Download Evolutionary Theory Evolution not a new idea in Darwin`s age

Evolutionary Theory
Theory = set of well-supported, interrelated hypotheses, explaining a
number of related natural phenomena
e.g.
– Gravitational theory
– Cell theory
– Evolutionary theory
Evolution not a new idea in
Darwin’s age
• Related indigenous concepts:
– transformation: animal human
– close kinship between animals, plants and
humans
– awareness of different “ages” or “worlds” and
“progression” throughout time in various
cultures
• Anaximander ~ 550 B.C. (Greek philosopher):
“humans descend from fishes”
• Erasmus Darwin, J-B Lamarck a.o. 18th century
(British naturalists): “life evolves as
environments change”
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• Charles Darwin 1859:
On the Origin of Species by Means of
Natural Selection
(also: Alfred Wallace)
– Descend with modification (=evolution)
– New: Natural selection
(=mechanism for evolution)
• C. Darwin’s ideas influenced by his
experience and observations…
England
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
PACIFIC
OCEAN
Galápagos
Islands
HMS Beagle in port
SOUTH
AMERICA
AUSTRALIA
Andes
Darwin in 1840,
after his return
AFRICA
Cape of
Good Hope
Tasmania
Cape Horn
New
Zealand
Tierra del Fuego
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…as well as by ideas of other scientists
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Mendel (inheritance)
American Revolution
French Revolution
Wallace (evolution, natural selection)
U.S. Civil War
1800
1750
1795
1850
Hutton proposes his theory of gradualism.
1900
1798 Malthus publishes “Essay on the Principle of Population.”
1809
S&T
Lamarck publishes his theory of evolution.
Lyell publishes Principles of Geology.
1830
Darwin travels around the world on HMS Beagle.
1831–1836
1837
Darwin begins his notebooks on the origin of species.
1844
Darwin writes his essay on the origin of species.
1858
Wallace sends his theory to Darwin.
The Origin of Species is published.
1859
1865
Mendel publishes inheritance papers.
The historical context of Darwin’s life and ideas
Logic of Evolutionary Theory:
•
•
•
•
Observation 1: individual variation (heritable)
Observation 2: over-reproduction & competition
Inference 1: unequal reproductive success
Inference 2: favored traits increase in population
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(a) Cactus eater. The long,
sharp beak of the cactus
ground finch (Geospiza
scandens) helps it tear
and eat cactus flowers
and pulp.
(c) Seed eater. The large ground
finch (Geospiza magnirostris)
has a large beak adapted for
cracking seeds that fall from
plants to the ground.
(b) Insect eater. The green warbler
finch (Certhidea olivacea) uses its
narrow, pointed beak to grasp insects.
Beak variation in Galápagos finches
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
Camouflage as an example of evolutionary adaptation
4
Evidence of Evolution
1. Natural Selection “in action”
2. Homologies: structures of common
origin (anatomical & molecular)
indicative of divergent evolution
3. Biogeography: geographic
distribution of species
4. Fossil Record
1. Natural Selection “in action”
a. Differential predation on guppy populations:
EXPERIMENT
John Endler transplanted guppies from pools with pike-cichlids (active guppy
predators) to pools with killifish (less active predators), and measured number and area of brightcolored spots on male guppies over 15 generations (22 months).
Pools with killifish,
but not guppies prior
to transplant
Experimental
transplant of
guppies
Predator: Killifish; preys
mainly on small, juvenile
guppies which do not
express color gene
Guppies:
Adult males have brighter
colors
Predator:
Pike-cichlid; preys mainly on larger, adult guppies
Guppies: Adult males are more drab in color
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b. Evolution of drug-resistant microbes:
e.g. HIV
Patient
No. 1
Patient No. 2
Patient No. 3
Weeks
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e.g. Staphylococcus aureus
c. “Artificial” Selection (breeding)
Terminal
bud
Cabbage
Lateral
buds
Brussels sprouts
Flower
cluster
Leaves
Cauliflower
Kale
Stem
Flower
and
stems
Broccoli
Wild mustard
Kohlrabi
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Humans select desirable traits in crops,
farm animals, pets (e.g. dogs)…
resulting in very different new forms
over time, e.g. Hopi people breeding
different strains of corn adapted to
different environments
d. Response to change in food source
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2. Homologies
• Anatomical Homologies:
a. Adult homologous structures, e.g. fore limbs
Human
Cat
Whale
Bat
b. Vestigial structures
= remnants of structures that served
important functions in the organism’s
ancestors
e.g. vestiges of pelvis & leg bones in some
snakes and whales
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c. Embryonic homologous structures
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Human embryo
Figure 22.15 Anatomical similarities in vertebrate embryos
• Molecular Homologies:
d. DNA & universal genetic code
Second mRNA base
C
UUU
UUC
U
UUA
First mRNA base (5′ end)
UUG
C
Phe
Leu
UCC
UCA
UAC
Ser
CCU
CAU
CAC
AUC
Leu CCA Pro
CAA
CCG
lle
CAG
ACU
AAU
ACC
AAC
AUA
ACA
AUGMet or
start
ACG
Thr
AAA
AAG
GUU
GCU
GAU
GUC
GCC
GAC
GUA
GUG
Val
GCA
GCG
Tyr
UGC
U
Cys
C
S&T
UAG Stop UGG Trp G
UCG
CCC
CUA
G
UGU
UAA Stop UGA Stop A
CUU
AUU
G
UAU
CUC
CUG
A
A
UCU
Ala
GAA
GAG
His
Gln
Asn
Lys
U
CGU
CGC
CGA
Arg
Glu
A
CGG
G
AGU
U
Ser C
AGC
A
AGG Arg G
AGA
U
GGU
Asp
C
GGC
GGA
GGG
Gly
Third mRNA base (3′ end)
U
Figure 17.5
The dictionary of
the genetic code
C
A
G
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e. Gene products (proteins), e.g. hemoglobin
Species
Percent of Amino Acids That Are
Identical to the Amino Acids in a
Human Hemoglobin Polypeptide
100%
Human
Rhesus monkey
95%
Mouse
8 7%
Chicken
69%
Frog
Lamprey
54%
14%
Figure 22.16 Comparison of a protein
found in diverse vertebrates
3. Biogeography
• Closely related species found in same
geographic region
• Islands have many endemic species
• Analagous structures may evolve in
different geographic areas - indicative
of convergent evolution
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NORTH
AMERICA
Sugar
glider
AUSTRALIA
Flying
squirrel
4. Fossil Record
• (Incomplete) Succession of life forms from oldest
(in deeper strata) to youngest (in shallower strata)
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Some fossils represent
evolutionary “dead-ends” while
others represent ancestral forms
= transitional species
•
Cetaceans evolved from terrestrial mammals
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