History of systematics III

Phylogenetic grouping

1. Monophyly: arise from a common ancestor including all descendents.

2. Paraphyletic: does not include one or more of the descendents.

3. Polyphyly: arise from more than one ancestor. Does not include all descendents.

Homologous and analogous

1. Homologous: have a common evolutionary origin. Look the same because they have a common ancestor.

2. Analogous: may seem to have a common evolutionary origin but dont. Convergent evolution.

Phonetic classification

Taxa defined statistically using equal weighting of morphological units. Taxa are grouped together on the degree of their overall morphological/genetic similarities

Cladistic classification

Established by Wili Hennig (1960s). Evolutionary trees with clades (lineage that splits from an earlier lineage). Tree obtained by tracing the change of characters from a primitive state to an advanced state in a group or organisms. Only clades exists, it is the relationship of these to each other on a cladogram that is important. There is no hierarchy therefore no taxa.

Molecular systematics

Development of technologies and equipment allowed scientists to analyze DNA/RNA from organisms. Developed into a new branch of taxonomy.

1. Extract DNA

2. Amplify desired segment of DNA marker with PCR

3. Agarose gels used to visualize amplified DNA

4. Sequence amplified DNA (marker)

5. Align sequences.

Beyesian inference tree

Molecular phylogeny, teams of botanical scientists all over the world presentkt attempting to produce a classification for the angiosperms based on the phenetic and cladistic analysis of this molecular evidence.