1. Darwin and His Theory
4/20/2017
Evolution
Nothing in biology makes sense except in the light of evolution. – Theodosius Dobzhansky
Charles Darwin in later years
G. Podgorski, Biol. 1010

2. Darwin and His Theory
4/20/2017
What is Evolution?
The kind we’re talking about is sometimes called organic evolution to distinguish it from non-biological changes over time.
Working definition: Evolution is the progressive change in populations over time.
NOT SPECIES, NOT INDIVIDUALS
G. Podgorski, Biol. 1010

3. Evolution Holds a Unique Place in Biology
Darwin and His Theory
4/20/2017
Evolution Holds a Unique Place in Biology
Other disciplines ask how?
Evolutionary biology asks why?
G. Podgorski, Biol. 1010

4. Evolution’s Core Principles
Darwin and His Theory
4/20/2017
Evolution’s Core Principles
Natural selection.
G. Podgorski, Biol. 1010

5. Evolution’s Core Principles
Darwin and His Theory
4/20/2017
Evolution’s Core Principles
Common descent with modification.
G. Podgorski, Biol. 1010

6. Evolutionary Time Scales
Darwin and His Theory
4/20/2017
Evolutionary Time Scales
Macroevolution: Long time scale events that create and eliminate species.
G. Podgorski, Biol. 1010

7. Evolutionary Time Scales
Darwin and His Theory
Evolutionary Time Scales
4/20/2017
Microevolution: Short time scale events (generation-to-generation) that change the genotypes and phenotypes of populations.
We’ll begin our more intensive look at evolution with microevolution.
G. Podgorski, Biol. 1010

8. Darwin’s Voyage of Discovery
Darwin and His Theory
4/20/2017
Darwin’s Voyage of Discovery
A reconstruction of the HMS Beagle sailing off Patagonia.
G. Podgorski, Biol. 1010

9. The Voyage of the Beagle
Darwin and His Theory
4/20/2017
The Voyage of the Beagle
G. Podgorski, Biol. 1010

10. Darwin’s Ideas Did Not Develop in a Vacuum
Darwin and His Theory
4/20/2017
Darwin’s Ideas Did Not Develop in a Vacuum
Charles Lyell –(geologist) uniformatarianism.
The Earth is older than 6,000 years
Contributor’s to Darwin’s thinking included:
Georges Cuvier – species extinction.
Fossils
G. Podgorski, Biol. 1010

11. Darwin’s Ideas Did Not Develop in a Vacuum
Darwin and His Theory
4/20/2017
Darwin’s Ideas Did Not Develop in a Vacuum
Contributor’s to Darwin’s thinking included:
Thomas Malthus – struggle for existence.
Carrying capacity: J curve/S curve
Jean Baptiste de Lamarck – evolution by acquired characteristics. First evolution
Theory, Giraffes get taller due to stretching
In parents
G. Podgorski, Biol. 1010

12. Darwin and His Theory
4/20/2017
Alfred Russel Wallace Independently Drew the Same Conclusions as Darwin
Papers from Wallace and Darwin were jointly presented (with little impact) to the Linnaean Society in 1858.
G. Podgorski, Biol. 1010

13. Haeckel: ontogeny recapitulates phylogeny
Thomas Hunt Morgan: Darwin’s bulldog

14. Darwin’s Observations and Inferences Organized by Ernst Mayr
Darwin and His Theory
4/20/2017
Darwin’s Observations and Inferences
Organized by Ernst Mayr
Observation 1: Left unchecked, the number of organisms of each species will increase exponentially, generation to generation.
Observation 2: In nature, populations tend to remain stable in size.
Observation 3: Environmental resources are limited.
Inference 1: Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals, with only a fraction of offspring surviving in each generation.
G. Podgorski, Biol. 1010

15. Darwin’s Observations and Inferences
Darwin and His Theory
4/20/2017
Darwin’s Observations and Inferences
Observation 4: Individuals of a population vary extensively in their characteristics with no two individuals being exactly alike.
Observation 5: Much of this variation between individuals is heritable.
G. Podgorski, Biol. 1010

16. Darwin’s Observations and Inferences
Darwin and His Theory
4/20/2017
Darwin’s Observations and Inferences
Inference 2: Survival in the struggle for existence is not random, but depends in part on the heritable characteristics of individuals. Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals.
G. Podgorski, Biol. 1010

17. Darwin’s Observations and Inferences
Darwin and His Theory
4/20/2017
Darwin’s Observations and Inferences
Inference 3: The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection).
Taken together, these three inferences are a statement of Darwin’s Theory of Evolution.
G. Podgorski, Biol. 1010

18. The Weak Link of Genetics and the Modern Synthesis
Darwin and His Theory
4/20/2017
The Weak Link of Genetics and the Modern Synthesis
Darwin in his early years.
A major problem in Darwin’s theory was the lack of a mechanism to explain natural selection. (No mitosis, meiosis, replication, chromosomes, laws of inheritance)
How could favorable variations be transmitted to later generations?
With the rediscovery of Mendel’s work and its vast extension in the first half of the 20th century, the missing link in evolutionary theory was forged.
Darwinian theory supported by genetics is known as the modern synthesis.
G. Podgorski, Biol. 1010

19. Discomfort With Evolution
Darwin and His Theory
4/20/2017
Discomfort With Evolution
An early disparaging view of evolutionary theory and its creator.
The upheaval surrounding evolution began with publication of On the Origin of Species and continues nearly 150 years later.
1925
G. Podgorski, Biol. 1010

20. Discomfort With Evolution
Darwin and His Theory
4/20/2017
Discomfort With Evolution
November, 2005
G. Podgorski, Biol. 1010

21. Discomfort With Evolution
Darwin and His Theory
4/20/2017
Discomfort With Evolution
December, 2005
G. Podgorski, Biol. 1010

22. Discomfort With Evolution
Darwin and His Theory
4/20/2017
Discomfort With Evolution
Two of many arguments made against evolution are:
Evolution is only a theory.
No one’s ever seen evolution.
The first point is true, but misses the meaning of scientific theory, and the second point is easily countered.
G. Podgorski, Biol. 1010

23. Evidence for Evolution – The Fossil Record
Darwin and His Theory
Evidence for Evolution – The Fossil Record
4/20/2017
G. Podgorski, Biol. 1010

24. Evidence for Evolution - Comparative Morphology Homologous structures
Darwin and His Theory
4/20/2017
Evidence for Evolution - Comparative Morphology
Homologous structures
Why use the same skeletal plan for these very different appendages?
G. Podgorski, Biol. 1010

25. Evidence for Evolution - Comparative Embryology
Darwin and His Theory
4/20/2017
Evidence for Evolution - Comparative Embryology
Why do embryos of different animals pass through a similar developmental stage?
Recent discoveries of the conservation of molecular mechanisms of development are even more compelling.
G. Podgorski, Biol. 1010

26. Darwin and His Theory
4/20/2017
Evidence of Evolution –Conservation and Diversification at the Molecular Level
Why should different organism possess related genes?
Why does the degree of relationship of genes match their degree of relationship established by other methods?
G. Podgorski, Biol. 1010

27. Evidence for Evolution – Evolution Observed
Darwin and His Theory
Evolution of pesticide resistance in response to selection.
4/20/2017
Evidence for Evolution – Evolution Observed
G. Podgorski, Biol. 1010

28. Evidence for Evolution – Evolution Observed
Darwin and His Theory
4/20/2017
Evidence for Evolution – Evolution Observed
Evolution of drug-resistance in HIV
G. Podgorski, Biol. 1010

29. Modes of Selection

30. Special Examples
Kin Selection: relative fitness includes fitness of close relatives
Artificial selection: farming/animal breeding
Sexual selection: based on mating
Convergent evolution: different ancestor common lifestyle (analogous structures result)
Divergent evolution: common ancestor different lifestyle (homologous structures result)
Parallel evolution: evolving in the same pattern
Coevolution: two evolving each other

31. Speciation Steps in the process: Subdivision of the population
Evolution of each subpopulation in independent directions
Change in population that reproductively isolates the population from the other.
Return to same setting and no longer can members of the two populations mate.

32. Speciation
Allopatric: Geographical separation leads to initial subdivision of the population.
Rivers, volcanoes, earthquakes, roads, train lines, etc..

33. Sympatric speciation
Sympatric: Isolation of populations occurs while organisms have physical contact with each other.

34. More sympatric
Apple maggot flies

35. Temporal/Sympatric speciation

36. Reproductive Isolation
Prezygotic vs. Postzygotic
Needed for speciation: Organisms can look somewhat different and still be one species if this does not occur.
Organisms can look very much alike, but be two species if this occurs.
The idea is that eventually diversity will build up in the populations independently and thus would eventually look different.

37. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Darwin and His Theory
4/20/2017
Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Courtship rituals, like these, are critical for mating within a species, but ineffective for attracting members of other species.
G. Podgorski, Biol. 1010

38. Behavioral Isolation Mechanisms
Darwin and His Theory
4/20/2017
Behavioral Isolation Mechanisms
Courtship rituals, like these, are critical for mating within a species, but ineffective for attracting members of other species.
G. Podgorski, Biol. 1010

39. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Darwin and His Theory
4/20/2017
Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
(different habits within an overlapping range)
G. Podgorski, Biol. 1010

40. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Darwin and His Theory
4/20/2017
Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
G. Podgorski, Biol. 1010

41. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
Darwin and His Theory
4/20/2017
Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation
G. Podgorski, Biol. 1010

42. Speciation Dynamics - Gradualism or Punctuated Equilibrium?
Darwin and His Theory
4/20/2017
Speciation Dynamics - Gradualism or Punctuated Equilibrium?
Punctuated equilibrium appears to be a more accurate view of speciation dynamics.
: long period lacking speciation where variation builds up followed by some dramatic change in the environment that leads to a struggle for survival and lots of speciation and microevolution.
G. Podgorski, Biol. 1010

43. Evolution possibilities
Convergent evolution: leads to analogous structures. (same function/different ancestry)

44. Parallel evolution vs. Coevolution
A: divergent B: convergent C. parallel

45. Divergent evolution
Divergent evolution: leads to homologous structures. (same ancestry/different function)

46. Coevolution
Yucca moth and Yucca flower

47. Does coadaptation mean coevolution?