Phylogenetic trees vs cladograms.

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Phylogenetic trees vs cladograms.

Post by NewtoBiology » Sat Jan 26, 2008 5:15 pm

Hello again,

Well I have come to the end of my evolutionary section but can't quite wrap my head around the difference between phylogenetic trees and cladograms. The more I re-read the text and research on the internet I get more confused.

I realize that a phylogenetic tree are diagrams which specify the biological relationship between organisms.
and I also realize that cladograms are branching diagrams of organims united by unique characteristics.

isn't that the same darn thing??? Both show common ancestry, both show branching are these two things different?

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Re: Phylogenetic trees vs cladograms.

Post by blcr11 » Sun Jan 27, 2008 2:54 pm

This isn't really my department, and anyone who knows better feel free to correct me; the two are similar, yet different. They both attempt to show relationships, but phylogeny (at least classical phylogeny) relates organisms based on comparisons of the similarities/dissimilarities of their anatomies. Cladistics attempts to trace evolutionary relationships directly by analyzing gene sequences. Often the two methods give the same tree, but sometimes they differ.

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Post by mith » Sun Jan 27, 2008 4:11 pm

I think you reversed cladistics and phylogeny.
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Re: Phylogenetic trees vs cladograms.

Post by wbla3335 » Mon Jan 28, 2008 8:13 am

Both phenetics (classical phylogeny) and cladistics can be used for either morphological or molecular analyses. Phenetics measures degrees of similarity. Cladistics traces the sharing of derived characters. Cladistics needs to define some ancestral state (usually a sister taxon) to which your samples are compared. For example, if the ancestral state has an A at some nucleotide position and some of your samples have a G at this position, it is assumed that those sharing the G have inherited this change from the same source and so are related to each other by descent. Of course you need to look at many characters to determine who is related to whom. In phenetics, you do not need to determine what is ancestral and what is a shared derived character. You only care about who appears most similar to whom at one point in time. Cladistics is generally considered to be more reliable for the determination of evolutionary relatedness. Hope this helps.

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