685 research outputs found
A soluble model of evolution and extinction dynamics in a rugged fitness landscape
We consider a continuum version of a previously introduced and numerically
studied model of macroevolution (PRL 75, 2055, (1995)) in which agents evolve
by an optimization process in a rugged fitness landscape and die due to their
competitive interactions. We first formulate dynamical equations for the
fitness distribution and the survival probability. Secondly we analytically
derive the law which characterizes the life time distribution of
biological genera. Thirdly we discuss other dynamical properties of the model
such as the rate of extinction and conclude with a brief discussion.Comment: 6 pages LaTeX source with 2 figures. Submitted to PRL (Jan. 97
Financing Legal Education Through Student Loans: Results from a Quasi-Experiment in Tuition Remission
Humble Adorations Behind Kakawin Banawa Sekar Tanakung: a Critical Discourse Analysis
This research which deals with critical discourse analysis aims (1) to find out meanings of terms and vocabularies in Kakawin Banawa Sekar Tanakung, (2) to analyze meanings of Kakawin Banawa Sekar Tanakung in religious context, and (3) to reveal ideology behind the Kakawin Banawa Sekar Tanakung. The subject of this study was Kakawin Banawa Sekar Tanakung in ancient Javanese language, while the techniques of data collections were documentation. The data was then analyzed descriptively based on theory of Critical Discourse Analysis, theory of Natural Semantic Metalanguage and theory of meaning. The results of data analysis show that (1) most meanings of terms and vocabularies in the Kakawin Banawa Sekar Tanakung were reduced and broadened due to the influence of local culture and historical events. Some words are still common in today\u27s society, especially the Balinese in which ancient Javanese literatures are kept preserved today. (2) Kakawin Banawa Sekar Tanakung has a religious and ethical meaning, that people\u27s life in the ancient Java was religiously patterned. Besides, the kakawin showed that people of the ancient Java maintained their respects and submissiveness to the royal authorities. (3) The ideology of Kakawin Banawa Sekar Tanakung is submissive adoration, seen from the way the poet selected words and presented the kakawin through humble language choices. Considering that kakawins have valuable religious, moral, and educational values, further research on ancient Javanese literature are needed. Critical analysis according to the context of the kakawin should be conducted for the raise of Indonesian research on local assets. 2 PUJIAN DENGAN KERENDAHAN HATI DALAM KAKAWIN BANAWA SEKAR TANAKUNG: SEBUAH ANALISIS WACANA KRITIS oleh Ida Bagus Arya Lawa Manuaba NIM. 1029011062 Jurusan Pendidikan Bahasa Program Pascasarjana Universitas Pendidikan Ganesha Juli 201
Avalanche dynamics in Bak-Sneppen evolution model observed with standard distribution width of fitness
We introduce the standard distribution width of fitness to characterize the
global and individual features of a ecosystem in the Bak-Sneppen evolution
model. Through tracking this quantity in evolution, a different hierarchy of
avalanche dynamics, avalanche is observed. The corresponding gap
equation and the self-organized threshold are obtained. The critical
exponents and , which describe the behavior of the
avalanche size distribution, the average avalanche size and the relaxation to
attractor, respectively, are calculated with numerical simulation. The exact
master equation and equation are derived. And the scaling relations
are established among the critical exponents of this new avalanche.Comment: 14 pages, 3 figure
Mechanical basis of morphogenesis and convergent evolution of spiny seashells
Convergent evolution is a phenomenon whereby similar traits evolved independently in not closely related species, and is often interpreted in functional terms. Spines in mollusk seashells are classically interpreted as having repeatedly evolved as a defense in response to shell-crushing predators. Here we consider the morphogenetic process that shapes these structures and underlies their repeated emergence. We develop a mathematical model for spine morphogenesis based on the mechanical interaction between the secreting mantle edge and the calcified shell edge to which the mantle adheres during shell growth. It is demonstrated that a large diversity of spine structures can be accounted for through small variations in control parameters of this natural mechanical process. This physical mechanism suggests that convergent evolution of spines can be understood through a generic morphogenetic process, and provides unique perspectives in understanding the phenotypic evolution of this second largest phylum in the animal kingdom.\ud
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Homoplasy, the appearance of similar traits in separate evolutionary lineages as a result of convergence, parallelism, or evolutionary reversals, is a major concern in phylogenetic analysis for which it is viewed as noise. However, over the past two decades, homoplasy has also become a subject of increasing interest, stimulated by the rise of evolutionary developmental biology (evo devo) and the wish to uncover the developmental basis of this phenomenon (1ââ3). Spines constitute the most prominent ornamentation of mollusk shells and have evolved in many distantly related fossil and current mollusk species (at least 55 genera and 21 families of current gastropods; 10 genera and 8 families of current bivalves; 11 genera and 8 families of ammonoids; and 6 fossil nautiloid genera; see Fig. 1 for examples). Convergent evolution of spines in mollusks has been addressed in functional terms, these structures being interpreted as having evolved as a defense in response to shell-crushing predators (4ââ6). This hypothesis is itself the basis of the widely cited âescalation hypothesis,â according to which long-term trends in the fossil record were caused by the evolutionary response of prey to predation pressure (7). The idea that convergent evolution of similar mollusk ornamentations might be fully explained in functional terms is based on the premise that similar characters, perceived as well designed for a presumed function, cannot conceivably have independently evolved fortuitously. Therefore, natural selection is thought to have repeatedly shaped similar functional traits out of random variations
Punctuated Equilibrium in Software Evolution
The approach based on paradigm of self-organized criticality proposed for
experimental investigation and theoretical modelling of software evolution. The
dynamics of modifications studied for three free, open source programs Mozilla,
Free-BSD and Emacs using the data from version control systems. Scaling laws
typical for the self-organization criticality found. The model of software
evolution presenting the natural selection principle is proposed. The results
of numerical and analytical investigation of the model are presented. They are
in a good agreement with the data collected for the real-world software.Comment: 4 pages, LaTeX, 2 Postscript figure
Biological Effects of Stellar Collapse Neutrinos
Massive stars in their final stages of collapse radiate most of their binding
energy in the form of MeV neutrinos. The recoil atoms that they produce in
elastic scattering off nuclei in organic tissue create radiation damage which
is highly effective in the production of irreparable DNA harm, leading to
cellular mutation, neoplasia and oncogenesis. Using a conventional model of the
galaxy and of the collapse mechanism, the periodicity of nearby stellar
collapses and the radiation dose are calculated. The possible contribution of
this process to the paleontological record of mass extinctions is examined.Comment: gzipped PostScript (filename.ps.Z), 12 pages. Final version, Phys.
Rev. Lett., in pres
The Impact of the SpeciesâArea Relationship on Estimates of Paleodiversity
Estimates of paleodiversity patterns through time have relied on datasets that lump taxonomic occurrences from geographic areas of varying size per interval of time. In essence, such estimates assume that the speciesâarea effect, whereby more species are recorded from larger geographic areas, is negligible for fossil data. We tested this assumption by using the newly developed Miocene Mammal Mapping Project database of western North American fossil mammals and its associated analysis tools to empirically determine the geographic area that contributed to species diversity counts in successive temporal bins. The results indicate that a speciesâarea effect markedly influences counts of fossil species, just as variable spatial sampling influences diversity counts on the modern landscape. Removing this bias suggests some traditionally recognized peaks in paleodiversity are just artifacts of the speciesâarea effect while others stand out as meriting further attention. This discovery means that there is great potential for refining existing time-series estimates of paleodiversity, and for using speciesâarea relationships to more reliably understand the magnitude and timing of such biotically important events as extinction, lineage diversification, and long-term trends in ecological structure
Self-organized criticality in deterministic systems with disorder
Using the Bak-Sneppen model of biological evolution as our paradigm, we
investigate in which cases noise can be substituted with a deterministic signal
without destroying Self-Organized Criticality (SOC). If the deterministic
signal is chaotic the universality class is preserved; some non-universal
features, such as the threshold, depend on the time correlation of the signal.
We also show that, if the signal introduced is periodic, SOC is preserved but
in a different universality class, as long as the spectrum of frequencies is
broad enough.Comment: RevTex, 8 pages, 8 figure
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