scholarly journals Mesozoic mass extinctions and angiosperm radiation: does the molecular clock tell something new?

Geologos ◽  
2012 ◽  
Vol 18 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Dmitry Ruban
Keyword(s):  
Molecular Clock ◽  
Global Scale ◽  
Flowering Plants ◽  
Mass Extinctions ◽  
Geological Time ◽  
Late Mesozoic ◽  
Environmental Perturbation ◽  
History Of

Mesozoic mass extinctions and angiosperm radiation: does the molecular clock tell something new?Angiosperms evolved rapidly in the late Mesozoic. Data from the genetic-based approach called ‘molecular clock’ permit an evaluation of the radiation of flowering plants through geological time and of the possible influences of Mesozoic mass extinctions. A total of 261 divergence ages of angiosperm families are considered. The radiation of flowering plants peaked in the Albian, early Campanian, and Maastrichtian. From the three late Mesozoic mass extinctions (Jurassic/Cretaceous, Cenomanian/Turonian, and Cretaceous/Palaeogene), only the Cretaceous/Palaeogene event coincided with a significant, abrupt, and long-term decline in angiosperm radiation. If their link will be further proven, this means that global-scale environmental perturbation precluded from many innovations in the development of plants. This decline was, however, not unprecedented in the history of the angiosperms. The implication of data from the molecular clock for evolutionary reconstructions is limited, primarily because this approach deals with only extant lineages.

scholarly journals The origins of modern biodiversity on land

2010 ◽  
Vol 365 (1558) ◽  
pp. 3667-3679 ◽  
Author(s):  
Michael J. Benton
Keyword(s):  
Regional Scale ◽  
Global Scale ◽  
Scale Model ◽  
Time Range ◽  
Geological Time ◽  
New Methods ◽  
Evolution Of Life ◽  
History Of ◽  
Extinction Events ◽  
Mass Extinction Events

Comparative studies of large phylogenies of living and extinct groups have shown that most biodiversity arises from a small number of highly species-rich clades. To understand biodiversity, it is important to examine the history of these clades on geological time scales. This is part of a distinct ‘phylogenetic expansion’ view of macroevolution, and contrasts with the alternative, non-phylogenetic ‘equilibrium’ approach to the history of biodiversity. The latter viewpoint focuses on density-dependent models in which all life is described by a single global-scale model, and a case is made here that this approach may be less successful at representing the shape of the evolution of life than the phylogenetic expansion approach. The terrestrial fossil record is patchy, but is adequate for coarse-scale studies of groups such as vertebrates that possess fossilizable hard parts. New methods in phylogenetic analysis, morphometrics and the study of exceptional biotas allow new approaches. Models for diversity regulation through time range from the entirely biotic to the entirely physical, with many intermediates. Tetrapod diversity has risen as a result of the expansion of ecospace, rather than niche subdivision or regional-scale endemicity resulting from continental break-up. Tetrapod communities on land have been remarkably stable and have changed only when there was a revolution in floras (such as the demise of the Carboniferous coal forests, or the Cretaceous radiation of angiosperms) or following particularly severe mass extinction events, such as that at the end of the Permian.

In search of possible causes of mass extinctions

2004 ◽  
Author(s):  
Tony Hallam
Keyword(s):  
Science Fiction ◽  
High Rate ◽  
Mass Extinctions ◽  
Geological Time ◽  
Steven Spielberg ◽  
Geological Past ◽  
History Of ◽  
The Subject ◽  
Cretaceous Period ◽  
Land Vertebrates

When the subject of extinctions in the geological past comes up, nearly everyone’s thoughts turn to dinosaurs. It may well be true that these long-extinct beasts mean more to most children than the vast majority of living creatures. One could even go so far as to paraphrase Voltaire and maintain that if dinosaurs had never existed it would have been necessary to invent them, if only as a metaphor for obsolescence. To refer to a particular machine as a dinosaur would certainly do nothing for its market value. The irony is that the metaphor is now itself obsolete. The modern scientific view of dinosaurs differs immensely from the old one of lumbering, inefficient creatures tottering to their final decline. Their success as dominant land vertebrates through 165 million years of the Earth’s history is, indeed, now mainly regarded with wonder and even admiration. If, as is generally thought, the dinosaurs were killed off by an asteroid at the end of the Cretaceous, that is something for which no organism could possibly have been prepared by normal Darwinian natural selection. The final demise of the dinosaurs would then have been the result, not of bad genes, but of bad luck, to use the laconic words of Dave Raup. In contemplating the history of the dinosaurs it is necessary to rectify one widespread misconception. Outside scientific circles the view is widely held that the dinosaurs lived for a huge slice of geological time little disturbed by their environment until the final apocalypse. This is a serious misconception. The dinosaurs suffered quite a high evolutionary turnover rate, and this implies a high rate of extinction throughout their history. Jurassic dinosaurs, dominated by giant sauropods, stegosaurs, and the top carnivore Allosaurus, are quite different from those of the Cretaceous period, which are characterized by diverse hadrosaurs, ceratopsians, and Tyrannosaurus. Michael Crichton’s science-fiction novel Jurassic Park, made famous by the Steven Spielberg movies, features dinosaurs that are mainly from the Cretaceous, probably because velociraptors and Tyrannosaurus could provide more drama.

scholarly journals A comprehensive history of climate and habitat stability of the last 800&thinsp,000 years

2019 ◽  
Author(s):  
Mario Krapp ◽  
Robert Beyer ◽  
Stephen L. Edmundson ◽  
Paul J. Valdes ◽  
Andrea Manica
Keyword(s):  
Climate Model ◽  
Temporal Dynamics ◽  
Global Climate ◽  
Global Climate Model ◽  
Regional Scale ◽  
Geological Time ◽  
Comprehensive Overview ◽  
Long Term Stability ◽  
History Of

Abstract. A detailed and accurate reconstruction of the past climate is essential in understanding the interactions between ecosystems and their environment through time. We know that climatic drivers have shaped the distribution and evolution of species, including our own, and their habitats. Yet, spatially-detailed climate reconstructions that continuously cover the Quaternary do not exist. This is mainly because no paleoclimate model can reconstruct regional-scale dynamics over geological time scales. Here we develop a statistical emulator, the Global Climate Model Emulator (GCMET), which reconstructs the climate of the last 800 000 years with unprecedented spatial detail. GCMET captures the temporal dynamics of glacial-interglacial climates as an Earth System Model of Intermediate Complexity would whilst resolving the local dynamics with the accuracy of a Global Climate Model. It provides a new, unique resource to explore the climate of the Quaternary, which we use to investigate the long-term stability of major habitat types. We identify a number of stable pockets of habitat that have remained unchanged over the last 800 thousand years, acting as potential long-term evolutionary refugia. Thus, the highly detailed, comprehensive overview of climatic changes through time delivered by GCMET provides the needed resolution to quantify the role of long term habitat change and fragmentation in an ecological and anthropological context.

scholarly journals Most Compositae (Asteraceae) are descendants of a paleohexaploid and all share a paleotetraploid ancestor with the Calyceraceae

2016 ◽  
Author(s):  
Michael S. Barker ◽  
Zheng Li ◽  
Thomas I. Kidder ◽  
Chris R. Reardon ◽  
Zhao Lai ◽  
...  
Keyword(s):  
Gene Family ◽  
Linkage Map ◽  
Evolutionary History ◽  
Genome Duplication ◽  
Nuclear Gene ◽  
Flowering Plants ◽  
The Family ◽  
History Of ◽  
Phylogenomic Analyses

AbstractPremise of the studyLike many other flowering plants, members of the Compositae (Asteraceae) have a polyploid ancestry. Previous analyses found evidence for an ancient duplication or possibly triplication in the early evolutionary history of the family. We sought to better place this paleopolyploidy in the phylogeny and assess its nature.MethodsWe sequenced new transcriptomes for Barnadesia, the lineage sister to all other Compositae, and four representatives of closely related families. Using a recently developed algorithm, MAPS, we analyzed nuclear gene family phylogenies for evidence of paleopolyploidy.Key resultsWe found that the previously recognized Compositae paleopolyploidy is also in the ancestry of the Calyceraceae. Our phylogenomic analyses uncovered evidence for a successive second round of genome duplication among all sampled Compositae except Barnadesia.ConclusionsOur analyses of new samples with new tools provide a revised view of paleopolyploidy in the Compositae. Together with results from a high density Lactuca linkage map, our results suggest that the Compositae and Calyceraceae have a common paleotetraploid ancestor and most Compositae are descendants of a paleohexaploid. Although paleohexaploids have been previously identified, this is the first example where the paleotetraploid and paleohexaploid lineages have survived over tens of millions of years. The complex polyploidy in the ancestry of the Compositae and Calyceraceae represents a unique opportunity to study the long-term evolutionary fates and consequences of different ploidal levels.

scholarly journals Education Reform and the Normalisation of Private Education in Slovenia

2021 ◽  
Vol 11 (2) ◽  
pp. 125-143
Author(s):  
Marjan Šimenc
Keyword(s):  
Education Reform ◽  
Private Education ◽  
Global Scale ◽  
White Paper ◽  
Constitutional Court ◽  
Long Term Effects ◽  
Starting Point ◽  
History Of ◽  
Guiding Principles

This article examines the long-term effects of the regulation of private education adopted in the course of the education reform in 1996 and the sustainability of the guiding principles that served as the starting point for this regulation. It reviews the guiding principles of the introduction of private education, the goals of the reform laid down in the White Paper in 1995 and the regulations introduced on the basis of these tenets. It follows up on the ‘life’ of the legal solutions and the history of (attempted) amendments of the legislation, which generally start in the Slovenian Parliament and then proceed all the way to the Constitutional Court. The article also examines the effects of the adopted regulation: how the private education sector has established itself and what kind of relationship it has developed vis-a-vis public education. The second part of the article explores certain developments in the field of education in Slovenia and on the global scale, using them as the basis for assessing the sustainability of the goals that guided the education reform. The thesis proposed by the article is that it is the normalisation of private education in Slovenia should be considered the main achievement of the education reform.  

scholarly journals Basal polyphagan beetles in mid-Cretaceous amber from Myanmar: biogeographic implications and long-term morphological stasis

2019 ◽  
Vol 286 (1894) ◽  
pp. 20182175 ◽  
Author(s):  
Chenyang Cai ◽  
John F. Lawrence ◽  
Shûhei Yamamoto ◽  
Richard A. B. Leschen ◽  
Alfred F. Newton ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Geological Time ◽  
Burmese Amber ◽  
Incertae Sedis ◽  
Morphological Stasis ◽  
New Synonym ◽  
Extant Species ◽  
History Of ◽  
Living Species

The origin and early evolutionary history of polyphagan beetles have been largely based on evidence from the derived and diverse ‘core Polyphaga’, whereas little is known about the species-poor basal polyphagan lineages, which include Scirtoidea (Clambidae, Decliniidae, Eucinetidae, and Scirtidae) and Derodontidae. Here, we report two new species Acalyptomerus thayerae sp. nov. and Sphaerothorax uenoi sp. nov., both belonging to extant genera of Clambidae, from mid-Cretaceous Burmese amber. Acalyptomerus thayerae has a close affinity to A. herbertfranzi , a species currently occurring in Mesoamerica and northern South America. Sphaerothorax uenoi is closely related to extant species of Sphaerothorax , which are usually collected in forests of Nothofagus of Australia, Chile, and New Zealand. The discovery of two Cretaceous species from northern Myanmar indicates that both genera had lengthy evolutionary histories, originated at least by the earliest Cenomanian, and were probably more widespread than at present. Remarkable morphological similarities between fossil and living species suggest that both genera changed little over long periods of geological time. The long-term persistence of similar mesic microhabitats such as leaf litter may account for the 99 Myr morphological stasis in Acalyptomerus and Sphaerothorax . Additionally, the extinct staphylinoid family Ptismidae is proposed as a new synonym of Clambidae, and its only included species Ptisma zasukhae is placed as incertae sedis within Clambidae.

IX. Discussion

1965 ◽  
Vol 258 (1088) ◽  
pp. 107-108
Keyword(s):  
Geophysical Methods ◽  
Continental Drift ◽  
Tectonic Activity ◽  
Geological Time ◽  
The Past ◽  
Current State ◽  
The Earth ◽  
Long Term Changes ◽  
History Of

Although the primary subject of the Symposium was continental drift, this is only one aspect of a larger problem. Eventually, consideration of changes in magmatic, metamorphic and tectonic activity through the history of the crust should enable us to put forward a hypothesis to account for the behaviour of the upper parts of the Earth through geological time. As had been pointed out, most geophysical methods provided information about the current state of the Earth and part of the great value of palaeomagnetic studies lay in the fact that they produced information about the past. Some information about the behaviour of possible convection cells during continental drift could be obtained from other long-term changes in the crust. The incidence of magmatic and metamorphic activity gave some indication as to the distribution of regions where there had been an unusually high accession of heat in the past.

scholarly journals Macroevolución en plantas vasculares.

2003 ◽  
Vol 28 ◽  
pp. 155-177
Author(s):  
José S. Carrión ◽  
Juan Guerra
Keyword(s):  
Vascular Plants ◽  
Evolutionary Model ◽  
Plant Evolution ◽  
Model Systems ◽  
Mass Extinctions ◽  
Terrestrial Plants ◽  
Geological Time ◽  
Living Fossils

RESUMEN. Macroevolución en plantas vasculares. Se revisan los sistemas jerarquizados de evolución vegetal, desde una perspectiva paleoecológica y con énfasis en los controles del nivel superior para las plantas vasculares. Este nivel supone la existencia de breves episodios de intensa radiación, seguidos por largas fases de estabilización y declive taxonómico. El registro fósil sugiere que no han existido extinciones masivas entre las plantas terrestres, en el sentido en que ésta expresión se emplea para la evolución de animales, es decir, la existencia de fuertes pérdidas de biodiversidacl en períodos breves de tiempo geológico comparados con la vida media de las especies. Durante los episodios de estrés ambiental, las plantas han reaccionado haciendo valer sus capacidades de migración, recolonización, desplazamiento competitivo y, en suma, reorganizando la estructura ecológica o fitogeográfica. A un nivel taxonómico elevado, la mayoría de los grandes grupos exhiben un importante componente de supervivencia (fósiles vivientes). El único estrés al que no han podido escapar parece haber sido el de tipo abiótico y extrínseco que supone el incremento atmosférico del dióxido de carbono durante los eventos de superpluma asociados a las pulsaciones tectónicas. De entre estas, aquellas constatables para el Ordovícico Medio-Silúrico (460- 430 Ma), Devónico Medio-Carbonífero Inferior (375-350 Ma), Jurásico (150 Ma) y Cretácico Inferior (120-80 Ma), se correlacionan con fases de incremento rápido en la especiación y con la aparición de nuevos proyectos reproductores, a saber embriófitos, espermatófitos, gimnospermas actuales y angiospermas respectivamente. El artículo concluye considerando las opciones dialécticas de la radiación difusiva frente a la hipótesis adaptacionista, el papel de la preadaptación y la evolución de la complejidad.Palabras clave. Evolución, paleobottinica, paleoecología, plantas terrestres, extinciones masivas, preadaptación, pulsaciones tectónicas.ABSTRACT. Macroevolution in vascular plants. Here we review hierarchical, evolutionary model systems for vascular plants from a palaeoecological perspective, with emphasis in the controls for the highest tier.This involves the existence of rapid events of radiation, followed by enduring phases of stabilization and taxonomic declining. The fossil record fails to recognize mass extinctions among terrestrial plants, at least in the sense adopted for the evolution of animals, namely, short periods of geological time involving strong losses of biodiversity if compared with average lifetimes of the extinct species. During stages of environmental stress, the vascular plants have exploted their capabilities to migration, recolonization, and competitive displacement; shortly, reorganization of the ecological and fitogeographic structure. At high taxonomic levels, most groups exhibit persistence, inertia, and survival rather than extinction, demonstrably through the existence of a number of living fossils among the main clades. The only environmental factor to which plants could not escape was extrinsic abiotic stress in the form of increasing atmospheric CO, during superplumes associated to tectonics pulsations. In fact, those dated at the Mid-Ordovician u; Silurian (460- 430 Ma), Mid-Devonian to Lower Carboniferous (375-350 Ma), Jurassic (150 Ma), and Lower Cretaceous (120-80 Ma), correlate with phases of rapid speciation within the principal reproductive groups, namely embriophytes, seed plants, gymnosperms, and angiosperms respectively. We conclude discussing related issues of palaeoecological concern, such as diffusive versus adaptive hypotheses of radiation, the role of preadaptation in plant evolution, and the long-term patterns of complexity.-Key words. Evolution, palaeobotany, palaeoecology, land plants, mass extinctions, preadaptation, pulsation tectonics.

scholarly journals The evolution of diversity in ancient ecosystems: a review

1998 ◽  
Vol 353 (1366) ◽  
pp. 327-345 ◽  
Author(s):  
S. Conway Morris
Keyword(s):  
Fossil Record ◽  
Molecular Data ◽  
Cambrian Explosion ◽  
Mass Extinctions ◽  
Geological Time ◽  
Biological Communities ◽  
History Of ◽  
Lag Times ◽  
Extinction Events ◽  
Ancient Ecosystems

On a perfect planet, such as might be acceptable to a physicist, one might predict that from its origin the diversity of life would grow exponentially until the carrying capacity, however defined, was reached. The fossil record of the Earth, however, tells a very different story. One of the most striking aspects of this record is the apparent evolutionary longueur, marked by the Precambrian record of prokaryotes and primitive eukaryotes, although our estimates of microbial diversity may be seriously incomplete. Subsequently there were various dramatic increases in diversity, including the Cambrian ‘explosion’ and the radiation of Palaeozoic–style faunas in the Ordovician. The causes of these events are far from resolved. It has also long been appreciated that the history of diversity has been punctuated by important extinctions. The subtleties and nuances of extinction as well as the survival of particular clades have to date, however, received rather too little attention, and there is still a tendency towards blanket assertions rather than a dissection of these extraordinary events. In addition, some but perhaps not all mass extinctions are characterized by long lag–times of recovery, which may reflect the slowing waning of extrinsic forcing factors or alternatively the incoherence associated with biological reassembly of stable ecosystems. The intervening periods between the identified mass extinctions may be less stable and benign than popularly thought, and in particular the frequency of extraterrestrial impacts leads to predictions of recurrent disturbance on timescales significantly shorter than the intervals separating the largest extinction events. Even at times of quietude it is far from clear whether biological communities enjoy stability and interlocked stasis or are dynamically reconstituted at regular intervals. Finally, can we yet rely on the present depictions of the rise and falls in the levels of ancient diversity? Existing data is almost entirely based on Linnean taxa, and the application of phylogenetic systematics to this problem is still in its infancy. Not only that, but even more intriguingly the pronounced divergence in estimates of origination times of groups as diverse as angiosperms, diatoms and mammals in terms of the fossil record as against molecular data point to the possibilities of protracted intervals of geological time with a cryptic diversity. If this is correct, and there are alternative explanations, then some of the mystery of adaptive radiations may be dispelled, in as much as the assembly of key features in the stem groups could be placed in a gradualistic framework of local adaptive response punctuated by intervals of opportunity.

Atypical Femoral Fracture in McCune-Albright Syndrome

2020 ◽  
Vol 7 (3) ◽  
pp. 147-152
Author(s):  
Salman Ghaffari ◽  
◽  
Mehran Razavipour ◽  
Parastoo Mohammad Amini ◽  
◽  
...  
Keyword(s):  
Femoral Fracture ◽  
Dynamic Compression ◽  
Plate Fixation ◽  
Medullary Canal ◽  
Mccune Albright Syndrome ◽  
Café Au Lait Spots ◽  
History Of ◽  
Albright Syndrome ◽  
Mccune Albright

McCune-Albright Syndrome (MAS) is characterized by endocrinopathies, café-au-lait spots, and fibrous dysplasia. Bisphosphonates are the most prescribed treatment for reducing the pain but their long-term use has been associated with atypical fractures of cortical bones like femur in patients. We present a 23-year-old girl diagnosed with MAS. She had an atypical mid-shaft left femoral fracture that happened during simple walking. She also had a history of long-term use of alendronate. Because of the narrow medullary canal, we used 14 holes hybrid locking plate for the lateral aspect of the thigh to fix the fracture and 5 holes dynamic compression plate (instead of the intramedullary nail) in the anterior surface to double fix it, reducing the probability of device failure. With double plate fixation and discontinuation of alendronate, the complete union was achieved five months after surgery

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