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II. Darwin

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II. Darwin s Contributions A. Overview B. Argument: Evidence for Evolution by Common Descent C. Mechanism: Natural Selection D. Dilemmas: Long before having ... – PowerPoint PPT presentation

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Title: II. Darwin


1
II. Darwins Contributions A. Overview B.
Argument Evidence for Evolution by Common
Descent C. Mechanism Natural Selection D.
Dilemmas
Long before having arrived at this part of my
work, a crowd of difficulties will have occurred
to the reader. Some of them are so grave that to
this day I can never reflect on them without
being staggered but, to the best of my judgment,
the greater number are only apparent, and those
that are real are not, I think, fatal to my
theory. Charles Darwin, The Origin of Species
(1859).
2
II. Darwins Contributions A. Overview B.
Argument Evidence for Evolution by Common
Descent C. Mechanism Natural Selection D.
Dilemmas 1. The evolution of complex
structures addressing Paley
Can we believe that natural selection could
produce, on the one hand, organs of trifling
importance, such as the tail of a giraffe, which
serves as a fly-flapper, and, on the other hand,
organs of such wonderful structure, as the eye,
of which we hardly as yet fully understand the
inimitable perfection? Charles Darwin, The
Origin of Species (1859).
3
II. Darwins Contributions A. Overview B.
Argument Evidence for Evolution by Common
Descent C. Mechanism Natural Selection D.
Dilemmas 1. The evolution of complex
structures
To suppose that the eye, with all its inimitable
contrivances for adjusting the focus to different
distances, for admitting different amounts of
light, and for the correction of spherical and
chromatic aberration, could have been formed by
natural selection, seems, I freely confess,
absurd in the highest possible degree. Yet reason
tells me, that if numerous gradations from a
perfect and complex eye to one very imperfect and
simple, each grade being useful to its possessor,
can be shown to exist if further, the eye does
vary ever so slightly, and the variations be
inherited, which is certainly the case and if
any variation or modification in the organ be
ever useful to an animal under changing
conditions of life, then the difficulty of
believing that a perfect and complex eye could be
formed by natural selection, though insuperable
by our imagination, can hardly be considered
real. Charles Darwin, The Origin of Species
(1859).
4
Dawkins Evolution of the Camera Eye
5
D. Dilemmas 1. The evolution of complex
structures
6
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates?
why, if species have descended from other
species by insensibly fine gradations, do we not
everywhere see innumerable transitional forms?
Why is not all nature in confusion instead of the
species being, as we see them, well defined? as
by this theory innumerable transitional forms
must have existed, why do we not find them
embedded in countless numbers in the crust of the
earth? Charles Darwin, The Origin of Species
(1859)
7
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates?
?
X
X
X
?
X
X
X
8
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates?
As natural selection acts solely by the
preservation of profitable modifications, each
new form will tend in a fully-stocked country to
take the place of, and finally to exterminate,
its own less improved parent or other
less-favoured forms with which it comes into
competition. Thus extinction and natural
selection will, as we have seen, go hand in hand.
Hence, if we look at each species as descended
from some other unknown form, both the parent and
all the transitional varieties will generally
have been exterminated by the very process of
formation and perfection of the new form. ,The
Origin of Species (Darwin 1859)
9
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates?
X
Better adapted descendant outcompetes ancestral
type
X
10
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates?
X
X
Better adapted descendant outcompetes ancestral
type
X
X
11
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates?
X
X
X
Better adapted descendant outcompetes ancestral
type
X
X
X
12
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates?
?
X
X
X
I believe the answer mainly lies in the record
being incomparably less perfect than is generally
supposed - Charles Darwin, The Origin of
Species (1859)
X
X
X
13
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates?
1861 Archaeopteryx lithographica
and still more recently, that strange bird, the
Archeopteryx, with a long lizardlike tail,
bearing a pair of feathers on each joint, and
with its wings furnished with two free claws, has
been discovered in the oolitic slates of
Solenhofen. Hardly any recent discovery shows
more forcibly than this, how little we as yet
know of the former inhabitants of the world.
Charles Darwin, The Origin of Species, 6th ed.
(1876)
14
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates? 3. What is the source of
heritable variation?
15
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates? 3. What is the source of
heritable variation? "These laws, taken in the
largest sense, being Growth with Reproduction
Inheritance which is almost implied by
reproduction Variability from the indirect and
direct action of the external conditions of life,
and from use and disuse a Ratio of Increase so
high as to lead to a Struggle for Life, and as a
consequence to Natural Selection". - The Origin
of Species (Darwin 1859). - Inheritance of
acquired characters (wrong) - Use and disuse
(sort of, but not as he envisioned it) -
Blending heredity and the action of selection
should reduce variation in a population over
time. - gemmules and grafting experiments.
16
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates? 3. What is the source of
heritable variation? 4. How do instincts
evolve? - if there is heritable variation in
behavior, then selection can act on that, also
17
D. Dilemmas 1. The evolution of complex
structures 2. Where are modern and fossil
intermediates? 3. What is the source of
heritable variation? 4. How do instincts
evolve? 5. How can sterility, and the
evolution of entire sterile castes (like in
social insects) evolve? - Sterile organisms
dont reproduce how can they be favored by
selection? Some form of group selection groups
with steriles do bet and their reproductives
outperform the combined reproductive success of
sexual competitors.
18
II. Darwins Contributions A. Overview B.
Argument Evidence for Evolution by Common
Descent C. Mechanism Natural Selection D.
Dilemmas E. Darwins Model of Evolution
19
II. Darwins Contributions A. Overview B.
Argument Evidence for Evolution by Common
Descent C. Mechanism Natural Selection D.
Dilemmas E. Darwins Model of
Evolution Sources of Variation Agents Causing
Evolution
?
Natural Selection
V A R I A T I O N
20
III. Post-Darwinian Developments A. Physics 1.
The Age of the Earth a. 1862 - William
Thompson - "Lord Kelvin - Earth was
15-20mya. b. 1896 - Henri Becquerel -
discovers emission of Uranium c. 1903 -
Pierre and Marie Curie - discover emission from
new element - Radium d. 1904 - Ernst
Rutherford - "The discovery of the radio-active
elements, which in their disintegration liberate
enormous amounts of energy, thus increases the
possible limit of the duration of life on this
planet, and allows the time claimed by the
geologist and biologist for the process of
evolution."
21
III. Post-Darwinian Developments A. Physics 1.
The Age of the Earth 2. Radioactive Decay and
Geological Clocks - measure amt of parent and
daughter isotopes total initial parental -
with the measureable1/2 life, determine time
needed to decay this fraction - K40-Ar40 suppose
1/2 of total is Ar40 1.3by (Now, you might
say "be real"! How can we measure something that
is this slow?) Well, 40 grams of Potassium (K)
contains 6.0 x 1023 atoms (Avogadro's number,
remember that little chemistry tid-bit?). So,
For 1/2 of them to change, that would be 3.0 x
1023 atoms in 1.3 billion years (1.3 x 109) So,
divide 3.0 x 1023 by 1.3 x 109 2.3 X 1014
atoms/year. Then, divide 2.3 x 1014 by 365 (3.65
x 102) days per year 0.62 x 1012 atoms per day
( shift decimal 6.2 x 1011) Then, divide 6.2 x
1011 by 246060 86,400 seconds/day ( 8.64 x
104) 0.7 x 107 atoms per second 0.7 x 107 7
x 106 7 million atoms changing from Potassium
to Argon every second!!!
22
III. Post-Darwinian Developments A. Physics B.
Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian transition
23
D. Devonian (417-354 mya) - Placoderms -
Sharks - Lobe-finned Fishes
24
III. Post-Darwinian Developments A. Physics B.
Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian transition

25
Eusthenopteron

26
Tiktaalik roseae

27
Acanthostega gunnari

28
Ichthyostega sp.

29
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds
30
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds
31
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds
Epidipteryx 165 mya
32
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds
Microraptor 120 mya
33
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds
Anchiornis 160mya
34
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds
Sinosauropteryx 120mya
35
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds
Tianyulong 200 mya
36
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37
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds 3. The
evolution of mammals
38
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39
B. Paleontology and Transitional Fossils 1.
Ichthyostega and the fish-amphibian
transition 2. The evolution of birds 3. The
evolution of mammals 4. The evolution of
humans
40
4. The evolution of humans
Australopithecines Australopithecus afarensis
41
4. The evolution of humans
Teeth
42
Legs
4. The evolution of humans
43
4. The evolution of humans
Skulls
44
4. The evolution of humans
45
III. Post-Darwinian Developments A. Physics B.
Paleontology and Transitional Fossils C. Geology
46
III. Post-Darwinian Developments A. Physics B.
Paleontology and Transitional Fossils C.
Geology Continental Drift - 1915 - Alfred
Wegener
47
- Not accepted until the 1960s and 1970s, when
sea floor spreading was observed, sonar was used
to map the ocean, and paleomagnetism demonstrated
where continents had been in the past relative to
magnetic north.
48
Explained disjunct distributions as a consequence
of vicariance
49
III. Post-Darwinian Developments A. Physics B.
Paleontology and Transitional Fossils C.
Geology D. Genetics and Population Genetics 1.
Heredity and Variation Hereditary units are
particulate, and Chromosomes assort
independently during gamete formation. Sexually
reproducing species can produce an extraordinary
amount of genetic variation in their offspring
as a consequence of passing on different
combinations of chromosomes and genes.
A single pair of humans can produce any of 246
(70 trillion) combinations of chromosomes in
their offspring.
50
D. Genetics and Population Genetics 1. Heredity
and Variation 2. Genetic Tests/Analyses of
Phylogeny - gross chromosomal patterns
51
D. Genetics and Population Genetics 1. Heredity
and Variation 2. Genetic Tests/Analyses of
Phylogeny - gross chromosomal patterns -
sequence analyses
52
D. Genetics and Population Genetics 1. Heredity
and Variation 2. Genetic Tests/Analyses of
Phylogeny 3. Population Genetics -
demonstrated that selection and drift were the
major agents of evolutionary change.
53
D. Genetics and Population Genetics 1. Heredity
and Variation 2. Genetic Tests/Analyses of
Phylogeny 3. Population Genetics 4. The Modern
Synthesis
Sources of Variation Agents of
Change Mutation N.S. Recombination Drift
- crossing over Migration - independent
assortment Mutation Non-random Mating
VARIATION
54
D. Genetics and Population Genetics 1. Heredity
and Variation 2. Genetic Tests/Analyses of
Phylogeny 3. Population Genetics 4. The Modern
Synthesis 5. Beyond the Synthesis -
Peripatric Speciation
55
D. Genetics and Population Genetics 1. Heredity
and Variation 2. Genetic Tests/Analyses of
Phylogeny 3. Population Genetics 4. The Modern
Synthesis 5. Beyond the Synthesis -
Peripatric Speciation - Punctuated
Equilibrium
56
- Punctuated Equilibrium
1. Consider a large, well-adapted population
VARIATION
TIME
57
- Punctuated Equilibrium
1. Consider a large, well-adapted
population Effects of Selection and Drift are
small - little change over time
VARIATION
TIME
58
- Punctuated Equilibrium
2. There are always small sub-populations
"budding off" along the periphery of a species
range...
VARIATION
TIME
59
- Punctuated Equilibrium
2. Most will go extinct, but some may survive...
VARIATION
X
X
X
TIME
60
- Punctuated Equilibrium
2. These surviving populations will initially be
small, and in a new environment...so the effects
of Selection and Drift should be strong...
VARIATION
X
X
X
TIME
61
- Punctuated Equilibrium
3. These populations will change rapidly in
response...
VARIATION
X
X
X
TIME
62
- Punctuated Equilibrium
3. These populations will change rapidly in
response... and as they adapt (in response to
selection), their populations should increase in
size (because of increasing reproductive success,
by definition).
VARIATION
X
X
X
TIME
63
- Punctuated Equilibrium
3. As population increases in size, effects of
drift decline... and as a population becomes
better adapted, the effects of selection
decline... so the rate of evolutionary change
declines...
VARIATION
X
X
X
TIME
64
- Punctuated Equilibrium
4. And we have large, well-adapted populations
that will remain static as long as the
environment is stable...
VARIATION
X
X
X
TIME
65
- Punctuated Equilibrium
5. Since small, short-lived populations are less
likely to leave a fossil, the fossil record can
appear 'discontinuous' or 'imperfect'
VARIATION
X
X
X
TIME
66
- Punctuated Equilibrium
5. Large pop's may leave a fossil....
VARIATION
X
X
X
TIME
67
- Punctuated Equilibrium
5. Small, short-lived populations probably
won't...
VARIATION
X
X
X
TIME
68
- Punctuated Equilibrium
6. So, the discontinuity in the fossil record is
an expected result of our modern understanding of
how evolution and speciation occur...
VARIATION
X
X
X
TIME
69
- Punctuated Equilibrium
6. both in time (as we see), and in SPACE (as
changing populations are probably NOT in same
place as ancestral species).
VARIATION
X
X
X
TIME
70
D. Genetics and Population Genetics 1. Heredity
and Variation 2. Genetic Tests/Analyses of
Phylogeny 3. Population Genetics 4. The Modern
Synthesis 5. Beyond the Synthesis -
Peripatric Speciation - Punctuated
Equilibrium - Evo-Devo
71
- Evo-Devo the influence of developmental
programs
1. Core Processes - Basic biological processes
are CONSERVED, and the enzymes that perform them
are CONSERVED - Many enzymes are more than 50
similar in AA sequence in E. coli and H. sapiens,
though separated by 2 billion years of
divergence. - Of 548 metabolic enzymes in E.
coli, 50 are present in ALL LIFE, and only 13
are unique to bacteria.
72
- Evo-Devo the influence of developmental
programs
1. Core Processes - Basic biological processes
are CONSERVED, and the enzymes that perform them
are CONSERVED - Many enzymes are more than 50
similar in AA sequence in E. coli and H. sapiens,
though separated by 2 billion years of
divergence. - Of 548 metabolic enzymes in E.
coli, 50 are present in ALL LIFE, and only 13
are unique to bacteria. - So the variation and
diversity of life is NOT due to changes in
metabolic or structural genes... we are all built
out of the same stuff, that works the same way at
a cellular level.
73
- Evo-Devo the influence of developmental
programs
- Variation is largely due to HOW these
processes are REGULATED... 300 cell types in
humans, all descended from the zygote all
genetically the same. - Best (and most
fundamental) examples are HOX genes. These are
'homeotic genes' that produce a variety of
transcription factors. The production and
localization of these transcription factors are
CRITICAL in determining the developmental
compartments' of bilaterally symmetrical
animals.
74
- Evo-Devo the influence of developmental
programs
- Effects can be profound
- 'Master Switches' that initiate downstream
cascades that can be very different... like
compound or vertebrate eyes.
75
D. Genetics and Population Genetics 1. Heredity
and Variation 2. Genetic Tests/Analyses of
Phylogeny 3. Population Genetics 4. The Modern
Synthesis 5. Beyond the Synthesis -
Peripatric Speciation - Punctuated
Equilibrium - Evo-Devo
Sources of Variation
Agents of Change
Selection Drift Mutation Migration Non-Random
Mating
Mutation Recombination
PHYSIOLOGY DEVELOPMENT
VARIATION
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