Evolution has been studied for many years, in the past the main system that came to the forefront called by some : Mendelian genetics more correctly -Classical genetics. Under this school of thought, animals (and plants) were put in to various family groups depending on their characteristics. For example, if you had feathers you were a bird, mammals had fur (a little simplified, but you get the idea). In short all phylogeny classification was based on anatomical factors, mainly by examination of bone structure.
In the 1950's there was a huge breakthrough in biology, courtesy of James Watson and Francis Crick who were working in Oxford University where they came across the double helical shape of DNA. At this point I don’t think they knew just how profound and influential this discovery would become. Finding DNA's structure was the beginning of our understanding of DNA at the molecular level, giving birth to molecular biology, which really came to the forefront in the 1980s.
A branch of molecular biology is Evolutionary Genetics. The logic of relationship is similar to previous work on evolution but differs in some very important ways.
- Classical approach:
If two organisms share a common feature e.g. limb type, then they are probably closer in relation to each other than another organism not sharing that characteristic.
- Molecular approach:
If two organisms share a common feature e.g. unique DNA strand sequence, then they are probably closer in relation to each other than another organism not sharing that characteristic.
On this superficial
level, you may wonder what the big fuss is about. But there are certain discrepancies
in placing a certain phylogeny
on an organism
based on there physical appearance
. The main problem comes from convergent evolution
, two organisms may share a similar characteristic e.g. beak
, due to experiencing the same environmental
conditions, but may be quite divergent
from each other. If you have two organisms that have converged
, genetic techniques
can show their differences with much greater clarity
. The tool that is used for this is 'junk' DNA.
Junk DNA is a term generally working its way out of molecular biology, but still used in the media (hence my usage). More correct terms would be non-coding, or non-functional DNA. Basically these are stretches of DNA with no evolutionary pressure on them (basis for the theory of the molecular clock). As you could guess, there is no reason for such DNA to be prone to 'convergent evolution' as they are not affected by evolution in any particular direction.
In summary, evolutionary genetics is the study of non-coding DNA to deduce the evolutionary relationships between species.
See also :
Medelian Genetics Vs. Molecular Genetics (not written yet, but will be added latter).
Population Genetics (Similar to population genetics, but concerned with relationships within a group that interact with each other).