|
gluadys -> RE: Darwin's Finches (5/11/2008 7:45:04 AM)
|
quote:
ORIGINAL: Kames
http://en.wikipedia.org/wiki/Darwin%27s_finches
i know my excess use of wikipedia [:)] but that's how knowledge works
and it's readily falsifiable by other users so in fact wikipedia is a theory [:D]
anyway
i saw a science channel program about evolution that talked about Darwin's whole journey and evolutionary thought
one thing that stood out for me was his comparison of pigeon breeders with the environment and thus natural selection versus articial
however, science lacks clarity or criteria with some fundamental definitions like, species, planets ..
from pigeons i went to finches and then i read this on the article above
Real-time evolution
One of Darwin's finches (Geospiza fortis) helped prove their namesake's theory of evolution when scientists observed a shift in the species to birds with smaller beaks after competition was introduced by the arrival of another species with larger beaks. This happened over a twenty year span and was the first instance where scientists were able to document the type of evolutionary change known as character displacement from the start to completion of the process.[9]
isn't it too fast in an evlutionary timeframe?
No. As Stephen J. Gould pointed out, "gradual" as applied to evolution, has two meanings. One is that it takes place slowly over time. The other is that it occurs in small increments of change. The latter meaning is the correct one in evolution. The first not always so. Under strong selection pressure evolution can occur fairly rapidly over time (geologically speaking), although it still occurs in small increments. (This was the basis of his theory of punctuated equilibrium.)
Peter and Rosemary Grant, who observed the finches over a period of nearly 30 years, through both a severe 3-year drought and an El Nino flood, saw changes in beak size over less than 5 years, due to changes in available food supply.
The observation that the presence of two species on the same island went along with greater differences in beak size had been made previously, and from that character displacement had been inferred. The importance of this study is that it was observed after competition was introduced, not inferred from competition already there.
|
|
|
|