1. Evolution and Biodiversity
Apes Chapter 5

2. Darwin’s Ideas – An “evolution”, not a “revolution”
Pre-darwininan ideas
Species are fixed, permanent, no change
Earth young – less than 10,000 years old
New ideas
Georges Buffon – earth much older – fossils
Lamark
Species changed, process of adaptation
Inheritance of acquired characteristics

3. Voyage of the Beagle 1831 Charles Darwin – 22-year old college student
The Galapagos Islands – Why Important?
Lyell and geology –
Earth’s geological features changing over very long periods of time – Earth is OLD
Results in a changing environments – living things faced with constant change

4. Darwin Analyzes Data – And Formulates his Theory
Thomas Malthus – Populations can grow much faster than food supplies, other resources – exponential growth
Darwin’s interpretation – Struggle for Survival
Published The Origin of Species

5. Darwin’s Main Points What were Darwin’s two main points?
Descent with Modification
Natural Selection

6. Why is this type of rock important?

7. Dating Fossils Sedimentary rock – relative ages Radiometric dating
Half-life of radioactive elements
U-238 –4.5 billion
C-14 – 5600 years
How does carbon get into living organisms?
Accurate to 50,000 years

8. Homologous Structures
What are some similarities?
How is the use of these structures different?
Do you think homologous are evidence of common ancestors? Explain.

9. Evidence - vestigial structures

10. Evidence -
Similarities in embryological development

11. Evidence in molecules of life
Proteins such as hemoglobin (page 304)
DNA analysis - humans and chimps - 2% difference in species

12. Microevolution (14.4) What is a gene pool ?
What is “stored” in a
population’s gene pool?
Microevolution – genetic
changes in an organisms
gene pool.
Evolution acts on populations
– not on individuals

13. Changes in Gene Pools
Microevolution: the frequency of alleles in a gene pool changes; evolution on the smallest scale

14. “Ingredients” for microevolution (101)
Variation within population
Trait must be inherited (genetic basis)
Trait must lead to differential reproduction

15. Why Variation? Mutation – most often random
Can chances be increased
May not offer any advantage or disadvantage
Especially important in changing gene pool in asexual, rapidly reproducing individuals
Examples??
In Sexually reproducing organisms – variation also caused by:
“shuffling” of different chromosomes – independent assortment
Crossing over during meiosis

16. Natural Selection
Variation is always present in a population due to genetic variation (variation in gene pool of the population)
What decides what individuals survive and reproduce?
If organisms reproduce, genetic makeup is passed to their young!
Thus, organisms that are better adapted have better chance of survival to reproductive age – and pass on genetic traits

17. Natural Selection – Not by Chance
Think of peppered moth, pesticide resistance, AIDS
This selection leads to adaptations
Is a favorable adaptation always remain a favorable adaptation? EXPLAIN

18. Directional Natural Selection
Snail coloration
best adapted
to conditions
Average
New average
Previous
average
Natural
selection
Number of individuals
Number of individuals
Average shifts
Coloration of snails
Coloration of snails
Proportion of light-colored
snails in population increases
Figure 5-6 (1) Page 102

19. Diversifying Natural Selection
Intermediate-colored snails
are selected against
Snails with light and dark
colors dominate
Natural
selection
Light
coloration
is favored
Dark
coloration
is favored
Number of individuals
Number of individuals
Coloration of snails
Coloration of snails
Number of individuals
with light and dark coloration
increases, and the number with
intermediate coloration decreases
Figure 5-6 (3) Page 102

20. Peppered Moth – directional microevolution

21. Evolution of antibiotic resistance
Drug kills most bacteria
Survivors reproduce quickly – develop resistant population

22. What Else can cause changes in Gene Pool?
Chance changes in allele frequency - no selection for advantageous traits
Genetic Drift
Bottleneck Effect
Founder Effect
Gene Flow
Mutation

23. Founder Effect Small population migrates to a location
Limited gene pool
Population may differ from original population

24. Gene Flow
Migration of organisms from “outside” populations

25. Artificial Selection
Humans act as environment - choose those genetic traits that will survive
What are some factors that “replace” humans in natural selection?

26. Coevolution
Interaction between species results in microevolution in both species populations
Predator-prey
Symbiosis – may be much more important than proposed by Darwin

27. NO!! Convergent evolution
Are similar structures always evidence of evolutionary relationships?
NO!!
Consider - animals that eat insects
Called analogous structures
Examples

28. Convergent Evolution (from PBS website)

29. Convergent Evolution
Are these homologous structures? Why or why not?

30. Ecological Niches and Adaptation (103)
Niche – species “way of life” or functional role in ecosystem
Range of tolerance for physical/chemical conditions
Resources it uses
Interactions
Role in food webs/energy cycling
Habitat
Functional niche vs realized niche

31. Generalist vs. Specialist
Niche
separation
Number of individuals
Generalist species
with a broad niche
Generalist species
with a narrow niche
Niche
breadth
Region of
niche overlap
Resource use
Figure 5-7 Page 104
What are examples of generalist vs. specialist species?

32. Why not a superorganism?
Traits must be already present “somewhere” in population for organism to adapt to changing environmental conditions
Limited by reproductive potential
Only so much DNA

33. Macroevolution Changes that move beyond changes in allele frequency
Including origin of new species - speciation,
Explains development of new genera and beyond
Explains major new features of living organisms
Progressive and incremental – example – complex eyes
In many cases links between simple and complex are “missing”

34. Are these different species?

35. How about these animals?

36. Defining a Species Population of organisms that can and do: Interbreed
Produce fertile offspring

37. The Ultimate of Divergent Evolution
Origin of Species
The Ultimate of Divergent Evolution

38. Disruptive selection animation.

39. Northern population Arctic Fox Spreads northward and southward
Adapted to heat
through lightweight
fur and long ears,
legs, and nose, which
give off more heat.
Adapted to cold
through heavier
fur, short ears,
short legs, short
nose. White fur
matches snow
for camouflage.
Gray Fox
Arctic Fox
Different environmental
conditions lead to different
selective pressures and evolution
into two different species.
Southern population
Northern population
Spreads
northward
and
southward
separates
Early fox
population

40. Reproductive Isolation – Why can’t different species interbreed?
Timing - skunks
frogs in same pond
Behavior -
birds - songs
courtship rituals
Other reproductive barriers
zygote does not develop - chromosomal differences
Live in different geographical areas or in different habitats

43. What comes first??
Geographical isolation always precedes reproductive isolation
What is geographical isolation?
How can this lead, usually over long time periods, to reproductive isolation?
Continual microevolution causes populations to become so different, no longer interbreed
Natural selection (in the different environments)
Genetic drift and random mutations

45. Tempo of Speciation
Darwin’s theory – relatively slow progression to new species as result of geographical isolation
Punctuated equilibrium–
Long periods, little change, THEN..
rapid changes to new species
May be caused by rapid changes in environment
Most species last 5 million years before extinction

46. Plate Tectonics
Why matching Mesozoic fossils in West Africa and Brazil
How does crust movements affect life’s evolution?
Pangea – When began to split?

47. Figure 5-9 Page 106 PANGAEA LAURASIA GONDWANALAND
120°
80°
40°
80°
120°
120°
80°
80°
120°
GONDWANALAND
135 million years ago
225 million years ago
NORTH AMERICA
EURASIA
AFRICA
120°
80°
120°
120° 0°
40°
120°
INDIA
SOUTH
AMERICA
MADA-
GASCAR
AUSTRALIA
ANTARCTICA
Figure 5-9 Page 106
65 million years ago
Present

48. Mass Extinctions End of Cretaceous –
What changes in life forms?
What was the cause?
What organisms underwent widespread adaptive radiation?
End of Permian – 90% of life went extinct

49. Rate of Extinction Biodiversity = speciation minus extinction
Background vs mass extinctions
As species become extinct, genes “remain” from ancestral species
Estimate – human caused extinction increase of 100X to 1000X background
READ: The Future of Evolution – answer #1, then #2 (assume you agree)
What could be the effect on humans of a mass extinction?