Final answer:
In evolutionary biology, gradualism is the model of evolution where gradual change over a long period leads to biological diversity. However, the fossil record also supports the model of punctuated equilibrium, where long periods of little change are interrupted by bursts of rapid change.
Step-by-step explanation:
In evolutionary biology, the model of evolution in which gradual change over a long period leads to biological diversity is called gradualism. According to gradualism, species evolve slowly and continuously over time, with morphological, behavioral, and genetic changes accumulating gradually and accumulating in a single unbroken line. However, the fossil record also supports an alternative model called punctuated equilibrium, where long periods of little change are interrupted by bursts of rapid change. This model suggests that sudden geologic and climatic changes can lead to rapid evolution and the development of new species.