L'Origine des espèces

Résumé

L'Origine des espèces (On the Origin of Species) est un ouvrage scientifique de Charles Darwin, publié le pour sa première édition anglaise sous le titre L'origine des espèces au moyen de la sélection naturelle ou la préservation des races favorisées dans la lutte pour la survie. Cet ouvrage est considéré comme le texte fondateur de la théorie de l'évolution. Dans ce livre, Darwin présente la théorie scientifique de l'évolution des espèces vivantes à partir d'autres espèces généralement éteintes, au moyen de la sélection naturelle. Darwin avance un ensemble de preuves montrant que les espèces n'ont pas été créées indépendamment et ne sont pas immuables. Diverses idées de la théorie de l'évolution avaient déjà été proposées pour expliquer les nouvelles découvertes en biologie. Il y avait un soutien croissant à de telles idées parmi les dissidents anatomistes et le grand public, mais au cours de la première moitié du l’establishment scientifique anglais était étroitement lié à l'Églis

Source officielle

https://fr.wikipedia.org/wiki/L'Origine_des_esp%C3%A8ces

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'Charles Robert Darwin' , né le à Shrewsbury dans le Shropshire et mort le à Downe dans le Kent, est un naturaliste et paléontologue britannique dont les travaux sur l'évolution des espèces vivantes

En biologie, l’évolution est la transformation du monde vivant au cours du temps, qui se manifeste par des changements phénotypiques des organismes à travers les générations. Ces changements général

vignette|Selon les principes de la sélection naturelle de Darwin, les pinsons des Galápagos sont issus d'une espèce souche venue du continent. La sélection s'est traduite par une spécialisation de la

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, ,

Hydrodynamic phenomena can be leveraged to confine a range of biological and chemical species without needing physical walls. In this review, we list methods for the generation and manipulation of microfluidic hydrodynamic confinements in free-flowing liquids and near surfaces, and elucidate the associated underlying theory and discuss their utility in the emerging area of open space microfluidics applied to life-sciences. Microscale hydrodynamic confinements are already starting to transform approaches in fundamental and applied life-sciences research from precise separation and sorting of individual cells, allowing localized bio-printing to multiplexing for clinical diagnosis. Through the choice of specific flow regimes and geometrical boundary conditions, hydrodynamic confinements can confine species across different length scales from small molecules to large cells, and thus be applied to a wide range of functionalities. We here provide practical examples and implementations for the formation of these confinements in different boundary conditions - within closed channels, in between parallel plates and in an open liquid volume. Further, to enable non-microfluidics researchers to apply hydrodynamic flow confinements in their work, we provide simplified instructions pertaining to their design and modelling, as well as to the formation of hydrodynamic flow confinements in the form of step-by-step tutorials and analytical toolbox software. This review is written with the idea to lower the barrier towards the use of hydrodynamic flow confinements in life sciences research.

ROYAL SOC CHEMISTRY2022

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Coalescent inferences in conservation genetics: should the exception become the rule?

Valeria Montano

Genetic estimates of effective population size (Ne) are an established means to develop informed conservation policies. Another key goal to pursue the conservation of endangered species is keeping the connectivity across fragmented environments, to which genetic inferences of gene flow and dispersal greatly contribute. Most current statistical tools for estimating such population demographic parameters are based on Kingman's coalescent (KC). However, KC is inappropriate for taxa displaying skewed reproductive variance, a property widely observed in natural species. Coalescent models that consider skewed reproductive success-called multiple merger coalescents (MMCs)-have been shown to substantially improve estimates of Ne when the distribution of offspring per capita is highly skewed. MMCs predictions of standard population genetic parameters, including the rate of loss of genetic variation and the fixation probability of strongly selected alleles, substantially depart from KC predictions. These extended models also allow studying gene genealogies in a spatial continuum, providing a novel theoretical framework to investigate spatial connectivity. Therefore, development of statistical tools based on MMCs should substantially improve estimates of population demographic parameters with major conservation implications.

Royal Soc2016

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Evolution of nucleosomes position in yeasts: conservation of global pattern and divergence of gene-specific patterns

Sébastien Dubuis

This master project describes computational analysis of nucleosomes positioning in four yeast species: S. cerevisiae, S. kudriavzevii, S. bayanus (three relatively close species, ~75% of sequence similarity) and C. glabrata (more distant, ~57% of sequence similarity). We found that the global organization of nucleosomes previously described in S. cerevisiae (Nucleosome Depleted Region followed by an array of nucleosomes) was largely conserved among the different species also with the conservation of occupied/depleted promoters' classification from previous works redefined here in a more specific way. However, this conservation of general pattern does not reflect the evolution of gene specific pattern. Indeed, we show that nucleosome pattern diverged rapidly leaving practically no similarities between S. cerevisiae and C. glabrata orthologs. This was confirmed by different analysis and additional data from other species. In contrast, the pattern of gene expression and the response to stress were largely conserved among this species. Together, these results suggest that the general properties of nucleosome patterns and some specific features are conserved even if the gene specific patterns diverge much faster than the DNA sequence and the expression patterns. This argues strongly in favor of a model where different configurations of nucleosomes positions can encode the same expression output and where nucleosomes features evolve mainly by neutral drift

2010

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