Relations between organisms and the environment in the ageing process
  We have modified the sexual Penna model by introducing the fluctuating environment and fluctuations representing physiological functions of individuals. Additionally, we have introduced the mother care corresponding to the protection against the deleterious influence of the environment, the learning capacity of individuals corresponding to their immunity and adaptation to the environment fluctuations and the other risk factors appearing at puberty. Each of the above mentioned elements influences mainly the survival of newborns and young individuals while genetic defects accumulated in the genomes increase the noise of individuals and were responsible for higher mortality of older individuals. All these modifications enable precise fitting the age structure of the simulated populations to the age distributions of human populations. 
Przemyslaw Biecek, Katarzyna Bonkowska, Stanislaw Cebrat