Some girls find older chaps pretty kinky
Common mnemonic for memorising the biological taxonomy groups (see The Five Kingdoms).
Respectively, in order of decreasing similarity, these are:
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
In case you've ever wondered the common couplet of latin words found in biology textbooks are the species and the genus, and two species with the same genus share a common ancestor, for example
Homo sapiens are related to Homo erectus in genetic terms*
It is of course perfectly permissible for the species and genus to be identical, for example in the case of ratus ratus - a creature we all probably know to some degree.
Mathematicians of course will recognise the taxonomy system as hierachical ordering, indeed a very similar system is in use for the very inorganic computer DNS system. Such a system of classification is useful wherever objects must be grouped in distinct classes, with each subsuquent class giving further information about the object.
*Not strictly true in some religions