How do birds fit into the study of all
living things, and how are they classified?
The standard method for classifying living
things is to group them together into categories that define them according to
features that they share and which set them apart from other categories. This
method gives rise to an increasingly detailed set of categories that been given
standard names, although these are not universally agreed and changes to them
have been made at various times.
According to one commonly agreed method,
birds belong to the kingdom of animals, the phylum of chordata (animals having
spinal cords) and the subphylum of vertebrata (animals with backbones).
They then form their own class, namely that
of aves. A special subclass has been assigned to Archaeopteryx, the
long-extinct feathered reptile that has been thought to be the earliest bird
(although this is disputed), which leaves all other birds in the subclass of
neornithes.
The bird world is then split into about 30
groups that are designated as orders, and these are further divided into a
total of around 200 families. Further divisions are into genus and species, of
which there are around 10,000.
An example of an order is passeriformes,
which includes all perching birds. This contains more than 70 family groups and
has more species than all the other bird orders put together.
A species is defined according to whether
individual members can mate and produce offspring that will themselves be
fertile. Sometimes it is necessary to define sub-species where there are
distinctions between populations (often geographically remote from each other)
but which are still capable of interbreeding.
As with all living species, birds are
classified according to invented Latin names that consist of a genus and a species
(and sometimes sub-species). Examples include Parus major (great tit) and Hirundo
rustica (swallow).
© John Welford
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