1. Darwin’s Theory of Evolution Darwin Presents his Case
Image from: Biology by Miller and Levine; Prentice Hall Publishing©2006

2. results in changes in the inherited characteristics of a population.
WHAT IS DARWIN’S THEORY?
Over time,
NATURAL SELECTION
results in changes in the
inherited characteristics of a population.
These changes increase a
species’ fitness in its environment.
How Does Evolution Really Work?

3. WHAT IS DARWIN’S THEORY?
SURVIVAL OF THE FITTEST =
Organisms which are better adapted
to their environment tend to produce
more offspring than organisms without
those traits.

4. WHAT IS DARWIN’S THEORY?
OVERPRODUCTION of OFFSPRING
Capacity to over-reproduce seems characteristic of all species.

5. WHAT IS DARWIN’S THEORY?
STRUGGLE FOR EXISTANCE means
that members of each species must
compete for food, space, and
other resources.

6. WHAT IS DARWIN’S THEORY?
GENETIC VARIATION is found naturally in all populations
Image from

7. WHAT IS DARWIN’S THEORY?
Some organisms in a population are less likely to survive.

8. IMPORTANT TO REMEMBER ! POPULATIONS evolve NOT INDIVIDUALS.
NATURAL SELECTION only works on heritable traits.
A trait that is favorable in one environment may be useless or detrimental in another.

9. DESCENT WITH MODIFICATION
WHAT IS DARWIN’S THEORY?
DESCENT WITH MODIFICATION
suggests that each species has
descended with changes
from other species over time.
This idea suggests that all living
species are related to each other
and that all species, living and extinct,
share a common ancestor.

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

11. 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.

12. WE’VE DONE IT WITH PLANTS
BIOLOGY by Campbell and Reece Prentice Hall Publishing©2005

13. 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?

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

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

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

17. 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!

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

19. 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

20. 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!

21. 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.

22. 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

23. 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

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

25. 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

26. 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

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

28. MOLECULAR HOMOLOGIES
All life forms share same genetic machinery (DNA & RNA)
Universal genetic code
Important genes share highly conserved sequences

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

30. 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

31. 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.

32. 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.

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

34. → → → 2. TELOMERES IN MIDDLE
Human chromosome 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. → →

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

36. ________________________
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

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

38. Slide by Kim Foglia@www.biologyzone.com