Chapter 20
Phylogenies and the History of Life
By Boundless
![Thumbnail](../../../../../figures.boundless-cdn.com/19049/square/figure-20-01-01.jpeg)
Phylogenetic trees illustrate the hypothetical evolution of organisms and their relationship to other species.
![Thumbnail](../../../../../figures.boundless-cdn.com/19051/square/figure-20-01-03.jpeg)
Limitations of phylogenetic trees include the inability to distinguish evolutionary time and relatedness between distinct species.
![Thumbnail](../../../../../figures.boundless-cdn.com/19053/square/figure-20-01-05.jpg)
Taxanomic classification divides species in a hierarchical system beginning with a domain and ending with a single species.
![Thumbnail](../../../../../figures.boundless-cdn.com/19054/square/figure-20-02-01.jpeg)
Similar traits can be either homologous structures that share an embryonic origin or analogous structures that share a function.
![Thumbnail](../../../../../figures.boundless-cdn.com/19057/square/figure-20-02-04.jpg)
A phylogenetic tree sorts organisms into clades or groups of organisms that descended from a single ancestor using maximum parsimony.
![Thumbnail](../../../../../figures.boundless-cdn.com/20380/square/tree-20of-20life.jpeg)
The concepts of phylogenetic modeling are constantly changing causing limitations to the classic model to arise.
![Thumbnail](../../../../../figures.boundless-cdn.com/19059/square/figure-20-03-02.jpeg)
Horizontal gene transfer (HGT) is the passing of genetic material between species by mechanisms other than from parent to offspring.
![Thumbnail](../../../../../figures.boundless-cdn.com/19060/square/figure-20-03-03.jpeg)
Genome fusion occurs during endosymbiosis, which is the mechanism proposed as responsible for the first eukaryotic cells.
![Thumbnail](../../../../../figures.boundless-cdn.com/19063/square/figure-20-03-06.jpeg)
To more accurately describe the phylogenetic relationships of life, web and ring models have been proposed as updates to tree models.