The gradualist population theory states that genetic change in a population occurs extremely slowly, over a long period of time. however, the catastrophist theory claims that populations may change drastically over a short period of time, due to catastrophic events like large-scale natural disasters. the theory is a sort of hybrid of the two above, and it contends that long stretches of incremental evolution are interspersed with short periods wherein drastic evolutionary changes occur. a) uniformist b) intermittent burst c) catastrophe-bottleneck d) punctuated equilibrium