PHylogenetic trees & other related information
quick Definitions
- Phylogeny- the evolutionary history of species.
- Phylogenetic trees- branching diagrams that help scientists create hypotheses about evolutionary relationships between different species.
- Taxonomy- how organisms are named and classified.
- Taxon- the named taxonomic unit at any level of the Hierarchical classification.
Here is an quick introductory video on phylogenetics from Bozeman.
PHylogenetic trees
An important subgroup within phylogenetics is the phylogenetic tree, also known as a cladogram. Phylogenetic trees are branching diagrams that show the inter-relatedness between species and their evolutionary history. Remember that they show patterns of descent between species and not how similar they are in terms of phenotypes.
The picture above shows typical clades in a phylogenetic tree, which are groups of an ancestral species and all of its descendants. However, there are different types of types.
- Monophyletic group (clade)- consists of an ancestral species and all of its descendants.
- Paraphyletic group- consists of an ancestral species but not all of its descendants.
- Polyphyletic group- consists of taxa with different ancestors.
The branch points on cladograms represents the divergence of two evolutionary lineages from a common ancestor. Typically, you will be asked to determine the most recent common ancestor from a cladogram.
In the picture, branch point 1 is a common ancestor for all A, B, C, D, and E. Branch point 2 is a common ancestor for C, D, and E. If there was an additional taxa F that shared the same branch point 3 as A and B, that branch point would be called a polytomy. This signifies that the evolutionary relationship between A, B, and G is not clear. |
Now that you know the basics of phylogeny and phylogenetic trees, try watching the videos below.
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