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At a conservative estimate, there are about 1 million different types (species) of animal, and over 300,000 species of plants. More have yet to be discovered, mainly in tropical areas of the world.

Biologists divide up living organisms into groups, according to features which are thought to be of biological significance. Organisms sharing major features are grouped together, and separated from other different organisms. For instance, animals and plants are often placed into different kingdoms, but some authorities propose more than 2 kingdoms - 5 kingdoms are usually mentioned nowadays.
Each group can be repeatedly subdivided into smaller groups which differ in more minor ways, and these levels of subdivision have special descriptions and names. This gradually becomes more precise, as different organisms become excluded, so there are fewer and fewer organisms, sharing more and more important features, in each group. The final stage is called a species, which amounts to a unique description for an individual organism.
The usual groupings are as follows, but there can be sub- and super-sections too :
Some examples are given below: you should be able to add more.

singular/plural Example 1 Example 2
Kingdom/ KingdomsAnimalPlant
Phylum / Phyla
(sometimes Division/Divisions
in Plant Kingdom)
(Vertebrates)Flowering plants (angiosperms)
Class / ClassesMammalsDicots
Order / OrdersPrimatesRanales/Ranunculales
Family / FamiliesHominidae (apes)Ranunculaceae
Genus / GeneraHomoRanunculus
Species/ Speciessapiensacris
Common nameManField buttercup

This method of classification can be used in descriptions to cover anything from large groups to individual organisms, i.e. it can be general or specific (see above!).
Latin and Greek words are used to give special names to each individual organism, and also to the groups. This has the disadvantage of unfamiliarity, but it is a fairly international system which cuts out many of the disadvantages of "common names" for organisms, (assuming they have one!).

There is also a special way of writing the scientific name for an individual organism or (species) - which confusingly is always in 2 parts:
1)The genus name always starts with a capital letter,- Homo
2)The species name (sometimes called the trivial name) is always in small (lower case) letters - sapiens.

Both words (called the binomial - e.g. Homo sapiens) should be printed in italics, or underlined if handwritten.

Sometimes an organism seems to have been given several different names by different authorities at different times, and there are rules about this (often broken!) so sometimes you have to make allowances!


Scientific, and common, names may be found in books, by simply looking for a description to match the organism in question.

It is sometimes easier, but often not more informative, to use a KEY, prepared by a specialist, which identifies an organism in a particular situation, on the basis of a series of paired descriptions, or questions with a limited number of possible answers. Sometimes these keys are based on the same features used in classification, but sometimes they are based on arbitrary differences.

What drawbacks of a key can you think of?
> someone needs to know what is likely to be there (& what is not likely to be there), and produce the key accordingly - but being a specialist they may make it more complicated than the user expects!

What features are not a good idea to have in a key?
> overall size, internal features, colour if variable

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