Search results for " Population"
showing 10 items of 1682 documents
¿Podemos favorecer el proceso de aprendizaje y la inclusión social y académica en la universidad de los estudiantes con más dificultades? Propuesta d…
2018
Durante el primer curso universitario, los estudiantes deben hacer frente a nuevas exigencias académicas, (evaluación, metodologías docentes...), con el fin de superar ese primer curso, al tiempo de integrarse socialmente en un contexto, la universidad, nuevo para ellos. Para ello, deben adquirir o reforzar distintas habilidades. La literatura científica ha evidenciado la relación entre estas variables con el rendimiento académico y el ajuste al primer año de universidad: actitudes ante el aprendizaje (Gargallo et al, 2007-A-), estrategias de aprendizaje (Gargallo et al., 2009), estrés académico (Rayle y Chung, 2007; Robotham y Julian 2006), autoeficacia académica (Palacio et al., 2012; Sal…
Noise in ecosystems: a short review
2004
Noise, through its interaction with the nonlinearity of the living systems, can give rise to counter-intuitive phenomena such as stochastic resonance, noise-delayed extinction, temporal oscillations, and spatial patterns. In this paper we briefly review the noise-induced effects in three different ecosystems: (i) two competing species; (ii) three interacting species, one predator and two preys, and (iii) N-interacting species. The transient dynamics of these ecosystems are analyzed through generalized Lotka-Volterra equations in the presence of multiplicative noise, which models the interaction between the species and the environment. The interaction parameter between the species is random …
Population dynamics of the Swedish Ornithological Society
2003
It has recently been recognized that there is declining interest in ornithology among the younger generations. In this paper we analyse the short and long-term dynamics of the Swedish Ornithological Society (SOF) and the Swedish Society for Nature Conservation (SNF) by using analytical tools from population ecology. We first show that the increasing number of SOF and SNF members is not the result of a constant proportion of ornithologists or people interested in nature conservation among a growing Swedish population. Hence, the number of members most likely reflects the true interest in joining organizations such as SOF. We also demonstrate that the growth rate of SOF can be fairly well est…
The voyage of an invasive species across continents: genetic diversity of North American and European Colorado potato beetle populations
2005
The paradox of successful invading species is that they are likely to be genetically depauperate compared to their source population. This study on Colorado potato beetles is one of the few studies of the genetic consequences of continent-scale invasion in an insect pest. Understanding gene flow, population structure and the potential for rapid evolution in native and invasive populations offers insights both into the dynamics of small populations that become successful invaders and for their management as pests. We used this approach to investigate the invasion of the Colorado potato beetle (Leptinotarsa decemlineata) from North America to Europe. The beetles invaded Europe at the beginnin…
Continental-scale patterns of pathogen prevalence: a case study on the corncrake
2014
Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient…
A population genetics view of animal domestication
2012
The fundamental shift associated with the domestication of plants and animals allowed for a dramatic increase in human population sizes and the emergence of modern society. Despite its importance and the decades of research devoted to studying it, questions regarding the origins and processes of domestication remain. Here, we review recent theoretical advances and present a perspective that underscores the crucial role that population admixture has played in influencing the genomes of domestic animals over the past 10000 years. We then discuss novel approaches to generating and analysing genetic data, emphasising the importance of an explicit hypothesis-testing approach for the inference of…
REPLICATED ORIGIN OF FEMALE-BIASED ADULT SEX RATIO IN INTRODUCED POPULATIONS OF THE TRINIDADIAN GUPPY (POECILIA RETICULATA)
2014
There are many theoretical and empirical studies explaining variation in offspring sex ratio but relatively few that explain variation in adult sex ratio. Adult sex ratios are important because biased sex ratios can be a driver of sexual selection and will reduce effective population size, affecting population persistence and shapes how populations respond to natural selection. Previous work on guppies (Poecilia reticulata) gives mixed results, usually showing a female-biased adult sex ratio. However, a detailed analysis showed that this bias varied dramatically throughout a year and with no consistent sex bias. We used a mark-recapture approach to examine the origin and consistency of fema…
Prevalence of lip lesions in an Indian population
2014
Objectives: Lip lesions are a frequent cause of consultation in dentistry, as they comprise a signifi cant proportion of the oral lesions. The aim of the present study was to identify the different lip lesions and determine their prevalence in an Indian population. Material and methods: 5231 patients visiting a Department of Oral Medicine and Radiology were examined for the presence of different lip lesions during the period from October, 2011 to May, 2013. The statistical analysis was done using Chi-square test and p<0.05 was considered to be statistically signifi cant. Results: The age of the patients ranged from 8-70 years with a mean age of 32.6 years. The prevalence of lip lesions was …
Aging on Indian Reservations: The Ugly, the Bad, and the Good
2012
This chapter examines the conditions for the older population on Indian reservations and how those conditions compare to the non-Indian population. The discussion opens on a national level, though the focus is on tribes in the Western United States. Older Indians on reservations are aging in a society where they are an almost invisible part of rural America. Yet the reservations, despite the poor socioeconomic conditions on many, represent home and a place for off-reservation Native Americans to come back to. To include the voices of Indian elders and gain insights into how they perceive being elders, we report on interviews conducted with older Indians on the Nez Perce reservation in Idaho…
Time evolution of non-lethal infectious diseases: a semi-continuous approach.
2005
A model describing the dynamics related to the spreading of non-lethal infectious diseases in a fixed-size population is proposed. The model consists of a non-linear delay-differential equation describing the time evolution of the increment in the number of infectious individuals and depends upon a limited number of parameters. Predictions are in good qualitative agreement with data on influenza.