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Darwin’s Voyage of Discovery
Darwin’s Voyage of
Discovery
 As a child Darwin loved collecting
organisms….did not like school or
medicine (unlike his father/grandfather)
 Asked at age 22 to voyage to S. America
as a naturalist (from a former professor)
 Set sail in 1831 on the HMS Beagle
 Voyage lasted 5 years!
Darwin’s Voyage of
Discovery
 Cpt Fitzroy was surveying and mapping waters
for the British Navy.
 Hoped that Darwin would discover evidence to
support Biblical creation
 Darwin was to observe, record (journals) and
collect rocks, minerals, plants and animals
 He collected thousands of specimens and
shipped them back to England
Darwin’s Voyage of
Discovery
 In S. America, Darwin discovered
species, fossils and began making
observations
Darwin’s Voyage of
Discovery
 Not only were they similar in appearance
but both modern and extinct animals
shared the same pattern of distribution
Galapagos Islands
Galapagos Islands
 A series of volcanic islands where species
were similar (to those on S.A.) yet had unique
traits
 Did not discover until much later that each
island supported unique species of plants and
animals
 Darwin had believed the “immutable” nature of
species before he had left England…
 Upon returning in 1836 he spent much time
analyzing his findings. His conclusions have
made him a most famous scientist
What did he observe?
 Darwin wondered why continents
separated by large distances would have
entirely different species occupying
similar niches
 What is a niche?
Niche
 The place where an organism lives and
the roles that an organism has in its
habitat.
Geographic Distribution
 His observations and analysis of
geographic distribution of organisms
provided a foundation for the later
scientific study of biogeography
Biogeography
 The careful
observation and
analysis of the
geographic
distribution of
organisms
 Single ancestry gave
rise to similar new
species in different
locations
Darwin’s birds…
 Of the 26 birds he found on the
Galapagos islands, 25 were different
species (ornithologist Gould). Primarily
finches and mockingbirds
 Gould suggested that a single ancestral
species transported from a nearby land
might give rise to a # of similar but
distinct new species (especially when
isolated)
Darwin’s birds…
 Darwin also observed
that remote islands were
populated by flying
organisms and land
animals such as lizards,
turtles (no mammals)
Why?
Darwin
 Committed his life to
analyzing his
discoveries
Homologous and
Analogous Features
 Darwin was also curious about
comparing species that were very
different in outward appearance
 Found that body parts of organisms with
entirely different functions were similar in
structure
 Can you think of any?
Homologous features
 Structures that share a common origin but
may serve different functions in modern
species
Homologous features
 Darwin wrote;
 “What can be more curious than that the
hand of a man, formed for grasping, that
of a mole for digging, the leg of a horse,
the paddle of the porpoise, and the wing
of the bat, should all be constructed on
the same pattern, and should include the
same bones, in the same relative
positions?”
Analogous Features
 Structures similar in function but not in origin
or anatomical structure
Conclusion…
 Organisms with homologous features
likely shared a more recent common
ancestor, while those with analogous
features did not.
Embryonic Development
 Homologous features can also appear
during embryonic development
 Such features serve no function as the
organisms grow
 Human tail
 Anteater teeth
Vestigial Features and
Anatomical Oddities
 Vestigial features are
rudimentary and nonfunctioning structures
that are homologous
to fully functioning
structures in closely
related species
 Dogs have a vestigial
toe (as do pigs)
Vestigial structures in humans
 BODY HAIR: Brows help keep sweat from the eyes, and male facial hair
may play a role in sexual selection, but apparently most of the hair left on
the human body serves no function.
 THIRTEENTH RIB: Our closest cousins, chimpanzees and gorillas, have
an extra set of ribs. Most of us have 12, but 8 percent of adults have the
extras.
 MALE UTERUS: A remnant of an undeveloped female reproductive organ
hangs off the male prostate gland.
 FEMALE VAS DEFERENS: What might become sperm ducts in males
become the epoophoron in females, a cluster of useless dead-end
tubules near the ovaries
 APPENDIX: This narrow, muscular tube attached to the large intestine
served as a special area to digest cellulose when the human diet
consisted more of plant matter than animal protein. It also produces some
white blood cells. Annually, more than 300,000 Americans have an
appendectomy.
 WISDOM TEETH: Early humans had to chew a lot of plants to get enough
calories to survive, making another row of molars helpful, but unless you
chew a lot of branches, these will eventually come out in a painful
procedure. Only about 5 percent of the population has a healthy set of
these third molars.
Anatomical Oddities
 Geese with webbed
feet who never enter
water (frigate bird)
 Whales with
hipbones
Artificial Selection
 Darwin knew there was some mechanism of
inheritance that was key to the evolutionary
process….but what was it?
 He reasoned that if humans could alter the
appearance and behaviour of species
through artificial selection (crops, dog
breeds), then the env’t could have a similar
selective effect on wild species
Artificial Selection
 If the Earth was as old as scientists were
predicting and if the fossil evidence
supported a comparable age for organic
life, there could be time for even small
changes in species to accumulate over
many thousands of generations
The Struggle for Survival
 Darwin was convinced of the evidence of
biogeography and comparative anatomy
which supported evolution
 He also supported the idea of artificial
selection…but how did nature chose
individuals with particular desirable
variables for reproduction?
Malthus
 Postulated that in nature both plants and
animals produce more offspring than are
able to survive
 Darwin realized that there must be
competition among individuals of the
same species to survive (most do not
survive to reproduce)
Practice questions
 Complete the “Try this activity” on p.527
 Complete Q 3, 5-7, 9, 10 on p.528
Theory of Evolution by
Natural Selection
 Wallace a young naturalist had arrived at
the same theory as Darwin for Evolution
(it had taken him 2 yrs vs. Darwin’s 20
yrs)
 They presented their findings in 1858
 Darwin knew it would be controversial
 He published his Origin of Species in
1859
Natural Selection
 The means of preserving
favourable genetic
variations and rejecting
injurious variations
 Individuals pass on inherent
variations to their offspring.
The ones with favourable
variations survive.
(selection)
 Survival is NOT random,but
mutation is.
 The process by which
favourable variations
become more common
The Theory of Evolution by Natural
Selection
Observation 1
Individuals w/in a species vary in many ways
Observation 2
Some of this variability can be inherited
Observation 3
Every generation produces more offspring than can survive
(pass on variations)
Observation 4
Pop. Of species tend to remain stable in size
Inference 1
Members of the same species compete with each other
for survival
Inference 2
Individuals with more favourable variations are more
likely to survive and pass them on. Survival is not
random
Inference 3
As these individuals contribute proportionately more
offspring to succeeding generations, the favourable
variations will become more common (This is natural
selection)
Survival of the Fittest
 Only those
organisms best
adapted to
existing
conditions are
able to survive
and reproduce.
NATURAL SELECTION
 At the opposite end scale, natural selection is
sometimes interpreted as a random process.
This is also a misconception. The genetic
variation that occurs in a population because of
mutation is random-but selection acts on that
variation in a very non-random way: genetic
variants that aid survival and reproduction are
much more likely to become common than
variants that don't. Natural selection is NOT
random!
Unanswered questions…
 For Natural Selection to result in the
formation of a new species….time was
needed…and lots of it!
 Not everyone agreed that the Earth was
many millions of years old.
 Also, the fossil record did not show
transitional forms of organisms
Unanswered questions…
 Today we have radiometric dating (giving us
absolute age) and have unearthed fossils that
show intermediate species of vertebrates
Unanswered questions…
 Over time, the role of environmental change
became more evident-peppered moth
Unanswered questions…
 But what about the mechanism for variation?
 The answer became clearer when Mendel
came onto the scene 6 years later.
 This paved the way for the revelation in
molecular genetics that mutation and
recombination provide the source for new
inheritable variations
Practice Questions
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


Complete the “Try This Activity” on p.532
Complete Questions 1, 5, 7 on p.533
Quiz-Tuesday, December 8th-Chp. 11
Unit Test-Wednesday, December 16th