The population in affected by various factors influencing its health status and thus its mortality rate. Part of the adult population have spent their lives in degraded environments, and part live in favourable environmental conditions. The author refers to the results of a study carried out in 22 towns with populations of more than 100 000, with different environmental conditions. The results confirmed that towns that are environmentally threatened show higher levels of adult mortality, reflected in higher risk death rates, higher probability of death and lower average life expectancy.
Grasses are the clonal plants of modular structure. Formation of the tussock grasses and the system of numerous branching in stoloniferous grasses is realized by multiple repeatibility of the basic units - modules. The clonal growth is accompanied by simultaneous processes of plant growth and death. Persistence, understood as a sustained maintenance of the species in meadow plant community, is the notion very wide and complicated; it includes the complex of problems to be considered just on the onthogenetic and population levels.