The phase diagrams survival-extinction for the Penna model with parameters:
(mutations rate)-(birth rate), (mutation rate)-(harmful mutations threshold),
(harmful mutation threshold)-(minimal reproduction age) are presented. The
extinction phase may be caused by either mutational meltdown or overpopulation.
When the Verhulst factor is responsible for removing only newly born babies and
does not act on adults the overpopulation is avoided and only genetic factors
may lead to species extinction.Comment: RevTex4, 5 pages, 4 figures (8 eps files