______________________________________________ ______________________________________________ Phylogeny and classification are combined through the creation of a phylogenetic tree. Again, this is hierarchical and becomes more inclusive as you move through it. Phylogenetic Trees Homologous and Analogous Traits Reconstructing a species’ evolutionary history involves sorting homologous from analogous features and then infering phylogeny. This sorting is often not as clear cut as it sounds because of: a) Phenotypical similarities that are products of common ancestory can be difficult to distinguish from analogous traits. *It is important to separate phenotype and genotype when construting phylogenetic trees. b) Molecular sequences are affected by mutations, masking homologous segments. Additionally, they can also contain analogous segments! The diagram right illustrates how computer programs can find homologous DNA segments in separate species that would not be obvious to scientists. Statistical have been developed that can determine if molecular segments are analogous. In general, very similar molecular segments are most likely homologies. In distantly related organisms identicle bases are most likely coincidental. uses data from DNA and other moelcules to determine evolutionary Molecular systematics relationships. The tree right illustrates the characteristics of a general phylogenetic tree: What are sister taxa? ____________________________________ ____________________________________ What does a polytomy represent? ____________________________________ ____________________________________ What does Taxon G represent?
______________________________________________ ______________________________________________ Phylogeny and classification are combined through the creation of a phylogenetic tree. Again, this is hierarchical and becomes more inclusive as you move through it. Phylogenetic Trees Homologous and Analogous Traits Reconstructing a species’ evolutionary history involves sorting homologous from analogous features and then infering phylogeny. This sorting is often not as clear cut as it sounds because of: a) Phenotypical similarities that are products of common ancestory can be difficult to distinguish from analogous traits. *It is important to separate phenotype and genotype when construting phylogenetic trees. b) Molecular sequences are affected by mutations, masking homologous segments. Additionally, they can also contain analogous segments! The diagram right illustrates how computer programs can find homologous DNA segments in separate species that would not be obvious to scientists. Statistical have been developed that can determine if molecular segments are analogous. In general, very similar molecular segments are most likely homologies. In distantly related organisms identicle bases are most likely coincidental. Molecular systematics uses data from DNA and other moelcules to determine evolutionary relationships. The tree right illustrates the characteristics of a general phylogenetic tree: What are sister taxa? ____________________________________ ____________________________________ What does a polytomy represent? ____________________________________ ____________________________________ What does Taxon G represent?
classification_2014.docx