Darwin, mais complexidade - mensagens encriptadas em processos biológicos: mero acaso, fortuita necessidade ou design inteligente?

quarta-feira, junho 20, 2018

Transient N-6-Methyladenosine Transcriptome Sequencing Reveals a Regulatory Role of m6A in Splicing Efficiency

Annita Louloupi5, Evgenia Ntini5, Thomas Conrad, Ulf Andersson Vang Ørom6

5These authors contributed equally

6Lead Contact

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DOI: https://doi.org/10.1016/j.celrep.2018.05.077 |

Article Info

Publication History

Published: June 19, 2018 Accepted: May 23, 2018

Received in revised form: April 30, 2018 Received: January 10, 2018

User License

Creative Commons Attribution – NonCommercial – NoDerivs (CC BY-NC-ND 4.0)

Source/Fonte: Ulf Andersson Vang Ørom 

Highlights

•A time-resolved high-resolution picture of m6A on nascent RNA transcripts

•m6A is deposited at nascent RNA and in introns

•m6A deposition at splice-junctions increases splicing kinetics

•High m6A levels in introns is associated with slow and alternative splicing

Summary

Splicing efficiency varies among transcripts, and tight control of splicing kinetics is crucial for coordinated gene expression. N-6-methyladenosine (m6A) is the most abundant RNA modification and is involved in regulation of RNA biogenesis and function. The impact of m6A on regulation of RNA splicing kinetics is unknown. Here, we provide a time-resolved high-resolution assessment of m6A on nascent RNA transcripts and unveil its importance for the control of RNA splicing kinetics. We find that early co-transcriptional m6A deposition near splice junctions promotes fast splicing, while m6A modifications in introns are associated with long, slowly processed introns and alternative splicing events. In conclusion, we show that early m6A deposition specifies the fate of transcripts regarding splicing kinetics and alternative splicing.

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A Via Láctea é duas vezes maior do que os cientistas pensavam

quarta-feira, junho 13, 2018

A&A 612, L8 (2018)

Letter to the Editor

Disk stars in the Milky Way detected beyond 25 kpc from its center

M. López-Corredoira1,2, C. Allende Prieto1,2, F. Garzón1,2, H. Wang3,4, C. Liu3,4 and L. Deng3,4

1 Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain 

2 Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain 

3 Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China 

4 University of Chinese Academy of Sciences, Beijing 100012, PR China 

Received: 22 February 2018 Accepted: 5 April 2018

Source/Fonte: NASA

Abstract

Context. The maximum size of the Galactic stellar disk is not yet known. Some studies have suggested an abrupt drop-off of the stellar density of the disk at Galactocentric distances R ≳ 15 kpc, which means that in practice no disk stars or only very few of them should be found beyond this limit. However, stars in the Milky Way plane are detected at larger distances. In addition to the halo component, star counts have placed the end of the disk beyond 20 kpc, although this has not been spectroscopically confirmed so far. Aims. Here, we aim to spectroscopically confirm the presence of the disk stars up to much larger distances.

Methods. With data from the LAMOST and SDSS-APOGEE spectroscopic surveys, we statistically derived the maximum distance at which the metallicity distribution of stars in the Galactic plane is distinct from that of the halo populations.

Results. Our analysis reveals the presence of disk stars at R > 26 kpc (99.7% C.L.) and even at R > 31 kpc (95.4% C.L.).

Key words: Galaxy: structure – Galaxy: disk – Galaxy: abundances

© ESO 2018

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O mais antigo mamífero do Brasil viveu na era dos dinossauros

A Late Cretaceous mammal from Brazil and the first radioisotopic age for the Bauru Group

Mariela C. Castro, Francisco J. Goin, Edgardo Ortiz-Jaureguizar, E. Carolina Vieytes, Kaori Tsukui, Jahandar Ramezani, Alessandro Batezelli, Júlio C. A. Marsola, Max C. Langer

Published 30 May 2018. DOI: 10.1098/rsos.18048


Abstract

In the last three decades, records of tribosphenidan mammals from India, continental Africa, Madagascar and South America have challenged the notion of a strictly Laurasian distribution of the group during the Cretaceous. Here, we describe a lower premolar from the Late Cretaceous Adamantina Formation, São Paulo State, Brazil. It differs from all known fossil mammals, except for a putative eutherian from the same geologic unity and Deccanolestes hislopi, from the Maastrichtian of India. The incompleteness of the material precludes narrowing down its taxonomic attribution further than Tribosphenida, but it is larger than most coeval mammals and shows a thin layer of parallel crystallite enamel. The new taxon helps filling two major gaps in the fossil record: the paucity of Mesozoic mammals in more northern parts of South America and of tribosphenidans in the Cretaceous of that continent. In addition, high-precision U-Pb geochronology provided a post-Turonian maximal age (≤87.8 Ma) for the type stratum, which is overlain by the dinosaur-bearing Marília Formation, constraining the age of the Adamantina Formation at the site to late Coniacian–late Maastrichtian. This represents the first radioisotopic age for the Bauru Group, a key stratigraphic unit for the study of Cretaceous tetrapods in Gondwana.

KEYWORDS

Tribosphenida enamel reduction Bauru Basin South America U-Pb geochronology mesozoic

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O formato da água: a estrutura e ligação de hidrogênio nos limites da estabilidade da água líquida

sábado, junho 02, 2018

Structure and hydrogen bonding at the limits of liquid water stability

Flaviu Cipcigan, Vlad Sokhan, Glenn Martyna & Jason Crain

Scientific Reports volume 8, Article number: 1718 (2018) | Download Citation

How water molecules are arranged in the liquid around a central reference molecule. The white areas show high-density "shells" while the orange area shows regions where no water molecules can reside.

Abstract

Liquid water exhibits unconventional behaviour across its wide range of stability – from its unusually high liquid-vapour critical point down to its melting point and below where it reaches a density maximum and exhibits negative thermal expansion allowing ice to float. Understanding the molecular underpinnings of these anomalies presents a challenge motivating the study of water for well over a century. Here we examine the molecular structure of liquid water across its range of stability, from mild supercooling to the negative pressure and high temperature regimes. We use a recently-developed, electronically-responsive model of water, constructed from gas-phase molecular properties and incorporating many-body, long-range interactions to all orders; as a result the model has been shown to have high transferability from ice to the supercritical regime. We report a link between the anomalous thermal expansion of water and the behaviour of its second coordination shell and an anomaly in hydrogen bonding, which persists throughout liquid water’s range of stability – from the high temperature limit of liquid water to its supercooled regime.

Acknowledgements

This work was supported by the NPL Strategic Research programme and the STFC Hartree Centre’s Innovation Return on Research programme. FSC acknowledges the Scottish Doctoral Training Centre in Condensed Matter Physics, the NPL Postgraduate Institute and EPSRC for funding under an Industrial CASE studentship. We acknowledge use of Hartree Centre, EPCC and NPL computational resources.

Author information

Affiliations

IBM Research UK, Hartree Centre, Daresbury, WA4 4AD, United Kingdom

Flaviu Cipcigan & Jason Crain

STFC Daresbury Laboratory, Daresbury, WA4 4AD, United Kingdom

Vlad Sokhan

IBM T. J. Watson Research Center, Yorktown Heights, New York, 10598, USA

Glenn Martyna

Contributions

F.S.C., V.P.S., G.J.M., J.C. designed research. F.S.C., V.P.S. conducted research. F.S.C., V.P.S., G.J.M., J.C. analysed and interpreted the results. All authors reviewed the manuscript.

Competing Interests

The authors declare that they have no competing interests.

Corresponding author

Correspondence to Flaviu Cipcigan.

About this article

Publication history

Received 13 October 2017 Accepted 14 December 2017

Published 29 January 2018


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Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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A água, quem diria, são dois líquidos!

Diffusive dynamics during the high-to-low density transition in amorphous ice

Fivos Perakis, Katrin Amann-Winkel, Felix Lehmkühler, Michael Sprung, Daniel Mariedahl, Jonas A. Sellberg, Harshad Pathak, Alexander Späh, Filippo Cavalca, Daniel Schlesinger, Alessandro Ricci, Avni Jain, Bernhard Massani, Flora Aubree, Chris J. Benmore, Thomas Loerting, Gerhard Grübel, Lars G. M. Pettersson, and Anders Nilsson

PNAS August 1, 2017. 114 (31) 8193-8198; published ahead of print June 26, 2017. https://doi.org/10.1073/pnas.1705303114

Edited by Pablo G. Debenedetti, Princeton University, Princeton, NJ, and approved May 31, 2017 (received for review March 31, 2017)

Source/Fonte: New Scientist

Significance

The importance of a molecular-level understanding of the properties, structure, and dynamics of liquid water is recognized in many scientific fields. It has been debated whether the observed high- and low-density amorphous ice forms are related to two distinct liquid forms. Here, we study experimentally the structure and dynamics of high-density amorphous ice as it relaxes into the low-density form. The unique aspect of this work is the combination of two X-ray methods, where wide-angle X-ray scattering provides the evidence for the structure at the atomic level and X-ray photon-correlation spectroscopy provides insight about the motion at the nanoscale, respectively. The observed motion appears diffusive, indicating liquid-like dynamics during the relaxation from the high-to low-density form.

Abstract

Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at T = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid–liquid transition in the ultraviscous regime.

liquid–liquid transitionglass transitionamorphous iceX-ray photon-correlation spectroscopysupercooled water

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Cientistas brasileiros mediram a radiação de uma mandíbula humana do ataque nuclear em Hiroshima: resultados impressionantes!

quarta-feira, maio 30, 2018

Electron spin resonance (ESR) dose measurement in bone of Hiroshima A-bomb victim

Angela Kinoshita , Oswaldo Baffa , Sérgio Mascarenhas 

Published: February 6, 2018 https://doi.org/10.1371/journal.pone.0192444


Abstract

Explosion of the bombs in Hiroshima and Nagasaki corresponds to the only historical moment when atomic bombs were used against civilians. This event triggered countless investigations into the effects and dosimetry of ionizing radiation. However, none of the investigations has used the victims’ bones as dosimeter. Here, we assess samples of bones obtained from fatal victims of the explosion by Electron Spin Resonance (ESR). In 1973, one of the authors of the present study (SM) traveled to Japan and conducted a preliminary experiment on the victims’ bone samples. The idea was to use the paramagnetism induced in bone after irradiation to measure the radiation dose. Technological advances involved in the construction of spectrometers, better knowledge of the paramagnetic center, and improvement in signal processing techniques have allowed us to resume the investigation. We obtained a reconstructed dose of 9.46 ± 3.4 Gy from the jawbone, which was compatible with the dose distribution in different locations as measured in non-biological materials such as wall bricks and roof tiles.

Citation: Kinoshita A, Baffa O, Mascarenhas S (2018) Electron spin resonance (ESR) dose measurement in bone of Hiroshima A-bomb victim. PLoS ONE 13(2): e0192444. https://doi.org/10.1371/journal.pone.0192444

Editor: Sergey Sholom, Oklahoma State University Stillwater, UNITED STATES

Received: July 3, 2017; Accepted: January 11, 2018; Published: February 6, 2018

Copyright: © 2018 Kinoshita et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper.

Funding: The authors received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

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Por uma rede de interação dinâmica da vida para unificar e expandir a teoria da evolução

terça-feira, maio 29, 2018

Towards a Dynamic Interaction Network of Life to unify and expand the evolutionary theory

Eric Bapteste and Philippe Huneman

BMC Biology201816:56


Published: 29 May 2018


Abstract

The classic Darwinian theory and the Synthetic evolutionary theory and their linear models, while invaluable to study the origins and evolution of species, are not primarily designed to model the evolution of organisations, typically that of ecosystems, nor that of processes. How could evolutionary theory better explain the evolution of biological complexity and diversity? Inclusive network-based analyses of dynamic systems could retrace interactions between (related or unrelated) components. This theoretical shift from a Tree of Life to a Dynamic Interaction Network of Life, which is supported by diverse molecular, cellular, microbiological, organismal, ecological and evolutionary studies, would further unify evolutionary biology.

Keywords Evolutionary biology Interactions Theoretical biology Tree of Life Web of Life

FREE PDF GRATIS: BMC Biology

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NOTA DESTE BLOGGER:

E na maior falta de honestidade científica, a Nomenklatura científica, não ousa discutir publicamente as razões por que da nova teoria geral da evolução - a Síntese Evolutiva Ampliada/Estendida, lançada em agosto de 2015, e o que isso significou em termos de robustez ou falência da teoria da evolução de Darwin, vez que era tida como verdade científica tanto quanto a Lei da Gravidade. Nada mais falso!

E agora vem Bapteste e sugere uma rede de interação dinâmica da vida para  unificar e expandir a teoria da evolução? Tem algo de podre nos porões da Nomenklatura científica!!!

Darwin kaput desde 1859 - nunca explicou a origem e evolução das espécies e muito menos a origem das variações genéticas!

Darwin morreu! Viva Darwin!!!

Pesquisa genética abrangente revela novas facetas da evolução: 90% das espécies são jovens - 100.000-200.000 anos!!!

Why should mitochondria define species?

HUMAN EVOLUTION Vol. 33 - n. 1-2 (1-30) - 2018

Stoeckle M.Y.
Program for the Human Environment
The Rockefeller University
1230 York AVE
New York, NY 10065
USA

Email: mark.stoeckle@rockefeller.edu

Thaler D.S.
Biozentrum, University of Basel
Klingelbergstrasse 50/70
CH - 4056 Basel
Switzerland

Email: david.thaler@unibas.ch davidsthaler@gmail.com


The amount of color variation within each red box of the Klee diagram illustrates the far greater mitochondrial diversity among chimpanzees and bonobos than among living humans. (From the journal Ecology and Evolution, online at https://onlinelibrary.wiley.com/doi/epdf/10.1002/ece3.2394).

Abstract

More than a decade of DNA barcoding encompassing about five million specimens covering 100,000 animal species supports the generalization that mitochondrial DNA clusters largely overlap with species as defined by domain experts. Most barcode clustering reflects synonymous substitutions. What evolutionary mechanisms account for synonymous clusters being largely coincident with species? The answer depends on whether variants are phenotypically neutral. To the degree that variants are selectable, purifying selection limits variation within species and neighboring species may have distinct adaptive peaks. Phenotypically neutral variants are only subject to demographic processes—drift, lineage sorting, genetic hitchhiking, and bottlenecks. The evolution of modern humans has been studied from several disciplines with detail unique among animal species. Mitochondrial barcodes provide a commensurable way to compare modern humans to other animal species. Barcode variation in the modern human population is quantitatively similar to that within other animal species. Several convergent lines of evidence show that mitochondrial diversity in modern humans follows from sequence uniformity followed by the accumulation of largely neutral diversity during a population expansion that began approximately 100,000 years ago. A straightforward hypothesis is that the extant populations of almost all animal species have arrived at a similar result consequent to a similar process of expansion from mitochondrial uniformity within the last one to several hundred thousand years.  

Key words: Species evolution, mitocondrial evolution, speciation, human evolution. 

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Darwin acertou no varejo e errou por atacado: o que está errado com a biologia evolucionária?

quinta-feira, maio 24, 2018

Biology & Philosophy

March 2017, Volume 32, Issue 2, pp 263–279 | Cite as

What’s wrong with evolutionary biology?

Authors and affiliations

John J. Welch1

Email author

1.Department of GeneticsUniversity of CambridgeCambridgeUK

Open Access Article

First Online: 20 December 2016

Image result for theory of evolution darwin
Source/Fonte: skat

Abstract

There have been periodic claims that evolutionary biology needs urgent reform, and this article tries to account for the volume and persistence of this discontent. It is argued that a few inescapable properties of the field make it prone to criticisms of predictable kinds, whether or not the criticisms have any merit. For example, the variety of living things and the complexity of evolution make it easy to generate data that seem revolutionary (e.g. exceptions to well-established generalizations, or neglected factors in evolution), and lead to disappointment with existing explanatory frameworks (with their high levels of abstraction, and limited predictive power). It is then argued that special discontent stems from misunderstandings and dislike of one well-known but atypical research programme: the study of adaptive function, in the tradition of behavioural ecology. To achieve its goals, this research needs distinct tools, often including imaginary agency, and a partial description of the evolutionary process. This invites mistaken charges of narrowness and oversimplification (which come, not least, from researchers in other subfields), and these chime with anxieties about human agency and overall purpose. The article ends by discussing several ways in which calls to reform evolutionary biology actively hinder progress in the field.

Keywords

Adaptation Extended evolutionary synthesis Neo-Darwinism Inclusive fitness

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Tchau, Darwin: o papel da epigenética na evolução humana

The role of epigenetics in human evolution 

Alexander Osborne

Bioscience Horizons: The International Journal of Student Research, Volume 10, 1 January 2017, hzx007, https://doi.org/10.1093/biohorizons/hzx007

Published: 28 July 2017 Article history

Received: 25 July 2016 Revision Received: 20 June 2017

Accepted: 10 July 2017


Source/Fonte: David Krantz

Abstract

This review aims to highlight the key areas in which changes to the epigenome have played an important role in the evolution and development of our species. Firstly, there will be a brief introduction into the topic of epigenetics to outline the current understanding of the subject and inform the reader of the basic mechanisms and functions of the epigenome. This will lead on to more focussed detail on the role played by epigenetic changes in the rapid evolution of our species and emergence from our ancestor species, as well as the Human Accelerated Regions that played a role in this. The discussion highlights how epigenetics has helped and hindered our species’ development via changes to the epigenome in more modern times, discussing case examples of documented instances where it is shown that epigenetics has played a role in the evolution of humanity.

epigenetics, evolution, human, methylation, HARs, modification

Issue Section: Review Article

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A matemática lança luz sobre como as células vivas "pensam"

quarta-feira, maio 23, 2018

The topological requirements for robust perfect adaptation in networks of any size

Robyn P. Araujo & Lance A. Liotta

Nature Communications volume 9, Article number: 1757 (2018)


Download Citation

Biochemical networks Complexity Modularity Robustness

Received: 28 February 2017 Accepted: 03 April 2018

Published: 01 May 2018


Abstract

Robustness, and the ability to function and thrive amid changing and unfavorable environments, is a fundamental requirement for living systems. Until now it has been an open question how large and complex biological networks can exhibit robust behaviors, such as perfect adaptation to a variable stimulus, since complexity is generally associated with fragility. Here we report that all networks that exhibit robust perfect adaptation (RPA) to a persistent change in stimulus are decomposable into well-defined modules, of which there exist two distinct classes. These two modular classes represent a topological basis for all RPA-capable networks, and generate the full set of topological realizations of the internal model principle for RPA in complex, self-organizing, evolvable bionetworks. This unexpected result supports the notion that evolutionary processes are empowered by simple and scalable modular design principles that promote robust performance no matter how large or complex the underlying networks become.

Acknowledgements

This study was partially supported by NIH grants R33CA206937 and R01AR068436.

Author information

Affiliations

School of Mathematical Sciences, Queensland University of Technology, Brisbane, QLD, 4000, Australia

Robyn P. Araujo

Institute of Health and Biomedical Innovation (IHBI), 60 Musk Avenue, Kelvin Grove, Brisbane, QLD, 4059, Australia

Robyn P. Araujo

Center for Applied Proteomics and Molecular Medicine, George Mason University, 10920 George Mason Circle, Manassas, Virginia, 20110, USA

Lance A. Liotta

Contributions

R.P.A. conceived of the analytical methodology, and performed all derivations, proofs and computational simulations. R.P.A. and L.A.L. wrote the paper.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Robyn P. Araujo.

Nós devemos exigir evidência no processo de revisão por pares, especialmente nas pesquisas sobre a origem e evolução do universo e da vida!!!


Opinion: We Must Demand Evidence of Peer Review

Peer review varies in quality and thoroughness. Making it publicly available could improve it.

ISTOCK, TEMMUZCAN

By Nikolai Slavov | May 21, 2018

Have you read a paper and thought: “How could peer reviews support the publication of such a paper?” I have. More than once. Other times, I have read fascinating papers outside of my field and wondered what the concerns of the experts who peer reviewed the study were. What important caveats am I missing?




Sometimes, I am lucky and find the answers to such questions: A few publications, including those from EMBO Press and eLife, publish the peer reviews alongside the papers. Reading such peer reviews has provided an additional dimension of appreciating and understanding the experiments and the findings, especially when I am not very familiar with the topic. But for most other journals I cannot access the peer reviews that supported a paper’s publication because most journals hide them. 

How do we know that a journal conducts peer review? For most journals, the evidence is limited to our anecdotal experiences with the manuscripts that we review ourselves or that we and our friends have submitted. For me this evidence is mixed. I know of manuscripts that have been thoughtfully reviewed and manuscripts that have undergone very expedited peer review or no peer review at all before appearing in the most prestigious journals. This anecdotal evidence is rather weak. If you ask me to substantiate it, I have to refer you to a friend who may or may not be willing to tell you that his or her paper was barely peer reviewed. It is a huge problem that the evidence for such a centrally important process is hidden from public view.       
...

READ MORE HERE: The Scientist

A análise mais abrangente já feita dos primeiros fósseis de artrópodes do Período Cambriano: praticamente completo!

terça-feira, maio 22, 2018

Early fossil record of Euarthropoda and the Cambrian Explosion

Allison C. Daley, Jonathan B. Antcliffe, Harriet B. Drage, and Stephen Pates

PNAS May 22, 2018. 115 (21) 5323-5331; published ahead of print May 22, 2018. https://doi.org/10.1073/pnas.1719962115

Reconstruction of the Cambrian predator and stem-lineage euarthropod Anomalocaris canadensis, based on fossils from the Burgess Shale, Canada. Credit: Reconstruction by Natalia Patkiewicz
Source/Fonte: PhysOrg

Abstract

Euarthropoda is one of the best-preserved fossil animal groups and has been the most diverse animal phylum for over 500 million years. Fossil Konservat-Lagerstätten, such as Burgess Shale-type deposits (BSTs), show the evolution of the euarthropod stem lineage during the Cambrian from 518 million years ago (Ma). The stem lineage includes nonbiomineralized groups, such as Radiodonta (e.g., Anomalocaris) that provide insight into the step-by-step construction of euarthropod morphology, including the exoskeleton, biramous limbs, segmentation, and cephalic structures. Trilobites are crown group euarthropods that appear in the fossil record at 521 Ma, before the stem lineage fossils, implying a ghost lineage that needs to be constrained. These constraints come from the trace fossil record, which show the first evidence for total group Euarthropoda (e.g., Cruziana, Rusophycus) at around 537 Ma. A deep Precambrian root to the euarthropod evolutionary lineage is disproven by a comparison of Ediacaran and Cambrian lagerstätten. BSTs from the latest Ediacaran Period (e.g., Miaohe biota, 550 Ma) are abundantly fossiliferous with algae but completely lack animals, which are also missing from other Ediacaran windows, such as phosphate deposits (e.g., Doushantuo, 560 Ma). This constrains the appearance of the euarthropod stem lineage to no older than 550 Ma. While each of the major types of fossil evidence (BSTs, trace fossils, and biomineralized preservation) have their limitations and are incomplete in different ways, when taken together they allow a coherent picture to emerge of the origin and subsequent radiation of total group Euarthropoda during the Cambrian.

paleontology Paleozoic evolution Arthropoda Cambrian explosion

Source: PNAS

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Professores, pesquisadores e alunos de universidades públicas e privadas com acesso ao site Portal de Periódicos - CAPES/MEC podem ler gratuitamente este artigo do PNAS e mais 33.000 publicações científicas.

Causa da Explosão Cambriana: terrestre ou cósmica???

segunda-feira, maio 21, 2018

Progress in Biophysics and Molecular Biology

Available online 13 March 2018

In Press, Corrected Proof What are Corrected Proof articles?

Progress in Biophysics and Molecular Biology

Cause of Cambrian Explosion - Terrestrial or Cosmic?

Author Edward J. Steele a j Shirwan Al-Mufti b Kenneth A. Augustyn c Rohana Chandrajith d John P. Coghlan e S. G. Coulson b Sudipto Ghosh f Mark Gillman g Reginald M. Gorczynski h Brig Klyce b Godfrey Louis i Kithsiri Mahanama  j Keith R. Oliver k Julio Padron l Jiangwen Qu m John A. Schuster n W. E. Smith o Duane P. Snyder b…Yongsheng Liu v w


Under a Creative Commons license open access


Source/Fonte: Nature

Abstract

We review the salient evidence consistent with or predicted by the Hoyle-Wickramasinghe (H-W) thesis of Cometary (Cosmic) Biology. Much of this physical and biological evidence is multifactorial. One particular focus are the recent studies which date the emergence of the complex retroviruses of vertebrate lines at or just before the Cambrian Explosion of ∼500 Ma. Such viruses are known to be plausibly associated with major evolutionary genomic processes. We believe this coincidence is not fortuitous but is consistent with a key prediction of H-W theory whereby major extinction-diversification evolutionary boundaries coincide with virus-bearing cometary-bolide bombardment events. A second focus is the remarkable evolution of intelligent complexity (Cephalopods) culminating in the emergence of the Octopus. A third focus concerns the micro-organism fossil evidence contained within meteorites as well as the detection in the upper atmosphere of apparent incoming life-bearing particles from space. In our view the totality of the multifactorial data and critical analyses assembled by Fred Hoyle, Chandra Wickramasinghe and their many colleagues since the 1960s leads to a very plausible conclusion – life may have been seeded here on Earth by life-bearing comets as soon as conditions on Earth allowed it to flourish (about or just before 4.1 Billion years ago); and living organisms such as space-resistant and space-hardy bacteria, viruses, more complex eukaryotic cells, fertilised ova and seeds have been continuously delivered ever since to Earth so being one important driver of further terrestrial evolution which has resulted in considerable genetic diversity and which has led to the emergence of mankind.

Keywords

Cosmic biology Cambrian Explosion Retroviruses Panspermia Hypermutation & evolution Origin epidemics & pandemics

Último artigo de Stephen Hawking: uma saída simples da inflação eterna do universo???

domingo, maio 20, 2018

Journal of High Energy Physics

April 2018, 2018:147 | Cite as

A smooth exit from eternal inflation?

Authors and affiliations

S. W. Hawking 1

Thomas Hertog 2

Email author

1.DAMTP, CMS Cambridge U.K.

2.Institute for Theoretical Physics University of Leuven Leuven Belgium

Open AccessRegular Article - Theoretical Physics

First Online: 27 April 2018

Source/Fonte: Universe Review CA

Abstract

The usual theory of inflation breaks down in eternal inflation. We derive a dual description of eternal inflation in terms of a deformed Euclidean CFT located at the threshold of eternal inflation. The partition function gives the amplitude of different geometries of the threshold surface in the no-boundary state. Its local and global behavior in dual toy models shows that the amplitude is low for surfaces which are not nearly conformal to the round three-sphere and essentially zero for surfaces with negative curvature. Based on this we conjecture that the exit from eternal inflation does not produce an infinite fractal-like multiverse, but is finite and reasonably smooth.

Keywords

AdS-CFT Correspondence Gauge-gravity correspondence Models of Quantum Gravity Spacetime Singularities

Primeira pesquisa anatômica detalhada de bonobos revela e expõe as estórias da carochinha da evolução humana, bipedalismo e uso de ferramentas

REVIEW ARTICLE

Front. Ecol. Evol., 26 April 2018 | https://doi.org/10.3389/fevo.2018.00053

First Detailed Anatomical Study of Bonobos Reveals Intra-Specific Variations and Exposes Just-So Stories of Human Evolution, Bipedalism, and Tool Use

Rui Diogo*

Department of Anatomy, Howard University, Washington, DC, United States

Figure 1. Differences between head muscles of common chimps, bonobos, and humans, based and modified from Diogo et al. (2017b).

Just-so stories are prominent in human evolution literature because of our tendency to create simple progressionist narratives about our “special” place in nature, despite the fact that these stories are almost exclusively based on hard tissue data. How can we be so certain about the evolution of human facial communication, bipedalism, tool use, or speech without detailed knowledge of the internal anatomy of for instance, one of the two extant species more closely related to us, the bonobos? Here I show how many of these stories now become obsolete, after such a comprehensive knowledge on the anatomy of bonobos and other primates is finally put together. Each and every muscle that has been long accepted to be “uniquely human” and to provide “crucial singular functional adaptations” for our bipedalism, tool use and/or vocal/facial communication, is actually present as an intra-specific variant or even as normal phenotype in bonobos and/or other apes.

Just-so stories (Smith, 2016) are frequent in the literature about human evolution because of our tendency to build simple progressionist narratives about our “special” evolutionary history and place in nature (Gould, 1993, 2002). This is particularly striking because these stories are in reality almost exclusively based on hard tissue data. In fact, descriptions of the soft tissues of apes have been relatively scarce and mainly referred to just a few muscles of the head or limbs of a single taxon, in most cases (e.g., Tyson, 1699; Bischoff, 1880; Raven, 1950; Swindler and Wood, 1973; Diogo and Wood, 2011, 2012; Persaud and Loukas, 2014). For instance, the only study that specifically focused on the musculature of bonobos (Pan paniscus) was that of Miller (1952), which was based on dissections of a single adult and did not provide information for numerous head and limb muscles (Diogo and Wood, 2011, 2012). Strikingly, despite this scarcity of information, biologists and anthropologists have displayed a remarkable confidence in their stories about the origin and evolution of human soft tissues, including their phylogenetic distribution and “singular functional adaptations.”

To illustrate this fact, in this short paper I will refer here briefly to seven muscles that have long been generally seen as “unique human features” and linked with specific adaptations for our bipedalism, tool use, and vocal or facial communication. Firstly, the facial expression muscle risorius (Figure 1) has been generally accepted as a unique feature crucial for the evolution of our “gracile” smile and “specially sophisticated” facial communication abilities (Huber, 1931). In a very influential paper, Susman et al. argued—although (fortunately) not as confidently as the assertions done by some of the other authors cited here—that the hand muscle adductor pollicis accessorius (Figure 2; “Henle” or “interosseous volaris primus” muscle: Bello-Hellegouarch et al., 2013) is a unique feature likely related to our increased ability to manufacture and/or use tools (Susman et al., 1999). Similarly, the foot muscle adductor hallucis accessorius—which topologically corresponds to the adductor pollicis accessorius of the hand—is also often considered to be uniquely found in our bipedal species, being at least consistently present at early stages of our ontogenetic development (Cihak, 1972). The foot muscle fibularis tertius (Figure 3) is, according to Lewis' (1989) highly influential monograph on the evolution of our limbs, a unique feature most likely associated with our bipedal evolution (Lewis, 1989). The flexor pollicis longus and extensor pollicis brevis (Figure 2) are forearm muscles that insert onto the thumb and that are generally considered to be unique adaptations for human tool manufacture and use (Lewis, 1989). For instance, it has been experimentally shown that the recruitment to these two muscles allows human subjects to maintain the metacarpophalangeal joint in extension while flexing the distal phalanx of the thumb, i.e., two primary movements usually done when we grab/manipulate objects (Marzke et al., 1998; Williams et al., 2012). Lastly, the laryngeal muscle arytenoideus obliquus has long been considered to be a unique feature of humans—which also have an arytenoideus transversus, in contrast to the single arytenoideus muscle said to occur in all other primates—associated to our enhanced vocal communication (reviewed in Diogo and Wood, 2012).

Usando e navegando a árvore da vida das plantas

Using and navigating the plant tree of life

Douglas E. Soltis Michael J. Moore Emily B. Sessa Stephen A. Smith Pamela S. Soltis

First published: 27 April 2018 https://doi.org/10.1002/ajb2.1071


Image result for plants tree of life
Source/Fonte: One Zoom Tree of Life

Abstract

The “tree of life” has become a metaphor for the interconnectivity and breadth of all life on Earth. It also has come to symbolize the broad investigation of biodiversity, including both the reconstruction of phylogeny and the numerous downstream analyses that are possible with a firm phylogenetic underpinning. Only a few decades ago, the construction of large phylogenetic trees of hundreds of taxa (or more) was considered an impossible task due to the immense computational challenges posed by analyses of large data sets. And no wonder—the number of possible trees that can describe the relationships of just 200 species exceeds the number of atoms in the universe (Hillis, 1996). As a result, building the tree of all named life, including the green plant branch (Viridiplantae)—a major clade with perhaps 500,000 species—has long been considered a grand challenge in biology. However, a perfect storm of algorithm development, increases in computational power, and DNA sequencing improvements over the last decade has not only made the construction of large trees more feasible, but also allowed us to attain some far‐reaching goals—a noteworthy example being the recent publication of a first draft tree of all life (Hinchcliff et al., 2015).

In plant biology, the frequent reconstruction of large phylogenetic trees has had an immense impact on the field. Large trees have helped to resolve deep‐level relationships and resulted in the revision of classifications, including some of the most profound changes in our view of plant relationships over the past 200 years (e.g., reviewed in part by Gitzendanner et al., 2018, in this issue). Large trees have also ushered in a renaissance in the study of conservation, ecology, methods development, crop improvement, genome evolution, and much more. Building the plant tree of life has come to represent the biodiversity equivalent of the human genome project, with numerous and often unanticipated downstream outcomes.

Accompanying these exciting advances are equally significant challenges that remain for the construction of a better and more complete picture of the evolution of plant lineages. In addition to the computational challenges of larger data sets, these include conceptual and methodological barriers. For example, where it was once thought that simply increasing DNA sequence data would increase resolution of relationships, we now understand that increasing data leads to increasing analytical complexity. Furthermore, this complexity is not due solely to limitations in computational power and methodology, but in part reflects the underlying complexity of the evolutionary process and its impact on genomes. Nevertheless, current conceptual and computational limitations present fantastic opportunities for transformative developments in our understanding of plant evolution. In this special issue, we explore many of the uses and challenges of big trees and big data in plant biology. Diverse papers provide overviews of the current status of the green plant tree of life and describe some of the myriad applications of the knowledge of phylogenetic relationships as well as some of the challenges inherent in handling plant phylogenomic data.

FREE PDF GRATIS: American Journal of Botany