Evolution Darwin
“ Hence, both in space and time, we seem to be brought somewhat near to the great fact-mystery of mysteries-the first appearance of new beings on Earth”
The voyage Recommended at age 22, to be the naturalist aboard a vessel heading to S. America In December of 1831, he set sail on the HMS Beagle, on what can be considered one of the most influential voyages in human history. Initially slated to take years, instead it took 5. Captained by Robert FitzRoy, with the primary objective to map the S. American coast for the British navy. Darwin’s role? Find evidence for the creation story.
The voyage Supplies: jars, a microscope, binoculars, a compass, notebooks, pistols, a rifle, and a book authored by Lyell In regular intervals, he sent his findings back to England. Found fossils of giant Glyptodon and Megatherium Significance? Found a resemblance to the modern armadillo and sloth respectively. Also noted that this set of animals along with the extinct shared the same patterns of distribution
The Galapagos Sailed west from S. America to reach the Galapagos Darwin immediately noticed that the flora and fauna was very similar to that he just observed in S. America, yet they also had unique traits… Furthermore the species differed from island to island Similarly he found the same phenomena with respect to the Cape Verde Islands and Africa Thus he went in search of the creation story and left with the exact opposite==his conclusions and those of others, make him one of the foremost scientist of all time!
Darwin's issue Why would continents separated by large distances have entirely different species occupying similar niches? This is now known as biogeography: which is the observation and analysis of the geographic distribution of organisms. It was later confirmed that the fossils he found were in fact larger versions of the current species. How? ...maybe they were ancestral forms
Further observations It was found that 25 of 26 bird species found were different species… How? …maybe a single ancestral species was brought there, and diverged based on what island they were occupying Darwin dedicated the rest of his life to this investigation
Homologous/analogous features Homologous feature: structures that share a common origin but serve different functions in different species. (i.e. dolphin’s flipper vs human hand) Note: homologous features need not be not be physically visible==can also be embryonic Analogous feature: structures that share a similar function but do not share a common source nor are they anatomically similar. (i.e. bird wings vs fly wings) Darwin guessed that species with similar homologous features shared a common ancestor while those with analogous features did not.
Vestigial features Structures that serve no useful function in living species. Examples: digits in dogs, pigs and horses; humans have the same muscles present that dogs do to move their ears; some snakes and whales have hip bones; appendix in humans. Further evidence for evolution.
Artificial selection Darwin became sure that there must exist some mechanism of inheritance. Shifted focus from looking at fossils and single specimens, to observing populations of reproducing species. He started to breed his own pigeons==model evolution Examples of artificial (Human) selection today: domesticated plant and animal species. Darwin guessed that if humans could alter the morphology of certain species, then perhaps the environment could be exhibiting the same kind of process in the wild.
Final piece to the puzzle At this point, Darwin’s observations/research and that of others led him to be fully convinced about the evolution of life forms. But how does nature choose who to breed? 1798, Thomas Malthus: essay on the principle of population==in nature both plants and animals produce more offspring then can survive… VOILA!!==favourable traits would be preserved and less favourable ones would be eliminated due to intense competition within the species
References Text pgs: 519-528 Quiz Tuesday covering everything up to and including Friday’s notes.