Biological ageing with birth rate controlled by mutations in the Penna model

Abstract

Within the Penna model, we assume a modification with a reproduction rate B that depends on the health state of the individual defined by the number of bad mutations. The idea is that biologically weaker individuals has got less chance to produce offsprings. The results obtained from simulations and for typical set of model parameters show that then the mortality rate q(a) is increasing faster with age a. The maximum age is also limited from about 50 percent of the biological maximum lifespan for the standard Penna model, to about 40 percent. We also conclude that bad mutation distribution r(a) is altered so that younger individuals may accommodate significantly more bad mutations, up to 25 percent, as compared with the standard model (5 percent). In summary, it makes sense to force less productivity for older and weaker individuals.

Analytical solution of a generalized Penna model

“…Traditionally this has been a genome-independent chance of death for every individual regardless of age. This model also considers a birth rate that decreases as the population grows and resources become more scarce [21]. In agreement with earlier work [16], we find a maximum permitted genetic lifespan and predict the existence of catastrophic senescence for organisms whose reproductive life is terminated by an upper age limit.…”

“…Such simulations also regulate the total population which is realistic in any system with finite resources. It has been suggested [21] that by regulating the birth rate, the system will adopt a biologically realistic equlibrium. The Simple Penna model solved here can be used to explain behaviour of these simulations that replace the constant birth rate with a population dependent one.…”

Anomalous Relaxation of the Penna Model

“…To be able of decomposing the dynamics on independent modes, they ruled out the Verhulst factor and chose the reproduction rate as function of the number of individuals. 9 Nevertheless, under special conditions, the influence of the Verhulst factor can be weak and their treatment and conclusions can be applied. In this work, we recover the original model with the Verhulst factor.…”

Complex networks generated by the Penna bit-string model: Emergence of small-world and assortative mixing

“…Even if the population size is much smaller than the environmental carrying capacity N max , this would predict that many individuals die in each year "due to the limit of space and food". The existing simulation results indicate that the population size is usually very small compared to N max (in [7], the simulation results show that the population size never even reaches 0.3N max ), and the individuals usually die at a very young age (in [8], the simulation results show that almost all the individuals die below the age of 20). These results are mainly "due to the restriction of space and food", although there is (more than) enough space and food.…”