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Classification
There is a huge variety of living things on the earth.
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Scientists needed to come up with a way of putting plants and animals into groups,
based on similarities between them. This is known as classification.
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Classification: a method of grouping or categorising living things, based on similarities
of structure and function.
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The practice of classification by scientists is known as taxonomy.
The Beginning of Classification
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Carl Linnaeus introduced classification of organisms in the 1700s.
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He classified organisms as belonging to either the plant or animal kingdom, depending
on whether they had a cell wall or not.
How Classification Works
In classification, each kingdom is sub-divided into smaller groups called phyla, the phyla
are divided into classes, the classes into orders, the orders into families, the families into
genera and finally the genera into species.
Organisms in the same kingdom can be very different from each other, but as you move
down the chain towards species, organisms are more similar to each other.
Binomial Naming System
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Lineaus also introduced the binomial naming system to name plants and animals.
All organisms are named by their genus and species.
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The first name is the genus and is given a capital letter.
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The second name is the name of the species and is given a small letter.
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Both names are written in italics.
Examples:
Human = Homo sapien,
Cat = Felis domestica
The Difference between Genus and Species
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Organisms of the same species have very similar features and can interbreed with each
other. (Example: leopards can breed with other leopards)
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Organisms of the same genus may have similar features, but may not be able to
interbreed with each other.
(Example: a leopard and a lion are of the same genus, but cannot mate)
Problems with Linnaeus’ system
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Linnaeus’ system was not perfect.
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He classified everything with a cell wall as belonging to the plant kingdom and
everything without a cell wall as belonging to the animal kingdom.
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But there were problems when classifying organisms such as fungi.
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Fungi have a cell wall, but they have no chlorophyll in their cells (cannot make food) so
are not really plants.
Five Kingdom System
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A five kingdom system was then introduced by Robert Whittaker in 1969.
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He classified organisms based on:
– whether they could make food or not
– prokaryotic or eukaryotic cells
– unicellular or multicellular
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His five kingdoms were: Monera, Protista, Fungi, Plants and Animals
Six Kingdom System
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Even more recently scientists have decided to divide the Monera kingdom into two
distinct kingdoms – Bacteria and Archaea.
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This means that there are currently six kingdoms: Bacteria, Archaea, Protista,
Fungi, Plants and Animals.
These 3 domains of life (Bacteria, Archaea and Eukarya)
are divided into 6 kingdoms.
Domain (bacteria, archaea, eukarya): group of organisms that are classified according to their cell
structure.
If we take a Ring-tailed Lemur, we can trace it through the hierarchy of nature, taxonomy as
follows, it belongs to:

The Animal …Kingdom
sharing with all other members of this group the need to feed on organic matter (unlike plants
which can create energy using light and minerals)

The Chordate (or vertebrate) … Phylum
sharing with all other members of this group of animals, a back bone with a hollow nerve chord

The Mammal … Class
sharing with all other members of this group of vertebrates, the ability to feed their offspring
on milk and having a body covering which includes fur

The Primate … Order
Sharing with all other members of this group of mammals, a thumb that can be opposed to the
other digits, binocular vision and various more broadly defined characteristics (including high
intelligence, relatively long maturation period for the young, dental similarities, tendency for
complex social organization, and generally bearing one or two young)

The Lemuridae … Family
Sharing with other members of this group of primates, a slightly longer nose, smaller brain,
long slender limbs, a tail, more specific dental features including the grooming comb formed by
the lower incisor and canine teeth

The Lemur … Genus
other members of this group of lemurs, scent marking methods, vocalizations, aspects of
social structure and overall body shape
Sharing

with
The Ring-tailed Lemur … Species
A species is the primary unit of biological classification or taxonomy. Species members share a
basic genetic similarity and can interbreed and produce viable or fertile offspring.
The Six Kingdoms of Living Things