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An incredible amount of diverse organisms live in the world, and biology has the daunting task of putting all these different things into a logical order. The world wide system, used by everyone, is called binomial nomenclature. It was developed by a European named Carolus Linnaeus, who devised a system by which every organism is grouped into specific categories and given two names, which are known as the scientific or latin name of the organism. They are the Genus and species, with the genus always capitalized and the species not. For example, the latin name of the red maple is Acer rubrum. Acer is the genus, and is capitalized. rubrum is the species. Genus and species will be discussed more later. All names come from Latin or Greek roots, because those were the languages of educated people at Linnaeus' time.

There are seven classification levels, or taxa(taxon singular),from kingdom, the most inclusive(many organisms), to species, the most exclusive(only one organism). The levels are:

In the generally accepted system, there are 5 Kingdoms. They are:
Animalia: Animals. The defining characteristic is that all organisms develop from an embryo with a blastula stage. Animals also have senses and nervous systems, to aid in locamotion and searching for food. All are heterotrophs; they get there food from other organisms and can't make their own food.
Plantae: Plants. The main characteristic is that plants develop from an embryo without a blastula stage and have cellulose in their cell walls. They are autrophs, organisms that can make their own food. Plants produce food through photosynthesis, and have chloroplasts for this purpose. Most are immobile. A few eat insects for extra nutrients, such as the venus fly trap.
Fungi: These are heterotrophic organisms that develop from spores and have chitin in their cell walls. They are mostly immobile. Most are decomposers. Examples are mushrooms, molds, and bracket fungus.
Protista: The protists are basically a miscellaneous category, with no defining characteristic. the only real similarity is that they are all eukaryotes(cells have nucleus). Some are autotrophs, some heterotrophs, and some are decomposers. They can be single celled or multi celled. Examples are slime molds, algae, protozoa, and ameobas.
Monera: Also called prokayota, this kingdom includes bacteria and all prokaryotes. Prokaryotes are organisms with cells that have no nucleus or membrane-enclosed organelles. Monera is the only kingdom which includes prokaryotes, so that is the determining factor for inclusion in this kingdom. Most are single-celled organisms. In terms of number of species and places where they live, bacteria are the most diverse group of organisms.

A new system of classification at the kingdom level has recently been gaining favor. It breaks up life into 3 kingdoms: Archea, Bacteria, and Eucarya(eukaryotes). This new system is more phylogenetically correct, meaning it is a more accurate representation of how life evolved. Archea, or ancient prokaryotes, is very different from bacteria and eukaryotes in terms of its DNA. Archea used to be classified together with bacteria, but more detailed DNA analysis has shown that it should be a separate kingdom. The bacteria kingdom includes the prokaryotes that evolved after Archea, going off on a separate branch. The third branch of life is eukaryotes, the more complex life that evolved much later than Archea and Bacteria split. Animals, Plants, and Fungi are at the very top of this branch, showing how recently they evolved. This system will probably replace the old five kingdom classification, which does not recognize the diversity of microbial life.

Genus and Species are the two levels of classification that are used to identify a particular organism. They are known as the scientific name of a organism. The genus is a small group of very similar organisms, and the species name refers to only one organism. No two different organism can have the same scientific name.