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“ 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
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.
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
 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
Sailed west from S. America to reach the
 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
 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!
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
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 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
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.
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
 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.
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
Text pgs: 519-528
Quiz Tuesday covering everything up to and including
Friday’s notes.