Zoology 10th Edition by Stephen Miller,John Harley

تمرين 5

Phyletic gradualism is the accumulation of very small changes in organisms over very long periods of time, eventually resulting in the formation of new species. Punctuated equilibrium involves long periods of constancy (stasis) interrupted by short periods of evolutionary change. Both phyletic gradualism and punctuated equilibrium have been documented in different animal groups.
How would you explain the presence of gaps in the fossil record of a group of organisms to someone challenging evolution? List at least three reasons why gaps appear.