Scientific Classification

Taxonomy is the scientific method of classifying, that is, ranking lifeforms into hierarchical units called taxa (singular taxon). This method of describing life is based on a binomial nomenclature system initiated by the Swedish naturalist Carolus Linnaeus in 1735. Over time the system has become a bit more complicated because the number of units or ranks has increased and sometimes additional subdivisions are required. However, the accepted complete scientific description requires 8 ranks known as DOMAIN, KINGDOM, PHYLUM, CLASS, ORDER, FAMILY, GENUS and SPECIES. As one goes from left to right in this list the description becomes less and less general, the number of applicable life forms in a rank gets less, until finally we have a unique species. The complete description of a species requires an appropriate name in each rank. In practice only Genus and Species may be sufficient or perhaps Family, Genus and Species. Taxon names are usually Latin or Greek.

As an aside there are several mnemonics to jog the memory as to the 8 ranks in taxonomy. For example, Do Kings Play Chess On Fine Grained Sand

The taxonomic classification is best understood by showing by some examples. We shall use some animals and plants mentioned elsewhere in this website. First of all some animals

Rank

yabby

echidna

glossy black

Domain

Eukaryota

Eukaryota

Eukaryota

Kingdom

Animalia

Animalia

Animalia

Phylum

Arthropoda

Chordata

Chordata

Class

Crustacea

Mammalia

Aves

Order

Decapoda

Monotrema

Psittaciformes

Family

Parastacoidea

Tachyglossidae

Cacatuidae

Genus

Cherax

Tachyglossus

Calyptorhynchus

Species

destructor

aculeatu

lathami

The concept of domains is a fairly new one – as recently as 1990 – and domains are quite often omitted in scientific descriptions. Only three domains are recognised; Eukaryota (multi-celled life including plants, animals and fungi), Archaea (single celled micro-organisms where the cell has no nucleus; some of which don’t need oxygen, or sunlight for photosynthesis, but absorb CO2, N2 or H2S), and Bacteria. On this website all life forms described are eukaryotes and the taxonomic rank of domain is considered superfluous.

When we come to describe plants the equivalent table is slightly different – a domain is not given and the word Division is used instead of Phylum. Very often only Family, Genus and Species are given; and usually written in italics.

Rank

boronia

grass tree

Kingdom

Plantae

Plantae

Division (Phylum)

Magnoliophyta

Magnoliophyta

Class

Magnoliopsida

Liliopsida

Order

Sapindales

Asparagales

Family

Rutaceae

Xanthorrhoaceae

Genus

Boronia

Xanthorrhoea

Species

pinnata

resinosa

 

There are international scientific bodies which are responsible for the naming of animals, plants and bacteria; for example, the International Commission on Zoological Nomenclature (ICZN). These bodies are responsible for maintaining nomenclature codes; for example the International Code of Botanical Nomenclature (ICBN) and the International Code of Nomenclature of Bacteria (ICNB).

Australia is a continent which has been isolated for a long time. It was once part of the super-continent called Gondwana which began to break up in the Cretaceous period (i.e. between 150 and 65 million years ago). Gondwana was made up of Australia, Antarctica, South America, Africa and the sub-continent of India. In the Eocene (about 50 million years ago) the last separation occurred when Australia broke away from Antarctica and headed north-east; which it is presently doing at about 73 mm per year. Australia's isolation since this time has resulted in flora and fauna which in some cases are unique and in other cases have "relations" in ex-Gondwana continents. For example, marsupials are also to be found in South America.

Australia's isolation and the length of time involved has led to some twists of evolution. Some plant families have many genera (plural of genus ), while some have few; some genera have many species, some have very few, For example Grevillea, (a member of the Proteaceae family) is a very well known genus with Gondwana connections, and has about 250 Australian species. At the opposite extreme there are some species which are found in small numbers and in isolated locations. As an example a rare and vulnerable (officially) plant in our wider region is the Budawang Cliff-heath (Budawangia gnidioides), a member of the family Epacridaceae. Not only is the gnidioides very rare but it is the only member of its genus (Budawangia). The plant grows on the back wall of sandstone overhangs which are often found at the base of cliffs in Morton national park. The plant is not at all spectacular in appearance and can easily be overlooked.

Recently some experts have suggested that the heaths of the southern hemisphere (i.e. the family Epacridaceae) should be more correctly assigned to Ericaceae; so re-classification may well take place. Such re-classifications occur occasionally.

Budawangia gnidioides

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