Showing results 121 to 140 on 1323 in total
A recent paper in Science (January 2015) claimed that the majority, 64% to be precise, of cancers is due to bad luck, so non-preventable. The message was spread quickly through media, including serious ones like BBC (and also radio Slovenia, if I may add). And while the paper has been criticized by many, the authors seem to stick to the original message.In this talk I'll give my view of the paper and try to defend a counter message that their analysis gives them absolutely no grounds to make such a claim. The arguments that I'll present have, to my knowledge, not appeared in published reactions to the paper. Obviously, if I am right, they are wrong, and vice versa. If I was Bayesian, I would, at present, give a 0.99 prior probability to the first option. Either way, it should be fun.
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Thèse de Clément Goubert le vendredi 4 décembre 2015 à 14 h - amphithéâtre BU (La Doua)
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The net reproductive rate, R_0, measures the expected lifetime reproductive output of an individual, and plays an important role in demography, ecology, evolution, and epidemiology. Well-established methods exist to calculate it from age- or stage-classified demographic data. Because it is an expected value, however, R_0 provides no information on variability. Many empirical measurements of lifetime reproduction have revealed high levels of variability, and often positive skewness. This is often interpreted as evidence of heterogeneity, and thus of an opportunity for natural selection. However, variability provides evidence of heterogeneity only if it exceeds the level of variability that would be expected in a cohort of identical individuals all experiencing the same vital rates. Such comparisons require a way to calculate the statistics (variance, coefficient of variation, skewness) of lifetime reproduction from demographic data. These calculations have not been possible; here, I present a new approach, using the theory of Markov chains with rewards, that gives all the moments of the distribution of lifetime reproduction. The approach applies to age- or stage-classified models, to constant, periodic, or stochastic environments, and to any kind of reproductive schedule. As examples, I analyze data from several empirical studies of a variety of animal and plant taxa.For more details, please go to http://cgphimc.univ-lyon1.fr/CGphiMC/Semovi/13avril2011.php
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To meet the Water Framework Directive requirements, a new multimetric index (I2M2) has been designed for the invertebrate-based ecological assessment of French wadeable streams. Integrating five taxonomy- and trait-based metrics selected for their high discrimination efficiency, low pressure specificity, high stability in least impaired conditions and low redundancy, this index is meant to identify impaired reaches for 17 anthropogenic pressure categories potentially impairing water quality or habitat. Based on I2M2, any river reach is assigned an ecological quality class among "Bad", "Poor", "Moderate", "Good" and "High". I will present the I2M2, the strategy underlying its construction and on-going developments to help local managers for restoration and conservation programs: (i) assessment of the uncertainty associated to the I2M2 to make it a probabilistic ecological indicator, (ii) development of diagnostic tools based on conditional tree forest models to estimate the risk that each pressure category occurred at any river reach from sampled community traits (iii) simulation of reference conditions for large streams
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Susana Coelho will present a paper recently published in Nature by an international consortium coordinated by Roscoff on the Ectocarpus genome and the independent evolution of multicellularity in brown algae. Denis Roze will present his theoretical work on deleterious mutations and selection for sex and recombination.
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Cancer is a disease that affects the majority of metazoan species and prior to directly causing host death, is likely to influence the competitive abilities of individuals, their susceptibility to pathogens, their vulnerability to predators and their ability to disperse. Despite the potential importance of these ecological impacts, cancer is rarely incorporated into model ecosystems. In this talk, I will describe the diversity of ways in which oncogenic phenomena, from precancerous lesions to generalized metastatic cancers, may affect ecological processes that govern biotic interactions. I will argue that oncogenic phenomena, despite their complexity, have predictable ecological consequences. Our aim is to provide a new perspective on the ecological and evolutionary significance of cancer in wildlife, and to stimulate research on this topic.