) ◽  
pp. 166-173 ◽  
Author(s):  
Hisashi Nagata ◽  
Keyword(s):  
Global Warming ◽  
Theoretical Background ◽  
Natural Process ◽  
Habitat Destruction ◽  
Mass Extinctions ◽  
Species Extinction ◽  
Biodiversity Crisis ◽  
The Past ◽  
Extinction Rates ◽  
Conservation Of Biodiversity

Over 25% of species are currently categorized as threatened. Extinction is a natural process in organism evolution, and 99% of all organisms that have thus far existed are already extinct. Current extinction rates, however, is progressing at least 2,500 times faster than in the past. Ongoing extinction is so fast, in fact, that organisms may not be able to adapt environment and to evolve. Current biodiversity crisis is called “sixth extinction” because it is severer than five geological mass extinctions. Habitat destruction, overexploitation, and invasion of species through human activities are currently the major causes of species extinction. Global warming is also expected to pose a considerable threat to Earth’s organisms. I briefly review the nature of species extinction, its processes, causes, theoretical background, and ongoing threats.

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