scholarly journals A long-term record of early to mid-Paleozoic marine redox change

2021 ◽  
Vol 7 (28) ◽  
pp. eabf4382
Author(s):  
Erik A. Sperling ◽  
Michael J. Melchin ◽  
Tiffani Fraser ◽  
Richard G. Stockey ◽  
Una C. Farrell ◽  
...  
Keyword(s):  
Biological Evolution ◽  
Independent Evidence ◽  
Early Devonian ◽  
Anoxic Waters ◽  
Early Diversification ◽  
Continuous Record ◽  
Bottom Waters ◽  
Redox Change ◽  
Nearly Continuous

The extent to which Paleozoic oceans differed from Neoproterozoic oceans and the causal relationship between biological evolution and changing environmental conditions are heavily debated. Here, we report a nearly continuous record of seafloor redox change from the deep-water upper Cambrian to Middle Devonian Road River Group of Yukon, Canada. Bottom waters were largely anoxic in the Richardson trough during the entirety of Road River Group deposition, while independent evidence from iron speciation and Mo/U ratios show that the biogeochemical nature of anoxia changed through time. Both in Yukon and globally, Ordovician through Early Devonian anoxic waters were broadly ferruginous (nonsulfidic), with a transition toward more euxinic (sulfidic) conditions in the mid–Early Devonian (Pragian), coincident with the early diversification of vascular plants and disappearance of graptolites. This ~80-million-year interval of the Paleozoic characterized by widespread ferruginous bottom waters represents a persistence of Neoproterozoic-like marine redox conditions well into the Phanerozoic.

The Tempo and mode(S) of Prebiotic Evolution

1997 ◽  
Vol 161 ◽  
pp. 419-429 ◽  
Author(s):  
Antonio Lazcano
Keyword(s):  
Origin Of Life ◽  
Organic Compounds ◽  
Biological Evolution ◽  
Current Evidence ◽  
Early Diversification ◽  
Time Period ◽  
The Galaxy ◽  
History Of ◽  
Widespread Phenomenon ◽  
The Origin Of Life

AbstractDifferent current ideas on the origin of life are critically examined. Comparison of the now fashionable FeS/H2S pyrite-based autotrophic theory of the origin of life with the heterotrophic viewpoint suggest that the later is still the most fertile explanation for the emergence of life. However, the theory of chemical evolution and heterotrophic origins of life requires major updating, which should include the abandonment of the idea that the appearance of life was a slow process involving billions of years. Stability of organic compounds and the genetics of bacteria suggest that the origin and early diversification of life took place in a time period of the order of 10 million years. Current evidence suggest that the abiotic synthesis of organic compounds may be a widespread phenomenon in the Galaxy and may have a deterministic nature. However, the history of the biosphere does not exhibits any obvious trend towards greater complexity or «higher» forms of life. Therefore, the role of contingency in biological evolution should not be understimated in the discussions of the possibilities of life in the Universe.

scholarly journals Content analysis for <i>Agricultural Records</i> of the United Kingdom, AD 200 to 1977: a study of frequency in human records concerning climate phenomenon

2011 ◽  
Vol 7 (4) ◽  
pp. 2555-2577
Author(s):  
D. H. Holt
Keyword(s):  
Content Analysis ◽  
Ice Age ◽  
Climate Data ◽  
The United Kingdom ◽  
Weather Phenomenon ◽  
Continuous Record ◽  
Frequency Occurrence ◽  
The Uk ◽  
Climate Events

Abstract. A content analysis has been completed on a text from the UK that has gathered agricultural and climate data from the years AD 220 to 1977 from 100s of sources. The content analysis coded all references to climate and agriculture to ascertain which climate events were recorded and which were not. This study addressed the question: is there bias in human records of climate? This evaluated the continuous record (AD 1654–1977), discontinous record (AD 220–1653), the whole record (AD 220–1977), the Little Climate Optimum (AD 850–1250) and the Little Ice Age (AD 1450–1880). This study shows that there is no significant variation in any of these periods in frequency occurrence of "good" or "bad" climate suggesting humans are not recording long-term changes in climate, but they are recording weather phenomenon as it occurs.

Impact of Chelicorophium curvispinum on the concentration-discharge response of suspended sediment in the Rhine River

2021 ◽  
Author(s):  
Marcel van der Perk
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Sudden Increase ◽  
Rhine River ◽  
Rating Curve ◽  
Independent Evidence ◽  
Sediment Rating Curve ◽  
Suspended Sediment Concentrations

&lt;p&gt;In an ongoing study to the decline in suspended sediment concentrations and loads in the Rhine river since the mid-1950s, the temporal changes in the power-law sediment rating curve parameters were examined. This revealed that the rating exponent of the rating curve increased substantially between the early and late 1980s. Until the early 1980s, the ratings curves were relatively flat with values of the rating exponent b varying around 0.2. In the mid-1980s, the exponent suddenly increased to a value between 0.4 and 0.6 and since then has remained within this range. This change in the rating exponent was mainly caused by a decrease in suspended sediment concentrations during low discharges. During high discharges, the suspended sediment concentration initially increased during the late 1980s, but this increase was nullified soon afterwards due to the declining trend in suspended sediment concentration.&lt;/p&gt;&lt;p&gt;The sudden increase of the rating exponent coincided with the period that the Ponto-Caspian &lt;em&gt;Chelicorophium curvispinum&lt;/em&gt; (Caspian mud shrimp) invaded the Rhine river basin. This suggests that this suspension-feeder species bears the prime responsibility for this increase, although this hypothesis requires further independent evidence. The sudden increase in the rating exponent does however not manifest itself in the long-term gradual trend of declining suspended sediment concentrations and vice versa. Apparently, the sequestration of sediment by &lt;em&gt;Chelicorophium curvispinum&lt;/em&gt; is only temporary: the suspended sediment sequestered during periods of relatively low discharges is likely remobilised again during periods of high discharge. This implies that the invasion of &lt;em&gt;Chelicorophium curvispinum&lt;/em&gt; has not played a significant role in the decline of suspended sediment concentrations. The precise reasons for the gradual long-term decline in suspended sediment concentration remain yet unknown.&lt;/p&gt;

Paleolimnology in Deep Time: The Evolution of Lacustrine Ecosystems

2003 ◽  
Author(s):  
Andrew S. Cohen
Keyword(s):  
Fossil Record ◽  
World Ocean ◽  
Biological Evolution ◽  
Body Distribution ◽  
Freshwater Organisms ◽  
History Of ◽  
Living Organisms ◽  
Lake Basins ◽  
Lake Beds

Most lakes are geologically ephemeral; even the longest-lived individual lakes persist only for tens of millions of years. However there is a continuity to lake systems that transcends the geologically short history of individual lake basins. This continuity comes from the long-term biological evolution of life in freshwater, and fittingly, forms the final subject of this treatment of paleolimnology. Like the oceans, lakes have provided habitats for living organisms for most of the earth’s history. Yet the patterns of aquatic ecosystem evolution in rivers and lakes have differed dramatically from those of the oceans. In large part this can be traced to the fundamentally ephemeral nature of most continental aquatic habitats and the ‘‘disconnectedness’’ in both time and space that exists between individual lakes and rivers compared with the world ocean. This pattern of temporal and spatial patchiness in water body distribution on the continents has shaped the evolution of lacustrine species and communities. Some understanding of this history can be gleaned from the study of modern ecology and molecular genetics of living freshwater organisms. But to understand long-term trends in lacustrine biodiversity and their relationship to the history of the lacustrine environment we must turn to the pre- Quaternary fossil record. Understanding this history, the timing and tempo of major species diversification and extinction events, and the evolution of key ecological innovations is critical for correctly interpreting ancient lake deposits. The fossil record of pre-Quaternary lakes is more difficult to interpret than that of more recent lake basins. Robust phylogenies are largely unavailable for clades of ancient lacustrine fossils, hindering our ability to test hypotheses of evolutionary ecology, although that situation hopefully will improve in coming years. Many major clades of fossil lacustrine organisms are extinct, and ecologies must be inferred from their depositional context. Even for organisms that have close-living relatives, our certainty in making inferences about habitat and relationship with other species weakens as we go back in time. Also the record we have to work with deteriorates with age, the result of (a) a declining volume of lake beds available for study with increasing age, (b) difficulties associated with processing lithified lake beds for their fossil content, and (c) an increasing likelihood of destruction by diagenesis with increasing age.

Identifying keystone plant resources in an Amazonian forest using a long-term fruit-fall record

2014 ◽  
Vol 30 (4) ◽  
pp. 291-301 ◽  
Author(s):  
Zoë Diaz-Martin ◽  
Varun Swamy ◽  
John Terborgh ◽  
Patricia Alvarez-Loayza ◽  
Fernando Cornejo
Keyword(s):  
Resource Scarcity ◽  
Forest Stand ◽  
Community Stability ◽  
Plant Resources ◽  
Continuous Record ◽  
Amazonian Rain Forest ◽  
Amazonian Forests ◽  
Conservation And Management ◽  
Fruit Crop Size

Abstract:The keystone plant resources (KPR) concept describes certain plant species in tropical forests as vital to community stability and diversity because they provide food resources to vertebrate consumers during the season of scarcity. Here, we use an 8-y, continuous record of fruit fall from a 1.44-ha mature forest stand to identify potential KPRs in a lowland western Amazonian rain forest. KPRs were identified based on four criteria: temporal non-redundancy; year-to-year reliability; abundance of reproductive-size individuals and inferred fruit crop size; and the variety of vertebrate consumers utilizing their fruit. Overall, seven species were considered excellent KPRs: two of these belong to the genusFicus, confirming that this taxon is a KPR as previously suggested.Celtis iguanaea(Cannabaceae) – a canopy liana – has also been previously classified as a KPR; in addition,Pseudomalmea diclina(Annonaceae),Cissus ulmifolia(Vitaceae),Allophylus glabratus(Sapindaceae) andTrichilia elegans(Meliaceae) are newly identified KPRs. Our results confirm that a very small fraction (<5%) of the plant community consistently provides fruit for a broad set of consumers during the period of resource scarcity, which has significant implications for the conservation and management of Amazonian forests.

Late Pliocene to late Pleistocene environments preserved at the Palisades Site, central Yukon River, Alaska

2003 ◽  
Vol 60 (1) ◽  
pp. 33-43 ◽  
Author(s):  
Paul Matheus ◽  
James Begét ◽  
Owen Mason ◽  
Carol Gelvin-Reymiller
Keyword(s):  
Late Pleistocene ◽  
Volcanic Ash ◽  
Silt Loam ◽  
Common Elements ◽  
Yukon River ◽  
Taiga Forest ◽  
Continuous Record ◽  
Ice Wedge ◽  
Nearly Continuous

AbstractThe Palisades Site is an extensive silt-loam bluff complex on the central Yukon River preserving a nearly continuous record of the last 2 myr. Volcanic ash deposits present include the Old Crow (OCt; 140,000 yr), Sheep Creek (SCt; 190,000 yr), PA (2.02 myr), EC (ca. 2 myr), and Mining Camp (ca. 2 myr) tephras. Two new tephras, PAL and PAU, are geochemically similar to the PA and EC tephras and appear to be comagmatic. The PA tephra occurs in ice-wedge casts and solifluction deposits, marking the oldest occurrence of permafrost in central Alaska. Three buried forest horizons are present in association with dated tephras. The uppermost forest bed occurs immediately above the OCt; the middle forest horizon occurs below the SCt. The lowest forest bed occurs between the EC and the PA tephras, and correlates with the Dawson Cut Forest Bed. Plant taxa in all three peats are common elements of moist taiga forest found in lowlands of central Alaska today. Large mammal fossils are all from common late Pleistocene taxa. Those recovered in situ came from a single horizon radiocarbon dated to ca. 27,000 14C yr B.P. The incongruous small mammal assemblage in that horizon reflects a diverse landscape with both wet and mesic environments.

scholarly journals Stability-based sorting: The forgotten process behind (not only) biological evolution

2017 ◽  
Author(s):  
Jaroslav Flegr ◽  
Jan Toman
Keyword(s):  
Natural Selection ◽  
Biological Evolution ◽  
Evolutionary Process ◽  
Static Stability ◽  
Main Process ◽  
Strict Sense ◽  
Broad Distribution ◽  
Evolutionary Consequences ◽  
Insight Into

AbstractNatural selection is considered to be the main process that drives biological evolution. It requires selected entities to originate dependent upon one another by the means of reproduction or copying, and for the progeny to inherit the qualities of their ancestors. However, natural selection is a manifestation of a more general persistence principle, whose temporal consequences we propose to name “stability-based sorting” (SBS). Sorting based on static stability, i.e., SBS in its strict sense and usual conception, favours characters that increase the persistence of their holders and act on all material and immaterial entities. Sorted entities could originate independently from each other, are not required to propagate and need not exhibit heredity. Natural selection is a specific form of SBS—sorting based on dynamic stability. It requires some form of heredity and is based on competition for the largest difference between the speed of generating its own copies and their expiration. SBS in its strict sense and selection thus have markedly different evolutionary consequences that are stressed in this paper. In contrast to selection, which is opportunistic, SBS is able to accumulate even momentarily detrimental characters that are advantageous for the long-term persistence of sorted entities. However, it lacks the amplification effect based on the preferential propagation of holders of advantageous characters. Thus, it works slower than selection and normally is unable to create complex adaptations. From a long-term perspective, SBS is a decisive force in evolution—especially macroevolution. SBS offers a new explanation for numerous evolutionary phenomena, including broad distribution and persistence of sexuality, altruistic behaviour, horizontal gene transfer, patterns of evolutionary stasis, planetary homeostasis, increasing ecosystem resistance to disturbances, and the universal decline of disparity in the evolution of metazoan lineages. SBS acts on all levels in all biotic and abiotic systems. It could be the only truly universal evolutionary process, and an explanatory framework based on SBS could provide new insight into the evolution of complex abiotic and biotic systems.

scholarly journals Cladogenesis and replacement in the fossil record of Microsyopidae (?Primates) from the southern Bighorn Basin, Wyoming

2021 ◽  
Vol 17 (2) ◽  
Author(s):  
Mary T. Silcox ◽  
Keegan R. Selig ◽  
Thomas M. Bown ◽  
Amy E. Chew ◽  
Kenneth D. Rose
Keyword(s):  
Fossil Record ◽  
Evolutionary Change ◽  
Local Extinction ◽  
Bighorn Basin ◽  
Early Eocene ◽  
Evolutionary Transitions ◽  
Continuous Record ◽  
Extinction Event ◽  
Nearly Continuous

The early Eocene of the southern Bighorn Basin, Wyoming, is notable for its nearly continuous record of mammalian fossils. Microsyopinae (?Primates) is one of several lineages that shows evidence of evolutionary change associated with an interval referred to as Biohorizon A. Arctodontomys wilsoni is replaced by a larger species, Arctodontomys nuptus , during the biohorizon interval in what is likely an immigration/emigration or immigration/local extinction event. The latter is then superseded by Microsyops angustidens after the end of the Biohorizon A interval. Although this pattern has been understood for some time, denser sampling has led to the identification of a specimen intermediate in morphology between A. nuptus and M. angustidens , located stratigraphically as the latter is appearing. Because specimens of A. nuptus have been recovered approximately 60 m above the appearance of M. angustidens , it is clear that A. nuptus did not suffer pseudoextinction. Instead, evidence suggests that M. angustidens branched off from a population of A. nuptus , but the latter species persisted. This represents possible evidence of cladogenesis, which has rarely been directly documented in the fossil record. The improved understanding of both evolutionary transitions with better sampling highlights the problem of interpreting gaps in the fossil record as punctuations.

scholarly journals Radiance-based Retrieval Bias Mitigation for the MOPITT Instrument: The Version 8 Product

2019 ◽  
Author(s):  
Merritt N. Deeter ◽  
David P. Edwards ◽  
Gene L. Francis ◽  
John C. Gille ◽  
Debbie Mao ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
Atmospheric Transport ◽  
Radiative Transfer Model ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Bias Drift ◽  
Atmospheric Carbon Monoxide ◽  
Nearly Continuous ◽  
Retrieval Bias

Abstract. The MOPITT (Measurements of Pollution in the Troposphere) satellite instrument has been making nearly continuous observations of atmospheric carbon monoxide (CO) since 2000. Satellite observations of CO are routinely used to analyze emissions from fossil fuels and biomass burning, and the atmospheric transport of those emissions. Recent enhancements to the MOPITT retrieval algorithm have resulted in the release of the Version 8 (V8) product. V8 products benefit from updated spectroscopic data for water vapor and nitrogen used to develop the operational radiative transfer model and exploit a new method for minimizing retrieval biases through parameterized radiance bias correction. Validation results illustrate clear improvements with respect to long-term bias drift and geographically variable retrieval bias.

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