Bacteria Classifying and Ordering Help (page 2)

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By — McGraw-Hill Professional
Updated on Aug 30, 2011

Finer Classification Below The Kingdom Level

Taxonomists also recognize a number of levels of classification of organisms below the kingdom level. You may remember (from Chapter 2) that there is a Pyramid of Life. In this pyramid, the horizontal layers are the various levels of biological organization, starting with subatomic particles at the base, and finishing with an ecosystem at the peak. Taking a similar approach, Figure 6.2 shows a Pyramid of Classification . At the broad base of this new pyramid lies the species . A species consists of individual organisms of a certain “kind” ( species ). In a practical sense, two different organisms (male and female) are considered to be members of the same species if they can successfully reproduce to create fertile offspring.


Above the species level lies the genus ( JEE -nus). The word genus comes from the Latin for “stock” or “kind.” A genus usually consists of two or more species belonging to the same “stock.” This means that the related species making up a particular genus or stock have certain structural and functional characteristics in common. Further, these shared characteristics make the members of a particular genus distinctly different from any other group. In Kingdom Animalia, for example, we have the genus Homo ( HOH -moh) or “man.”


Taxonomists give a two-part Latin name to each species of organism. The first name (capitalized) is the genus, while the second is the species. We modern humans, for example, are classified as Homo sapiens ( SAY -peeenz) or “wise” ( sapiens ) “man.” The human race, for all its problems, may not really be considered wise, but it is the only surviving species of the genus Homo . The Fossil Record has provided abundant evidence of other (now extinct) species within the Homo genus, such as Homo habilis ( HA -bih-lis), Homo erectus (e- REK -tus), and Homo australopithecus ( aw -stray-loh- PITH -eh-cuss).


Above the genus in the Pyramid of Classification lies the Family level. In taxonomy, a family consists of a group of related genera ( JEN -er-ah, the plural of genus). Members of Homo sapiens, for instance, belong to the hominid ( HAHM -ih-nid) or “man-shaped” family. Modern human beings and the man-like apes belong to the hominid family.


Next comes an Order of organisms. An order is a collection of related families or organisms. Homo sapiens belongs to the Primate Order, as do apes, monkeys, and lemurs.


Beyond the order is the Class . In taxonomy, a class is a particular group of related orders. Human beings and other members of the Primate Order, for instance, belong to the wider and more general Class Mammalia (mah- MAY -lee-ah) or “mammals.”


Similar classes are grouped into a certain phylum (FIGH-lum). All Class Mammalia creatures are found within the still-larger category of the Phylum chordata (kor- DAY -tuh). The chordates ( KOR -dates) are organisms with a slender “cord” in their backs, sometime during their development. All members of the Class Mammalia have such a slender cord, which eventually develops into a mature vertebral (ver- TEE -bral) column, or “jointed backbone,” in the adult.


Finally, the highest taxonomic category of them all is the Kingdom. A kingdom consists of a group of related phyla ( FIGH -lah, plural of phylum). All backboned organisms in the Phylum Chordata (including humans, of course), belong to the Kingdom Animalia.

Bacteria and the “Homeless” Viruses Classifying and Ordering: The Work of Taxonomy Finer Classification Below The Kingdom Level

Fig. 6.2 The Pyramid of Classification for all types of organisms.

Practice problems for these concepts can be found at:  Bacteria and Viruses Test

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