I'm looking for good "case studies" documenting an obvious branching in a phylogenic tree, or a large phenotypical change within the species itself. Preferably the case study would include potential selection factors and evidence for each, fossil evidence of the change, and any other evidence that would help bring the whole story together. I have a friend who is having a hard time understanding how selection pressures can lead to large changes in a species over time. I know there are some good papers out there, but I'm not sure how to go about finding them.

A very clear life evolution case study of "a large phenotypical change within the species itself" would be the rise and establishment of Christianity. A large group's change of religion/culture is a clear case of biological phenotypical evolution.

If you're looking for a very well illustrated evolutionary line, the fossil record of the evolution of horses is fairly complete, from the first Eohippus all the way to modern Equus. Whale evolution also has quite a few specimens of "fossil evidence."

 

Marsupials provide great examples of convergence, also, a variety of placentals from bats to moles to lions have (or have had in the past) marsupial counterparts due to adaptations to similar niches.

Talk origins always has some good stuff:

http://www.talkorigins.org/faqs/comdesc/

http://www.talkorigins.org/faqs/horses/horse_evol.html

http://www.talkorigins.org/faqs/homs/

 

This site is very anti-Christian for some reason, but it has some good evolution articles:

http://www.skepticfiles.org/evo2/index.htm

 

Here is another good one with lots of articles:

http://www.gate.net/~rwms/EvoContents.html

 

http://www.txtwriter.com/Backgrounders/Evolution/EVcontents.html

Thanks for those links, even though this isn't "my" thread I appreciate you sharing them, those are some good resources, I knew of Talk Origins but not the others.

Fossil whales are another nice example. We've got a very nice series of fossils from a terrestrial carnivorous mesonychid (looks like a weird dog, but actually related to a sheep) all the way to modern whales.

 

Google around for them, I'm sure you'll find better stuff than I could present here.

 

Mokele

You could do a study on the controversy over mesonychid versus artiodactyl ancestry for whales, I believe the latter has recently been considered to be the stronger case, and you could highlight the fossil record of wrist evolution as evidence.

http://www.sciencenews.org/articles/20010922/fob1.asp