An Idiots Guide
to DNA barcoding - 1.
Prelude:
This document is designed as a simple introduction
to DNA barcoding for non-scientists. As such, we will need
to introduce a few concepts and definitions that are necessary
in order to understand this exciting and important new approach
to the discovery, cataloging and monitoring of biodiversity.
I will not go into any significant detail about modern molecular
biology and the methods it employs. The object here is to
explain a new subject that is at the cutting edge of biodiversity,
molecular biology and bioinformatics research to non-specialists
and to make it fun and interesting. So, lets not worry too
much if we oversimplify some concepts in our quest to catalog
and identify all living organisms on planet earth.
Background and a few definitions:
Taxonomy is the practice
and science of classification. The word comes from the greek
words for “order” and “science”. Taxonomies or taxonomic
schemes are composed of taxonomic units known as taxa
(taxon in the singular) and arrange things
to be classified in hierarchichal structures, typically
related by subtype-supertype relationships.
Linnaean taxonomy is a method
of classifying living things, originally devised by (and
named for) Carl Linnaeus, although it has changed considerably
since his time. The greatest innovation of Linnaeus, and
still the most important aspect of this system, is the general
use of binomial nomenclature, the combination of a genus
name and a single specific epithet to uniquely identify
each species of organism. For example,
the human species is uniquely identified by the binomial
Homo sapiens. No other species of organism
can have this binomial. Prior to Linnaean taxonomy, animals
were classified according to their mode of movement.
All species are classified in a ranked hierarchy,
starting with kingdoms. Kingdoms are divided into phyla
(singular: phylum) Phyla are divided into classes, and they,
in turn, into orders, families, genera (singular: genus),
and species (singular: species).
Linnean taxonomy is considered to be a
natural classification system for living organisms
as all living things are indeed descendend from a single
common ancestor and have diverged from one-another through
a series of speciation events though the process known as
evolution. As a result, some groups of
species are more closely related than others and might reasonably
be classified within the same genus, family, order etc.
Evolution is the process
of change in all forms of life over generations, and evolutionary
biology is the study of how and why evolution occurs. An
organism inherits features (called traits) from its parents
through genes. Changes (called mutations)
in these genes, occur randomly and can produce a new trait
in the offspring of an organism. If a new trait makes these
offspring better suited to their environment, they will
be more successful at surviving and reproducing. This process
is called natural selection, and it causes
useful traits to become more common. Over many generations,
a population can acquire so many new traits that it becomes
a new species.
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