1. Isolation and Diversion in Allopatry Colonization events are more common on islands. When a physical barrier separates a population, a vicariance event is said to occur.

2. DISPERSAL AND COLONIZATION 1. Start with one continuous population. Then, a colonist floats to an island on a raft. 2. Finish with two populations isolated from one another. Island Continent Figure 23.8 left

3. VICARIANCE 1. Start with one continuous population. Then a chance event occurs that changes the landscape (river changes course). 2. Finish with two populations isolated from one another. River River changes course Figure 23.8 right

4. Phylogeny Evolutionary history of a species or group of species From Greek phylon, tribe and genesis, origin

5. Systematics Study of biological diversity in an evolutionary context Includes taxonomy - the naming and classification of species and groups of species The first taxonomic framework was the Scala Naturae of Linnaeus

6. Darwin wrote: “Our classications will come to be, as far as can be made, genealogies” In other words, our taxonomic system should reflect evolutionary relationships

7. Cladistics - a method for developing phylogenetic trees Conceived by the German biologist, Willi Hennig - first described in his 1951 book Phylogenetic Systematics Relies on identification of clades - a collection of an ancestral species and all of its descendant species The resultant phylogenetic tree using cladistics is called a cladogram

8. How we go about constructing a cladogram? Fossil record can be helpful Morphology Behavior Molecular information (DNA sequences or proteins)

9. Morphological similarity can be very useful in reconstructing phylogenies However, there are two problems with morphology: Not all similarity represents common ancestry Primitive characteristics are not useful in reconstructing a phylogeny