4 Identification and naming
Before we can start to investigate how the organisms in an ecosystem interact with the environment we have to be able to give them names. The naming of living things has always had an important practical function, allowing us to understand the natural environment and exploit it more effectively. As soon as something has a name, all sorts of useful information can be attached to the label. Is this plant good to eat or poisonous? Is this animal rare or plentiful? The information can then be passed from one member of a group to another, and from one generation to the next.
Scientists face a similar need. To understand an ecosystem we need to be able to name and list the organisms involved in a precise and accurate way. Naming – like reductionism – is a strategy that allows us to impose some order on the complexity of the natural world.
The science writer Richard Fortey explains the importance of this in his book Life: An Unauthorised Biography
Discrimination and identification have value beyond the obvious separation of edible from poisonous, valuable from worthless, or safe from dangerous. This is a means to gain an appreciation of the richness of the environment and our human place within it. The variety of the world is the product of hundreds of millions of years of evolution, of catastrophes survived, and of ecological expansion. To begin to grasp any of this complexity the first task is to identify and recognise its component parts: for biologists, this means the species of animals and plants, both living and extinct.
(Fortey, 1998, p. 14)
As Richard Fortey notes, the species is the fundamental unit of biological diversity. But what is a ‘species’? And how do we distinguish one species from another?
In the field, scientists use two approaches to identify a species. Neither is without its problems.
Members of the same species normally resemble each other.
Male and female members of the same species can breed with each other to produce offspring that are also able to reproduce.
The first approach, appearance, is the most obvious one for most of us most of the time. We know that a robin is a robin because it looks like a robin – and the word ‘species’ is derived from the Latin verb specere (‘to look at’). But appearances can be deceptive. Males and females of a given species may look different, and many organisms change their appearance as they mature (say, from tadpole to frog or from caterpillar to butterfly).
The second approach is also fairly straightforward in most cases. We take it for granted that our robin can breed with other robins to produce more robins, and that these robins will, in their turn, breed with other robins. But in some circumstances, members of closely related species can and do breed with each other. For example, the horse and the donkey can breed with each other, although the offspring – a mule – is unable to reproduce.
The concept of the species is important to biologists and to our understanding of the working of ecosystems and the biosphere. That's why I've spent some time on it here. The number of species in an ecosystem, or the biosphere as a whole, is an important indicator of its health. Perhaps it is best to think of species as more or less permanent varieties of living things. Many biologists feel that although the definition of a species has its difficulties, in most cases they know one when they see one. The exceptions to the rules are a useful reminder that the complexity of the natural world does not always conform to the categories we attempt to impose on it, and that as a consequence the use of scientific terminology requires judgement and common sense.
Scientific names
Scientists use Latin for the formal names of living things. This means that people from different countries can be sure that they are talking about the same thing. You will come across these scientific names from time to time, so it is useful to know how they work.
Dogs and wolves share a lot of features in common, so they are put together in a genus – a grouping of related species – called Canis. They don't normally interbreed, so they are different species: for example, Canis familiaris (the domestic dog) and Canis lupus(the grey wolf). The Latin names of species are given in italics, or underlined if handwritten. The name of the genus starts with an upper-case letter; the name that indicates the species is given a lower-case letter. All human beings are members of the same species: Homo sapiens.
As far as I know, only one animal has a common name that is the same as its scientific name: the boa constrictor (Boa constrictor).