Phylogeny+and+Systematics

 Biologists trace phylogeney (the evolutionary history of a species) and draw fossil records which provide information about the ancient organisms. The fossil records that are created are based on fossils found in a strata. By creating these records, scientists can determine the ages of the fossils and what causes them to go extinct. They also use systematics, or an analytical approach to understand the diversity and relationships of organisms of both present and ancient. Systematics study morphological and biochemical resemblances in organism as a basis for evolution relationships. Scientists also use morphological and molecular homologies to indicate phlogenetic similarities. They also use the convergent evolution of anology(1).

Phylogenetic systems also use the taxonomy created by Swedish botanist and anatomist Carolus Linnaeus. Taxonomy is the ordered division of organisms into categories based on a set of characteristics that show similarities and differences. In taxonomy, every organism is given a two-part name called a binomial. The first part of the name is the genus or the species it belongs to, the second is the specific epithet or the unique name for each species in the genus. Along with naming them, Linnaeus grouped them into a hierarchy of categories. The hierarchy classification is:

Species--> Genus--> Family--> Order--> Class--> Phylum--> Kingdom--> Domain

Phylogeny uses branching diagrams called phylogenetic trees to show their hypothesis about evolutionary relationships. These trees reflect the hierarchy classification of groups that were nested within inclusive groups(1).




 * A cladogram alone does not imply evolutionary history, but if characteristics are shared and due to common ancestry, the cladogram forms the basis of a phylogenetic tree. The clade, which is within the tree, is the group of species that includes the ancestral species and its descendants. How the groups are analyzed and grouped into clades is called cladistics. The clades can be within larger clades. A valid clade is monophyletic, which shows its ancestors and descendants. When information is minimal about members of the clade, it is paraphyletic grouping, which shows the ancestors and some of its descendants. A polyphyletic grouping is several species which lack a common ancestor(1). **





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(1). AP Biology Book (2). http://scepticon.files.wordpress.com/2009/02/phylogenetictreeoflife.jpg (3). http://biology.unm.edu/ccouncil/Biology_203/Images/Phylogeny/cladogramDino.gif (4). http://origin.arstechnica.com/journals/science.media/collagenCladistics.jpg (5). http://www.trilobites.info/trilobite_clade.gif

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