Transcript Presentation3

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”
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
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

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!

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
not.

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
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.

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.