At the Charles Darwin Research Station, you see the Giant Turtles and the Galapagos land Iguana. Introduced aminamls to many of the islands threaten the existence of the indigenous species. Wild dogs that were brought to the island almost killed a colony of over 500 land iguanas in 1970’s. Cats, mice and goats were induced as well, the goats and dogs have been irraticated but getting all the mice and cats poses real challenges. The Research Station was able to rescue 60 iguanas and in an effort to re-build their population, they began a breeding program for iguanas in Santa Cruz. This breeding program is still active today.
Darwin Finches
We saw the Common Cactus, Small Ground, Green Warbler, Wood Pecker, and the Gray Warbler.
Darwin identified 13 species of Finches among the Galápagos Islands that were primarily differentiated by beak size. In contrast, only one species of this bird existed on the mainland South America to the east. Darwin correctly concluded that the different beaks were adaptations to different diets available among the islands.
Darwin ultimately generalized the observation from the finches that any population consists of individuals that are all slightly different from one another. Furthermore, individual organisms having a phenotype characteristic providing an advantage in staying alive to successfully reproduce will pass their phenotype traits more frequently to the next generation. Over time and generations the traits providing reproductive advantage become more common within the population. Darwin called this process "descent with modification". Adaptive radiation, as observed by Charles Darwin in Galapagos finches, is a consequence of allopatric speciation among island populations.
Darwin also correctly understood that the variability allowing adaptation already existed in the finch population, though its genetic (genotype) reason was not yet known by science at the time. Nature was NOT "producing" the variation within the finch populations - it already existed. Rather, nature "selected" from among the population variation the traits that better fostered survival and reproduction, a process known as "natural selection". The process guides evolution across the entire Tre of Life. http://www.fossilmuseum.net
"It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us." - Charles Darwin (1859)
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