Evidence for
Evolution
What does evolution mean?

Individual organisms do NOT evolve;
populations/species do.

Two meanings
1. History of life = change of populations
over time (really long time)
2. A Process = Natural Selection
1. FOSSILS

What is a fossil?
Anything left behind by a once
alive organism. Examples include
bones, shells, teeth, impressions,
and feces.
Rarely do soft tissues leave a fossil
behind.
2. Cladistics (later)
 Depicts the evolutionary history of
a group of related organisms over
time
 Ex=phylogenetic (family) trees of
birds, horses & whales
Whale Ear Bone is Unique

Note changes in
body proportions
and elongation of
feet for footpowered swimming
in Rodhocetus, then
later reduction of
the hind limbs and
feet as the tailpowered swimming
of modern whales
evolved in Dorudon.
Maicetus inuus
3. Transitional(intermediate) fossils
(aka, “missing links”)
 Organisms
that fit between major
splits in a phylogenetic tree.
 Examples
1. Archeopteryx (p.432)
part bird/part reptile
2. Tiktaalik (fishamphibian)
Inuit word for “fish”)
3. Platypus=part mammal/part
reptile
4. Comparative Anatomy
Homologous structures=
same design, different functions suggests
common ancestry with “descent w/
modification”
 Vestigial structures=
present but reduced in size w/ no
apparent function; Ex=appendix, tailbone,
hips in snakes, rear legs in whales

Vestigial Structures
5. Comparative Development

Studies the way organisms develop during
their life cycle—what controls how they
progress from an earlier to a later stage?
Genetics must control this process—the
more similar two organisms develop, the
more closely they should be related.
HOX genes found in all animals that control
body parts / organized from top down
Evolutionary Development =
“Evo Devo”

The genetic ingredients that assemble you are
strikingly similar to those that assemble a fly. So
why do you and a fly look so different as adults?
The answer lies in where, how, and for how long
those ingredients "turn on" during your embryonic
development. The intricacies of this early stage of
life are now being revealed thanks to the new field
of "evo devo," and that all animals share the same
basic toolkit of body-building genes.

http://www.pbs.org/wgbh/nova/beta/evolutio
n/what-evo-devo.html
Sticklebacks

shows that the control
of genes for the
development of unique
body parts can
accelerate speciation
depending when
during development
and where on the body
part the genes are
turned on/off
6. Comparative Biochemistry
Probably the greatest advance in
supportive evidence in last 25 years
 The more closely related proteins (amino
acid sequences) or DNA base sequences
between organisms, the more closely
related on the tree of life that they are.
 What accounts for the differences?

Examples of Comp. Biochem.
Human, chimp, gorilla, vs. orangutan
Ape vs. Human Karyotype
Used to be #12 and #13
Human #21 is actually the smallest at
50 mbp—originally looked the smallest.
The fused Chromosome #2
Evidence for fusion:


1. The correspondence of chromosome 2 to
two ape chromosomes. The closest human
relative, the bonobo, has near-identical DNA
sequences to human chromosome 2, but they
are found in two separate chromo-somes.
(True of the more distant gorilla & orangutan.)
2. The presence of a vestigial centromere.
Normally a chromosome has just one
centromere, but in chromosome 2 we see
remnants of a second.


3. The presence of vestigial telomeres. These are
normally found only at the ends of a chromosome, but in
chromosome 2 we see additional telomere sequences in
the middle.
Chromosome 2 is thus strong evidence in favor of the
common descent of humans and other apes. According
to researcher J. W. Ijdo (HHMI), "We conclude that the
locus cloned in cosmids c8.1 and c29B is the relic of an
ancient telomere-telomere fusion and marks the point at
which two ancestral ape chromosomes fused to give rise
to human chromosome 2.“ (Proceedings of the National
Academy of Sciences , 1991)
7. Biogeography
The study of past and present distribution of
individual species in the context of evolutionary
theory (over space & time).
 Finding related fossils/living species in different
locations suggests geographical isolation of
different populations of similar species.


Example: camels and llamas are related genetically
and have similar physical characteristics but evolved
on different continents (both have Eocene cannelid
ancestor found in N. America)
Geographical Movement & Isolation
of Organisms Over Time
Plate
Tectonics
225 mya
65 mya
Ex: Ring species

a geographic distribution that
forms a ring & overlaps at the
ends. The many subspecies of
Ensatina salamanders in CA
exhibit subtle morphological &
genetic differences all along
their range. They all interbreed
with their immediate neighbors
with one exception: where the
extreme ends of the range
overlap in Southern California,
E. klauberi and E. eschscholtzii
do not interbreed. Why not?
Biogeography=the study of how species are
scattered across the planet & how they got that
way—a historical tribute.

Alfred Wallace travelled (1840-1860s) the
Amazon & Indonesia, collecting and notating
thousands of different species including exactly
where he found them. He came to the same
conclusion as Darwin: biogeography was simply
a record of inheritance; as species colonized
new habitats and their old ranges were divided
by mountain ranges or other barriers, they took
on the different adaptations that led to
population distributions they have today.
The archipelago known as the
Galapagos Islands
Microevolution
 Changes
in allele frequencies of a
population as a result of natural
selection
 Ex=finches beak size from small to
big based on seeds available
 Ex=Heterozygote advantage in sickle
cell/ malaria lab simulation
Macroevolution
Involves origin of species
 Novel designs appear almost “out of thin
air” (Cambrian Explosion of Life)
 Evolutionary Trends begin in one branch
of the tree of life (ex: opposable thumbs
in primates, jaw bone in bony fish, the
amniotic egg in reptiles)
 Adaptive radiation (Darwin’s Finches,
Hawaiian honeycreepers)
 Extinction is a vital part of this.

Batesian Mimicry
Industrial Melanism
Variations of the Peppered Moth
How did they evolve into
separate species?
1. Ecological opportunity
 2. Isolation (geographic or reproductive)
 3. “Mistakes” = Changes in the gene pool
by
--natural selection --Evo. Devo. (HOX)
--symbiogenesis
--horizontal gene
(L. Margulis)
transfer

How fast does evolution happen?
 Metabolic
changes can happen in
fewer than 200 generations for
bacteria.
 Punctuated equilibrium vs. gradualism
(the work of Niles Eldridge and Stephen
Jay Gould)
The origin of species—walking stick
insect in Santa Ynez mountains of CA
Hawthorne flies
Historically mated and laid their eggs on
the fruit of the Hawthorne tree.
 Sometime in the mid-1800s, some began
to prefer apple trees.
 Now both have become genetically distinct
species.
 The species of wasps that prey on them
have become genetically separate as well!

Evolution—an absolute
dogma, right?
Never—great science in action but
remember there will always be “holes.”
The beauty of science is its ability to
analyze and adjust as evidence is
added. Obsevationsinferences is
where scientists often disagree.

Temporal Paradox=time controversy for
the ancestry of birds (Archeopteryx @ 150
mya and Microraptor/Deinonychus @ 120
mya)

The consensus view is that birds evolved from dinosaurs,
but the most bird-like dinosaurs, and those most closely
related to birds (the maniraptorans) are known mostly
from the Cretaceous, by which time birds had already
evolved and diversified. If bird-like dinosaurs are the
ancestors of birds they should be older than birds, but
Archaeopteryx is 155 million years old, while the very
bird-like Deinonychus is 120 my old. This idea is
sometimes summarized as "you can't be your own
grandmother.”
Deinonychous (“terrible claw”)
Note: have NOT found feathers ass. w/
Microraptor fossils
Haekel’s Drawings
Very few embryos actually look like his drawings!
Microevolution ≠ origin of
species

Bird studies in the Galapagos
demonstrates directional selection of
phenotype differences back and forth but
never to the creation of new species.
Industrial Melanism—moths often
not even found on birch trees
1. Large cactus finch (Geospiza conirostris)
2. Large ground finch (Geospiza magnirostris)
3. Medium ground finch (Geospiza fortis)
4. Cactus finch (Geospiza scandens)
5. Sharp-beaked ground finch (Geospiza
difficilis)
6. Small ground finch (Geospiza fuliginosa)
7. Woodpecker finch (Cactospiza pallida)
8. Vegetarian tree finch (Platyspiza
crassirostris)
9. Medium tree finch (Camarhynchus
pauper)
10. Large tree finch (Camarhynchus
psittacula)
11. Small tree finch (Camarhynchus parvulus)
12. Warbler finch (Certhidia olivacea)
13. Mangrove finch (Cactospiza heliobates)
(From BSCS, Biological Science: Molecules to Man,
Houghton Mifflin Co., 1963)
Fig. 4. Representative phenotypes of the parental complete armor (A), parental
low armor (B), F1 mapping hybrid (C), and F2 mapping hybrid (D–G) generations.
The major axes of variation in the F2 intercross generation indicate the
segregation of armor loss as a 9:3:3:1 dihybrid Mendelian ratio (red; observed
ratio in black) of the parental armor classes. (D) The complete-armor phenotype
of the F2 generation. (G) The low-armor phenotype. (E and F) The completeplate/low-pelvic structure and complete-pelvic/low-plate recombinant
phenotypes, respectively.
Evolution of Coelomates
Study finds “junk” DNA contributes to animal social interactions: The length
of a DNA region (in red) near the vasopressin receptor gene (green) was
discovered to have an effect on social behavior in voles. Genome data for
this same region reveals strong similarities in DNA sequences between
humans and bonobos (known for its strong social bonds), while DNA of the
more-aggressive chimpanzees differs from both humans and bonobos in
this region. <Credit: Nicole Fuller, Nat. Science Foundation>
Over 200 different species in Lk. Tanganyaki