Tag Archives: classification

Biological Classification


Classification of living organisms has been a human pastime throughout history – it is important that we can name and identify organisms, especially if they are harmful (venomous snakes and spiders for example) or beneficial (organisms that provide food, fibre, medicine or services). It also helps us to group and organize the huge variety of living organisms on our planet. The science of identifying and naming organisms is referred to as ‘taxonomy’. Carl Linnaeus, a Swedish scientist, is often referred to as the ‘father of taxonomy’ because he developed the naming system that we still use today, called binomial nomenclature, which literally means “two-name naming-system”. Every organism belongs to a particular species and is identified by two latin words – the Genus and species. So, Homo sapiens (modern humans) belong to the genus Homo and species sapiens. Note that the genus name is capitalized, but the species name is not.

Two organisms that belong to the same genus (Eg. Eucalyptus citriodora and Eucalyptus camaldulensis) are more closely related than two organisms with the same species name (Eg. Eucalyptus citiodora and Backhousia citriodora). This is because the species name (citriodora) is a descriptive name that can refer to a characteristic of different groups, in this case, Lemon-scented Gum and Lemon-scented Myrtle.

Within the Five Kingdoms of Living organisms (Protists, Prokaryotes, Fungi, Animals and Plants) are the Phyla, Classes, Orders, Genera and species. It helps to remember this sequence of groups:

  • Kingdom
  • Phylum (and sub-phyla)
  • Class (and sub-class)
  • Order (and sub-order)
  • Genus
  • Species

Some more resources to learn about classification:

Chapter 8: Classification


Carl von Linne – Image Source

Learning Intention: To understand the biological system of classification and how living organisms are named and identified.

Success Criteria: Given sufficient information, you will be able to identify relationships between living organisms and classify them into their appropriate groups.

Carolus Linnaeus was a swedish botanist and zoologist who developed the system of classification that biologists still use today to order our natural world – “binomial nomenclature“. Just like large shops and warehouses that need to store huge numbers of items, biologists find it useful to classify organisms using a hierarchical system that groups the same kinds of organisms together. All living things are grouped and named using the following sytem:

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

The latin binomial system uses the genus and species name as a universal, unique identifier for a particular type of organism. This minimises the problem of organims that might have different common names in different parts of the world (eg. Blackbird, brown snake) and uses a one language recognisable to scientists worldwide. If two particular organisms have the same genus name, they are more closely related than two that belong to the same family but belong to different genera. However, if two organisms have the same species name, but belong to a different genus, they may not be closely related at all. The species name is more of a descriptor, so, for example, Eucalyptus citriodora is the lemon-scented gum and Backhousia citriodora is the lemon myrtle. They belong to different genera, so are not as closely related as two eucalypts or two myrtles.


Melbourne Museum - Wild Exhibit

Image Source Wild Display at the Melbourne Museum.

It is important for biologists to classify living organisms so species can identified and organised into groups according to their common features. The National Science Foundation’s “Tree of Life” project estimates that there could be anywhere from 5 million to 100 million species on the planet, but science has only identified about 2 million. Of these two million, the IUCN red list estimates that over 17, 000 species are in one form or another threatened with extinction today. So as fast as taxonomists are identifying new specimens, we are losing known species to habitat loss, introduced pests, pollution, overkill and climate change.

We often hear about threatened extinction of some conspicuous animals or plants, but it is usually not realized that each large species is host to many species of parasites, some of them specific to that host species and therefore doomed to extinction with it. The human species, for example, is host to far more than 100 parasite species, quite a few of these only found in humans. Species have not evolved in isolation – think of the co-evolution of flowering plants and their pollinators, toxic plants and their predators and animal camouflage.

This Chapter of work includes the Linnaean system of naming organisms, binomial nomenclature (Genus species system), heirarchical grouping (Kingdom, Phylum, Class, Order, Family, Genus and Species), dichotomous keys and cladograms. This site has some interesting mnemonics to remember biological terms for your upcoming exams.

Classification of Living Organisms

Photo Source

We are all relatively familiar with the five classes of vertebrates (mammals, birds, reptiles, fish and amphibians), but less familiar with species that account for about 97% of all known animal species – the invertebrates – or animals without backbones. The arthropods (including all insects, spiders and crustaceans) probably outnumber all other animals on earth, yet most of them are very small and easily overlooked. Invertebrates are found in every conceivable type of habitat, but they are most plentiful in the oceans, which is where animal life first arose. This week we will look at how living organisms are classified, some of the characteristics used in taxonomy and how different groups are related according to their evolution.

We often hear how many species are becoming extinct each year – less often we hear about the new species that have been discovered. In 2007, over 18,000 new species were described. This year a naturally decaffeinated coffee plant, a tiny seahorse and bacteria that thrive in hair spray have been discovered. Article from Scientific American, “Top 10 new Species“,  here.

I will be away at the school cross country on Tuesday, 26th May, so you are asked to complete Activity 8.1 in your practical manuals – “A key to sorting snakes”, about using a dichotomous key to extract information and identify various species. Please leave me a comment on this post to let me know how you went and waht you learnt.

A simple introduction to Classification from KidsBiology.com

Excellent site for Classification of Animals including characterisitics of each of the Phyla, images and links.

Go to ARKive for a growing collection of information, images and videos about all our magnificent organisms on earth. There is a collection of education resources, which includes downloads for different age groups. We will be looking at the ARKive Classification Resource in class on Wednesday, 27th May.

A more in-depth introductionabout the Linnaen Binomial System of Nomenclature and Principles of Taxonomy. 

Identify eight marine creatures from Chesapeake Bay, near Baltimore, USA using a dichotomous key.

Table of the Five kingdoms.

Excellent Glossary of terms.

Flashcards for Introduction and taxonomy.

Excellent interactive “Essential Study Guide” from McGraw Hill