microevolution - involves processes of evolutionary changes within populations - these changes...
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Microevolution
- involves processes of evolutionary changes within populations
- these changes result in shifts at the DNA level
- they lead to the sorts of variations that we see within species.
- examples are
- the differences in the beaks of finches
- the lengthening of a giraffes neck over time
- the predominance of light or dark peppered moths in an area
- is the resistance that bacteria develops against antibiotics.
Researchers from Princeton University observed a species of ground finch in the Galápagos Islands.
Within less than just two decades the finches have evolved smaller beaks and most of these changes happened within just one generation.
The evolution from medium to small beaks was a direct result of competition for food with large ground finch (arrived in 1982) and a clear display of natural selection.
These finches adapted by evolving even smaller beaks that are more suitable for breaking open smaller seeds that the larger and more dominant finches don’t bother with.
Finch Beaks
http://www.arkive.org/woodpecker-finch/camarhynchus-pallidus/video-08.html
http://www.youtube.com/watch?v=ytObEc1MfUk
http://delivery.gettyimages.com/xd/abvce135.mov?c=NewsMaker&d=A0ED2600064C09C003AE3B8B49979A6E&k=2&v=1
Predominance of Light or Dark Peppered Moths
Peppered moths come in two morphs: light and mottled (peppered) or black.
During the 18th century the black morph was a highly prized variant, but during the early stages of the industrial revolution more and more of the black forms began showing up around cities.
This trend continued until there were more black moths (98%) in the cities and less of the peppered ones.
The environment had changed and the moths had adapted to it. Soot from burning coal was coating the bark of the trees.
The black moths blended in quite well and were camouflage while the peppered ones were now highly visible, easy prey for birds.
However, in the countryside where the tree trunks were not polluted the peppered moths flourished.
The evolution of antibiotic resistance in a population of bacteria isa familiar example of natural selection in a clone.
Antibiotics are natural or synthetic substances that can kill or inhibit the growth of microorganisms. (Ex. Penicillin)
Bacteria occur in large numbers, so we can predict that in a culture of any size there will be one or more spontaneous genetic mutants which are penicillin-resistant. (1 organism in a population of a million)
If we then kill the population with penicillin except the resistant one we now have a population where 1 organism in a population of 1 is resistant – 100%
Since bacteria divide quickly in a very short time, we could have an entire vessel of penicillin resistant bacteria. This is especially bad if the vessel is your body.
Antibacterial Resistance in Bacteria
Macroevolution
- involves processes of evolutionary change that result on a much larger scale
- needs to be considered over a long geological time.
- An example would be the emergence of land creatures from sea creatures
http://www.youtube.com/watch?v=faRlFsYmkeY&NR=1