scholarly journals Characteristic disruptions of an excitable carbon cycle

2019 ◽  
Vol 116 (30) ◽  
pp. 14813-14822 ◽  
Author(s):  
Daniel H. Rothman
Keyword(s):  
Mathematical Model ◽  
Carbon Cycle ◽  
Mass Extinction ◽  
Rate Of Change ◽  
Stable Steady State ◽  
Mass Extinctions ◽  
Carbon Mass ◽  
History Of ◽  
External Sources ◽  
Major Disruption

The history of the carbon cycle is punctuated by enigmatic transient changes in the ocean’s store of carbon. Mass extinction is always accompanied by such a disruption, but most disruptions are relatively benign. The less calamitous group exhibits a characteristic rate of change whereas greater surges accompany mass extinctions. To better understand these observations, I formulate and analyze a mathematical model that suggests that disruptions are initiated by perturbation of a permanently stable steady state beyond a threshold. The ensuing excitation exhibits the characteristic surge of real disruptions. In this view, the magnitude and timescale of the disruption are properties of the carbon cycle itself rather than its perturbation. Surges associated with mass extinction, however, require additional inputs from external sources such as massive volcanism. Surges are excited when CO2 enters the oceans at a flux that exceeds a threshold. The threshold depends on the duration of the injection. For injections lasting a time ti≳10,000 y in the modern carbon cycle, the threshold flux is constant; for smaller ti, the threshold scales like ti−1. Consequently the unusually strong but geologically brief duration of modern anthropogenic oceanic CO2 uptake is roughly equivalent, in terms of its potential to excite a major disruption, to relatively weak but longer-lived perturbations associated with massive volcanism in the geologic past.

scholarly journals Diversification events and the effects of mass extinctions on Crocodyliformes evolutionary history

2015 ◽  
Vol 2 (5) ◽  
pp. 140385 ◽  
Author(s):  
Mario Bronzati ◽  
Felipe C. Montefeltro ◽  
Max C. Langer
Keyword(s):  
Mass Extinction ◽  
Fossil Record ◽  
Evolutionary History ◽  
Continuous Process ◽  
Mass Extinctions ◽  
Terrestrial Habitats ◽  
History Of ◽  
The Rich ◽  
A Minor ◽  
Diversification Event

The rich fossil record of Crocodyliformes shows a much greater diversity in the past than today in terms of morphological disparity and occupation of niches. We conducted topology-based analyses seeking diversification shifts along the evolutionary history of the group. Our results support previous studies, indicating an initial radiation of the group following the Triassic/Jurassic mass extinction, here assumed to be related to the diversification of terrestrial protosuchians, marine thalattosuchians and semi-aquatic lineages within Neosuchia. During the Cretaceous, notosuchians embodied a second diversification event in terrestrial habitats and eusuchian lineages started diversifying before the end of the Mesozoic. Our results also support previous arguments for a minor impact of the Cretaceous/Palaeogene mass extinction on the evolutionary history of the group. This argument is not only based on the information from the fossil record, which shows basal groups surviving the mass extinction and the decline of other Mesozoic lineages before the event, but also by the diversification event encompassing only the alligatoroids in the earliest period after the extinction. Our results also indicate that, instead of a continuous process through time, Crocodyliformes diversification was patchy, with events restricted to specific subgroups in particular environments and time intervals.

The Anthropocene Mass Extinction: An Emerging Curriculum Theme for Science Educators

2011 ◽  
Vol 73 (2) ◽  
pp. 78-83 ◽  
Author(s):  
Ron Wagler
Keyword(s):  
Human Activities ◽  
Mass Extinction ◽  
Science Curriculum ◽  
Habitat Modification ◽  
Mass Extinctions ◽  
Sixth Mass Extinction ◽  
History Of ◽  
Science Educators ◽  
Curriculum Topics ◽  
Great Mass

There have been five past great mass extinctions during the history of Earth. There is an ever-growing consensus within the scientific community that we have entered a sixth mass extinction. Human activities are associated directly or indirectly with nearly every aspect of this extinction. This article presents an overview of the five past great mass extinctions; an overview of the current Anthropocene mass extinction; past and present human activities associated with the current Anthropocene mass extinction; current and future rates of species extinction; and broad science-curriculum topics associated with the current Anthropocene mass extinction that can be used by science educators. These broad topics are organized around the major global, anthropogenic direct drivers of habitat modification, fragmentation, and destruction; overexploitation of species; the spread of invasive species and genes; pollution; and climate change.

Morphologic and taxonomic history of Paleozoic ammonoids in time and morphospace

Paleobiology ◽  
2008 ◽  
Vol 34 (1) ◽  
pp. 128-154 ◽  
Author(s):  
W. B. Saunders ◽  
Emily Greenfest-Allen ◽  
David M. Work ◽  
S. V. Nikolaeva
Keyword(s):  
Mass Extinction ◽  
Evolutionary History ◽  
Large Scale ◽  
Taxonomic Diversity ◽  
Mass Extinctions ◽  
History Of ◽  
Morphologic Variation ◽  
Components Analysis ◽  
Extinction Events ◽  
Mass Extinction Events

Principal components analysis (PCA) of 21 shell parameters (geometry, sculpture, aperture shape, and suture complexity) in 597 L. Devonian to L. Triassic ammonoid genera (spanning ~166 Myr) shows that eight basic morphotypes appeared within ~20 Myr of the first appearance of ammonoids. With one exception, these morphotypes persisted throughout the Paleozoic, occurring in ~75% of the ~5-Myr time bins used in this study. Morphotypes were not exclusive to particular lineages. Their persistence was not just a product of phylogenetic constraints or longevity, and multiple iterations of the same morphotypes occurred at different times and in different groups. Although mass extinction events severely condensed the range of morphologic variation and taxonomic diversity, the effects were short lived and most extinct morphotypes were usually iterated within 5 Myr. The most important effect of mass extinctions on ammonoid evolutionary history seems to have been their role in large scale taxonomic turnovers; they effectively eliminated previously dominant orders at the Frasnian/Famennian (F/F) (Agoniatitida), the Devonian/Mississippian (D/M) (Clymeniida), and the Permian/Triassic (P/T) (Goniatitida and Prolecanitida) extinctions. Survivors varied from two (P/T) to four (D/M) and five genera (F/F). These events generated sharp reductions in morphologic disparity at the D/M (58%) and at the P/T (59%), but there was a net increase at the F/F (38%). There was no obvious survival bias for particular morphotypes, but 64% are interpreted to have beenNautilus-like nektobenthic. The recurrence of particular combinations of morphology and their strong independence of phylogeny are strong arguments for functional constraint. Intervals between mass extinctions seem to have been relatively static in terms of morphotype numbers, in contrast to numbers of genera. Significant decreases in genus diversity (54%) and morphologic disparity (33%) commenced in the mid-Permian (Wordian/Capitanian boundary), well before the final P/T event.

scholarly journals Did a gamma-ray burst initiate the late Ordovician mass extinction?

2004 ◽  
Vol 3 (1) ◽  
pp. 55-61 ◽  
Author(s):  
A.L. Melott ◽  
B.S. Lieberman ◽  
C.M. Laird ◽  
L.D. Martin ◽  
M.V. Medvedev ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Gamma Ray ◽  
Late Ordovician ◽  
Mass Extinctions ◽  
Solar Ultraviolet Radiation ◽  
Observable Universe ◽  
The Earth ◽  
Global Cooling ◽  
History Of ◽  
Solar Ultraviolet

Gamma-ray bursts (GRBs) produce a flux of radiation detectable across the observable Universe. A GRB within our own galaxy could do considerable damage to the Earth's biosphere; rate estimates suggest that a dangerously near GRB should occur on average two or more times per billion years. At least five times in the history of life, the Earth has experienced mass extinctions that eliminated a large percentage of the biota. Many possible causes have been documented, and GRBs may also have contributed. The late Ordovician mass extinction approximately 440 million years ago may be at least partly the result of a GRB. A special feature of GRBs in terms of terrestrial effects is a nearly impulsive energy input of the order of 10 s. Due to expected severe depletion of the ozone layer, intense solar ultraviolet radiation would result from a nearby GRB, and some of the patterns of extinction and survivorship at this time may be attributable to elevated levels of UV radiation reaching the Earth. In addition, a GRB could trigger the global cooling which occurs at the end of the Ordovician period that follows an interval of relatively warm climate. Intense rapid cooling and glaciation at that time, previously identified as the probable cause of this mass extinction, may have resulted from a GRB.

scholarly journals The future of the oceans past

2010 ◽  
Vol 365 (1558) ◽  
pp. 3765-3778 ◽  
Author(s):  
Jeremy B. C. Jackson
Keyword(s):  
Ocean Acidification ◽  
Deep Sea ◽  
Mass Extinction ◽  
Mass Extinctions ◽  
Conservation Action ◽  
Isthmus Of Panama ◽  
Geological Past ◽  
History Of ◽  
Short Time ◽  
Oceanographic Conditions

Major macroevolutionary events in the history of the oceans are linked to changes in oceanographic conditions and environments on regional to global scales. Even small changes in climate and productivity, such as those that occurred after the rise of the Isthmus of Panama, caused major changes in Caribbean coastal ecosystems and mass extinctions of major taxa. In contrast, massive influxes of carbon at the end of the Palaeocene caused intense global warming, ocean acidification, mass extinction throughout the deep sea and the worldwide disappearance of coral reefs. Today, overfishing, pollution and increases in greenhouse gases are causing comparably great changes to ocean environments and ecosystems. Some of these changes are potentially reversible on very short time scales, but warming and ocean acidification will intensify before they decline even with immediate reduction in emissions. There is an urgent need for immediate and decisive conservation action. Otherwise, another great mass extinction affecting all ocean ecosystems and comparable to the upheavals of the geological past appears inevitable.

scholarly journals Prevalence of Antimicrobial Resistant Bacteria from Conjunctival Flora in an Eye Infection Prone Breed (Saint Bernard)

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2219
Author(s):  
George Cosmin Nadăș ◽  
Cristiana Ștefania Novac ◽  
Ioana Adriana Matei ◽  
Cosmina Maria Bouari ◽  
Zoltan Miklos Gal ◽  
...  
Keyword(s):  
Multidrug Resistant ◽  
Ocular Disease ◽  
Resistant Bacteria ◽  
Human Populations ◽  
Disease Treatment ◽  
Pseudomonas Spp ◽  
History Of ◽  
External Sources ◽  
Staphylococcus Spp ◽  
Saint Bernard

The conjunctival bacterial resident and opportunistic flora of dogs may represent a major source of dissemination of pathogens throughout the environment or to other animals and humans. Nevertheless, contamination with bacteria from external sources is common. In this context, the study of the antimicrobial resistance (AMR) pattern may represent an indicator of multidrug resistant (MDR) strains exchange. The present study was focused on a single predisposed breed—Saint Bernard. The evaluated animals were healthy, but about half had a history of ocular disease/treatment. The swabs collected from conjunctival sacs were evaluated by conventional microbiological cultivation and antimicrobial susceptibility testing (AST). The most prevalent Gram-positive was Staphylococcus spp.; regardless of the history, while Gram-negative was Pseudomonas spp.; exclusively from dogs with a history of ocular disease/treatment. Other identified genera were represented by Bacillus, Streptococcus, Trueperella, Aeromonas and Neisseria. The obtained results suggest a possible association between the presence of mixed flora and a history of ocular disease/treatment. A high AMR was generally observed (90%) in all isolates, especially for kanamycin, doxycycline, chloramphenicol and penicillin. MDR was recorded in Staphylococcus spp. and Pseudomonas spp. This result together with a well-known zoonotic potential may suggest an exchange of these strains within animal human populations and the environment.

On a Mathematical Model of the Carbon Cycle in Nature

Tellus ◽  
1956 ◽  
Vol 8 (2) ◽  
pp. 155-175 ◽  
Author(s):  
E. ERIKSSON ◽  
P. WELANDER
Keyword(s):  
Mathematical Model ◽  
Carbon Cycle

Biogeochemical disruptions across the Cretaceous-Paleogene boundary : insights from sulfur isotopes

2021 ◽  
Author(s):  
Arbia Jouini
Keyword(s):  
Mass Extinction ◽  
Environmental Changes ◽  
Sea Water ◽  
Sulfur Isotopes ◽  
Deep Understanding ◽  
Sulfur Cycle ◽  
Mass Extinctions ◽  
Deccan Volcanism ◽  
Organic Carbon Burial ◽  
Early Paleocene

<p><strong>Biogeochemical disruptions across the Cretaceous-Paleogene boundary : insights from sulfur isotopes</strong></p><p> </p><p>Arbia JOUINI<sup>1*</sup>, Guillaume PARIS<sup>1</sup>, Guillaume CARO<sup>1</sup>, Annachiara BARTOLINI<sup>2</sup></p><p><sup>1 </sup>Centre de Recherches Pétrographiques et Géochimiques, CRPG-CNRS, UMR7358, ,15 rue Notre Dame des Pauvres, BP20, 54501Vandoeuvre-lès-Nancy, France, email:[email protected]</p><p><sup>2</sup> Muséum National D’Histoire Naturelle, Département Origines & Evolution, CR2P MNHN, CNRS, Sorbonne Université, 8 rue Buffon CP38, 75005 Paris, France</p><p> </p><p>The Cretaceous–Paleogene (KPg) mass extinction event 66 million years ago witnessed one of the ‘Big Five’ mass extinctions of the Phanerozoic. Two major catastrophic events, the Chicxulub asteroid impact and the Deccan trap eruptions, were involved in complex climatic and environmental changes that culminated in the mass extinction including oceanic biogenic carbonate crisis, sea water chemistry and ocean oxygen level changes. Deep understanding of the coeval sulfur biogeochemical cycle may help to better constrain and quantify these parameters.</p><p>Here we present the first stratigraphic high resolution isotopic compositions of carbonate associated sulfate (CAS) based on monospecific planktic and benthic foraminifers' samples during the Maastrichtian-Danian transition from IODP pacific site 1209C. Primary δ34SCAS data suggests that there was a major perturbation of sulfur cycle around the KPg transition with rapid fluctuations (100-200kyr) of about 2-4‰ (±0.54‰, 2SD) during the late Maastrichtian followed by a negative excursion in δ34SCAS of 2-3‰ during the early Paleocene.</p><p>An increase in oxygen levels associated with a decline in organic carbon burial, related to a collapse in primary productivity, may have led to the early Paleocene δ34SCAS negative shift via a significant drop in microbial sulfate reduction. Alternatively, Deccan volcanism could also have played a role and impacted the sulfur cycle via direct input of isotopically light sulfur to the ocean. A revised correlation between δ34SCAS data reported in this study and a precise dating of the Deccan volcanism phases would allow us to explore this hypothesis.</p><p>Keywords : KPg boundary, Sulphur cycle, cycle du calcium, Planktic and benthic foraminifera</p><p> </p>

Sign in / Sign up

Export Citation Format

Share Document