Transcript Darwin`s Theory of Evolution

Darwin’s Theory of Evolution
Historical Context (early 1800s)
• Aristotle, Judeo-Christian culture,
book of Genesis…
–The earth is only 6000 years old
–All living species are “static” (put
here ‘as is’)
Pre-Darwin
• Lamarck (early 1800s)
• Buffon
• Inheritance of Acquired
Characteristics
Inheritance of Acquired Characteristics
• Why do giraffes have long
necks?
Because they stretch them
during their lifetime, then
their offspring have long
necks
The theory of “Use & Disuse”
Who was Darwin?
• Surgeon in training
• Minister
• Recruited by captain of HMS
Beagle
• Set sail in 1831 at the age of 22
Not just the Galapagos…
Not just finches…
Darwin made 3 main observations…
• 1. Members of a population vary in their
physical traits.
• 2. Many physical traits are inherited from
parent to offspring.
• 3. All species are capable of reproducing more
offspring than the environment can support.
And drew 2 conclusions:
• 1. Individuals who inherit traits that give
them a better chance of surviving tend to
leave more offspring than other individuals
• 2. This unequal reproduction of offspring
causes ‘favorable’ traits to accumulate in a
population over generations.
(“survival of the fittest; struggle for existence)
• Darwin called these
conclusions “Descent with
Modification”
• We call it “Natural Selection”
Important!!
• What is ‘favorable’ in one
environment may not be in another
environment.
• The environment determines what is
favorable and unfavorable.
4 Take-home Points about Natural
Selection
• 1. Individuals DO NOT evolve.
Evolution refers to generation-togeneration changes in a population.
• 2. Natural selection can only amplify
or diminish traits that are
inheritable.
4 Take-home Points about Natural
Selection
• 3. Evolution is NOT goal-directed.
No notion of “perfect species.”
Environmental factors vary in place &
time…’favorable’ traits will also vary.
4 Take-home Points about Natural
Selection
• 4. Evolution is about compromise.
It’s all about timing…
• Darwin formulated his idea of
natural selection in the early 1840s.
• He did not publish them until 1858.
Alfred Wallace
What Data did Darwin collect?
(i.e., what is the evidence for
evolution?)
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Fossil Record
Biogeography
Comparative Embryology
Comparative Anatomy
Molecular Biology
1. The Fossil Record
B Ammonite casts
A Skull of Homo erectus
D Fossilized organic
matter of a leaf
C Dinosaur tracks
E Insect in amber
F “Ice Man”
Pakicetus (terrestrial)
Rhodocetus (predominantly aquatic)
Pelvis and Dorudon (fully aquatic)
hind limb
Pelvis and
hind limb
Balaena (recent whale ancestor)
2. Biogeography
North
America
Asia
Europe
Africa
South
America
Australia
= Living lungfishes
= Fossilized lungfishes
Cenozoic
Present
Eurasia
Africa
India
South
America Madagascar
65.5
135
251
Mesozoic
Laurasia
Paleozoic
Millions of years ago
Antarctica
2. Biogeography
All the species of
finches on the
Galapagos Islands
look like finches
native to the West
Coast of South
America—but not
exactly the same
“Adaptive Radiation”
3. Comparative Embryology
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Human embryo
4. Comparative Anatomy
Homologous Structures = Divergent Evolution
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
4. Comparative Anatomy
Pelvis and
hind limb
Dorudon (fully aquatic)
Pelvis and
hind limb
Balaena (recent whale ancestor)
Vestigial Structures: What are left of
homologous structures
Dorudon
Balaena
Modern-Day Humpback Whale
Homologous
Analogous Structures = Convergent Evolution
Analogous
5. Molecular Biology
Comparison of DNA sequences from different
organisms is very helpful in determining
relationships.
Molecular analysis is best done together with
other types of analyses.
http://evolution.berkeley.edu/evosite/evo101/IIE1cMolecularclocks.sht
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http://www.geneticorigins.org/mito/media2.html