Bacteria Classifying and Ordering Help (page 2)
Introduction to Classifying and Ordering
This section looks at the different types of bacteria in much more detail.
Besides ancient bacteria, there are plants, fungi, and animals. Such defining and classifying of different groups of organisms is the essential work of taxonomy (tacks- ON -oh-me). Taxonomy looks for general rules or “laws” ( nom ) for the “arrangement” or “ordering” ( tax ) of organisms into groups of various sizes. As such, it is an essential feature of Natural History.
The Five-kingdom System Of Classification
Ever since Aristotle and other early naturalists began observing and collecting observations about organisms, just how to classify them into particular groups for convenient study has been a major issue. Taxonomy involves no set laws or rules of Nature. Rather, it is a human-constructed way of assigning organisms to particular groups, using highly orderly and systematic methods.
Because it is human-made, there is no single rock-solid way of classifying organisms. Instead, there are a number of different ordering systems or kingdoms commonly used by taxonomists (tacks- ON -oh-mists). Perhaps the most simple of these methods is the Five-Kingdom System. As Figure 6.1 clearly illustrates, the Five-Kingdom System consists of three kingdoms of multicellular (many-celled) organisms, plus two kingdoms of unicellular (single-celled) creatures. According to this system, most multicellular creatures belong to either the Kingdom Plantae ( PLAN -tie), Kingdom Fungi, or Kingdom Animalia (an-ih- MAIL -ee-uh). Obviously, these are the kingdoms of plants, fungi, and animals. And all single-celled organisms belong to either the Kingdom Protista (proh- TIS -tah) or Kingdom Monera (muh- NIR -uh).
Unicellular Kingdom Classifications
Kingdom Protista consists of the protists ( PROH -tists). Protists are often considered the “very first” ( protist ), that is, the most ancient, of all types of organisms. They are also among the simplest. The protists are eukaryotes, having a nucleus, but they are generally simpler than most plants, fungi, and animals. For example, the protist kingdom includes the amoebas (uh- ME -buhs). An amoeba is a single-celled eukaryote (Figure 6.1 below) that frequently “changes” ( amoeb ) the shape of its body as it moves through its environment.
Kingdom Monera is the one that includes the bacteria and all other types of prokaryotes. Since they lack a nucleus, all of the organisms within this kingdom have cells with cytoplasm that essentially stands “alone” (moner). The bacteria and other monerans (muh- NIR -uns) also lack other membrane-enclosed organelles, such as mitochondria and Golgi bodies. Monerans thus have only the most basic facets of cell anatomy and physiology.
Despite small cell size and structural simplicity, however, the Kingdom Monera and its vast populations of prokaryotes (such as bacteria) make up the majority of the Earth’s biomass or “living weight.” All of the bacteria on this planet, added together, weigh far more than all the elephants and whales and human beings combined!
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.
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