Woodlands Historic Park
Classification of Organisms

Classification Used on This Site

You can click on the check boxes to hide or show the taxa below. To hide or show all lower level groups click on the buttons.

What's it all about?

The following is an attempt by a non-scientist to understand and summarize the "science" of taxonomy, which is perhaps more equivalent to the legal system - having the inertia of hundreds of years of tradition, but nevertheless undergoing constant change. I would not use any of it to answer a question on a biology exam.

Science classifies organisms into named groups (or taxa), which are then subdivided hierarchically into smaller and smaller groups until we get the level of species (or subspecies). The traditional levels in the hierarchy in descending order are Kingdom, Phylum, Class, Order, Family, Tribe, Genus and Species, although tribe is not always used. These are called taxonomic ranks. The naming of organisms is intimately bound up with classification because of the tradition established by Carl von Linne in the 16th century of using the Genus name as part of the species name.

There are an infinite number of ways of classifying species. Although species can be considered to be a biological reality (despite the definition of species being an open question), there is no physical definition of the other ranks - they seem to be essentially arbitrary. The method of classification pioneered by von Linne was based on anatomical rather than superficial similarity - a whale is a mammal, not a fish. As organisms have become better understood, down to the cellular level and below, classification has changed to reflect this, including adding more Kingdoms. However more recently there is a push towards the principle that all members of taxa should have the same evolutionary ancestor. Under this system, the crocodile is grouped together with birds, rather than reptiles. This does not seem very useful to me. Furthermore a lot of people spend a lot of time reclassifying things to try and achieve this. Personally I would prefer to see the scarce resource of scientific effort go into better understanding the species themselves, including all the species (mainly insects and fungi) which have not even been named.

There seems to be a continual need to create new levels in the hierarchy. According to the Wikipedia page on taxonomic rank, "There is an indeterminate number of ranks, as a taxonomist may invent a new rank at will, at any time, if they feel this is necessary." New ranks are usually created by prefixing one of the main ranks with super-, sub- or infra-, with infra being below sub. However there are also other named ranks used only in zoology or botany respectively. For example Division can be used below Class in zoology, which is confusing because in botany Division is a synonym for Phylum. To further confuse things, sometimes groupings are introduced which have no rank, for example Acari (Mites) which is at the level of order but also has orders below it. To me this seems to make the rank names completely meaningless.

Source of Classification and Species Counts

Because classifications are constantly being changed there are multiple schemes in use. The five Kingdoms shown above are from a 1983 biology textbook by Helena Curtis. What you will find if you look in Wikipedia depends on what page you look at: if you look up a fungus you will indeed find it comes under Kingdom Fungi, but if you look up plasmodial slime mould (Myxomycota), rather than find it as a phylum under kingdom Protista you will find the highest level of classification is Domain Eukaryota, with no Kingdom mentioned, and Myxomycota reduced to the rank of class.

For animals I adopt the classification used by the Australian Faunal Directory.

For plants I use a "traditional" classification rather than the one used by Flora of Victoria where all the plant phyla used here are instead classes within the phylum Tracheophyta. I do however use the Vicflora classification at family level. (The Australian Plant Census has yet another complicated scheme with lots of sublevels I have never heard of.)

I will ignore the intermediate levels (ranks) unless they seem useful, which is mainly the case for insects because of the sheer number of species. For plants I also omit Order. For fungi I omit everything between Phylum and Genus.

The number of species given in the list above is the number of species in Australia that have been described. The actual number of species is considerably higher in the case of fungi and invertebrates. Numbers for animals are from the Australian Faunal Directory at January 2019 or later. Numbers for fungi are from Atlas of Living Australia at August 2020, and includes a number of unnamed species. Numbers for plants are from Chapman (2009). They include only native species, whereas the statistics for fungi and animals include non-native species which have become naturalized. The proportion of of species which are native is unknown for fungi. For animals is it probably fairly high, although there is no actual count available. Chapman gives estimates for the percentage of species that are endemic, i.e. only occurring in Australia. For insects it is estimated that about 70% are endemic, but species can be native without being endemic so the percentage of native species will be higher. There are however some insect groups such as Aphids where a smaller percentage of the species are native - according to Australian Faunal Directory, "Of the 150 species of Aphididae known from Australia probably only 13 are endemic, about 40 may have arrived without human assistance and the remainder were probably introduced with their host plants".