Concept and Uses of Classification Systems | Cambridge IGCSE Biology

[Please watch the video attached at the end of this blog for a visual explanation of this topic]

What is Classification?

In biology, classification is defined as the process of grouping either living or extinct organisms according to similar characteristics

A reason for such a classification system to be in place is since there are millions of species living on Earth, it is easier for biologists to group them appropriately.

Organisms are classified into groups based on the features that they share with each other with regard to their physical, genetic and behavioural characteristics, and this process of classification is known as taxonomy. Taxonomy helps scientists to better understand the relationship between organisms and how they have evolved over time. 

What is a species?

A species is defined as a group of organisms that can reproduce to produce fertile, viable offspring.

This is a very important definition in biology, so keep this in mind. 

This is the smallest natural group of organisms. Organisms in a species are very similar to one another (ex: humans, dogs, cats)

Carolus Linnaeus and his contribution to the world of Biology

When talking about classification, there is an important scientist who contributed a great deal to classification, and that is the Swedish scientist named Carolus Linnaeus. Linnaeus introduced the modern system of classifying and naming organisms, referred to as “binomial nomenclature”. He is also known as the “father of modern taxonomy”.

Very simply, he introduced a good and successful system of classification that is still used today.

After classifying organisms he even went to the extent of assigning a scientific name to every organism. 

Binomial Nomenclature and the usage of Scientific Names

Every single living organism is assigned a scientific name, and this scientific name is made up of two parts. The reason that organisms have scientific names is so that they will be recognised all over the world.

For example, the animal lion is called león in Spanish and simba in Swahili. However, the animal is one and the same. Therefore, to recognise an animal no matter the language used, Binomial Nomenclature and the usage of scientific names were used.


Homo sapien is the scientific name of a human. The scientific name is divided into two parts:

  1. Genus name (the generic name)
  2. Species name (the specific name)

Every single organism is assigned with a scientific name like this which comes in two parts.

Refer to the video below to look at a few more examples of scientific names to understand them completely!

Rules to follow when writing scientific names according to the Binomial Nomenclature System:

When writing any scientific name, there are several rules that are assigned by Linnaeus and we must always follow these rules.


  • The genus name is always written first and the species name is always written second.

Mangifera indica is the scientific name of mango. Mangifera is the genus name, and indica is the species name.


  • When typed, binomial names are always in italics. Therefore, if you type the scientific name of any organism, make sure they are italicised


  • When these names are handwritten, each of these names should be underlined separately. When written, they need not be in italics. 

Mangifera indica (There’s a space between the two words that is not underlined)

At the final exam, since it is a written exam, make sure to underline the names separately since you could otherwise lose marks!


  • Genus name always starts with an uppercase letter, while all letters in the species name are in lowercase.

Psidium guajava – the scientific name for the fruit guava where the genus name “Psidium” starts with a capital letter/ uppercase letter”, while all the letters in the species name “guajava” are simple letters/lowercase letters.


Why is this system called the “Binomial Nomenclature” system?

The word “binomial” means having two names. “Bi” means two, and “nomial” is derived from the Greek word nomos” which means parts. 

Linnaean Classification System

Earlier on in the article it was mentioned that Linnaeus introduced a system of classification that was very successful and is still in use today. (You did pay attention right??)

So let’s take a look at this system of classification which is called the Linnaean system of classification.

In this system, he first took all organisms and divided them into different levels known as taxa (singular is taxon). The first level is the Kingdom. Then he considered each kingdom and he further divided the organisms in the Kingdom into Phyla/Phylum. And within the Phylum, he further sub-divided organisms into Classes, and after classes he divided them into Orders and then into Family and then into a Genus, and finally into a Species.

  • It is important for you as a student to remember this hierarchy/order because plenty of past paper questions have questioned this.


  • A scientist by the name Carl Woese introduced the taxa called “Domain”, many years after the Linnaean system was introduced. It comes before the Kingdom taxon.


Here’s a little tip to remember this easily:
King Phillip Came Over For Good Spinach

What should you do next?

Make sure you study the definitions of species, binomial nomenclature, and scientific name. It is also good to know who introduced the classification system to us, so Carolus Linnaeus is a name you must remember! Every single paper will have one or more questions from this area. 

Your examiners will pay close attention to whether you have underlined the names separately or not, and as to whether the first letter of the genus name is capitalised. Be careful when writing them!

Since Biology questions tend to get repeated, practise as many as you can find. Some questions can be found here as well, and you can time your answers to see if you can stick to the time limit given.

If you are struggling with IGCSE revision or Biology in particular, you can reach out to us at Tutopiya to join revision sessions or find yourself the right tutor for you.

Watch the video below for a visual explanation of the lesson and make sure to attempt the quiz once you’re done!

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