Many species are distributed widely, and populations can be found in a variety of ecosystems or habitats within the species' range. Because of evolution, populations become adapted to their environment. As individuals die and new ones are created, the makeup of the population changes. Advantageous traits survive and are passed on. Over time, those traits (and their underlying genes) are found in more and more individuals in the population. This “small-scale” evolution (often referred to as microevolution - but see Mayr's quote on the right) is well-documented and is a first step toward speciation, creating different subspecies, races or varieties, each adapted to its own local environment[#](Futuyma 1998).

Ultimately, however, evolution is the origin of species(see illustration below). Speciation - the creation of new species by “budding off” from existing species - is simply the result of natural selection over longer time periods.[#](Mayr 1963)(Mayr 1982) [*] Isolated populations become more and more different, because what is advantageous in one ecosystem may not be advantageous in another.

But there is usually some interbreeding among populations. Seeds, spores or pollen may drift or be carried into a population from elsewhere. The same is true of larvae, eggs or sperm in aquatic systems. Young animals often disperse to other populations. As a result, divergence among populations is not extreme; individuals from different populations still recognize one another as potential mates[#](Endler 1973).

The discussion above describes allopatric speciationMeaning "different place", speciation that occurs when a population becomesgeographically isolated from other populations and adapts to local conditions.. There are ways new species can arise without physical isolation, however. As long as some subset of the population is unable to mate with members of the rest of the population, the potential for speciation exists. Sympatric speciationMeaning "same place", speciation that occurswithout geographic isolation. speciation can occur, for example, if some individuals begin to mate at a different time of day or year.

Not only is evolution the origin of species, but it is responsible for higher taxonomic groups as well.  All life originated as one or a few forms, and "blossomed" into many millions of species in many different kingdoms and phyla[#](Kutschera & Niklas 2004)(Valentine 2004).

There are seven major levels of taxonomic groupings in biology[**]: Kingdom, Phylum, Class, Order, Family, Genus, and Species. Any of these may have subgroupings.

Kingdoms are established based on similarity in cell structure.  There currently 6 recognized Kingdoms: Animalia, Plantae, Fungi, ProtoctistaEukaryotes that cannot be classified in any of the other kingdoms as fungi, animals, or plants., MoneraThe kingdom of unicellular prokaryotes (bacteria and cyanobacteria)characterized by the lack of a nuclear membrane enclosing the DNA., and Archaea Like bacteria, archaea are single-celled organisms that lack nuclei and are therefore prokaryotes..

Phyla can be thought of as grouping animals based on general body plan, i.e., this is a morphological grouping.  A Division is the equivalent of a phylum in the plant or the fungal kingdoms.

The other divisions are less and less inclusive, until the rank of species, which contains only those that are the same "type" - those that can interbreed (but see the illustration "What is a species?" above).

Two example taxonomies:

Table 1.  Taxonomic classification for Eastern white pine

Table 2.  Taxonomic classification for Banner-tailed kangaroo rat

Rundle, HD, F Breden, C Griswold, A Mooers, RA Vos, & J Whitton. 2001. Hybridization without guilt: gene flow and the biological species concept. Journal of Evolutionary Biology 14:868-869

Bohonak, AJ. 1999. Dispersal, gene flow, and population structure. Quarterly Review of Biology. 74:21-45

Thewissen, JGM & S Bajpai. 2001. Whale Origins as a Poster Child for Macroevolution. Bioscience 51:1037-1049