This is part of Macroevolution. That is where new species/genera are formed.

Species can usually be distinguished by behavioural/morphological differences.

Two main concepts of species:

BIOLOGICAL SPECIES CONCEPT

ECOLOGICAL SPECIES CONCEPT

Three main kinds of speciation which differ according to how important geographic isolation was in forming the new species.

ALLOPATRIC SPECIATION (Requires geographic isolation)

PARAPATRIC SPECIATION (Weak, partial reliance on geographic isolation) 

SYMPATRIC SPECIATION (No need for geographical isolation)

Organisms classified according to a hierarchical system of similarities.

The tree of life or genealogy of a species is sometimes called its Phylogeny.

1. It is the basis for the identification and classification of organisms.
2. Knowing phylogenetic relationships often helps to explain why a species evolved certain adaptations and not others.
3. To deduce the function of morphological features or behaviours by comparing the traits of different species.

By assuming species that are more phenotypically similar are closer related than ones that are less phenotypically similar.

Problem avoiding basic decisions of classification on convergent features (analogous features)

Need to be aware of homologous traits - ones that are ancestral. Only derived traits - features that have evolved since the time of the last common ancestor.

Genetic distance is increasingly being used.

The hierarchical pattern of similarity created by evolution provides the basis for the way science classifies and names organisms.

Scientific naming is based on a hierarchy of descent: Species that are closely related are classified together.

Closely related species put in a genus and closely related genera (pl. genus) are into family.

Question should it just be on descent (cladistics) or should it also be based on overall similarity.