Biology / Unit 8 Bio 1731 short lesson, about 20 seconds
Gradual Speciation and Punctuated Equilibrium
Captions available
The idea
The gradual model holds lineages diverge in small, steady steps; punctuated equilibrium holds change occurs in rapid bursts, followed by long stasis.
In practice
A fossil sequence with steady change across many strata fits the gradual model; sudden change then long unchanged stretches fits punctuated equilibrium.
Where people slip
Punctuated equilibrium describes a faster tempo, not a different mechanism — selection still drives change under either model.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
Something wrong in this lesson? Flag it · Sources for Biology