1. UNIT VIII EVOLUTION Big Campbell Baby Campbell Hillis Ch 22-28, 31

2. I. EVOLUTION - WHAT IS IT? “Descent with Modification” “Change”
Population
November 24, 1859

3. II. Hardy-Weinberg Principle
Means used to determine if a population is evolving
Predicts allele frequency in a non-evolving population; that is, a population in equilibrium
States that allele frequencies in a population will remain constant from generation to generation if five conditions are met 3

4. II. Hardy-Weinberg Principle, cont
Five Conditions for Hardy-Weinberg Equilibrium:
If any of these conditions are not met, evolutionary change will occur! 4

5. II. Hardy-Weinberg Principle, cont
Hardy-Weinberg Equation
p = frequency of one allele (A)
q = frequency of other allele (a)
p + q =
Therefore,
p =
q =
Genotype Frequency
AA =
aa =
Aa =
To determine distribution of genotype frequencies in a population → 5

6. II. Hardy-Weinberg Principle, cont
Hardy-Weinberg Practice Problems
If you know that you have 16% recessive fish (bb), . . .
q 2 =
q =
Therefore, p =
To calculate the frequency of each genotype …
p2 =
2pq =
What is the expected percentage of heterozygous fish? 6

7. II. Hardy-Weinberg Principle, cont
Hardy-Weinberg Practice Problems, cont
If in a population of 1,000, 90 show recessive phenotype (aa), use Hardy-Weinberg to determine frequency of allele combinations.
In people light eyes are recessive to dark. In a population of 100 people, 36 have light eyes. What percentage of the population would be …
Homozygous recessive?
Homozygous dominant?
Heterozygous? 7

8. II. Hardy-Weinberg Principle, cont
The ability to roll the tongue is a dominant trait. … 75% of the students at
Kingwood High School have the ability to roll the tongue. Assuming the
student population is 2526,
How many students would exhibit each of the possible genotypes?
How many students would exhibit each of the possible phenotypes?

9. III. A HISTORY OF EVOLUTIONARY THEORY
Aristotle ( BCE)
Scala Naturae
Carolus Linnaeus ( )
Taxonomy

10. III. A HISTORY OF EVOLUTIONARY THEORY, cont

11. III. A HISTORY OF EVOLUTIONARY THEORY, cont
Charles Darwin ( )

12. III. A HISTORY OF EVOLUTIONARY THEORY, cont
Darwin, cont
Observed many examples of adaptations
Inherited characteristics that enhance organisms’ survival and reproduction
Based on principles of natural selection
Populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others
Differential reproductive success

13. III. A HISTORY OF EVOLUTIONARY THEORY, cont
Darwin’s Conclusions
Based on his own observations and the work of other scientists, Darwin realized …
Members of a population often vary greatly in their traits.
Traits are inherited from parents to offspring.
All species are capable of producing more offspring that their environment can support, therefore …

14. III. A HISTORY OF EVOLUTIONARY THEORY, cont
Darwin concluded …
Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals.
This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.
Descent with Modification

15. III. A HISTORY OF EVOLUTIONARY THEORY, cont
Artificial Selection

16. III. A HISTORY OF EVOLUTIONARY THEORY, cont
Post-Darwin
Neo-Darwinism/Modern Synthesis Theory
Epigenetics

17. IV. EVIDENCE FOR EVOLUTION
Direct Observation
Antibiotic/Drug Resistance

18. IV. EVIDENCE FOR EVOLUTION, cont
Fossil Record
Succession of forms over time
Transitional Links
Vertebrate descent

19. IV. EVIDENCE FOR EVOLUTION, cont
Homology
Homologous structures
Vestigial organs
Snakes
Cetaceans
Flightless birds

20. IV. EVIDENCE FOR EVOLUTION, cont
Convergent Evolution
Independent evolution of similar features in different lineages
Analogous structures

21. IV. EVIDENCE FOR EVOLUTION, cont
Biogeography
Geographical distribution of species
Continental Drift
Pangaea
Endemic species
Islands are inhabited by organisms most closely resembling nearest land mass

22. IV. EVIDENCE FOR EVOLUTION, cont
Comparative Embryology
Pharyngeal Pouches
Gill slits
Tail

23. IV. EVIDENCE FOR EVOLUTION, cont
Molecular Biology
Similarities in DNA, proteins, genes, and gene products
Common genetic code

24. V. MICROEVOLUTION
A change in the gene pool of a population over a succession of generations
Five main causes:

25. V. MICROEVOLUTION, cont Genetic Drift
Changes in the gene pool due to chance.
More often seen in small population sizes.
Usually reduces genetic variability.
There are two situations that can drastically reduce population size:
Bottleneck Effect
Founder Effect

26. V. MICROEVOLUTION, cont Bottleneck Effect Founder Effect
Type of genetic drift resulting from a reduction in population (natural disaster)
Surviving population is no longer genetically representative of the original population
Founder Effect
Due to colonization by a limited number of individuals from a parent population
Gene pool is different than source population

27. V. MICROEVOLUTION, cont Gene Flow
Genetic exchange due to the migration of fertile individuals or gametes between populations – tends to reduce differences between populations

28. V. MICROEVOLUTION, cont Mutations
A change in an organism’s DNA (gametes; many generations); original source of genetic variation (raw material for natural selection)

29. V. MICROEVOLUTION, cont
Nonrandom Mating
Inbreeding
Assortative mating

30. V. MICROEVOLUTION, cont Natural Selection
Only form of microevolution that adapts a population to its environment

31. VI. VARIATION IN POPULATIONS
Genetic Variation is the “substrate” for evolution
Maintained through …
Polymorphism
Coexistence of 2 or more distinct forms of individuals (morphs) within the same population
Geographical Variation
Differences in genetic structure between populations (cline)

32. VI. VARIATION, cont Mutation and Recombination Diploidy
2nd set of chromosomes hides variation in the heterozygote
Balanced Polymorphism
Heterozygote Advantage
Frequency-Dependent Selection
Survival & reproduction of any 1 morph declines if it becomes too common
Parasite/host

33. VII. A CLOSER LOOK AT NATURAL SELECTION
Not a random process → Dynamic process
Increases frequency of alleles that provide reproductive advantage
Fitness

34. VII. CLOSER LOOK AT NATURAL SELECTION, cont
Natural selection is the only evolutionary mechanism for adaptive evolution

35. VII. CLOSER LOOK AT NATURAL SELECTION, cont
Three ways in which natural selection alters variation
Directional
Disruptive
Stabilizing

36. VII. CLOSER LOOK AT NATURAL SELECTION, cont
Sexual Selection
Can result in sexual dimorphism - secondary sex characteristic distinction
Intrasexual Selection
Intersexual Selection

37. VIII. MACROEVOLUTION Macroevolution “Species”
Refers to the formation of new taxonomic groups
Due to an accumulation of microevolutionary changes
AKA Speciation
“Species”
Morphological Species Concept
Ecological Species Concept
Phylogenetic Species Concept

38. VIII. MACROEVOLUTION, cont
Biological Species Concept
Described by Ernst Mayr in 1942
A population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring; in other words, similar organisms that can make babies that can make babies 
Can be difficult to apply to certain organisms . . .

39. VIII. MACROEVOLUTION, cont
Reproductive Isolation
Prevent closely related species from interbreeding when their ranges overlap.
Divided into 2 types
Prezygotic
Postzygotic

40. VIII. MACROEVOLUTION, cont
Prezygotic Reproductive Barriers

41. VIII. MACROEVOLUTION, cont
Postzygotic Reproductive Barriers

42. VIII. MACROEVOLUTION, cont
Speciation
Fossil record shows evidence of bursts of many new species, followed by periods of little chance
Known as punctuated equilibrium
Other species appear to change more gradually
Gradualism fits model of evolution proposed by Darwin

43. VIII. MACROEVOLUTION, cont
Modes of Speciation
Based on how gene flow is interrupted
Allopatric
Populations segregated by a geographical barrier; can result in adaptive radiation (island species)
Sympatric
Reproductively isolated subpopulation in the midst of its parent population (change in genome); polyploidy in plants; cichlid fishes

44. IX. HISTORY OF LIFE ON EARTH

45. IX. HISTORY OF LIFE ON EARTH, cont
Formation of Organic Molecules
Oparin/Haldane Hypothesis
Primitive Earth’s atmosphere was a reducing environment
No O2
Early oceans were an organic “soup”
Lightning & UV radiation provided energy for complex organic molecule formation
Miller/Urey Experiment
Tested Oparin/Haldane hypothesis
Simulated atmosphere composed of water, hydrogen, methane, ammonia
All 20 amino acids, nitrogen bases, ATP formed
Hypothesis was supported 45

46. IX. HISTORY OF LIFE ON EARTH, cont46

47. IX. HISTORY OF LIFE ON EARTH, cont47

48. IX. HISTORY OF LIFE ON EARTH, cont
Mass Extinctions

49. IX. HISTORY OF LIFE ON EARTH, cont
Adaptive Radiation
Periods of evolutionary change, increased speciation
Often due to increased ecological niches in communities
Also seen in organisms with major evolutionary innovations

50. IX. HISTORY OF LIFE ON EARTH, cont

52. X. PHYLOGENY
Taxonomy
Linnaeus
Binomial nomenclature
Taxon (taxa) 52

53. X. PHYLOGENY, cont
Evolutionary history of an organism

54. X. PHYLOGENY, cont Phylogenetics Tracing of evolutionary relationships
Illustrated with diagrams known as phylogenetic trees

55. X. PHYLOGENY, cont
Important to distinguish between homologies and analogies
Homologies are likenesses attributed to common ancestry
Analogies are likenesses attributed to similar ecological roles and natural selection
May also be done at a molecular level
Known as molecular systematics 55

56. X. PHYLOGENY, cont Cladistics
Use of common ancestry as primary criterion for classification
Species are put into groups known as clades
Includes ancestral species + descendents
Clades are sub-categorized as
Monophyletic – Includes ancestral group and all descendents
Paraphyletic – Includes ancestral group and some, but not all descendents
Polyphyletic – Includes taxa with multiple ancestors
Parsimony – Also known as Occam’s Razor

57. X. PHYLOGENY, cont 57

58. X. PHYLOGENY, cont