Search results for "Production"
showing 10 items of 7600 documents
Le due crisi: crisi del capitalismo e crisi ambientale. Una soluzione sostenibile? (parte II)
2016
Vista nella Parte I la gravità della crisi ambientale, soprattutto l’instabilità climatica che caratterizzerà le prossime decadi, nella parte II si esplicitano le ragioni profonde della necessità di cambiare, e come, il modello di sviluppo. Negli ultimi quarant’anni la crisi ecologica non è mai diventata una variabile importante nelle politiche economiche. Colpa del neo-liberismo imperante, dall’ “unilateralismo” dell’amministrazione USA al “fiscal compact” della UE? Sì, ma anche le altre scuole economiche commettono lo stesso errore. L’attuale crisi del capitalismo è una crisi di sovrapproduzione, il cui carattere quantitativo, dovuto all’innovazione tecnologica nel mercato globalizzato, r…
How important are terrestrial organic carbon inputs for secondary production in freshwater ecosystems?
2017
Article
Evolución de la investigación sobre actividad física en el medio natural en educación física: Resultados en Web of ScienceTM desde 1990 a 2016
2017
Monográfico con el título: "Actividades Físicas en el Medio Natural (1ª parte)" Resumen basado en el de la publicación Título, resumen y palabras clave también en inglés Se pretende analizar la evolución del número de publicaciones sobre actividad física en el medio natural en educación física. Para ello, se realizó una búsqueda bibliográfica en la base de datos Web of ScienceTM desde 1990 hasta 2016. Los términos de búsqueda usados se basaron en dos conceptos: 1) actividad física en el medio natural y 2) educación física. Se encontraron un total de 116 resultados, con una media de 4,3 publicaciones por año, observándose una tendencia a aumentar el número de publicaciones a lo largo de los …
Can a snow structure model estimate snow characteristics relevant to reindeer husbandry?
2014
Snow affects foraging conditions of reindeer e.g. by increasing the energy expenditures for moving and digging work or, in contrast, by making access of arboreal lichen easier. Still the studies concentrating on the role of the snow pack structure on reindeer population dynamics and reindeer management are few. We aim to find out which of the snow characteristics are relevant for reindeer in the northern boreal zone according to the experiences of reindeer herders and is this relevance seen also in reproduction rate of reindeer in this area. We also aim to validate the ability of the snow model SNOWPACK to reliably estimate the relevant snow structure characteristics. We combined meteorolog…
Delayed mixis in rotifers: an adaptive response to the effects of density-dependent sex on population growth
2004
In most cyclically parthenogenetic life cycles, sex is needed to produce resting stages. In several species of cyclically parthenogenetic rotifers, some generations of clones are not responsive to a density-dependent signal that triggers sexual female production. These unresponsive rotifers hatch from resting eggs and typically pass 8–12 generations of female parthenogenesis before becoming receptive to the mixis signal. We addressed the selection for mixis delay using a simulation model. A delay of sexual reproduction could increase population growth through parthenogenesis and thus the number of resting eggs ultimately produced. In a monomorphic population without mixis delay, we determin…
Variability for mixis initiation in Brachionus plicatilis
2001
Deductions from both evolutionary models and inductive argumentation from empirical data support the notion of intraspecific variability for the initiation of sexual reproduction (mixis) within rotifer populations. In this study, we focus on the time and density at which mixis is initiated in a growing population. Cyclical parthenogenetic clones of Brachionus plicatilis established by hatching of resting eggs, isolated from a natural habitat, have been tested at the start of their sexual phase. Clones exhibited great variation for this trait, their time of switching to sexual reproduction being correlated with population density. Most of the variation for mixis initiation has either low or …
Population dynamics of Cyclotella ocellata (Bacillariophyceae): endogenous and exogenous factors
1999
Population dynamics of Cyclotella ocellata PANTOCSEK were examined from 1991 to 1993 in an oligo-mesotrophic, gravel-pit lake near Madrid (Spain). Monthly and daily sampling was carried out to track seasonal- and auxosporulation dynamics, respectively. This species was the most abundant planktonic diatom in the lake. The population increased steadily in spring until the seasonal peak (3.8.10 6 ind/ L in April) and then abundance declined slowly through late winter. Time series techniques showed that the seasonal dynamics were driven by exogenous factors: there was a relationship between Cyclotella abundance and the chemical environment, both TP (synchronic) and SRSi (with delay). Auxosporul…
WHO BEARS THE COSTS OF INTERSPECIFIC COMPETITION IN AN AGE-STRUCTURED POPULATION?
2003
Social and density-dependent life history processes may differ according to age and the reproductive history of individuals. Arvicoline rodents have a typical, season-dependent, bimodal, age distribution of breeding individuals within a population. This distribution may influence population fluctuations. In this study, we measured effects of interspecific competition from field voles (Microtus agrestis) on various fitness components of female bank voles (Clethrionomys glareolus) in an age-structured breeding population in large (0.25 ha) outdoor enclosures. We monitored survival, reproduction, and space use of experimental bank vole populations with females from two different age groups. Wi…
Optimal rates of bisexual reproduction in cyclical parthenogens with density‐dependent growth
1999
This work explores theoretical patterns of reproduction that maximize the production of resting eggs and the long-term fitness of genotypes in cyclical parthenogens. Our focus is on density-dependent reproduction as it influences the consequences of a trade-off between producing amictic daughters – which reproduce parthenogenetically and subitaneously – and producing mictic daughters – which undergo meiosis and bisexual reproduction. Amictic females increase competitive ability and allow the population to achieve a larger size; mictic females directly contribute to population survival through harsh periods by producing resting eggs. Although morphologically indistinguishable, the two types …
Conflict and the Evolution of Societies
2012
The Malthusian theory of evolution disregards a pervasive fact about human societies: they expand through conflict. When this is taken account of the long-run favors not a large population at the level of subsistence, nor yet institutions that maximize welfare or per capita output, but rather institutions that maximize free resources. These free resources are the output available to society after deducting the payments necessary for subsistence and for the incentives needed to induce production, and the other claims to production such as transfer payments and resources absorbed by elites. We develop the evolutionary underpinnings of this model, and examine the implications of free resource …