The Monte Carlo Study Of The Diploid Penna Model

Death and the preceding period of functional decline is known as senescence or aging.Compared with other experiments, the aging experimental conclusions are seldom clear-cut,and the experiments are difficult to repeat, because of the limitation of the traditionalbiological tests method. So, many physicists have been involved in this research for a longtime. Just like people used the computational techniques, such as heredity algorithms andneural networks, which are inspired by mother nature, to solve the problems of other fields,thephysicists,instead,trytousestatisticalphysicstomodelbiology.In 1952, Medawar supposed that aging is the result of the balance of mutations andselection pressure, known as the mutation-accumulation theoryof biological aging. Based onthis theory, T.J.P. Penna proposed the biology aging model in 1995. Penna bit-stringbiologicalmodel,usingacomputerbit-stringtorepresentanindividualgenome,andconsidersome survival, diseases and reproduce strategies, simulates the dynamics of population. Thismodel can interpret many real phenomena, and has become one of the most popular waysbased on Monte Carlo simulation. Becauseoftheinsufficiency of the kineticstudy in the diploidPenna model and the flaw of the Verhulst factor, however, the application of the Penna model was limitedin the sexual species evolvement. So, the further parameter analysis and improvement of the diploidPennamodelwasmadeinthisarticle.In this paper, the asexual and sexual of the Penna model as well as some kinds of itsapplication had been summarized. The development of the research on this model's was alsointroduced. Then, the diploid Penna model of the sexual species was simulated in detail, andsome more important conclusions was drawn. For example, the sexual species can avoidmutational meltdown when the birth rate is small, and the dominant disease which acted atlate period of the life is the main reason that causes the high mortality on some age. Finally,threemainimprovementsofthediploidPennamodelwasbroughtforward:(1)Iputanormalgenome as well as a chronological genome in the model of an individual. (2) In this normalgenome, each site contains three different genes which give the degrees of expressivity andadaptabilityofthe genome.(3)Addingaadaptability-dependent Verhulst factor.Throughthesimulation of the improved model, I draw some logical conclusion, for example, it is theadvance in technology that causes the population boom, and the frequently great changes ofthe environment may cause the species extinct. All of these results proved that thoseimprovements on the model have increased the influence of environment on the evolvementofthespecies.This simulation study give a well understanding for the Penna model, and enlarge theapplicationofthemodelincertainextent.