Download The Evidence for Evolution by Natural Selection

Charles Darwin: Evolutionary Theory, Past and
Present
The Evidence for Evolution by Natural
Selection
from C. Darwin, 1859, Origin of Species
“There is grandeur in this view of life, with its
several powers, having been originally
breathed into a few forms or into one; and that,
whilst this planet has gone cycling on according
to the fixed law of gravity, from so simple a
beginning endless forms most beautiful and
most wonderful have been, and are being,
evolved.”
from C. Darwin, 1859, Origin of Species
PREDICTIONS OF THE THEORY
1) Descent with modification,
2) From common ancestors,
3) Producing a branching tree of life,
4) Connected by intermediate species,
5) Characterized by extinction of less fit taxa,
6) And superior adaptation of those who survived.
The variations acted on by selection are random, so there is
no apparent direction or purpose evident in the history of
life, but adaptation to environmental parameters, which
governs natural selection, is anything but random. The
biosphere is a marvel of myriad adaptations!
THE EVIDENCE FOR EVOLUTION
A. Fossil record
evidence of speciation,
adaptive radiation events,
and extinctions.
B. Observations of modern
organisms - biogeography,
homologous structures,
developmental trends,
molecular biology.
C. Examples of ongoing
evolution - Resistance to
pesticides, the pathology of
the AIDS virus, Galapagos
Finches.
EVIDENCE FROM
THE FOSSIL
RECORD
Stratigraphy
Stratigraphy
Faunal
succession
P
D
P
M
C
pC
Extinction
Stratigraphy
Faunal
succession
P
D
P
M
C
pC
Extinction
Paleogeography
W. W. Norton. Modified from Wegener A, The Origin of the Continents and Oceans.
Paleobiogeography
(land dwellers)
(seeds don’t spread far)
Paleobiogeography
©Blackwell, 1990 (Sheldon, 1987)
Microevolution
Parallel trends in trilobite morphology
Speciation in
Brachiopods 1.7
measured by
change in
ornament
through time
5.2
Definition of
paleospecies?
Average species
duration?
1.1
2.0
Speciation Patterns
Predicted
B
•Lack of intermediate forms
•Arbitrary paleospecies definitions
A
Speciation Patterns
Predicted
Observed
D
B
C
•Species stability
WHY?
A
What is the
average species
duration? 5 - 10 myr
B
A
Normalizing Selection
Habitat tracking
BRANCHING PHYLOGENY EXHIBITS GRADUAL PHYLETIC
EVOLUTION IN EOCENE MAMMAL LINEAGE
Gingerich, P.D., 1974, Stratigraphic record of Early Eocene Hyopsodus and the
geometry of mammalian phylogeny, Nature 248, 107 - 109.
Lineage evolution
Orthogenetic
Trend?
Or species selection?
Macroevolution and
the Evidence for
Transitional Forms
Macroevolutionary Events
F
A
M
T
L,S
C
Mesozoic
B
C
D
K
J
AR
T
Paleozoic
P
P
Birds (B)
M
Mammals (M)
D
Reptiles (T,L,S,C,D)
S
Amphibians (A)
Fish (F)
Macroevolution fish to amphibians
Where are the
missing links?
Macroevolution - fish to amphibians
Ichthyostega
Eusthenopteron
Fish
Land
Vertebrates
Can we find a transitional form at the exact
fish-to-amphibian transition?
Tiktaalik
Edward B. Daeschler, Neil H. Shubin and Farish A.
Jenkins, Jr (6 April 2006). "A Devonian tetrapod-like fish
and the evolution of the tetrapod body plan". Nature 440:
757–763.
Shubin, Neil (2008). Your Inner Fish. Pantheon. ISBN
9780375424472.
Theraspids
Macroevolution Reptiles to mammals
Mammal-like reptiles
A
M
T
L,S
C
B
C
D
K
J
AR
T
P
P
M
D
S
adaptation to terrestrial habitats
Birds
Mammals
Reptiles
Amphibians
Macroevolution reptiles to birds
A
M
C
T
L,S
B
C
D
K
J
AR
T
P
P
M
D
S
Birds
Mammals
Reptiles
Amphibians
Macroevolution - reptiles to birds
Adaptation to aerial habitats
A
M
C
T
L,S
B
C
D
K
J
AR
T
P
P
M
D
S
Birds
Mammals
Reptiles
Amphibians
Archaeopteryx lithographica
Macroevolution - tetrapods to whales
“Darwin seems to believe that a white bear …might be turned into a whale.”
Evolution of marine mammals
Re-adaptation to
marine habitats
Genetic
evidence shows
most closely
related living
land creature to
Cetaceans is…
Anthracotheriidae
Adaptation to
terrestrial habitats
What were they waiting for?
DINOSAURIA
Radiation of all mammal clades
The Cambrian Explosion
CAMBRIAN
EXPLOSION
Sudden appearance
of all extant body
plans, as well some
completely novel
plans never seen
again.
Total diversity far
exceeding that of
modern taxa.
Ediacarans
Innovation
Intense selection
Innovation
Burgess Shale Fauna
Intense selection
Large scale trends in the
history of life
Phanerozoic
Evolutionary
History
Ordovician
radiation
Cambrian
radiation
Mesozoic
radiation
Sepkoski’s
Evolutionary
Faunas
A. Marine Invertebrates
B. Vascular Plants
C. Tetrapods
No new body plans
Angiosperms
Gymnosperms
Turtles-mammals
Diapsids-Dinosaurs
Pteridophytes
Labyrinthodonts
Anapsids
Synapsids
Low diversity scavengers
Trilobites, Inarticulate Brachiopods
Generalized deposit feeding
Sessile benthos
Brachiopods, Bryozoa, Molluscs
Rise of vertebrates (Fish)
Dominant epifaunal suspension
feeders
Mobile benthos
Molluscs, Echinoderms
Marine reptiles
Marine mammals
Complex food webs, many more
guilds, durophagous predators
and deep tiering
Evolution of
Durophagous
Predators
Shell-crushing fish
Marine reptiles
Evidence for Natural Selection
THE FOSSIL RECORD shows…
Proof of extinction (ultimate selection)
Evidence of adaptive radiation (lineages)
Transitional or intermediate forms
Large scale trends in the history of life
No directionality, only adaptation and
contingency
B
D
Triassic
Permian
Equus
Consider the significance of the statement
“no reversals have been found.”
Descent with modification PREDICTS
that there should be no reversals in the
history of life - in other words, the
occurrence of a mammal in the
Precambrian would invalidate
evolutionary theory as we know it.
The History of Life is Contingent!
But how good is the fossil record?
•Overall disadvantages
Fragmentary and full of gaps
Subject to spatial/temporal biases
Environments - terrestrial vs. marine
Taxa - invertebrate vs. vertebrate
Historical - recent vs. deep past
How biased?
Diversity
“The Pull of the Recent”
amount of exposed rock of
a given time period
But this doesn’t explain
Sepkoski’s evolutionary
faunas…
Exposure
Equil model
©Blackwell, 1990
# of paleontologists working
within a time period
Sampling
©Blackwell, 1990
Exceptional Preservation: Fossil Lagerstätten
©Natl. Geographic
But the more
common
situation…
Is the fossil record a representative sample?
“…light will be thrown on the origin of man.”
©Natl. Geographic
African Rift
Valley
EVIDENCE FROM
MODERN
ORGANISMS
Island Biogeography
The role of geographic isolation
Galapagos Islands
Adaptation & Speciation
STRUCTURAL
ADAPTATIONS
RELATED TO
LIFE HABIT AND
RESOURCE
EXPLOITATION
©Benjamin Cummings Publ. 1979
Galapagos Finches
‘Island’ Biogeography & the Founder Effect
©Sci. American, 1978
“topographic
islands” &
isolation
since the
Last Glacial
Maximum
(20 Ka).
Biogeography
Ostrich
Rhea
Emu
(land dwellers)
Kiwi
Penguin
(seeds don’t spread far)
Convergent evolution
Analogous Structures
Anatomical structures that perform the same
function in different biological species and
evolved from different structures in unrelated
lineages
Analogous structures reflect convergent evolution
…reflecting the
constraints of
adaptation to a
particular set of
environmental
conditions.
©Sci. American, 1978
ANALOGOUS
STRUCTURES
Homologous Structures
Anatomical structures that perform the same
function in different biological species and
evolved from the same structure in some
ancestor species
HOMOLOGOUS
STRUCTURES
REPTILES
BIRDS
Bone
Differences
reflect
ADAPTATION
Sternum
Skin
©Sci. American, 1978
Forelimb
Homology in mammal forearms
…adaptation to different life habits
Diversification of CLAMS from common ancestor (HAM)
de
ep
er
©A. Seilacher, 1987
thicker
A great example of niche partitioning
VESTIGIAL ORGANS
Human hair follicle
VESTIGIAL ORGANS
Hind limbs
Neoteny in primates
Barnacle life histories
Homeotic genes
©Sci. American. 1978
DEVELOPMENTAL EVIDENCE
©Benjamin Cummings Publ. 1979
©S.J. Gould, 1989, Norton Publ.
CLASSIFICATION
CLADISTICS
Derived
Primitive
Systematics based on grouping of shared primitive vs.
shared derived characters to establish ancestordescendent relationships.
Cladistic Phylogeny
Derived
Primitive
Molecular Phylogeny
based on DNA
sequencing of
Galapagos Finches
Common ancestor
Molecular Phylogeny
DNA
Protein
Galapagos islands
Finch
BMP4
African lakes
Cichlid
National Geographic, Feb. 2009
Molecular Phylogeny
©National Acad. Sci., 1998
Divergence the in gene for Cytochrome C
Molecular Phylogeny
16S Ribosomal RNA sequence
©Natl. Acad. Sci., 1998
Homologies of molecular biology?
A. The genetic code is the same in all known
organisms.
B. The “Central Dogma” of cellular metabolism
is the same in all known organisms.
C. The fundamental biochemical agents that
mediate metabolism (hemoglobin,
cytochrome c, etc.) are found in a very wide
range of known organisms.
EXAMPLES OF
ONGOING
EVOLUTION
©Natl. Geographic
Artificial selection
Microevolution
Peppered Moths
Variations in dominant
coloration develop at the
population level as
environmental conditions
(tree color) change. The
selecting mechanism is
predation by birds.
©Sci. American, 1978
Due to environmental
changes in Britian since
the Industrial
Revolution…
The humble
Soapberry
bug
Galapagos Finches
DROUGHT
DROUGHT
DROUGHT
DROUGHT
Resistance to pesticides
Mosquitos in India
AIDS
The Global AIDS Epidemic
Selected areas shown w/total # infected
15-45 yr age group
2006: >38 million infected 2050: estimated >90 million
2.9 million died
dead
HIV
mechanism
1.Virion stage.
2. HIV gp120 prot.
binds to host CD4 &
coreceptor.
3. HIV RNA, RT, I, &
P enter host.
RT- Reverse
Transcriptase
I - Integrase
P - Protease
4. RT synthesizes
HIV DNA from HIV
RNA template.
5. I splices HIV DNA
into host genome, it
gets transcribed to
mRNA by host.
6.HIV mRNA is
translated to HIV
proteins by host
ribosomes; new
generation of virions
assembles, & buds
from host.
Progression of HIV infection in typical untreated patient
Immune
system
collapses
Evolution of the HIV population w/in a single patient
SHAMELESS
PROMOTION
~ 95 Ma
Modified from Sewall et al., 2007
Cretaceous Ocean Anoxic Events
Tibet
Carbon isotope excursion at the
Cenomanian - Turonian Boundary
δ13C ‰ PDB
Li, et al., 2006
secondary mass extinction
Carbonate
TOM
Hasegawa et al., 2002
SUN
H2O + CO2 <=> CH2O + O2
Photosynthesis
Respiration
CO2
PLANKTON
H2O
ventilation
O2
CO2
ventilation
H2O + CO2 <=> CH2O + O2
CO2
-O2
-O2
reduced
ventilation
reduced
ventilation
BLACK SHALE
M.m.
S.g.
N.j.
Rock Canyon Anticline, near
Pueblo, CO
δ13C
Eicher & Diner, 1991
Hartland SH
Bridge Creek LS
Cenomanian
Turonian
W.d P.f. V.b.
Cenomanian-Turonian stratotype
Detailed correlation of
marine record to coeval
terrestrial strata.
Bald Knoll Mine, UT
Development of
improved time
scale for marine
C-T
Roberts & Kirschbaum, 1995
Marine-terrestrial
linkage of OAE 2
Cuticle morphotyping
Lauraceae
(
Stomatal Index =
SD
SDSD
+ ED
x 100
+ ED
) X 100
pCO2 =
1
Stomatal Index
SD = #
stomata
per mm2
C. c.
M. mosbyense
S. gracile
Cenomanian
N. juddii
W. dev.
Turonian
SD vs SI
– CO2 concentrations
Modern
Eocene
RCO2 = 4x?
RCO2=1x
RCO2 = 3x - 2x
Cretaceous
Modern and Eocene Data from McElwain, 1988
CONCLUSIONS
•The evidence for descent with modification,
common ancestors, speciation to produce a
branching tree of life, intermediate species,
extinction, and superior adaptation is abundant
and uncontestable.
•Evolution by means of natural selection is the
central unifying principle of the biosphere…
“nothing in biology makes sense except in the
light of evolution.” (T. Dobzhansky)
•The biosphere IS a marvel of myriad adaptations!
•And there is indeed, grandeur in this view of life.