Transcript Darwin`s Epic Journey

Natural Selection
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How does something like THIS come about?!!
Darwin’s Epic Journey
“You care for nothing but shooting, dogs, and rat-catching,
and you will be a disgrace to yourself and all your family.”
Observations Aboard the Beagle
Rhea – South America
Ostrich - Africa
Emu - Australia
Species Vary Locally
Species Vary Over Time
Armadillo
0.5 m
3m
Glyptodonts
Putting the Pieces of the Puzzle Together
The Galapagos Islands
Darwin was amazed that any wildlife had reached such a remote place,
and suspected that the ALL the birds, plants and animals had arrived,
during the distant past, from the mainland
Ideas That Shaped Darwin’s Thinking
An Ancient, Changing Earth
Geologists James Hutton and Charles Lyell concluded that Earth
is ancient and still changing.
Hutton and Geological Change
Lyell’s Principles of Geology
Lamarck’s Evolutionary Hypotheses
Jean-Baptiste Lamarck was
one of the first naturalists to
argue strongly that species
are not fixed.
Lamarck’s Theory
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Lamarck believed organisms could adapt within their lifetime
to fit their environment, and then pass on their adaptations
(ex:fiddler crab)
• Lamark did not know
about mendelian genetics
and the rules of
inheritance
• His idea that animals are
adapted to their environment
did influence Darwin’s ideas on
adaptations
Population Growth
Thomas Malthus reasoned
that if the human population
grew unchecked, there
wouldn’t be enough living
space and food for
everyone.
Artificial Selection
Darwin’s Dangerous Idea
In the same way that dog-breeders and farmers altered the
appearance of animals by careful breeding (Artificial
Selection), Darwin proposed that there might also a NATURAL
mechanism which accomplished the same thing in nature…
Darwin Presents His Case
POPULATION GROWTH
Darwin’s Observations:
1. organisms produce so many offspring that their population
size would increase exponentially if all individuals that are
born reproduce successfully
2. populations tend to remain stable in size, except for seasonal
fluctuations.
3. environmental resources are limited.
Darwin’s Inference:
Production of more individuals than the
environment can support leads to a struggle
for existence, with only a fraction of offspring
surviving.
AHA!!!... SURVIVAL OF THE FITTEST
The Origin of Species
• Darwin knew his ideas were controversial
• 1858, after reading about Alfred Russell Wallace’s research in
the Malay Archipelago, Darwin decided to “go public” with his
dangerous idea
• In 1859, Darwin published his ideas in a book called:
“On the Origin of Species by means of Natural Selection, or the
Preservation of Favoured Races in the Struggle for Life”
“ORIGIN OF SPECIES”
In 1859, after 25 years of work, Darwin reluctantly publishes his
work to much ridicule.
Theory of Natural Selection
Darwin proposes that the diversity of life has
evolved because the most fit organism in an
environment survives and is able to pass on these
fitness traits.
Adaptations are
inherited
characteristics
which allow
organisms to
compete for
resources and
mates in their
particular
ecosystem.
Pinta Island
Hood Island
Intermediate shell
Saddle-backed shell
Isabela Island
Dome-shaped shell
Darwin Publishes
The Struggle for Existence
Variation and Adaptation
Scarlet king snake
Eastern coral snake
Adaptations –
– Anatomical/structural (flippers on a sea turtle)
– Physiological (CAM photosynthesis)
– Behavioral (live/hunt in groups)
Survival of the Fittest
Natural Selection
No Such Thing as Perfect
Common Ancestry