scholarly journals A fresh look at the fossil evidence for early Archaean cellular life

2006 ◽  
Vol 361 (1470) ◽  
pp. 887-902 ◽  
Author(s):  
Martin Brasier ◽  
Nicola McLoughlin ◽  
Owen Green ◽  
David Wacey
Keyword(s):  
Critical Analysis ◽  
Fossil Record ◽  
Volcanic Glass ◽  
New Approach ◽  
Microbial Origin ◽  
Cellular Life ◽  
Fossil Evidence ◽  
Rock Record ◽  
Inclusion Trails ◽  
Self Organizing

The rock record provides us with unique evidence for testing models as to when and where cellular life first appeared on Earth. Its study, however, requires caution. The biogenicity of stromatolites and ‘microfossils’ older than 3.0 Gyr should not be accepted without critical analysis of morphospace and context, using multiple modern techniques, plus rejection of alternative non-biological (null) hypotheses. The previous view that the co-occurrence of biology-like morphology and carbonaceous chemistry in ancient, microfossil-like objects is a presumptive indicator of biogenicity is not enough. As with the famous Martian microfossils, we need to ask not ‘what do these structures remind us of?’, but ‘what are these structures?’ Earth's oldest putative ‘microfossil’ assemblages within 3.4–3.5 Gyr carbonaceous cherts, such as the Apex Chert, are likewise self-organizing structures that do not pass tests for biogenicity. There is a preservational paradox in the fossil record prior to ca 2.7 Gyr: suitable rocks (e.g. isotopically light carbonaceous cherts) are widely present, but signals of life are enigmatic and hard to decipher. One new approach includes detailed mapping of well-preserved sandstone grains in the ca 3.4 Gyr Strelley Pool Chert. These can contain endolithic microtubes showing syngenicity, grain selectivity and several levels of geochemical processing. Preliminary studies invite comparison with a class of ambient inclusion trails of putative microbial origin and with the activities of modern anaerobic proteobacteria and volcanic glass euendoliths.

A New Approach to Machinery Monitoring and Diagnostics Using Self-Organizing Maps

1995 ◽  
Author(s):  
Siyu Zhang ◽  
R. Ganesan ◽  
T. S. Sankar
Keyword(s):  
Neural Network ◽  
Service Life ◽  
Trend Analysis ◽  
New Approach ◽  
Machine System ◽  
Network Algorithm ◽  
On Line ◽  
Neural Network Algorithm ◽  
Monitoring And Diagnostics ◽  
Self Organizing

Abstract The problem of estimating an unknown multivariate function from on-line vibration measurements, for determining the conditions of a machine system and for estimating its service life is considered. This problem is formulated into a multiple-index based trend analysis problem and the corresponding indices for trend analysis are extracted from the on-line vibration data. Selection of these indices is based on the simultaneous consideration of commonly-observed faults or malfunctions in the machine system being monitored. A neural network algorithm that has been developed by the present authors for multiple-index based regression is adapted to perform the trend analysis of a machine system. Applications of this neural network algorithm to the condition monitoring and life estimation of both a bearing system as well as a gearbox are fully demonstrated. The efficiency and computational supremacy of the new algorithm are established through comparing with the performance of Self-Organizing Mapping (SOM) and Constrained Topological Mapping (CTM) algorithms. Further, the usefulness of multiple-index based trend analysis in precisely predicting the condition and service life of a machine system is clearly demonstrated. Using on-line vibration signal to constitute the set of variables for trend analysis, and employing the newly-developed self-organizing neural algorithm for performing the trend analysis, a new approach is developed for machinery monitoring and diagnostics.

scholarly journals Major features of protistan evolution: controversies, problems and a few answers

2006 ◽  
Vol 29 (1) ◽  
pp. 55-80
Author(s):  
Jere H Lipps
Keyword(s):  
Fossil Record ◽  
Molecular Data ◽  
Trophic Levels ◽  
Early Earth ◽  
Huge Number ◽  
Geologic Time ◽  
Earth History ◽  
Important Development ◽  
Fossil Evidence

The major features of protist evolution are fraught with controversies, problems and few answers, especially in early Earth history. In general they are based on molecular data and fossil evidence that respectively provide a scaffold and details of eukaryotic phylogenetic and ecologic histories. 1. Their origin, inferred from molecular sequences, occurred very early (>;3Ga). They are a chimera of different symbiont-derived organelles, including possibly the nucleus. 2. The initial diversification of eukaryotes may have occurred early in geologic time. Six supergroups exist today, each with fossils known from the Proterozoic and Phanerozoic. 3. Sex, considered an important development, may have been inherited from bacteria. 4. Precambrian protists were largely pelagic cyst-bearing taxa, but benthic forms were probably quite diverse and abundant. 5. Protists gave rise to animals long before 600 Ma through the choanoflagellates, for which no fossil record exists. 6. Acritarchs and skeletonized protists radiated in the Cambrian (544-530 my). From then on, they radiated and became extinct at all the major events recorded in the metazoan fossil record. 7. Protists dominated major environments (shelves and reefs) starting with a significant radiation in the Ordovician, followed by extinctions and other radiations until most died out at the end of the Permian. 8. In the Mesozoic, new planktic protozoa and algae appeared and radiated in pelagic environments. 9. Modern protists are important at all trophic levels in the oceans and a huge number terrestrial, parasitic and symbiotic protists must have existed for much of geologic time as well. 10. The future of protists is likely in jeopardy, just like most reefal, benthic, and planktic metazoans. An urgent need to understand the role of protists in modern threatened oceans should be addressed soon.

scholarly journals Diversity-dependence brings molecular phylogenies closer to agreement with the fossil record

2011 ◽  
Vol 279 (1732) ◽  
pp. 1300-1309 ◽  
Author(s):  
Rampal S. Etienne ◽  
Bart Haegeman ◽  
Tanja Stadler ◽  
Tracy Aze ◽  
Paul N. Pearson ◽  
...  
Keyword(s):  
Standard Model ◽  
Fossil Record ◽  
Evolutionary Dynamics ◽  
Planktonic Foraminifera ◽  
Fossil Evidence ◽  
Rate Of Increase ◽  
The Standard Model ◽  
Molecular Phylogenies ◽  
Biological Realism

The branching times of molecular phylogenies allow us to infer speciation and extinction dynamics even when fossils are absent. Troublingly, phylogenetic approaches usually return estimates of zero extinction, conflicting with fossil evidence. Phylogenies and fossils do agree, however, that there are often limits to diversity. Here, we present a general approach to evaluate the likelihood of a phylogeny under a model that accommodates diversity-dependence and extinction. We find, by likelihood maximization, that extinction is estimated most precisely if the rate of increase in the number of lineages in the phylogeny saturates towards the present or first decreases and then increases. We demonstrate the utility and limits of our approach by applying it to the phylogenies for two cases where a fossil record exists (Cetacea and Cenozoic macroperforate planktonic foraminifera) and to three radiations lacking fossil evidence ( Dendroica , Plethodon and Heliconius ). We propose that the diversity-dependence model with extinction be used as the standard model for macro-evolutionary dynamics because of its biological realism and flexibility.

The early Mesozoic radiation of dinoflagellates

Paleobiology ◽  
1996 ◽  
Vol 22 (3) ◽  
pp. 329-338 ◽  
Author(s):  
R. A. Fensome ◽  
R. A. MacRae ◽  
J. M. Moldowan ◽  
F. J. R. Taylor ◽  
G. L. Williams
Keyword(s):  
Detailed Analysis ◽  
Fossil Record ◽  
The Past ◽  
Early Mesozoic ◽  
Fossil Evidence ◽  
Evolutionary Radiation ◽  
Molecular Phylogenetic ◽  
Sudden Appearance ◽  
New Evidence

Dinoflagellates are a major component of the marine microplankton and, from fossil evidence, appear to have been so for the past 200 million years. In contrast, the pre-Triassic record contains only equivocal occurrences of dinoflagellates, despite the fact that comparative ultrastructural and molecular phylogenetic evidence indicates a Precambrian origin for the lineage. Thus, it has often been assumed that the dearth of Paleozoic fossil dinoflagellates was due to a lack of preservation or recognition and that the relatively sudden appearance of dinoflagellates in the Mesozoic is an artifact of the record. However, new evidence from a detailed analysis of the fossil record and from the biogeochemical record indicates that dinoflagellates did indeed undergo a major evolutionary radiation in the early Mesozoic.

The causes of extinction

1989 ◽  
Vol 325 (1228) ◽  
pp. 241-252 ◽  
Keyword(s):  
Fossil Record ◽  
Species Turnover ◽  
Rapid Evolution ◽  
Taxonomic Diversity ◽  
Species Selection ◽  
Biotic Factors ◽  
Taxonomic Distribution ◽  
Interacting Species ◽  
Fossil Evidence ◽  
Different Types

A species may go extinct either because it is unable to evolve rapidly enough to meet changing circumstances, or because its niche disappears and no capacity for rapid evolution could have saved it. Although recent extinctions can usually be interpreted as resulting from niche disappearance, the taxonomic distribution of parthenogens suggests that inability to evolve may also be important. A second distinction is between physical and biotic causes of extinction. Fossil evidence for constant taxonomic diversity, combined with species turnover, implies that biotic factors have been important. A similar conclusion emerges from studies of recent introductions of predators, competitors and parasites into new areas. The term ‘species selection’ should be confined to cases in which the outcome of selection is determined by properties of the population as a whole, rather than of individuals. The process has been of only trivial importance in producing complex adaptations, but of major importance in determining the distribution of different types of organisms. An adequate interpretation of the fossil record requires a theory of the coevolution of many interacting species. Such a theory is at present lacking, but various approaches to it are discussed.

scholarly journals Diversification dynamics of total-, stem-, and crown-groups are compatible with molecular clock estimates of divergence times

2021 ◽  
Vol 7 (24) ◽  
pp. eabf2257
Author(s):  
Alan J. S. Beavan ◽  
Davide Pisani ◽  
Philip C. J. Donoghue
Keyword(s):  
Time Scales ◽  
Molecular Clock ◽  
Fossil Record ◽  
Divergence Times ◽  
Evolutionary Time ◽  
Crown Group ◽  
Total Group ◽  
Fossil Evidence ◽  
Evolutionary Radiations ◽  
Birth Death

Molecular evolutionary time scales are expected to predate the fossil evidence, but, particularly for major evolutionary radiations, they can imply extremely protracted stem lineages predating the origin of living clades, leading to claims of systematic overestimation of divergence times. We use macroevolutionary birth-death models to describe the range of total-group and crown-group ages expected under constant rates of speciation and extinction. We extend current predictions on origination times for crown- and total-groups, and extinction of stem-groups, demonstrating that there is broad variance in these predictions. Under constant rates of speciation and extinction, we show that the distribution of expected arthropod total-group ages is consistent with molecular clock estimates. The fossil record cannot be read literally, and our results preclude attempts to interpret the antiquity of clades based on the co-occurrence of stem- and crown-representatives.

scholarly journals Improving the Methodology for Assessing the Effectiveness of Economic Entities in Modern Conditions

2022 ◽  
Vol 2021 (4) ◽  
pp. 560-567
Author(s):  
Elena Orehova ◽  
Irina Korovnikova ◽  
Galina Korovnikova
Keyword(s):  
Performance Indicators ◽  
Critical Analysis ◽  
Methodological Approach ◽  
Comprehensive Model ◽  
New Approach ◽  
Economic Entity ◽  
Efficiency Assessment ◽  
Business Efficiency ◽  
Modern Economic ◽  
Classical Economic

Modern conditions impose special requirements to the assessment of economic entities. Efficiency is an important parameter of the activity of any business. The present research involved a critical analysis of standard methods for assessing the effectiveness of both domestic and foreign practices. The analysis revealed a need to apply new approaches to business efficiency assessment because the standard approach is not systematic and its indicators repeat themselves. The article offers a new conceptual methodological approach to understanding the term efficiency. The new methodological concept is hybrid in nature and includes classical economic, financial, and institutional methods. It also adopts some methods and approaches from management and natural sciences. The authors built a comprehensive model for assessing the effectiveness of an economic entity in modern conditions. It is based on the idea that the optimal methods are those that do not use relative indicators. This model includes three levels of indicators: standard, qualitative, and synergistic. The new approach is systemic and corresponds to modern economic environment, which resolves the issue of relative performance indicators.

scholarly journals A New Approach to Conservation: A Critical Analysis of DOC’s Commercial Partnership Strategy

2021 ◽  
Author(s):  
◽  
Ben Stantiall
Keyword(s):  
New Zealand ◽  
Critical Analysis ◽  
Conservation Strategies ◽  
New Approach ◽  
External Resources ◽  
Conservation Movement ◽  
Aotearoa New Zealand ◽  
New Concepts ◽  
Neoliberal Ideology ◽  
National Significance

<p>The complex range of challenges facing the environment has prompted the conservation movement to evolve and incorporate new concepts, attitudes and strategies. A prominent approach that has attracted scholarly attention is the appeal for broader societal involvement and an increased human-focus for the conservation movement. This new approach is particularly notable for the inclusion of private business in conservation strategies. Subsequently, these strategies have prompted criticism of their links to neoliberal ideology and the encouragement of consumption-based measures.  Conservation in Aotearoa New Zealand has followed this strategy of business involvement, represented by the Department of Conservation’s (DOC) commercial partnerships. The deliberate use of large businesses is used to access external resources and expertise alongside exposure to their respective customer bases. However, the criticisms of neoliberal ideology, matched by the national significance of the conservation estate and its relationship with the New Zealand public has created numerous challenges and considerations for DOC to navigate.  To acknowledge the different attitudes and relationships that people have to the environment and conservation, a constructivist approach was used to examine the implementation of DOC’s partnership strategy. A case study consisting of seven interviews with representatives from DOC, environmental NGOs and the businesses involved in the partnerships was carried out. The data revealed three central themes; initially, of the need for a wider approach to conservation, followed by the intrusion and influence of neoliberal ideology into the domain, and the presentation of win-win strategies. This research provides a critical analysis of DOC’s recent shift in strategy and the implications of it on future strategies.</p>

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