Was the Ediacaran–Cambrian radiation a unique evolutionary event?

Paleobiology ◽  
2015 ◽  
Vol 41 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Douglas H. Erwin
Keyword(s):  
Evolutionary Theory ◽  
Physical Environment ◽  
Redox State ◽  
Initial Conditions ◽  
Ecological Interactions ◽  
Developmental Mechanisms ◽  
Evolutionary Event ◽  
History Of ◽  
Cambrian Radiation ◽  
Sensitivity To Initial Conditions

AbstractThe extent of morphologic innovation during the Ediacaran–Cambrian diversification of animals was unique in the history of metazoan life. This episode was also associated with extensive changes in the redox state of the oceans, in the structure of benthic and pelagic marine ecosystems, in the nature of marine sediments, and in the complexity of developmental interactions in Eumetazoa. But did the phylogenetic and morphologic breadth of this episode simply reflect the unusual outcome of recurrent evolutionary processes, or was it the unique result of circumstances, whether in the physical environment, in developmental mechanisms, or in ecological interactions? To better characterize the uniqueness of the events, I distinguish among these components on the basis of the extent of sensitivity to initial conditions and unpredictability, which generates a matrix of possibilities from fully contingent to fully deterministic. Discriminating between these differences is important for informing debates over determinism versus the contingency in the history of life, for understanding the nature of evolutionary theory, and for interpreting historically unique events.

An Entangled Bank

2016 ◽  
Author(s):  
Marc W. Cadotte ◽  
T. Jonathan Davies
Keyword(s):  
Evolutionary Theory ◽  
Community Assembly ◽  
Charles Darwin ◽  
Neutral Theory ◽  
Species Distributions ◽  
Ecological Interactions ◽  
Carl Linnaeus ◽  
History Of ◽  
Neutral Theory Of Biodiversity ◽  
Diversity Of Life

This chapter reviews the history of the use of phylogenetics in ecology, beginning with a discussion of early attempts to classify the diversity of life and the development of evolutionary theory. In particular, it examines how early taxonomists, starting with Carl Linnaeus, have grouped species by similarity in their traits and how early ecologists and biologists such as Charles Darwin recognized the importance of relatedness in influencing ecological interactions and species distributions. The chapter proceeds by focusing on the introduction of the neutral theory of biodiversity into mainstream ecology and the development of the niche-based model of community assembly. It also considers how some ecologists questioned the relevance of phylogenetic corrections for ecology and concludes by analyzing the emergence of ecological phylogenetics or ecophylogenetics.

scholarly journals A history of chaos theory

2007 ◽  
Vol 9 (3) ◽  
pp. 279-289 ◽  
Keyword(s):  
Mathematical Models ◽  
Chaos Theory ◽  
Cardiac Arrhythmias ◽  
Initial Conditions ◽  
Fractal Dimensions ◽  
Biological Clocks ◽  
Deterministic Models ◽  
Endogenous Rhythms ◽  
History Of ◽  
Sensitivity To Initial Conditions

Whether every effect can be precisely linked to a given cause or to a list of causes has been a matter of debate for centuries, particularly during the 17th century, when astronomers became capable of predicting the trajectories of planets. Recent mathematical models applied to physics have included the idea that given phenomena cannot be predicted precisely, although they can be predicted to some extent, in line with the chaos theory. Concepts such as deterministic models, sensitivity to initial conditions, strange attractors, and fractal dimensions are inherent to the development of this theory A few situations involving normal or abnormal endogenous rhythms in biology have been analyzed following the principles of chaos theory. This is particularly the case with cardiac arrhythmias, but less so with biological clocks and circadian rhythms.

Disparity and constraint in olenelloid trilobites and the Cambrian Radiation

Paleobiology ◽  
1999 ◽  
Vol 25 (4) ◽  
pp. 459-470 ◽  
Author(s):  
Loren H. Smith ◽  
Bruce S. Lieberman
Keyword(s):  
Morphological Changes ◽  
Early Cambrian ◽  
Morphological Disparity ◽  
Time Period ◽  
Animal Phyla ◽  
Evolutionary Event ◽  
History Of ◽  
Cambrian Radiation ◽  
Active Research ◽  
Morphological Constraint

The Cambrian Radiation marks the appearance of representatives of virtually all major skeletonized phyla in the fossil record and clearly represents a fundamental episode in the history of life. Furthermore, the tempo and mode of this evolutionary event have been the subject of intense debate. One area that has been debated is how so many phylum-level body plans can have evolved in such a geologically brief period. Some have argued that there was enhanced morphological flexibility and fewer evolutionary constraints at this time, leading to greater morphological disparity of Early Cambrian faunas. Others have claimed that this is not true because the evolution of most of the animal phyla significantly predates the radiation or because they failed to detect a signature of decreasing morphological disparity through time. At present, the higher-level patterns of diversification during this time period and the relevant implications for Early Cambrian uniqueness are areas of active research interest and debate. Recognizing this debate, we used both a phylogenetic and a morphometric framework to study whether there is a signature of increasing morphological constraint and decreasing flexibility through time within one of the clades that is a significant constituent of the Early Cambrian biota, specifically, the olenelloid trilobites. In this species-rich clade, we found no evidence that morphological changes were becoming either increasingly constrained or less flexible in one of the dominant Early Cambrian metazoan clades as it passed through the Cambrian Radiation.

A New Image Encryption Scheme Using Dual Chaotic Map Synchronization

2020 ◽  
Vol 18 (1) ◽  
Keyword(s):  
Image Encryption ◽  
Chaotic Systems ◽  
Initial Conditions ◽  
Chaotic Map ◽  
Security Applications ◽  
The Common ◽  
And Diffusion ◽  
Confusion And Diffusion ◽  
Sensitivity To Initial Conditions ◽  
Diffusion Properties

Chaotic systems behavior attracts many researchers in the field of image encryption. The major advantage of using chaos as the basis for developing a crypto-system is due to its sensitivity to initial conditions and parameter tunning as well as the random-like behavior which resembles the main ingredients of a good cipher namely the confusion and diffusion properties. In this article, we present a new scheme based on the synchronization of dual chaotic systems namely Lorenz and Chen chaotic systems and prove that those chaotic maps can be completely synchronized with other under suitable conditions and specific parameters that make a new addition to the chaotic based encryption systems. This addition provides a master-slave configuration that is utilized to construct the proposed dual synchronized chaos-based cipher scheme. The common security analyses are performed to validate the effectiveness of the proposed scheme. Based on all experiments and analyses, we can conclude that this scheme is secure, efficient, robust, reliable, and can be directly applied successfully for many practical security applications in insecure network channels such as the Internet

Missing Links in the History of Life

2002 ◽  
Vol 11 ◽  
pp. 97-118
Author(s):  
Charles R. Marshall
Keyword(s):  
Evolutionary Theory ◽  
Fossil Record ◽  
Theory Of Evolution ◽  
History Of ◽  
Living Species

Ever since Darwin proposed his theory of evolution (or more correctly, theories; see Mayr, 1991) it has been assumed that intermediates now extinct once existed between living species. For some, the hunt for these so-called missing links in the fossil record became an obsession, a search for evidence thought needed to establish the veracity of evolutionary theory. Few modern paleontologists, however, search explicitly for ancestors in the fossil record because we now know that fossils can be used to chart the order of evolution regardless of whether they are directly ancestral either to extinct organisms or to those living today.

scholarly journals Current understanding on the Cambrian Explosion: questions and answers

PalZ ◽  
2021 ◽  
Author(s):  
Xingliang Zhang ◽  
Degan Shu
Keyword(s):  
Environmental Changes ◽  
Size Variation ◽  
Progressive Increase ◽  
Cambrian Explosion ◽  
Time Interval ◽  
Early Cambrian ◽  
Ecological Processes ◽  
Questions And Answers ◽  
Evolutionary Event ◽  
History Of

AbstractThe Cambrian Explosion by nature is a three-phased explosion of animal body plans alongside episodic biomineralization, pulsed change of generic diversity, body size variation, and progressive increase of ecosystem complexity. The Cambrian was a time of crown groups nested by numbers of stem groups with a high-rank taxonomy of Linnaean system (classes and above). Some stem groups temporarily succeeded while others were ephemeral and underrepresented by few taxa. The high number of stem groups in the early history of animals is a major reason for morphological gaps across phyla that we see today. Most phylum-level clades achieved their maximal disparity (or morphological breadth) during the time interval close to their first appearance in the fossil record during the early Cambrian, whereas others, principally arthropods and chordates, exhibit a progressive exploration of morphospace in subsequent Phanerozoic. The overall envelope of metazoan morphospace occupation was already broad in the early Cambrian though it did not reach maximal disparity nor has diminished significantly as a consequence of extinction since the Cambrian. Intrinsic and extrinsic causes were extensively discussed but they are merely prerequisites for the Cambrian Explosion. Without the molecular evolution, there could be no Cambrian Explosion. However, the developmental system is alone insufficient to explain Cambrian Explosion. Time-equivalent environmental changes were often considered as extrinsic causes, but the time coincidence is also insufficient to establish causality. Like any other evolutionary event, it is the ecology that make the Cambrian Explosion possible though ecological processes failed to cause a burst of new body plans in the subsequent evolutionary radiations. The Cambrian Explosion is a polythetic event in natural history and manifested in many aspects. No simple, single cause can explain the entire phenomenon.

scholarly journals Nonlinear Behavior of a Magnetic Bearing System

1995 ◽  
Vol 117 (3) ◽  
pp. 582-588 ◽  
Author(s):  
L. N. Virgin ◽  
T. F. Walsh ◽  
J. D. Knight
Keyword(s):  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Nonlinear Behavior ◽  
Analytical Techniques ◽  
Magnetic Bearing ◽  
Forced Response ◽  
The Mathematical Model ◽  
Two Degree Of Freedom ◽  
Sensitivity To Initial Conditions ◽  
Bearing System

This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bearings and subject to rotating unbalance and feedback control. Geometric coupling between the degrees of freedom leads to a pair of nonlinear ordinary differential equations, which are then solved using both numerical simulation and approximate analytical techniques. The system exhibits a variety of interesting and somewhat unexpected phenomena including various amplitude driven bifurcational events, sensitivity to initial conditions, and the complete loss of stability associated with the escape from the potential well in which the system can be thought to be oscillating. An approximate criterion to avoid this last possibility is developed based on concepts of limiting the response of the system. The present paper may be considered as an extension to an earlier study by the same authors, which described the practical context of the work, free vibration, control aspects, and derivation of the mathematical model.

scholarly journals Storytelling through experiencescape: Creating unique stories and extraordinary experiences in farm tourism

2018 ◽  
Vol 20 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Xiang Y Mei ◽  
Ann-Margret S Hågensen ◽  
Heidi S Kristiansen
Keyword(s):  
Physical Environment ◽  
Research Method ◽  
Tourism Industry ◽  
Limited Resources ◽  
Explorative Study ◽  
Extraordinary Experiences ◽  
History Of ◽  
Farm Tourism ◽  
Depth Interviews ◽  
Lack Of Knowledge

Creating unique stories through storytelling as a way to stage extraordinary experiences has become increasingly important in the tourism industry, particularly in experience-based activities such as farm tourism. However, limited resources and the lack of knowledge of the experiencescape suggest that many farm tourism operators struggle to integrate the experiencescape as part of storytelling. The research method chosen was an explorative study with the use of semi-structured in-depth interviews with key farm tourism operators in the Inland region in Norway. How stories and concepts are created is dependent on the resources available, the perception of authenticity, the history of the farm as well as the environment. Storytelling can be facilitated through tangible elements in the experiencescape such as the physical environment as well as intangible elements including the interaction and dynamics between the host and guest. The farmer or the person telling the story also need to possess certain skills, engagement, and interest in order to be committed to deliver the story or the concept. Essentially, the farmer becomes a part of the product and the experience.

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