Name: Jane D.
Date: February 2003
How can one observe microevolution in brief periods of time?
A perfect way is to observe antibiotic resistance in bacteria. In any
population there is variation and natural selection acts on those variations.
Since bacteria have such a quick generation time, they appear to accumulate
changes faster than other living things. ( They do not necessarily, but they
multiply so fast they seem to). So, you can put bacteria on an agar plate
and put an antibiotic disk on the surface. The bacteria that are closest to
the disk are the most resistant and the bacteria further away are more
sensitive. You can keep choosing the bacteria closest to the disk over
successive generations and they size of the clear zone around the bacteria
should decrease over generations.
This shows that when the most resistant
bacteria are chosen, more of their offspring make it to the next generation
and then more are resistant and they reproduce and more are resistant and so
on. Of course this depends on the trait being in the population in the first
place. Unless a random mutation occurs, which is rare, the trait has to be
present to be acted upon by natural selection.
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Update: June 2012