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Phylogenetic analysis was first invented by systematists on a morphological basis. By comparing large numbers of species of varying degrees of morphological similarity, one could infer ancient ancestral relationships. Now by comparing sequence data across many organisms that share the same gene, one can construct molecular phylogenies. Here is a phylogenetic tree for the hemoglobin gene : |
| Given a gene sequence from one organism, one can now look for similar sequences in molecular data banks of many diverse species. Molecular phylogenies now routinely show us that widely diverse organisms share similarities in their chemical makeup. For example, hemoglobins exist in vertebrates, plants, and even bacteria. Homeobox sequences exist in fruit flies, mice and humans. |