In what sense are humans currently acting as agents of selection on
other species? Names some organisms that are favored by the
environmental changes humans cause

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Clarification of Question by pat53-ga on 11 May 2004 17:05 PDT

I am talking about evolution not the sea. In what sense are humans
currently acting as agents of selection on other species? Name some
organisms that are favored by the environmental changes humans
causesaaaaaaaaaaaaaaaaaaaaaaaaa/

algal blooms are often thought to be the result of global warming
(increased CO2 means more food for algae).

the more common example is microbes that become resistant to human
made antibiotics:  for example, 50 years ago Staphylococcus aureus
(common bacterium) was easily killed by most antibiotics.  however,
the widespread use of antibiotics (like penicillin) have made a large
percentage of Staph aureus isolates resistant to a WIDE array of
antibiotics.  these are typically called methicillin-resistant staph
aureus (or MRSA for short).

http://www.ivillagehealth.com/experts/infectious/qas/0,,166096_170156,00.html
http://www.npm.ac.uk/papers/plym_bloom_jul01/bloom_29jul01.gif

Finally, sea surface warming and sea level rise could increase health
threats from marine-borne illnesses and shellfish poisoning in
Florida. Warmer seas could contribute to the increased intensity,
duration, and extent of harmful algal blooms.

http://ess.geology.ufl.edu/ess/Notes/070-Global_Warming/Climate%20Change%20and%20Florida/!index.html

you wrote:  "Names some organisms that are favored by the
environmental changes humans cause"

I named Algae--living organisms found in the ocean in greater
abundance because of human influence on the climate.

BUT!!!! As I mentioned, the simpler example is that of bacteria.

-Bacteria (like Staph aureus) have always caused numerous human infections.
-Back when the 1st antibiotics were identified (~60 years ago), the
antibiotics were able to kill off virtually all types of bacteria that
caused infections.
-But the fact that we humans use MORE and MORE and MORE antibiotics
has NATURALLY SELECTED for bacteria that are NO LONGER KILLED by many
commonly used antibiotics.
-This is probably one of the foremost examples of humans causing
evolution of other species.

http://www.fda.gov/oc/opacom/hottopics/anti_resist.html

Think of it in this crazy way:  Imagine a world where bears normally
give birth to bears with normal 'fleshy' skin...BUT every
once-in-a-while a bear is born with a mutation that makes its skin as
hard as STONE.  These "mutant" bears can't run as fast...they have a
hard time catching food, and they usually die at a young age because
the "normal" fleshy bears outcompete them for food and mates.
Now imagine that hunters with guns begin hunting these bears.  The
hunters can ONLY kill the bears with fleshy skin and they CAN'T kill
the bears with stone-like skin.  Because of this, the bears with
fleshy-skin begin to die off and the bears with stone-like skin are
able to survive better than the "fleshy" ones.
This would be EVOLUTION.  And this is essentially what has happened to
bacteria over the past 60 years because we humans (hunters) have used
antibiotics (guns) to kill off bacterial infections.

Check out http://www.utm.edu/~rirwin/moth.htm it describes one of the
most famous examples of humans effecting evolution and natural
selection.

The peppered moth of England (Biston betularia) exists in two basic
formes a dark and a light.   This is a simmple case, because it is
with regards to only one gene.  In pre industrial england, the
peppered moth was most commonly found in the grey form.  This made
sense, as it was more easily able to camoflouge itself against the
grey background of the trees, thus making it less succeptible to
predation, and more likely to reproduce.  The black isoform was
occasionally found, but was more succeptible to predation.  The
industrial revolution came along, and air pollution increased
significantly.  This resulted in a nice thick coat of grime on trees. 
The color change from grey to black suddenly made the light isoform
very much  more succepitlbe to predation and the darker allele became
the favored allele.  Humans, because we are so much fun, imposed
restrictions on smog emissions, the clean air act reduced smog, and
accordingly reduced pollution.  With pollution down, the trees
returned to grey, and the light isoform again became favorable.

So, thats a classic case.

Here are some species that have been significantly effected by humans...

Bacteria are prime examples.  We have selected for antibiotic
resistance in bacteria, including many in the Staphlococcus family.

Fringe species, such as deer, have been profoundly effected and
favored by humans.  We have eliminated their predation (wolves,
cyotes) and have increased the amount of "fringe" area (the area at
the edge of a forest) which is their prefered habitat.

Here is another famous case... 

http://preview.thinkquest.org/03oct/00128/en/rabbits/history_light.htm

The european rabbit was introduced into Australia by man in the mid
1800's and without any natural predators it flourished.  It became
epidemic.  We, of course, had a clever solution, the myxoma virus. 
The myxoma virus was deadly to rabbits in the lab, so we introduced it
into Australia.  We had an unfortunate problem.  Through natural
selection, weaker strains of the virus, and more resistant strains of
rabbit were produced; while the population dipped temporarily, it
later skyrocketed as it had initially, this time with rabbits who
couldn't be killed off by myxoma.

Hope this is helpful -

Patrick

i think there is some recent controversy about the peppered moth:

c.f.
http://biocrs.biomed.brown.edu/Elephant%20stuff/Chapters/Ch%2014/Moths/Moth-Update.html