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6.3 Evidence for Evolution
EVIDENCE OF EVOLUTION:
selection
1. Artificial
________________
Fossil record
2. ________________
Geographic Distribution
3. _______________
Anatomical homologies
4. _______________
Embryology
5. _______________
Molecular homologies
6. _______________
7. Cellular homologies
Can see Natural selection happen
8. _______________
ARTIFICIAL SELECTION WORKS
Nature provides the variation through
mutation and sexual reproduction and
humans select those traits that they find
useful
EX: We have selected
for and bred cows to
produce more milk,
turkeys with more
breast meat, etc.
http://www.pp3moo.com/hm2cow.jpg
http://lazerbrody.typepad.com/photos/uncategorized/turkey.gif
WE’VE DONE IT WITH PLANTS
• Loss of genetic
diversity within crop
species
BIOLOGY by Campbell and Reece Prentice Hall Publishing©2005
WE’VE DONE IT WITH ANIMALS
If humans can
select for
beneficial traits,
why can’t nature?
If artificial selection
can achieve so much
change in relatively
short time, why can’t
major changes happen
over thousands of
generations?
http://www.windows.ucar.edu/earth/geology/images/dogs_sm.jpg
How Do We Know Evolution Happens?
The Fossil Record
provides evidence that
organisms have changed
over time.
http://www.bbc.co.uk/schools/gcsebitesize/img/bifossils.gif
If evolution has happened, we should be
able to find evidence of evolution in the
fossil record AND WE HAVE !
http://en.wikipedia.org/wiki/Image:Tiktaalik_BW.jpg
BBC Tiktaalik video
http://evolution.berkeley.edu/evosite/lines/IAtransitional.shtml
Lots of TRANSITIONAL FOSSILS have been found
Scientific American; Dec 2005; Vol 293; p100-107
http://evolution.berkeley.edu/evolibrary/images/news/tiktaalik_reconstruction.jpg
TIK-TAALIK
Intermediate between fish and early tetrapods
• Fins have basic wrist bones and simple fingers
• Earliest fish with a neck
• Discovered by Neil Shubin and Ted Daeschler in 2004
• Fossils can be dated by a variety of
methods that provide evidence for
evolution
– Age of rocks where fossils are found
– Rate of decay of isotopes like carbon-14
GEOGRAPHIC DISTRIBUTION =
BIOGEOGRAPHY
If Darwin’s theory is correct you would
expect to find closely related yet
different species living in a
geographic region as they spread into
nearby habitats and evolve.
That’s EXACTLY what we do see!
http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T014608A.gif
GALAPAGOS FINCHES
The beaks of Galapagos finches have
adapted to eating a variety of foods
http://www.newtonswindow.com/problem-solving.htm
GALAPAGOS TORTOISES
Intermediate vegetation
Intermediate necks
Little vegetation
Long necks
Image from: BIOLOGY by Miller and Levine; Prentice Hall Publisher©2006
Lots of vegetation
Short necks
Tortoises adapted to different habitats as they
spread from the mainland to the different islands.
= DIVERGENT EVOLUTION = ADAPTIVE RADIATION
If Darwin’s theory is correct you would
also expect to find different species
living in far apart geographic regions
but similar habitats becoming more alike
as they adapt to similar environments.
That’s EXACTLY what we do see!
BOTH LIVE IN FOREST ECOSYSTEMS
Adapted to similar
environments, but
evolved independently
from different ancestors.
SUGAR GLIDER
in Australia is a marsupial
more closely related to
Kangaroos than North
American
FLYING SQUIRRELS
because
its ancestors were
marsupials.
http://www.flmnh.ufl.edu/fish/gallery/descript/TigerShark/scars.JPG
http://news.bbc.co.uk/2/shared/spl/hi/guides/456900/456973/html/nn1page1.stm
Whales and sharks have a similar body design
even though they are very different organisms
(one is a fish; the other, a mammal)
because they have independently adapted to
living in a similar environment.
= CONVERGENT EVOLUTION
HOMOLOGOUS STRUCTURESForelimbs of all mammals share same
arrangement of bones that can be
traced to same embryological origin
BIOLOGY by Campbell and Reece Prentice Hall Publishing©2005
EVOLUTION explains why certain
characteristics
in related species have an
Section 15-3
underlying similarity.
Turtle
Alligator
Ancient lobe-finned fish
Bird
Mammal
amnion /am·ni·on/ (am´ne-on) bag of waters; the extraembryonic membrane of
birds, reptiles, and mammals, which lines the chorion and contains the fetus and
the amniotic fluid
http://media-2.web.britannica.com/eb-media/27/117227-050-E1C9ABEE.jpg
http://medical-dictionary.thefreedictionary.com/amnions
VESTIGIAL ORGANS
Some homologous structures are vestigial and
have no useful function even though they are
still present.
Examples:
Hipbones and pelvis in whales and boa constrictors
Cecum (appendix) in humans
Skink legs
http://www.txtwriter.com/backgrounders/Evolution/EVpage12.html
Most mammals have a pouch
between their small and large
intestine that contains bacteria
to digest plants called a cecum.
In humans the cecum
is shrunken and unused.
It is our appendix
http://www.medicalgeo.com/images/appendix.gif
EMBRYOLOGY
Development of vertebrate embryos
follows same path
Image from:
http://calspace.ucsd.edu/virtualmuseum/litu/03_3.shtml
Same groups of undifferentiated cells develop in
the same order to produce the same tissues and
organs of all vertebrates, suggesting that they all
evolved from a common ancestor.
Image from: http://io.uwinnipeg.ca/~simmons/16cm05/1116/16anim3.htm
Why grow a tail and then lose it?
HUMAN EMBRYO
has a tail at 4
weeks which
disappears at 8
weeks
Pharyngeal pouches
become gills in fish,
parts of throat/ears
in humans
http://www.suite101.com/files/topics/6234/files/tail_HumanTail.gif
Nonfunctional legs in skinks
Why would an organism
possess organs without
function?
Why would an organism
grow a part and then
discard it?
If organisms evolved from ancestors in which that
part functioned, the gene code to make the part
would still be there even though it doesn’t work.
If the organ is not vital to survival, then
natural selection would not cause its elimination.
http://www.medicalgeo.com/images/appendix.gif
MOLECULAR HOMOLOGIES
• All life forms share same genetic
machinery (DNA & RNA)
• Universal genetic code
• Important genes share
highly conserved
sequences
• Metabolic pathways are conserved across
all currently recognized domains
(creations of ATP, etc.)
Similarities in protein sequences
suggests similarities in DNA
Image from: Modern Biology by Holt, Rinehart, and Winston
MOLECULAR HOMOLOGIES
Similarities in
DNA and
protein
sequences
suggest
relatedness
Image from: BIOLOGY AP EDITION by Campbell and Reece; Prentice Hall Publishing©2005
Human- 46 chromosomes
Chimpanzee- 48 chromosomes
Similarities in karyotypes
suggest an evolutionary
relationship
Human: http://www.nationmaster.com/wikimir/images/upload.wikimedia.org/wikipedia/en/thumb/1/18/300px-Human_karyogram.png
Chimpanzee: Middle School Life Science , published by Kendall/Hunt.
Human- 46 chromosomes
Chimpanzee- 48 chromosomes
Even differences show relatedness
Chimpanzees have 2 smaller chromosome pairs we don’t have
Humans have 1 larger chromosome pair (#2) they don’t have.
Human: http://www.nationmaster.com/wikimir/images/upload.wikimedia.org/wikipedia/en/thumb/1/18/300px-Human_karyogram.png
Chimpanzee: Middle School Life Science , published by Kendall/Hunt.
Remember:
Protective TELOMERE
sequences found at
ends of chromosomes
http://joannenova.com.au/Speaking/Morslids.html
2. TELOMERES IN MIDDLE
Human chromosome 2 is only
human chromosome that has
telomere sequences at the
ends BUT ALSO IN THE
MIDDLE . . . suggesting it
was made by joining two
other chromosomes together.
→
→
→
http://www.evolutionpages.com/chromosome_2.htm
EXTRA CENTROMERE
_________________
Chromosome #2 has a second
inactive centromere region . . .
suggesting it was made by
joining two other chromosomes
together.
→
Which chromosomes?
http://www.evolutionpages.com/chromosome_2.htm
BANDING PATTERN MATCHES
________________________
If you take the two smaller
chromosomes they have that
we don’t, and place them end
to end, the banding pattern
is identical to human
chromosome #2
http://www.evolutionpages.com/chromosome_2.htm
Why don’t dogs and cats need to eat
fresh fruit, but you do?
http://www.naturescornermagazine.com/NaturesBlog/images/dog%20care%20in%20summer.jpg
http://www.alpo.com/where.aspx
Fish, amphibians, reptiles, and most
mammals can make their own vitamin C,
but humans can’t make vitamin C. Without
fresh fruit, humans end up with scurvy.
http://www.med.uc.edu/departme/cellbiol/Image7.gif
http://www.rachelleb.com/images/2005_02_22/scurvy.jpg
Human DNA contains the gene that
codes for the enzyme to make
vitamin C, but it is nonfunctional.
Guess what other group of organisms
lack the ability to make their own
Vitamin C?
PRIMATES…
which includes
chimpanzees, orangutans,
gorillas, and other apes.
http://groups.wfu.edu/ModelUN/images/Cover/Oranges.jpg
PSEUDOGENES are vestigial genes.
EX: Humans have more than 99
different odor receptor genes, but more
than 70% of them are nonfunctional.
http://www.animationplayhouse.com/new/dogs2.html
http://unraveling.typepad.com/photos/uncategorized/nose_1.jpg
Cellular Homologies
• Structural evidence supports relatedness
of all eukaryotes
– Cytoskeleton
– Membrane bound organelles (mitochondria
and/or chloroplast)
– Linear chromosomes
– Endomembrane systems (including nuclear
envelope)
Slide by Kim Foglia@ http://www.explorebiology.com/
BIOLOGY by Campbell and Reece
We can see Natural selection happen
BIOLOGY by Campbell and Reece
We can see Natural selection happen
Can see Natural selection happen
EX: Changes in disease-causing microbes that
produce new organisms and new diseases.
Bird flu
_______
HIV
___
http://www.hhmi.org/askascientist/images/hiv.gif
Antibiotic-resistant
tuberculosis
__________________________
Why does evolution matter now?
http://www.hipusa.com/eTools/webmd/A-Z_Encyclopedia/tuberculosis.jpg
Researchers have developed numerous
drugs to combat HIV
– But using these medications selects for
viruses resistant to the drugs
Patient
No. 1
Patient No. 2
Patient No. 3
Weeks
Graph from BIOLOGY by Campbell and Reece
PEPPERED MOTH
Data from Kim Foglia @ www.biologyzone.com
Slide from Kim [email protected]