Taxonomists, those who arrange and classify life, place all species past and present into one of three ‘Domains’, reflecting a very broad/high/ancient level of evolutionary association. Of the three Domains – Bacteria, Archaea and Eucarya, all but one of the hundreds of species we have recorded in the Garden belongs in the Domain Eucarya. There are plenty of non-Eucarya species present, for example the Garden will contain many different bacteria. We simply do not have the technology or knowledge to identify them (well not many of them).
All life evolved from a common ancestor, that first ‘example’ of life on earth. A simple organism or complex molecule able to reproduce independently, that scientists believe developed as far back as 4.28 billion years ago, shortly after the formation of the oceans and not all that long, relatively speaking, since the earth itself formed 4.54 billion years ago. Without going into detail, a point seems to have been reached when one group of organisms evolved in a completely different direction than the rest. This first major branching of life saw Bacteria and ‘everything else’ (our phrase) split and the Domain Bacteria was formed. Later the separately evolving ‘everything else’ itself divided into the Archaea and the Eucarya. Completing the three domains of life that have forever gone their own way.
Domain Eucarya
There are a number of differences that distinguish Eucarya from Bacteria and Archaea, but the main one is that all Eucaryotic cells contain their genetic information (DNA) within a nucleus. Evolution wasn’t done yet, and several more major splits within the Eucarya itself, over hundreds of millions of years, has resulted in the Domain being split into around 21 groups called Kingdoms, each with a unique set of characteristics. So far we have found representatives of three of these kingdoms in the garden. These Kingdoms are the Animals, Plants and Fungi. Other Kingdoms do exist in the Garden, such as the Diatoms, but we haven’t yet studied them.
A special note should be made regarding Slime Molds. These are life forms who’s cells have a nucleus surrounding their DNA and as such belong firmly in the Eucarya. However they don’t appear to sit well in any of the established Kingdoms. They are a bit of a random group, placed directly into the Phylum Amoebozoa (phyla are subdivisions of Kingdoms, see below), with members sharing certain characteristics but not necessarily being that closely related. To date we have identified only the one species in the Garden.
Domain Bacteria
We mentioned above that all but one species recorded in the Garden is Eucarya. This other species is called Nostoc. In fact Nostoc refers to its Genus (see below), the classification level above species, with several very closely related species being termed Nostoc. We suspect our Nostoc is the species called Nostoc commune. It is a long surviving colonial form of life that lives on the concrete steps in the Garden. It doesn’t have a cellular nucleus and has been placed in the Domain Bacteria, and within the phylum Cyanobacteria.
We have arranged our species list and galleries to reflect this form of classification. In the case of Eucarya and specifically Kingdom Animalia, we then subdivide the groups into ever smaller more closely related groups in the following order. Kingdom, Phylum, Class, Order, Family, Genus and Species.
If you are not familiar with how life is classified, which most people wont be, it would probably help to run through an example and what better example than our own species.
Most of us are aware that our DNA is enclosed in a nucleus within each of our cells. This means we belong in the Domain Eucarya as explained above. We can also move around, consume organic material, reproduce sexually and breath oxygen and we have a very specific embryonic phase which we wont go into now. These characteristics combined define animals and all species that share them are considered part of the Animal Kingdom.
Of course not all animals are the same. One major difference is the presence of a backbone. Relatively few species of animals actually have a backbone, only things like mammals, fish, birds and amphibians. Therefore all animals sharing this characteristic (plus a few more) are considered to be in the Phylum Chordata.
But clearly not all Chordata are the same, and as we noted above some are fish, some are birds but some like ourselves are Mammals. Species that produce milk (something other chordates like birds, fish and amphibians do not do) which we ourselves can are considered in the Class Mammalia.
As you can see, with each new grouping we are being grouped with fewer and fewer species that have more and more in common with us. The order to which we belong is the Order Primates, so it is at this level that we humans, the great apes and monkeys are all separated from the other mammals, such as lions and tigers which belong to the Order Carnivora and later the Family Felidae (felines or cats).
But continuing with Humans, we belong to the Family Hominidae, of which there is but one surviving species, ourselves. In the past there have been several species of Hominidae but the last of these died out several thousand years ago. As the sole survivor we alone belong to the Genus Homo and our Species is sapiens. Our most recent ancestors, such as Home neanderthalensis, were so closely related to us that hybridization is now believed to have occurred.
So to sum up, Humans or Homo sapiens are classified as follows: Domain Eucarya, Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Primates, Family Hominidae, Genus Homo and Species sapiens. You will notice that all species are named by combination of their Genus name (first name) and Species name (second name but never spelt with a upper case letter). Hence humans are called Homo sapiens.
Each species of animal has a similar classification, our lion example would be Eucarya, Animalia, Chordata, Mammalia, Carnivora, Felidae, Panthera and leo. Its scientific name therefore being Panthera leo.
Plants and Fungi have similar classifications, but plant classification in particular uses slightly different terminology, but basically the principle of smaller more closely related groups is followed.
If you are planning a project similar to ours (i.e. to produce a list of all species you encounter in your garden), then at some stage the list will become too long and unruly to be used in any meaningful way. You will need to consider how you wish to group together the species you record. It seemed to us logical to follow the system employed by the scientific community. Not because we are scientist but because that’s what everyone else has decided to do. This universal way of organising life is reflected in Wildlife Guides, Textbooks, Social Media Groups and several other important sources of information such as Zoo’s, Wikipedia, Magazines and Journals.
DC 03/06/2023
Wildlife Garden 