Protists and Phanerozoic Evolution in the Oceans

1987 ◽  
Vol 18 ◽  
pp. 248-264 ◽  
Author(s):  
Andrew H. Knoll
Keyword(s):  
Temporal Pattern ◽  
Taxonomic Diversity ◽  
Evolutionary Change ◽  
Morphological Data ◽  
Biological Interactions ◽  
Mass Extinctions ◽  
Oceanic Circulation ◽  
The Past ◽  
Circulation Patterns ◽  
History Of

In an essay published in 1977, S.J. Gould argued that three major questions have dominated paleontological thinking for more than a century. Does the history of life have direction? What is the motor of evolutionary change? And, what is the tempo of change? Certainly, these “eternal metaphors” have figured prominently in the research of invertebrate paleontologists during the past decade. Temporal pattern has been sought in changing morphologies within lineages, the changing structure and composition of communities, trends in taxonomic diversity, and even the occurrence of mass extinctions. Drifting continents, changing climates and oceanic circulation patterns, biological interactions, and extraterrestrial influences have all been championed as significant determinants of evolutionary change. The punctuation/gradualism debate has generated an impressive body of stratigraphic and morphological data, if not an unambiguous resolution of the issue.

Sampling, taxonomic description, and our evolving knowledge of morphological diversity

Paleobiology ◽  
1997 ◽  
Vol 23 (2) ◽  
pp. 181-206 ◽  
Author(s):  
Mike Foote
Keyword(s):  
Morphological Analysis ◽  
Biological Diversity ◽  
Marine Invertebrates ◽  
Morphological Diversity ◽  
Taxonomic Diversity ◽  
Past Century ◽  
General Tendency ◽  
The Past ◽  
Taxonomic Description ◽  
History Of

Morphological analysis of four higher taxa of fossil marine invertebrates shows that, over the history of paleontology, there is no general tendency for morphologically extreme or modal species and genera to be described preferentially early or late. Reconstructing the expected evolutionary sequences of morphological disparity that would have been estimated at various times during the past century and a half reveals features that are sensitive to sampling (for example, peak trilobite disparity in the Ordovician, peak of post-Paleozoic crinoid disparity in the Triassic, and peak blastoid disparity in the Permian), as well as more robust features (for example, increase in trilobite disparity from the Cambrian to the Ordovician, continued increase in trilobite disparity despite a drop in taxonomic diversity after the Early Ordovician, decrease in blastoid disparity from the Devonian to the Carboniferous, and increase in crinoid disparity from the Jurassic to the Cretaceous followed by decline during the Cretaceous). Although we still have much to learn about the evolution of form, in many respects our view of the history of biological diversity is mature.

scholarly journals A Cretaceous peak in family-level insect diversity estimated with mark–recapture methodology

2019 ◽  
Vol 286 (1917) ◽  
pp. 20192054 ◽  
Author(s):  
Sandra R. Schachat ◽  
Conrad C. Labandeira ◽  
Matthew E. Clapham ◽  
Jonathan L. Payne
Keyword(s):  
Early Cretaceous ◽  
Taxonomic Diversity ◽  
Mass Extinctions ◽  
Time Intervals ◽  
Mark Recapture ◽  
Deep Time ◽  
Steep Increase ◽  
Family Level ◽  
History Of ◽  
Uneven Sampling

The history of insects’ taxonomic diversity is poorly understood. The two most common methods for estimating taxonomic diversity in deep time yield conflicting results: the ‘range through’ method suggests a steady, nearly monotonic increase in family-level diversity, whereas ‘shareholder quorum subsampling’ suggests a highly volatile taxonomic history with family-level mass extinctions occurring repeatedly, even at the midpoints of geological periods. The only feature shared by these two diversity curves is a steep increase in standing diversity during the Early Cretaceous. This apparent diversification event occurs primarily during the Aptian, the pre-Cenozoic interval with the most described insect occurrences, raising the possibility that this feature of the diversity curves reflects preservation and sampling biases rather than insect evolution and extinction. Here, the capture–mark–recapture (CMR) approach is used to estimate insects’ family-level diversity. This method accounts for the incompleteness of the insect fossil record as well as uneven sampling among time intervals. The CMR diversity curve shows extinctions at the Permian/Triassic and Cretaceous/Palaeogene boundaries but does not contain any mass extinctions within geological periods. This curve also includes a steep increase in diversity during the Aptian, which appears not to be an artefact of sampling or preservation bias because this increase still appears when time bins are standardized by the number of occurrences they contain rather than by the amount of time that they span. The Early Cretaceous increase in family-level diversity predates the rise of angiosperms by many millions of years and can be better attributed to the diversification of parasitic and especially parasitoid insect lineages.

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.

Atmospheric and Oceanic Circulation Patterns off Northwest Africa During the Past 25 Million Years

1982 ◽  
pp. 545-604 ◽  
Author(s):  
Michael Sarnthein ◽  
Jörn Thiede ◽  
Uwe Pflaumann ◽  
H. Erlenkeuser ◽  
Dieter Fütterer ◽  
...  
Keyword(s):  
Oceanic Circulation ◽  
The Past ◽  
Northwest Africa ◽  
Circulation Patterns

On The Possibility of an Autonomous History of Modern Southeast Asia

1961 ◽  
Vol 2 (2) ◽  
pp. 73-105 ◽  
Author(s):  
John R. W. Small
Keyword(s):  
Southeast Asia ◽  
Contemporary History ◽  
The Past ◽  
History Of

It is generally accepted that history is an element of culture and the historian a member of society, thus, in Croce's aphorism, that the only true history is contemporary history. It follows from this that when there occur great changes in the contemporary scene, there must also be great changes in historiography, that the vision not merely of the present but also of the past must change.

Stellar Evolution

1962 ◽  
Vol 11 (02) ◽  
pp. 137-143
Author(s):  
M. Schwarzschild
Keyword(s):  
Solar System ◽  
Stellar Evolution ◽  
Space Craft ◽  
New Techniques ◽  
Substantial Body ◽  
Individual Stars ◽  
The Past ◽  
Evolution Of Galaxies ◽  
History Of ◽  
Fast Flow

It is perhaps one of the most important characteristics of the past decade in astronomy that the evolution of some major classes of astronomical objects has become accessible to detailed research. The theory of the evolution of individual stars has developed into a substantial body of quantitative investigations. The evolution of galaxies, particularly of our own, has clearly become a subject for serious research. Even the history of the solar system, this close-by intriguing puzzle, may soon make the transition from being a subject of speculation to being a subject of detailed study in view of the fast flow of new data obtained with new techniques, including space-craft.

A 200-Year History of the Study of Childhood Language Disorders of Unknown Origin: Changes in Terminology

2020 ◽  
Vol 5 (1) ◽  
pp. 6-11 ◽  
Author(s):  
Laurence B. Leonard
Keyword(s):  
Language Impairment ◽  
Specific Language Impairment ◽  
Scientific Literature ◽  
Language Disorder ◽  
Language Disorders ◽  
Unknown Origin ◽  
Developmental Language Disorder ◽  
The Past ◽  
History Of ◽  
The Many

Purpose The current “specific language impairment” and “developmental language disorder” discussion might lead to important changes in how we refer to children with language disorders of unknown origin. The field has seen other changes in terminology. This article reviews many of these changes. Method A literature review of previous clinical labels was conducted, and possible reasons for the changes in labels were identified. Results References to children with significant yet unexplained deficits in language ability have been part of the scientific literature since, at least, the early 1800s. Terms have changed from those with a neurological emphasis to those that do not imply a cause for the language disorder. Diagnostic criteria have become more explicit but have become, at certain points, too narrow to represent the wider range of children with language disorders of unknown origin. Conclusions The field was not well served by the many changes in terminology that have transpired in the past. A new label at this point must be accompanied by strong efforts to recruit its adoption by clinical speech-language pathologists and the general public.

Suicidal Ideation Among Medical Students in Dammam, Saudi Arabia

Crisis ◽  
2020 ◽  
pp. 1-6
Author(s):  
Mohammed Madadin ◽  
Ritesh G. Menezes ◽  
Maha A. Alassaf ◽  
Abdulaziz M. Almulhim ◽  
Mahdi S. Abumadini ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Medical Students ◽  
Suicidal Ideation ◽  
General Health Questionnaire ◽  
Cross Sectional Study ◽  
Eastern Province ◽  
Cross Sectional ◽  
The Past ◽  
Depression Subscale ◽  
History Of

Abstract. Background: Medical students are at high risk of suicidal ideation. Aim: We aimed to obtain information on suicidal ideation among medical students in Dammam located in the Eastern Province of Saudi Arabia. Method: This cross-sectional study was conducted at the College of Medicine affiliated with Imam Abdulrahman Bin Faisal University in the Eastern Province of Saudi Arabia. Suicidal ideation in the past 12 months was assessed based on responses to four questions in the depression subscale of the General Health Questionnaire 28 (GHQ-28). In addition, data were collected to examine the association of suicidal ideation with various factors. Results: We found that 1 in 3 medical students in the study had suicidal ideation in the past 12 months, while around 40% had lifetime suicidal ideation. Suicidal ideation was associated with feelings of parental neglect, history of physical abuse, and dissatisfaction with academic performance. Limitations: The cross-sectional nature of this study limits its ability to determine causality regarding suicidal ideation. Conclusion: These rates are considerably high when compared with rates from studies in other countries around the world. This study provides a reference in the field of suicidology for this region of Saudi Arabia.

Post-Soviet economy development: From the past to the future

2017 ◽  
pp. 5-21 ◽  
Author(s):  
E. Yasin
Keyword(s):  
Present Situation ◽  
Soviet Economy ◽  
Market Reforms ◽  
Democratic Development ◽  
The Past ◽  
Current Period ◽  
The Future ◽  
History Of ◽  
Working Out ◽  
A Current

The article is devoted to major events in the history of the post-Soviet economy, their influence on forming and development of modern Russia. The author considers stages of restructuring, market reforms, transformational crisis, and recovery growth (1999-2011), as well as a current period which started in2011 and is experiencing serious problems. The present situation is analyzed, four possible scenarios are put forward for Russia: “inertia”, “mobilization”, “decisive leap”, “gradual democratic development”. More than 30 experts were questioned in the process of working out the scenarios.

EPITAFIES OF THE RELATIVES OF HADJI IBRAHIM AL-URADI AS A SOURCE ON THE BIOGRAPHY OF THE SCIENTIST AND ON THE HISTORY OF GIDATL

2017 ◽  
Vol 13 (4) ◽  
pp. 13-21
Author(s):  
Sh M Khapizov ◽  
M G Shekhmagomedov
Keyword(s):  
18Th Century ◽  
Medieval History ◽  
Historical Sources ◽  
The Past ◽  
Arabic Script ◽  
History Of ◽  
History Of Culture ◽  
The Look ◽  
Cultural Monuments ◽  
Written Sources

The article is devoted to the study of inscriptions on the gravestones of Haji Ibrahim al-Uradi, his father, brothers and other relatives. The information revealed during the translation of these inscriptions allows one to date important events from the history of Highland Dagestan. Also we can reconsider the look at some important events from the past of Hidatl. Epitaphs are interesting in and of themselves, as historical and cultural monuments that needed to be studied and attributed. Research of epigraphy data monuments clarifies periodization medieval epitaphs mountain Dagestan using record templates and features of the Arabic script. We see the study of medieval epigraphy as one of the important tasks of contemporary Caucasian studies facing Dagestani researchers. Given the relatively weak illumination of the picture of events of that period in historical sources, comprehensive work in this direction can fill gaps in our knowledge of the medieval history of Dagestan. In addition, these epigraphs are of great importance for researchers of onomastics, linguistics, the history of culture and religion of Dagestan. The authors managed to clarify the date of death of Ibrahim-Haji al-Uradi, as well as his two sons. These data, the attraction of written sources and legends allowed the reconstruction of the events of the second half of the 18th century. For example, because of the epidemic of plague and the death of most of the population of Hidatl, this society noticeably weakened and could no longer maintain its influence on Akhvakh. The attraction of memorable records allowed us to specify the dates of the Ibrahim-Haji pilgrimage to Mecca and Medina, as well as the route through which he traveled to these cities.

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