Download The Darwinian Revolution

AP Environmental Science
Focus on Evolution
“Nothing in biology makes sense…
except in the light of evolution.”
Theodosius Dobzhansky (1973)
“Biology” during the 1800’s


Late 18th-early 19th c. was an
age of discovery and natural
history
Natural Theology
All plants & animals were
created “as is” ~ 6,000 to
10,000 years ago
William Paley---”a watch
demands a watchmaker --a design demands a
designer!”
Great Geological Debate
1810-1840
 Catastrophism
Cuvier, Buffon
All changes to
animals and
geology are due
to sudden
cataclysmic
events
 Uniformitarianism
Hutton & Lyell
The earth was
shaped by slow,
gradual
processes the we
see today.
Charles Darwin
(1809-1882)

Born February 12, 1809
in Shrewsbury, England
 Education
Entered the University of
Edinburgh at age 16 to
study medicine
Entered Cambridge
University’s Christ
College in 1828 to study
for the ministry
Darwin’s Parents
 Dr.
Robert Darwin
 Susannah
Wedgwood Darwin
Darwin’s Famous Grandfathers

Erasmus Darwin

Josiah Wedgwood
Wedgwood China
J.S. Henslow (1796-1861)
 Darwin’s
favorite
botany professor
 Recommends
Darwin to the
British Admiralty
to serve as ship’s
naturalist on the
H.M.S. Beagle
H.M.S. Beagle

Captain Robert
FitzRoy
 Mission was to map
the western coast of
South America for
the British Navy
 Darwin serves as
ship’s naturalist and
companion to the
captain.
Voyage of H.M.S. Beagle
(1831-1836)
Galapagos Islands
Galapagos Unique Animals
Return to England
H.M.S. Beagle by Conrad Martens


Publishes what came to be
known as the Voyage of
the Beagle
Begins notebook on
Transmutation of Species
Title page – 1905 edition
Settling Down


Marries his first cousin Emma Wedgwood on
January 29, 1839
Moves into an 18 acre estate in Down, England
Barnacles
Darwin’s Scientific Subjects
Establishes a Theory
of Atoll Formation
Keeping Quiet on Evolution

Despite working on
“transmutation” since
1837 Darwin publicly says
nothing.
Writes two private essays in
1842 & 1844.

Robert Chambers
publishes Vestiges of the
Natural History of Creation
in 1844.
Contains “evolutionary
ideas” but is severely
ridiculed.
Alfred Russel Wallace (1823-1913)

June 18, 1858
 Darwin receives a
manuscript from
Wallace, a young
naturalist working in the
Malay Archipelago.
On the Tendency of
Varieties to Depart
Indefinitely from the
Original Type
Joint Presentation


On July 1, 1858 Charles Lyell and
Joseph Hooker present both Darwin’s
1844 and Wallace’s manuscripts
before the Linnaean Society of
London.
Darwin does not attend due to his
son’s death from scarlet fever three
days before.
Publication of The Origin

Darwin finally
publishes his “big
book,” On the Origin of
Species by Means of
Natural Selection, or
the Preservation of
Favoured Races in the
Struggle for Life on
November 24, 1859.
 It’s 1250 copies sold
out on the first day.
Defending Darwin
Thomas Henry Huxley - “Darwin’s Bulldog”
Darwin’s
“Five Theories of Evolution”
 1)
Evolution as Such
 2) Common Descent
 3) Variation & Natural Selection
 4) “Population Thinking” and
Allopatric Speciation
 5) Gradualness
1) Evolution as Such
 Change
happens!
 This theory was not new with Darwin.
Others like Lamarck had said that change
happens over 50 years before!
However, the majority of scientists in 1859 did not
believe in evolutionary change.
 The
massive evidence that Darwin
presents was so overwhelming that
within a few years virtually every
biologist was convinced.
What we know now…
1
billion years of chemical change to form the
first cells, followed by about 3.7 billion years
of biological change.
Figure 4-2
Biological
Evolution
 This
has led to
the variety of
species we
find on the
earth today.
Figure 4-2
2) Common Descent




All organisms have descended from common
ancestors by a continuous process of “branching.”
Common descent explains so much about
comparative anatomy, embryology, biogeography,
systematics…and behavior.
Putting humans into this branching tree of common
descent takes humans away from their privileged
position…and causes many people to reject the idea.
What Darwin Doesn’t Do
Darwin stops short of publishing man’s place in this
evolutionary tree and he never speculates on the origins of
the first organisms
“I think…”
 Sketch
from
Darwin’s 1838
notebook on
transmutation
 First clue that
Darwin had
embraced the idea
of common descent
Common Descent Diagram
in The Origin of Species
Tetrapod Limb Homologies
Comparative Embryology
“Ontogeny recapitulates phylogeny”
3) Variation & Natural Selection

1) Individual variation in organisms within a
population is the norm not the exception.
 2) Populations reproduce at a geometric rate that is
faster than the environment can support.
Thomas Malthus, Essay on Population
3) Some organisms will survive…most will die.
 4) Which organisms will live and which will die?

Does each individual have an equal chance of survival?
Darwin says---NO!
Those individuals with the best adaptations will survive--Natural Selection!
Natural Selection and Adaptation: Leaving
More Offspring With Beneficial Traits
 Three
conditions are necessary for biological
evolution:
Genetic variability,
Traits must be heritable,
Trait must lead to differential reproduction.
 An
adaptive trait is any heritable trait that
enables an organism to survive through
natural selection and reproduce better under
prevailing environmental conditions.
Coevolution: A Biological Arms Race

Interacting species can engage in a back and forth
genetic contest in which each gains a temporary
genetic advantage over the other.
This often happens between predators and prey species.
Or results in symbioses
Hybridization and Gene Swapping:
other Ways to Exchange Genes
 New
species can arise through hybridization.
Occurs when individuals to two distinct species
crossbreed to produce a fertile offspring.
 Some
species (mostly microorganisms) can
exchange genes without sexual reproduction.
Horizontal gene transfer
Limits on Adaptation through
Natural Selection
A
population’s ability to adapt to new
environmental conditions through natural
selection is limited by its gene pool and how
fast it can reproduce.
Humans have a relatively slow generation time
(decades) and output (# of young) versus some
other species.
4)

“Population Thinking” &
Allopatric Speciation
Darwin recognizes that
it is populations that
change, not individuals.
Gives rise to “population
thinking”

Darwin realizes that
“varieties are no more
than incipient species.”
Geographic Isolation

Figure 4-10
Darwin realizes that when a population becomes split by
geographic barriers that these separate populations change
in their own unique ways---Geographic Isolation.
Allopatric Speciation
After a long period of time these changes become so great that the
individuals from the different populations can no longer reproduce
with one another---Reproductive Isolation
5) Gradualness
GEOLOGIC PROCESSES, CLIMATE
CHANGE, CATASTROPHES, AND
EVOLUTION
 The
movement of solid (tectonic) plates
making up the earth’s surface, volcanic
eruptions, and earthquakes can wipe out
existing species and help form new ones.
The locations of continents and oceanic basins
influence climate.
The movement of continents have allowed
species to move.
Extinction: Lights Out
 Extinction
occurs
when the population
cannot adapt to
changing
environmental
conditions.
The
golden toad of Costa Rica’s Monteverde cloud forest has
become extinct because of changes in climate.
Figure 4-11
Era
Period
Millions of
years ago
Cenozoic
Quaternary
Today
Tertiary
65
Bar width represents relative
number of living species
Extinction
Extinction
Mesozoic
Cretaceous
Jurassic
180
Extinction
Triassic
250
Extinction
345
Extinction
Permian
Paleozoic
Carboniferous
Devonian
Species and families
experiencing
mass extinction
Current extinction crisis caused
by human activities. Many species
are expected to become extinct
within the next 50–100 years.
Cretaceous: up to 80% of ruling
reptiles (dinosaurs); many marine
species including many
foraminiferans and mollusks.
Triassic: 35% of animal families,
including many reptiles and marine
mollusks.
Permian: 90% of animal families,
including over 95% of marine species;
many trees, amphibians, most
bryozoans and brachiopods, all
trilobites.
Devonian: 30% of animal families,
including agnathan and placoderm
fishes and many trilobites.
Silurian
Ordovician
Cambrian
500
Extinction
Ordovician: 50% of animal
families, including many
trilobites.
Fig. 4-12, p. 93
Effects of Humans on Biodiversity
 The
scientific consensus is that human
activities are decreasing the earth’s
biodiversity.
Figure 4-13
Darwin’s Later Life



Becomes even more
reclusive in later life.
Publishes extensively,
including The Descent of
Man (1871) and
Expressions of the
Emotions in Man and
Animals (1872).
Dies of a heart attack on
April 19, 1882 and is
buried in Westminster
Abbey near Sir Isaac
Newton.
Darwin’s Legacy

Darwin moved intellectual
thought from a paradigm of
untestable wonder at special
creation to an ability to
examine the workings of the
natural world, however
ultimately formed, in terms of
natural mechanisms and
historical patterns…he in effect
creates the “modern science of
biology.”
Work Cited
""gradualism vs. punctuated equilibrium"." 18 October 2009 <lhs2.lps.org/.../U6Evolution/gradualism.gif>.
Biello, David. "Gene Swapping Helps Bacteria." Scientific American 21 November 2005.
"Cool Bug #9 Acacia ants." 2 October 2007. Bioblog: Music and Biology in the News . 18 October 2009
<http://bioblog.biotunes.org/bioblog/2007/10/02/cool-bug-9-acacia-ants/>.
"Hand in hand saving the coral reef." 13 August 2008. 18 October 2009 <coralreeftoday.com/wpadmin/acropodia/1b.jpg>.
Martens, Conrad. ""HMS Beagle"." The Voyage of the Beagle by Charles Darwin. 18 October 2009 <www.sacredtexts.com/aor/darwin/beagle/beagle.jpg>.
Siegel, Robert David. ""Darwin's Finches"." 31 October 2008. Darwin Safari 2007. 18 October 2009
<http://stanford.edu/~siegelr/england/darwinsafari2007.html>.
Speciation. 30 March 2009. 18 October 2009
<http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html>.
Wyhe, John van. The Complete Works of Charles Darwin online. 6 October 2009. 18 October 2009 <darwinonline.org.uk/life14.html>.