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LIFE ON EARTH

ITIS DATABASE

NJSAS uses the ITIS database, up to the rank of Species. ITIS has a good level of detail on Plants and Animals but nothing on Protoctists (Protists), a little on Bacteria (Monera) and somewhat more on Fungi.

Many thanks to the ITIS folks for making this major resource freely available in a usable form.

Last updated to 080802.

TAXONOMIC RANKS

Ranks by kingdom.

LIFE ON EARTH

The modern view of life is one of organisms that have evolved from a Last Common Ancestor (LCA, probably extinct) into microscopic Bacteria and Protoctista, still the most abundant forms of life today, and from there into the Animals, Plants and Fungi we actually see around us.

Although much is being learned about present and past life forms, very basic questions about how they arose remain largely unresolved and are still active areas of research. How did the first bacterium emerge, the first protoctist? Was it inevitable, highly improbable or simply miraculous? A theoretical framework that would allow us to derive numerical answers to these questions does not yet exist, and until then our knowledge about evolution remains unsatisfactory.

Taxonomy (Systematics) is the centuries old science of classifying all known forms of life. Until recently taxonomists have had to rely on exernally visible, morphological, differences between species to assign them their proper place in the tree of life. Today, genetic sequencing exposes the contents of cell nuclei and is providing the definitive evidence with which to complete this task.

The traditional taxonomic hierarchy is still in common use (from Kingdom to Species, see the above table) but nobody inteprets these taxa litterally anymore. They are best thought of as suggestive of the main bifurcations in the phylogeny, or evolution, of each species. The number of actual bifurcations, as revealed by genetic methods, is actually far greater. The tree of life, it has been said, is turning into a thick bush.

TREE OF LIFE

The evolutionary Tree of Life (using genetic sequencing data).

SEE ALSO

High Order Taxonomy
The Onlince Biology Book
National Center for Biothechnology Information (NCBI)
NCBI Taxonomy
Expert Center for Taxonomic Identification (ETI-UNESCO)