From a new organism to a place in a group

You find a new plant

A plant is growing in the corner of the school garden, and you have never seen it. What do you do?

First you look at it with care: the shape of the leaf, the colour of the flower, the number of petals, the smell. Then you ask: is this a plant that people already know? If it is, you find its name. If it looks like some others, you put it in a group with them. And its name must be written by the rules.

The four processes

1. Characterisation. We study the features of the organism: its shape, size, structure and way of life. A good description is the base of all the rest.
2. Identification. We find out whether the organism is one that is already known. We compare it with known descriptions, pictures and preserved specimens.
3. Classification. We put the organism in a group with others that are similar. Classification is the process of grouping organisms into convenient categories based on some easily observable characters.
4. Nomenclature. We give it a correct scientific name. This is possible only after identification, and the name tells us the genus, so it is linked to classification.

These four processes are basic to taxonomy. Taxonomy is the study of how organisms are described, identified, classified and named.

Classification is grouping

You do classification all the time. In a shop, vegetables are on one shelf, soap on another and books on a third. The idea is the same: things that are alike are put together, so that you can find them and talk about them.

In biology, organisms are placed together because they share features that we can observe and often measure. A leaf can be described by its length divided by its width.

You should find that a line near $2.45$ puts every leaf in its own group. A line at $2$ calls three broad leaves narrow. A good character, used well, gives clean groups.

Systematics

The word systematics comes from the Latin word "systema", which means a systematic arrangement of organisms. Linnaeus used Systema Naturae as the title of his book. Later the scope of systematics was widened to include identification, nomenclature and classification. It also takes into account the evolutionary relationships between organisms. So systematics asks not only "where do we put it?", but also "how is it related to the others?".

Try it in Python

Classification is grouping, and Python can group too. This program has eight animals, each with its class. It sorts them into groups and counts each group.

Practise with new numbers

Common mistakes

• Naming before identifying. You must know whether the organism is already named before you name it.
• Mixing up taxonomy and systematics. Systematics adds the evolutionary relationships.
• Grouping by a character that varies a lot. A good character separates the groups cleanly.
• Thinking characterisation is only looking. It includes measuring, and noting how the organism lives.

Remember these

• The four basic processes of taxonomy: characterisation, identification, classification and nomenclature.
• Classification groups organisms by easily observable characters.
• Taxonomy is the study of all four processes.
• Systematics comes from the Latin systema, and includes the evolutionary relationships between organisms.

Check yourself

Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.

1. Which process comes first: classification or characterisation?

2. A student writes the correct scientific name of a plant that is already known. Which of the four processes is this?

3. What does systematics add to taxonomy?

4. Why must identification come before nomenclature?