Artículos con la etiqueta ‘población’

Evolution in a Changing Environment

Por • 24 abr, 2013 • Category: Ambiente

We propose a simple model for genetic adaptation to a changing environment, describing a fitness landscape characterized by two maxima. One is associated with «specialist» individuals that are adapted to the environment; this maximum moves over time as the environment changes. The other maximum is static, and represents «generalist» individuals not affected by environmental changes. The rest of the landscape is occupied by «maladapted» individuals. Our analysis considers the evolution of these three subpopulations. Our main result is that, in presence of a sufficiently stable environmental feature, as in the case of an unchanging aspect of a physical habitat, specialists can dominate the population. By contrast, rapidly changing environmental features, such as language or cultural habits, are a moving target for the genes; here, generalists dominate, because the best evolutionary strategy is to adopt neutral alleles not specialized for any specific environment. The model we propose is based on simple assumptions about evolutionary dynamics and describes all possible scenarios in a non-trivial phase diagram. The approach provides a general framework to address such fundamental issues as the Baldwin effect, the biological basis for language, or the ecological consequences of a rapid climate change.

¿Dónde están los campesinos?

Por • 10 feb, 2011 • Category: Nacionales

La fuerza de trabajo agrícola, entre empleados y campesinos o productores independientes, entre 600 y 900 mil personas, están ubicados sobre más de 30 millones de hectáreas o 60 millones, si incluimos el área potencial, entre 33 y 100 hectáreas por persona. Sobran tierras y falta gente al comparar nuestras cifras con otros países del mundo.