Biology of microbes
Philip A. Geis in Cosmetic Microbiology, 2006
Further research will refine evolutionary ideas and show that evolutionary processes represent far more than a mere selection by nature. For example, current evidence indicates that organismal change and even what is thought of as complexification over time is a result of lowered thermodynamic constraints and self-assembly governed by physical and chemical forces.3 Regardless of what mechanisms are finally determined to be operative for causing evolution, Futuyma’s definition4 of what evolution actually is seems sufficient at present: … biological evolution is a change over time of the proportions of individual organisms differing genetically in one or more traits; such changes transpire by the origin and subsequent alteration of the frequencies of alleles or genotypes from generation to generation within populations, by the alterations of the proportions of genetically differentiated populations of a species, or by changes in the numbers of species with different characteristics, thereby altering the frequency of one or more traits within a higher taxon.
Yellow Fever: Emergence and Reality
Jagriti Narang, Manika Khanuja in Small Bite, Big Threat, 2020
Moreover, the 3’-nontranslated region (3’-NTR) differs in repeating sequences among distinct genotypes of YFV. These redundant sequences of 3’-NTR are crucial for causing virulency and amplification of YFV. In addition to viral genetic information, the extent of virulency of YFV also relies on several other parameters such as adaptation conditions of host and vector, host behavior, weather, and environmental conditions. These interactions are very typical and create issues for understanding the mechanism of YFV outbreak as well as management at right time. The epigenetic study of YFV is focused on the sylvatic strains of YFV in West Africa. This study provides important information related to evolution: (i) In Senegal, six distinct lineages of YFV have been identified, which show more diversity in this region; (ii) the forest area of Kedougou is the chief reservoir of YFV lineages; (iii) vertical transmission of YFV in environment. Therefore, we can investigate the heterogeneity in distinct lineages found in Senegal and West African countries. Besides, we can also study the relationship with insect and human hepatic cells. From the nucleotide sequence obtained from the GenBank database, we can perform the phylogenetic investigation of the whole genome of different genotypes of YFV.
Structure and Evolution of the Small Blue Proteins
René Lontie in Copper Proteins and Copper Enzymes, 1984
The blue proteins have in common a copper(II) site with specific and unusual properties which suggests that the copper environment is similar in all of them. This situation — if true — can be the result of either convergent evolution, where similar requirements have promoted the evolution of the same structure from different origins (= analogy), or divergent evolution, where several or all of these proteins have evolved from a common ancestor ( = homology). If this latter possibility is valid, the evolutionary distances involved are tremendous: the common ancestor of say a pseudomonad bacterium and a higher plant inhabited our planet not later than some 3,000 million years ago. Nevertheless, molecular evolution aims at clarifying such relationships, many of which are inaccessible to traditional methods relying on morphology and the study of fossils.
Controlling the error probabilities of model selection information criteria using bootstrapping
Published in Journal of Applied Statistics, 2020
Michael Cullan, Scott Lidgard, Beckett Sterner
In a groundbreaking series of studies, Hunt [16–19], provided the first large-scale quantitative assessment of different modes of evolution in the fossil record. The substantial corpus of empirical fossil studies was harvested as time series describing morphological traits of single fossil species over some time duration, stretching from tens to hundreds of thousands of years. Example traits include the curvature of sea shells and the length of molars. In trait time series, each value represents the average of a sample of multiple specimens dated to approximately the same time (see [16] for more details). Hunt's approach allowed for simultaneous comparison of all three canonical models of evolutionary mode–stasis, gradualism, and random walk–against one another in a common statistical framework of penalized likelihood using the AICc, with the best-fit model [40] selected for a given fossil trait sequence. Most previous analyses compared models for evolutionary modes in pairwise tests and were typically based on a simple null model, hypothesizing either gradualism or stasis against a null expectation of a random walk (e.g. [3,29]).
An insight into technology diffusion of tractor through Weibull growth model
Published in Journal of Applied Statistics, 2018
Bishal Gurung, K. N. Singh, Ravindra Singh Shekhawat, Md Yeasin
To this end, a very efficient and powerful stochastic optimization technique, viz. GA technique first conceived by John Holland in 1975, can be employed. GA methodology, a computational method to find optimal solution, is capable of rectifying the above limitations. In GA, the parameters form a string, where each string represents a solution to the problem. An objective payoff function is used to measure how well a particular solution solves the problem. Improved solutions are subsequently evolved within a population of chromosomes over a number of generations. The GA algorithm optimizes a problem by iteratively trying to improve a candidate solution with respect to an objective function. GA simulates the evolution of living organisms, where the fittest individual dominates over the weaker ones, by mimicking the biological mechanism of evolution. It combines Darwin’s principle of ‘natural selection’ and ‘survival of the fittest’ with computer-constructed evolution mechanism to select better offspring from the original population. In the GA-literature, mainly two types of procedures are available, viz. Binary-coded GA (BCGA) and Real-coded GA (RCGA). In the former, the coded parameters form a string (chromosome), where each string represents a solution to the problem. Unlike the classical search and optimization methods, GA begins its search with a random set of solutions instead of just one solution. So, GA not only overcomes the traps of local optimization, but also reduces much computational time to find optimum solution [8].
An update on emerging drugs for the treatment of erectile dysfunction
Published in Expert Opinion on Emerging Drugs, 2018
U. Milenkovic, J. Campbell, E. Roussel, M. Albersen
Evolution and the process of natural selection requires a dependable manner of transferring genetic material from parent to offspring. Thus, processes that can affect this play an important role in the survival of a species. To produce healthy and adapted progeny, it is undesirable for a female to be impregnated by an unfit male; (i) it prevents the impregnation by a healthier, more suitable male, (ii) pregnancy may terminate in an abortion, and (iii) giving birth to a sick child is worse in times of scarce resources. Over the millions of years of evolution, there must be mechanisms in place that would decrease or prevent the probability of impregnation by an unfit or aged male. It is well-known that the quality of gametes deteriorates with age, diabetes mellitus, and other diseases, thus increasing the risk of having badly adapted or sick offspring. However, since male spermatogenesis never stops, fertilization of oocytes by spermatozoa is not prevented effectively. A recent hypothesis states that erectile dysfunction (ED) could fill this role and curb the possibility of unsuitable impregnation [1].
Related Knowledge Centers
- Biodiversity
- Genetic Drift
- Heredity
- Morphology
- Phenotype
- Phenotypic Trait
- Physiology
- Heritability
- Natural Selection
- Fitness