Convergent, Divergent, Parallel Evolution

[blazinfury]

I was looking online but was unable to get a clear understanding of the differences between them. Would anyone be able to clarify them.. Thanks so much.

[Ophiolite]

Convergent evolution is the emergence of a similar structure in organisms that are only distantly related. Thus most free moving vertebrates living in the sea have evolved a fish shape, since this is very efficient for movement in that environment. This has occured multiple times - five Classes of 'fish', ichthyosaurs and cetaceans.

 

Divergent evolution is 'normal' evolution, whereby as a consequence of mutations, natural slection and the other evolutionary mechanisms populations split and build differences until they are spearates species, or genera, or families, etc.

 

Parallel evolution is where similar, but different groups (species, genera, etc) evolve in similar directions in terms of one or more of their characteristics.

 

I think the last, parallel evolution, merits a better description, but its not one that I would typically use.

[pwagen]

From your description, at first I thought you made it sound like convergent and parallel evolution are very similar, so I had to read through what you said pretty carefully. But am I right in thinking that convergent evolution means the general shape of an animal (being fish shaped, as you mentioned, having large, flappy ears or having a tail with a tuft of hair at the end), while parallel evolution means two species can evolve something like wings without being related?

 

So bats and birds both having wings (though different) and being able to fly would be an example of the latter, while whales and salmon ("fish shaped" but quite unrelated) is an example of the former?

[Ophiolite]

From your description, at first I thought you made it sound like convergent and parallel evolution are very similar, so I had to read through what you said pretty carefully. But am I right in thinking that convergent evolution means the general shape of an animal (being fish shaped, as you mentioned, having large, flappy ears or having a tail with a tuft of hair at the end), while parallel evolution means two species can evolve something like wings without being related?

I have done a bad job of explaining these terms. I shall try again.

 

Convergent evolution involves quite diverse groups evolving a characteristic that is superficially similar and likely fills a comparable funciton, but is in detail quite different. Bats, birds and pterasaurs all had wings, used for flying. The portions of their anatomy adapted to become wings were, in detail, different. This is convergent evolution. Diverse groups converge to produce a similar, but not identical outcome. Fish shapes are a further example of convergent evolution.

 

Convergent evolution was a term frequently used when I studied palaeontology. No one spoke of divergent evolution since that is, as I noted above, just normal, standard, vanilla flavoured evolution. The term divergent is - as far as I can see - redundant. (However, it is possible that term is used in some applications in a specialised way, where a distinction exists fom 'normal evolution.)

 

Parallel evolution is perhaps best understood by looking at wikipedia article on it. If two canines, of different genera, both independently evolved semi-acquatic forms, that would be parallel evolution as I understand it.

 

Does that help?

[pwagen]

Absolutely. While I'm not going to pretend I'd be able to put it in my own words, I'm fairly sure I've wrapped my head around it!