Moth



Blackwell Publishing

Stasis

coelacanths.jpg

Stasis is the situation in which evolutionary lineages persist for long periods without change. In the fossil record, stasis is common but it has recently taken on a new importance with the punctuated equilibrium debate.

Living fossils such as lungfish are lineages which have experienced a long period of stasis.

The reasons for stasis are controversial in biology: Simon Conway Morris gives his own view.

An animation illustrates the well documented case of stasis occuring in the horseshoe crab lineage.

The coelecanth pictured opposite is a living fossil which has undergone stasis for the past three hundred million years.

Why does stasis exist?

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