Friday, July 29, 2011

Working with extinct animals: Basics (4): Evolution

Macro and Micro Evolution
Macroevolution is what most people think of when hearing the word “evolution”: major changes occur to taxonomic groups in various families and genera (genus) over a long period of time.  One example of macroevolution is modern whales evolving from primitive land dwelling mammals.  Of course, dinosaurs, mammals, and reptiles developed from the first animals that ventured forth on land, are  other examples of macroevolution.

The difference between macro and micro evolution is a vague one.  Microevolution is change to various species below genus level.  An example of microevolution is the various subspecies of Canada goose (Branta canadenis).  Because of their clannish natures, Canada geese tend to interbred amongst themselves.  The result is several subspecies which are differentiated by their size and plumage. 

An extreme example of microevolution is Hawaiian goose (Branta sandvicensis).  The Canada goose migrated to the Hawaiian Islands about a half-million years ago.  Moreover, DNA sampling has demonstrated that Hawaiian goose is a subspecies of Canada goose.  However, on sight, there are major differences between the two birds.

Convergent Evolution
Convergent evolution occurs when dissimilar species fill the same ecological niche in different parts of the world.  These unrelated species display similar traits and life styles.  Nature is rife with convergent evolution, hence the need for taxonomic identification.  Otherwise confusion amongst the species will make the study of them difficult.

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