Textbook pages 492 -497

II. Systematics: Connecting Classification to Phylogeny

    systematics= the study of biological diversity in an evolutionary context

A. Taxonomy employs a hierarchial system of classification

Taxonomy is done in two ways: binomial and a hierarchial classification
Binomial is the two part latinized name, first part genus, second part species.
The hierarchial classification system is done in the order of domain -> kingdom -> phylum -> class -> order -> family -> genus -> species.
Phylogentic tress allows us to construct the hierarchial system in more inclusive groups.

B. Modern phylogentic systematics is based on cladistic analysis

phylogentic systematics is classification based on evolutionary history.
Cladograms : a a phylogentic diagram based on cladistics and formed by a series of two way branch points.
Each branch point represents a common ancestor.
The deeper branch represents a evolutionary divergence from a common ancestor.
Each evolutionary branch is called a clade.
When a group consists of all its ancestral species, it is called mono phyletic.
When a group consists of an ancestor and SOME of its decendents, it is called para phyletic.
When a group consists of a group of decendents without a common ancestor it is called poly phyletic.

C. Constructing a Cladogram

It can be constructed through either homology or analogy (convergent evolution).
Homology is based on a common ancestor.
Analogy is based on organisms converging due to similar ecological roles and natural selection.
the greater number of homologous parts of 2 species, the more closely related they are.
Besides constructing a cladogram by eithe homology and analogy, we can include shared derived characteristics.
Phylogeny of the clad can also be broken down into shared primative character, a back bone that predates the homology, or a shared derived character, a evolutionary novelty unique to a particular clad.
To analyze clades, we have to find the characteristic that seen or shared by the most organisms, or closest to the group of species we are studying called the ingroup.
The organism least related to the ingroup is the outgroup!
NOTE: cladograms do not tell chronology!!