Final answer:
The model describing how species evolve through gradual changes is known as gradualism. It suggests that species divergence happens incrementally, as opposed to the rapid changes proposed by punctuated equilibrium.
Step-by-step explanation:
The model that describes the variety of relationship development patterns through gradual differentiation is named gradualism.
This model asserts that species diverge over time through small, incremental steps, and contrasts with the punctuated equilibrium model which proposes that change occurs quickly at first, followed by long periods of stability. An example of gradualism can be seen in Darwin's theory of evolution, where he posited that evolution happens slowly and incrementally. Punctuated equilibrium, on the other hand, begins with rapid change and then levels off. These concepts are not mutually exclusive and can be considered part of the spectrum of evolutionary theories.