Biology » Classification » Classification Schemes

Classification

Classification

This section introduces learners to the concept of taxonomy, which is the classification of living organisms. The activity below allows learners to practice classification.

The practice of classifying organisms is referred to as taxonomy. Classification is usually a hierarchical process. One begins with general and broad differences, and then one systematically introduces more and more detailed and specific criteria.

We have prepared an activity in order to show why we try and classify living organisms, what sort of mental process it entails, and how it is done. The activity below is not Life Sciences related, but conveys the process of classification. Try and think of the problems that arise while classifying the items below. Can BBC news be entertaining too? If so, should it not be under entertainment? Do you think that the final level of classification is the most definitive?

Activity: Classification

Aim

To understand how classification systems work.

Materials

Pen and paper

Instructions

  • Listed below are different TV programmes (it doesn’t really matter if you know them or not):
    1. Carte-Blanche
    2. Rocky
    3. Isidingo
    4. Rambo
    5. Hitler’s Bodyguards
    6. Generations
    7. Vietnam: Lost Films
    8. BBC news
  • Divide these TV programmes above into 2 groups, under the headings: Entertainment and Documentary.
  • Now further subdivide the Entertainment group into Action and Soapies groups.
  • Do the same for Documentary using the headings: News/Current Affairs and History.

Answers

EntertainmentDocumentary

Rocky

Isidingo

Rambo

Generations

Carte Blanche

Hitler’s Bodyguards

Vietnam: Lost Films

BBC News

EntertainmentDocumentary
ActionSoapiesNews/ Current AffairsHistory

Rocky

Rambo

Isidingo

Generations

Carte Blance

BBC News

Hitler’s Bodyguards

Vietnam: Lost Films

You have just drawn an example of a dichotomous branching diagram/ tree. All objects can be divided in this way. We call this a classification system.

 

Classification can be a tricky business. Problems arise when something can be classified to greater detail, or when an object or organism could belong to more than one category. Biologists have faced these classification conundrums for centuries when trying to classify organisms in one category or another.

Artificial classification systems, such as the grouping of vehicles into those that provide transport on land, water or air, are based on arbitrary groupings and have little meaning. The biological classification system, however, is based on research in anatomy, physiology, chemistry, genetics and many other branches of science. It is a scientific method of classification that groups organisms that share common features.

This classification is not random, but rather it describes evolutionary relationships. As a consequence, it is always necessarily hierarchical, where the important features inherited from a common ancestor determine the group in which the organisms are placed. For example, humans and whales both feed their young on milk, which is a characteristic inherited from a common ancestor. This similarity places them under the same class, mammals, even though their habitats are completely different.

Each organism is grouped into one of five large groups or kingdoms, which are subdivided into smaller groups called phyla (singular: phylum) and then smaller and smaller groups with other names.

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species

Schematic diagram showing hierarchy or ranking scheme used by taxonomists.

Optional Video: Taxonomy

Watch a video about taxonomy: life’s filing system

When trying to identify animals, it is this hierarchy or ranking scheme that we follow. We start by identifying the kingdom to which an organism belongs, then its phylum, class, family, order, and so on. This is similar to explaining how to find your house to a being from another planet. You would have to say Earth first, then Africa, then South Africa, then KZN, then Durban, then the suburb, then the road name and finally the house number. He would have to start searching in a big place and gradually work down to smaller places (or groupings).

A way to remember it is “Kwaito People Come Out From Gauteng Singing”. By learning this mnemonic you are going to remember the sequence in the classification system:

  • Kingdom – Kwaito
  • Phylum – People
  • Class – Come
  • Order – Out
  • Family – From
  • Genus – Gauteng
  • Species – Singing

Optional Activity: Constructing a mnemonic to remember the sequence of the classification system

Aim

Construct a mnemonic in order to remember the classification sequence easily.

Materials

  • pen
  • paper
  • imagination!

Instructions

Make an easy to remember memory aid to remember the sequence of levels of the classification system.

 

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