1. 6.3 Evidence for Evolution

2. EVIDENCE OF EVOLUTION:
________________
3. _______________
4. _______________
5. _______________
6. _______________ 7.
8. _______________
Artificial selection
Fossil record
Geographic Distribution
Anatomical homologies
Embryology
Molecular homologies
Cellular homologies
Can see Natural selection happen

3. 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.

4. WE’VE DONE IT WITH PLANTS
Loss of genetic diversity within crop species
BIOLOGY by Campbell and Reece Prentice Hall Publishing©2005

5. 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?

6. How Do We Know Evolution Happens?
The Fossil Record
provides evidence that
organisms have changed
over time.

7. If evolution has happened, we should be able to find evidence of evolution in the fossil record AND WE HAVE !
BBC Tiktaalik video

8. Lots of TRANSITIONAL FOSSILS have been found
Scientific American; Dec 2005; Vol 293; p

9. TIK-TAALIK Intermediate between fish and early tetrapods
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

10. 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

11. 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!

12. The beaks of Galapagos finches have
GALAPAGOS FINCHES
The beaks of Galapagos finches have
adapted to eating a variety of foods

13. GALAPAGOS TORTOISES Tortoises adapted to different habitats as they
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

14. 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!

15. 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.

16. Whales and sharks have a similar body design
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

17. HOMOLOGOUS STRUCTURES-Forelimbs 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

18. EVOLUTION explains why certain
characteristics in related species have an
underlying similarity.
Section 15-3
Turtle
Alligator
Bird
Mammal
Ancient lobe-finned fish

19. 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

20. 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

21. 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

22. EMBRYOLOGY Development of vertebrate embryos follows same path
Image from:

23. 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:

24. 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

25. 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.

26. 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.)

27. Similarities in protein sequences suggests similarities in DNA
Image from: Modern Biology by Holt, Rinehart, and Winston

28. DNA and protein sequences
MOLECULAR HOMOLOGIES
Similarities in
DNA and protein sequences
suggest
relatedness
Image from: BIOLOGY AP EDITION by Campbell and Reece; Prentice Hall Publishing©2005

29. Similarities in karyotypes suggest an evolutionary relationship
Human- 46 chromosomes Chimpanzee- 48 chromosomes
Similarities in karyotypes
suggest an evolutionary relationship
Human:
Chimpanzee: Middle School Life Science , published by Kendall/Hunt.

30. Even differences show relatedness
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:
Chimpanzee: Middle School Life Science , published by Kendall/Hunt.

31. Remember: Protective TELOMERE sequences found at ends of chromosomes

32. → → → 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. → →

33. → EXTRA CENTROMERE _________________
Chromosome #2 has a second inactive centromere region . . .
suggesting it was made by joining two other chromosomes together.
Which chromosomes? →

34. ________________________
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

35. Why don’t dogs and cats need to eat fresh fruit, but you do?

36. 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.

37. 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.

38. PSEUDOGENES are vestigial genes.
EX: Humans have more than 99 different odor receptor genes, but more than 70% of them are nonfunctional.

39. Cellular Homologies
Structural evidence supports relatedness of all eukaryotes
Cytoskeleton
Membrane bound organelles (mitochondria and/or chloroplast)
Linear chromosomes
Endomembrane systems (including nuclear envelope)

40. Slide by Kim Foglia@ http://www.explorebiology.com/

41. We can see Natural selection happen
BIOLOGY by Campbell and Reece
We can see Natural selection happen

42. We can see Natural selection happen
BIOLOGY by Campbell and Reece
We can see Natural selection happen

43. Why does evolution matter now?
EX: Changes in disease-causing microbes that produce new organisms and new diseases.
_______
___
__________________________
Can see Natural selection happen
Bird flu
HIV
Antibiotic-resistant tuberculosis
Why does evolution matter now?

44. 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
Percent of HIV resistant to 3TC
Patient No. 3
Weeks
Graph from BIOLOGY by Campbell and Reece

45. PEPPERED MOTH
Data from Kim

46. Slide from Kim Foglia@www.biologyzone.com