Rates of Evolution

2002 ◽  
Vol 11 ◽  
pp. 257-264
Author(s):  
Steven M. Stanley
Keyword(s):  
Rate Of Evolution ◽  
Rates Of Evolution ◽  
Or Groups

Any two biologic groups—populations, species, or groups of species—that are separated in time but connected by evolution provide us with the opportunity to measure a rate of evolution.

Rates of Evolution

1999 ◽  
Vol 9 ◽  
pp. 319-328
Author(s):  
Steven M. Stanley
Keyword(s):  
New Species ◽  
The Other ◽  
Appreciable Change ◽  
Rate Of Evolution ◽  
Geologic Time ◽  
Other Hand ◽  
Rates Of Evolution ◽  
Or Groups

Any two biologic groups — populations, species, or groups of species — that are separated in time but connected by evolution provide us with the opportunity to measure a rate of evolution.Rates are interesting because they vary greatly. Some species have survived for millions of years without appreciable change. On the other hand, some species have arisen from other, quite different species within just a few thousands or tens of thousands of years: very brief intervals of time. Similarly, some groups of organisms have diversified rapidly, producing many new species during brief intervals of geologic time, whereas others have added new species very slowly.

scholarly journals Rates of evolution and fossils in phylogenetic analysis: a computer simulation approach

1992 ◽  
Vol 6 ◽  
pp. 140-140
Author(s):  
John P. Huelsenbeck ◽  
David M. Hillis
Keyword(s):  
Phylogenetic Analysis ◽  
Wide Spectrum ◽  
Phylogenetic Reconstruction ◽  
Length Distribution ◽  
Temporal Position ◽  
Rate Of Evolution ◽  
Rates Of Evolution ◽  
Phylogenetic Resolution ◽  
Main Determinants ◽  
The Relationship

Whereas many studies have examined the performance of various character-data sets in phylogenetic analysis, little work has been done on the effect that various classes of taxa have on phylogenetic reconstruction. In particular, the “fossil versus living taxa” debate has concentrated mainly on the effects of fossils in reconstructing vertebrate and plant relationships. While this work has contributed to the understanding of the role that fossils play in systematics, a computer model clarifies the relationship among the main determinants of the fossil-taxa problem. In addition, simulations of phylogenies over a wide spectrum of evolutionary rates clarify the relative efficiencies of various tree-estimation procedures.In this study, computer generated phylogenies were used to examine the relationship between the temporal position and completeness of additional taxa in a phylogenetic analysis and the rate of evolution or, equivalently, the temporal scope of the phylogenetic problem. In the simulations, four fossil taxa of varying temporal position and completeness were added to an analysis that included four living taxa. Additional taxa varied in completeness (25%, 50%, 75%, and 100% completeness) and in temporal position (0%, 33%, 66%, and 100% of the distance from the ancestor to the living time plane). Fifty trees were generated each for low, low intermediate, high intermediate, and high rates of evolution or temporal scope. Because additional taxa that are 100% complete and 100% of the distance to the living time plane are equivalent to the addition of living taxa, this study directly compares the effects of addition of living versus fossil taxa in phylogenetic analysis.The importance of fossil taxa varied depending on their completeness and temporal position and on the rate of evolution under which the phylogeny was generated. In general, high completeness and temporal position near the ancestor of a clade improved phylogenetic resolution as measured by the percentage of the tree-length distribution that contains the real tree. Furthermore, the conditions of completeness and temporal position under which fossil taxa improved phylogenetic resolution over living taxa became less restrictive as the rate of evolution or the temporal scope of the tree increased.

Genomic versus morphologic rates of evolution: influence of morphologic complexity

Paleobiology ◽  
1975 ◽  
Vol 1 (1) ◽  
pp. 63-70 ◽  
Author(s):  
Thomas J. M. Schopf ◽  
David M. Raup ◽  
Stephen Jay Gould ◽  
Daniel S. Simberloff
Keyword(s):  
Cluster Analysis ◽  
Computer Simulation ◽  
Real World ◽  
Evolutionary Rates ◽  
The Real ◽  
Rate Of Evolution ◽  
Taxonomic Change ◽  
Rates Of Evolution ◽  
Evolutionary Changes ◽  
Complex Forms

The degree of perceived taxonomic change in various lineages may be directly related to their general morphologic complexity: more complex forms appear to change more rapidly. “Rates of evolution” as customarily reported by paleontologists may therefore be a poor indication of evolutionary changes in the underlying genome. Two approaches were used to examine this problem. (1) We have estimated the degree of morphologic complexity by using the number of descriptive terms per genus, and per family, for 12 major groups of animals. Three general levels of complexity occur: (i) gastropods, bivalves and ectoprocts have relatively few terms; (ii) echinoids, foraminiferans, ostracodes, nautiloids, corals, trilobites, and brachiopods have an intermediate number of terms; (iii) mammals and ammonoids appear to have a relatively large number of terms. These 3 levels of complexity also increase in rate of taxonomic turnover; i.e., an increasing rate of evolution. (2) Using a cluster analysis based on morphologic similarity, we grouped 200 lineages of a computer-generated phylogenetic sequence according to 4 phenetic bases: 3, 5, 10 and 20 morphologic traits. Groups based on a few characters are longer lived and are commonly polyphyletic in comparison with groups based on many characters. In both the real world and the computer simulation, the bias of differential morphologic complexity may account for the observation that “only complicated animals evolve.” Most paleontologic studies of the “rate of evolution” may tell us more about morphologic complexity than about evolutionary rates of genomes.

scholarly journals Diminishing returns of inoculum size on the rate of a plant RNA virus evolution

2017 ◽  
Author(s):  
Rebeca Navarro ◽  
Silvia Ambrós ◽  
Fernando Martínez ◽  
Santiago F. Elena
Keyword(s):  
Evolutionary Biology ◽  
Rna Virus ◽  
Inoculum Size ◽  
The Novel ◽  
Clonal Interference ◽  
Rate Of Evolution ◽  
Rates Of Evolution ◽  
Diminishing Returns ◽  
Phenotypic Fitness ◽  
Asexual Populations

AbstractUnderstanding how genetic drift, mutation and selection interplay in determining the evolutionary fate of populations is one of the central questions of Evolutionary Biology. Theory predicts that by increasing the number of coexisting beneficial alleles in a population beyond some point does not necessarily translates into an acceleration in the rate of evolution. This diminishing-returns effect of beneficial genetic variability in microbial asexual populations is known as clonal interference. Clonal interference has been shown to operate in experimental populations of animal RNA viruses replicating in cell cultures. Here we carried out experiments to test whether a similar diminishing-returns of population size on the rate of adaptation exists for a plant RNA virus infecting real multicellular hosts. We have performed evolution experiments with tobacco etch potyvirus in two hosts, the natural and a novel one, at different inoculation sizes and estimated the rates of evolution for two phenotypic fitness-related traits. Firstly, we found that evolution proceeds faster in the novel than in the original host. Secondly, we found the predicted diminishing-returns effect of inoculum size on the rate of evolution for one of the fitness traits, but not for the other, which suggests that selection operates differently on each trait.

Beyond internal OR groups

1998 ◽  
Vol 49 (4) ◽  
pp. 420-429 ◽  
Author(s):  
R J Ormerod
Keyword(s):  
Or Groups

PERANCANGAN SISTEM INFORMASI MANAJEMEN KEUANGAN DI AMIK GARUT

2020 ◽  
Vol 2 (2) ◽  
pp. 128-143
Author(s):  
Tedi Budiman
Keyword(s):  
Information System ◽  
Information Systems ◽  
Financial Management ◽  
Financial Information ◽  
Financial Problems ◽  
Technological Advances ◽  
Design Program ◽  
Or Groups ◽  
The Cost ◽  
Financial Information Systems

Financial information system is an information system that provides information to individuals or groups of people, both inside and outside the company that contains financial problems and information about the flow of money for users in the company. Financial information systems are used to solve financial problems in a company, by meeting three financial principles: fast, safe, and inexpensive.Quick principle, the intention is that financial information systems must be able to provide the required data on time and can meet the needs. The Safe Principle means that the financial information system must be prepared with consideration of internal controls so that company assets are maintained. The Principle of Inexpensive, the intention is that the cost of implementing a financial information system must be reduced so that it is relatively inexpensive.Therefore we need technology media that can solve financial problems, and produce financial information to related parties quickly, safely and cheaply. One example of developing information technology today is computer technology and internet. Starting from financial problems and technological advances, the authors make a website-based financial management application to facilitate the parties that perform financial management and supervision.Method of development application program is used Waterfall method, with the following stages: Software Requirement Analysis, Software Design, Program Code Making, Testing, Support, Maintenance.

PENERAPAN ALGORITMA K-MEANS UNTUK PENGELOMPOKAN DAERAH RAWAN BENCANA DI INDONESIA

2019 ◽  
Vol 1 (2) ◽  
pp. 1-10
Author(s):  
Amril Mutoi Siregar
Keyword(s):  
Natural Disasters ◽  
Accurate Data ◽  
Disaster Victims ◽  
Central Java ◽  
North Sulawesi ◽  
Natural Beauty ◽  
Or Groups ◽  
Disaster Data ◽  
The Government ◽  
Almost All

Indonesia is a country located in the equator, which has beautiful natural. It has a mountainous constellation, beaches and wider oceans than land, so that Indonesia has extraordinary natural beauty assets compared to other countries. Behind the beauty of natural it turns out that it has many potential natural disasters in almost all provinces in Indonesia, in the form of landslides, earthquakes, tsunamis, Mount Meletus and others. The problem is that the government must have accurate data to deal with disasters throughout the province, where disaster data can be in categories or groups of regions into very vulnerable, medium, and low disaster areas. It is often found when a disaster occurs, many found that the distribution of long-term assistance because the stock for disaster-prone areas is not well available. In the study, it will be proposed to group disaster-prone areas throughout the province in Indonesia using the k-means algorithm. The expected results can group all regions that are very prone to disasters. Thus, the results can be Province West java, central java very vulnerable categories, provinces Aceh, North Sumatera, West Sumatera, east Java and North Sulawesi in the medium category, provinces Bengkulu, Lampung, Riau Island, Babel, DIY, Bali, West Kalimantan, North Kalimantan, Central Sulawesi, West Sulawesi, Maluku, North Maluku, Papua, west Papua including of rare categories. With the results obtained in this study, the government can map disaster-prone areas as well as prepare emergency response assistance quickly. In order to reduce the death toll and it is important to improve the services of disaster victims. With accurate data can provide prompt and appropriate assistance for victims of natural disasters.

ERRORS ASSOCIATED WITH HERBAGE DISSECTION ANALYSES 2. Problems of species identification

1976 ◽  
pp. 213-225
Author(s):  
I.M. Ritchie ◽  
C.C. Boswell ◽  
A.M. Badland
Keyword(s):  
New Zealand ◽  
Dry Weight ◽  
Analytical Tool ◽  
Species Level ◽  
Weight Basis ◽  
Plant Identification ◽  
Leaf Fragment ◽  
Research Division ◽  
Or Groups ◽  
Botanical Analysis

HERBACE DISSECTION is the process in which samples of herbage cut from trials are separated by hand into component species. Heavy reliance is placed on herbage dissection as an analytical tool ,in New Zealand, and in the four botanical analysis laboratories in the Research Division of the Ministry of Agriculture and Fisheries about 20 000 samples are analysed each year. In the laboratory a representative subsample is taken by a rigorous quartering procedure until approximately 400 pieces of herbage remain. Each leaf fragment is then identified to species level or groups of these as appropriate. The fractions are then dried and the composition calculated on a percentage dry weight basis. The accuracy of the analyses of these laboratories has been monitored by a system of interchanging herbage dissection samples between them. From this, the need to separate subsampling errors from problems of plant identification was, appreciated and some of this work is described here.

Catalytic Enantioselective Benzylation Directly from Aryl Acetic Acids

2018 ◽  
Author(s):  
Patrick Moon ◽  
Zhongyu Wie ◽  
Rylan Lundgren
Keyword(s):  
Functional Group ◽  
Terminal Event ◽  
Radical Intermediates ◽  
Carbon Carbon Bond ◽  
Or Groups ◽  
Reaction Proceeds ◽  
Wide Availability ◽  
Metal Catalyzed ◽  
The Stability ◽  
Acetic Acids

The stability and wide availability of carboxylic acids make them valuable reagents in chemical synthesis. Most transition metal catalyzed processes using carboxylic acid substrates are initiated by a decarboxylation event that generates reactive carbanion or radical intermediates. Developing enantioselective methodologies relying on these principles can be challenging, as highly reactive species tend to react indiscriminately without selectivity. Furthermore, anionic or radical intermediates generated from decarboxylation can be incompatible with protic and electrophilic functionality, or groups that undergo trapping with radicals. We demonstrate that metal-catalyzed enantioselective benzylation reactions of allylic electrophiles can occur directly from aryl acetic acids. The reaction proceeds via a pathway in which decarboxylation is the terminal event, occurring after stereoselective carbon–carbon bond formation. The mechanistic features of the process enable enantioselective benzylation without the generation of a highly basic nucleophile. Thus, the process has broad functional group compatibility that would not be possible employing established protocols.<br>

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