2014-09-012014-09-012014-02-27AGUIAR JUNIOR, Dióscoros Brito. Tempo de sobrevivência em um modelo estocástico para evolução de espécies. 2014. 58 f. Dissertação (Mestrado em Matemática) - Universidade Federal de Goiás, Goiânia, 2014.http://repositorio.bc.ufg.br/tede/handle/tde/2976In this work ,we will consider two stochastic models for evolution os species. First, births and deaths of species occur with constant probabilities. Each new species is associated with a fitness sampled from the uniform distribution on [0,1]. Every time there is a death event then the type is killed is the one with smallest fitness. We show that there is a sharp phasetransitionwhentheprobabilityislargerthanthedeathprobability.Thesetofspecies with fitness higher than a certain critical value approach an uniform distribution. On the other hand all the species with fitness less than the crital disappear after a finite (random) time. The second model, we consider a stochastic model for species evolution. A new species is born at rateλ and a species dies at rate µ. A random number, sampled from a given distribution F, is associated with each new species and assumed as its fitness, at the time of birth. Likewise the first model, every time there is a death event, the species that is killed is the one with the smallest fitness. We consider the (random) survival time if a species with a given fitness f. We show that the survival time distribution depends crucially on whetherf<fc ,f=fc orf>fc where fc is a critical fitness that is computed explicit.application/pdfAcesso abertoModelo de sobrevivênciaEvoluçãoCadeia de nascimento e morteDeath and Birth ChainSurvival modelMATEMATICA::MATEMATICA APLICADADissertação