Once two populations of the original species are reproductively isolated, changes may occur. However, the process of speciation seems generally to be quite rapid, thus producing a distinct species in a short period of time. Thus, the species unit appears as a natural, most fundamental, unit for most organisms. It is sometimes difficult to pigeonhole bacteria into species categories. Different higher taxa have varying amounts of importance in classification.
Botanists usually speak of plant families , while entomologists refer to insect orders .
This may represent different branching patterns of the evolutionary tree for different groups or may be our attempt to break up the classification system into manageable units. Think about how you might be able to tell which one of these alternatives is most significant. Phenetic Classification Phenetics is also known as numerical taxonomy. It takes a large number of characters for each taxa and uses a measure of overall similarity between the taxa to calculate relationships. Imagine that one measured the weight, length of the ear, and distance been the eyes for both humans and house cats.