Darwin, Natural Selection
and Evolution
Tuesday, January 15, 2013
Science IS
Search for Understanding
Limited to Natural World
Observable
Testable/Measurable
Repeatable
Verifiable
Experimentation
Modifiable /Open to Change
Biased
Disprovable
Objective
Strong theories ...
Tuesday, January 15, 2013
Science IS NOT
Based on Proof
Based on Belief/Faith
Based on Authority
Decided by Debate
A search for truth
Certain
Fair
Rigid
Able to Solve All Problems
A collection of facts
Democratic
Absolute
Species
• Group of individuals that interbreed
extensively in nature
Tuesday, January 15, 2013
Fixity of Species
Species do not
change
Ideal structure and
function.
Linnaeus
Mid-1700’s
Tuesday, January 15, 2013
Fossil Record
Different organisms in different rock
layers.
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Catastrophism
Late1700’s
Fixity of species
After a catastrophe,
new organisms move
into an area to replace
those killed.
Cuvier
Tuesday, January 15, 2013
Evolution
Species change over time
Lamarck
Inheritance of acquired
characteristics
Tuesday, January 15, 2013
Charles Darwin
• 1809-1882
• England
• Grew up on estate, “The Mount”,
in rural England
• Wealthy family
• Spent much time outdoors, liked
to collect beetles and other items
of nature
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Education
• first attended medical school in
Edinburgh
• found anatomy boring, didn’t like to
watch surgery which was performed
without anesthesia.
• Father sent him to Cambridge
University to become a clergymen
• Met and studied with prominent
geologists and other naturalists
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H.M.S. Beagle
• Given job offer as Naturalist
• Ship was to survey coastline of S.
America
• Naturalist would be a social
companion for Captain Fitzroy
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H.M.S. Beagle 1831-1836
• See figure 15.1 for map of voyage
• Kept detailed notes with drawings of
his findings
• Send stuffed and pickled animals that
he collected to London
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Some Observations
• Saw effects of earthquake on land
• Saw fossils of sea creatures on
mountains
• Saw fossils of animals that differed
from modern.
• Started thinking about changes
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Galapagos Map
• Islands west of S. America
• Many unique species - iguanas, giant
tortoises, Darwin’s finches
• Different species on different islands
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Giant Tortoise
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Returns to England
• London-studying collections, writing
• Marries Emma Wedgewood
• Had 10 children, 7 survived to
adulthood
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Down House
Tuesday, January 15, 2013
The Sandwalk
Tuesday, January 15, 2013
Publications
• Voyage of the Beagle
• Zoology of the Beagle
• Formation of Coral Reefs
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Also Studied
• Barnacles
• Pigeons - variations, breeding
Tuesday, January 15, 2013
1838 Article by Malthus
•Human population
grows exponentially1,2,4,8,16,32…
•Food supply grows
arithmetically 1,2,3,4,5,6,….
•human population >food
supply ➔ starvation
Tuesday, January 15, 2013
Darwin’s Ideas
• Variety
• Overproduction
• Limited Resources
Tuesday, January 15, 2013
Variety
•Individuals vary
•Variations inherited
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Overproduction
Individuals produce more offspring
then needed for replacement.
There is no exception to the rule that every
organic being naturally increase at so high a
rate that if not destroyed, the earth would soon
be covered by the progeny of a single pair ....
The Elephant is reckoned to be the slowest
breeder of all known animals, and I have taken
some pains to estimate its probable minimum
rate of natural increase: it will be under the
mark to assume that it breeds when thirty years
old, and goes on breeding till ninety years old,
bringing forth three pairs of young in this
interval; if this be so, at the end of the fifth
century there would be alive fifteen million
elephants, descended from the first pair
- (Darwin, 1859 p.64)
Tuesday, January 15, 2013
Limited Resources
• Limited food, space, nutrients, etc.
• “struggle for existence”
Tuesday, January 15, 2013
Theory of Natural Selection
Those individuals with the traits
most suitable to their environment
are more likely to survive and
reproduce and pass those traits
on to the next generation.
Tuesday, January 15, 2013
Alfred Wallace
• naturalist
• voyage
• same idea
• 1858 Darwin
presented
Wallace’s and his
own paper to
Natural History
Society
Tuesday, January 15, 2013
Origin of
Species
1859
On the Origin of
Species by Means of
Natural Selection, or
the Preservation of
Favoured Races in
the Struggle for Life
Tuesday, January 15, 2013
Darwin’s Work After the Origin
•On the Various Contrivances by which Orchids are
Fertilised by Insects 1862
•On the Movement and Habits of Climbing Plants 1865
•The Variation of Animals and Plants under Domestication
1868
•The Descent of Man 1871
•The Expression of the Emotions in Man and Animals 1872
•Insectivorous Plants 1875
•The Effects of Cross Fertilisation in the Vegetable
Kingdom 1876
•The Different Forms of Flowers on Plants of the Same
Species 1877
•The Power of Movement of Plants 1880
•The Formation of Vegetable Mould through the Action of
Worms, with Observations on Their Habits 1881
Tuesday, January 15, 2013
Evidence for Evolution:
Fossils
see textbook figure 15.4
Tuesday, January 15, 2013
Evidence for
Evolution:
Biogeographical
see textbook figure 15.6, 15.14
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Evidence for Evolution:
Anatomical
Homologous
Structures
see textbook figure 15.15
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Evidence for Evolution:
Developmental
see textbook figure 15.16
Tuesday, January 15, 2013
Evidence for Evolution:
Biochemical
(DNA, Protein)
GACCGCAGATTACTAGGCATTGA
GACCGCAGATAACTAGGCATTGA
GACCGCAGATTACCTAACAATGA
Tuesday, January 15, 2013
Science IS
Search for Understanding
Limited to Natural World
Observable
Testable/Measurable
Repeatable
Verifiable
Experimentation
Modifiable /Open to Change
Biased
Disprovable
Objective
Strong theories ...
Tuesday, January 15, 2013
Science IS NOT
Based on Proof
Based on Belief/Faith
Based on Authority
Decided by Debate
A search for truth
Certain
Fair
Rigid
Able to Solve All Problems
A collection of facts
Democratic
Absolute