1. UNIT VIII EVOLUTION Baby Campbell Ch 19-23, 27 Big Campbell

2. I. A HISTORY OF EVOLUTIONARY THEORY

3. I. A HISTORY OF EVOLUTIONARY THEORY, cont
Darwin
As he traveled, he observed many examples of adaptations
He recognized adaptations lead to differential reproductive success
Based on his study of other works, he also knew
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.
His observations and subsequent reflections allowed him to propose his hypothesis for evolutionary change; descent with modification
Species are not immutable
Divergent species share a common ancestor
The mechanism that produces change in species is natural selection: the differential survival and reproduction of individuals in a population based on variation in their traits.

4. II. Hardy-Weinberg Principle
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
Used to identify evolving/study populations 4

5. II. Hardy-Weinberg Principle, cont
Five Conditions for Hardy-Weinberg Equilibrium: 5

6. 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 → 6

7. 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? 7

8. II. Hardy-Weinberg Principle, cont
If in a population of 1,000, 90 show recessive phenotype (aa), use Hardy-Weinberg to determine frequency of allele combinations. 8

9. II. Hardy-Weinberg Principle, cont
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?

10. 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?

11. II. Hardy-Weinberg Principle, cont
PTC
Taster or Non-taster?
75% Tasters
25% Non-tasters

12. III. EVIDENCE FOR EVOLUTION
Direct Observation
Antibiotic/Drug Resistance

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

14. III. EVIDENCE FOR EVOLUTION, cont
Homology
Homologous structures
Vestigial organs
Snakes
Cetaceans
Flightless birds

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

16. III. 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
Comparative Embryology
Pharyngeal Pouches
Gill slits
Tail

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

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

19. IV. 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

20. IV. MICROEVOLUTION, cont
Bottleneck Effect
Type of genetic drift resulting from a reduction in population (natural disaster)
Surviving population is no longer genetically representative of the original population

21. IV. MICROEVOLUTION, cont
Founder Effect
Due to colonization by a limited number of individuals from a parent population
Gene pool is different than source population

22. IV. MICROEVOLUTION, cont
Gene Flow
Genetic exchange due to the migration of fertile individuals or gametes between populations
Tends to reduce differences between populations

23. IV. MICROEVOLUTION, cont
Mutations

24. IV. MICROEVOLUTION, cont
Nonrandom Mating
Inbreeding
Assortative mating

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

26. V. VARIATION IN POPULATIONS
Genetic Variation
Critical for species/population success
“Substrate” for evolution
Mutation and Recombination
Diploidy
Balanced Polymorphism
Heterozygote Advantage
Frequency-Dependent Selection

27. VI. A CLOSER LOOK AT NATURAL SELECTION
Not a random process → Dynamic process
Increases frequency of alleles that provide reproductive advantage
Fitness
Natural selection is the only evolutionary mechanism for adaptive evolution

28. VI. CLOSER LOOK AT NATURAL SELECTION, cont
Three ways in which natural selection may alter variation
Directional
Disruptive
Stabilizing

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

30. VII. MACROEVOLUTION Macroevolution “Species”
Refers to the formation of new taxonomic groups
Due to an accumulation of microevolutionary changes
AKA Speciation
“Species”
Biological Species Concept

31. VII. MACROEVOLUTION Reproduction
Asexual vs Sexual Reproduction

32. VII. MACROEVOLUTION Reproduction, cont
Prokaryotes
Fungi
Plants

33. VII. MACROEVOLUTION Reproduction, cont
Animals
Asexual Reproduction
Budding
Fission
Fragmentation/Regeneration
Parthenogenesis
Sexual Reproduction
External Fertilization
Internal Fertilization

34. VII. MACROEVOLUTION Reproduction, cont
Sexual Reproduction
Strategies
Hermaphroditism
Sequential Hermaphroditism
Protogynous - female first
Protandrous – male first
Pheromes
Chemical signals released by organism
Influences behavior, physiology of organisms of same species
Active in minute amounts

35. VII. MACROEVOLUTION, cont
Reproductive Isolation
Important to maintain integrity & continuity of a species
Prevents closely related species from interbreeding when their ranges overlap.
Divided into 2 types
Prezygotic
Postzygotic

36. VII. MACROEVOLUTION, cont

37. VII. MACROEVOLUTION, cont

38. VII. 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

39. VII. MACROEVOLUTION, cont
Modes of Speciation
Based on how gene flow is interrupted

40. VII. MACROEVOLUTION, cont
Allopatric
Populations segregated by a geographical barrier; can result in adaptive radiation (island species)

41. VII. MACROEVOLUTION, cont
Sympatric
Reproductively isolated subpopulation in the midst of its parent population (change in genome); polyploidy in plants; cichlid fishes

42. VIII. HISTORY OF LIFE ON EARTH

43. VIII. 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

44. VIII. HISTORY OF LIFE ON EARTH, cont
Formation of Organic Molecules, cont
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 44

45. VIII. HISTORY OF LIFE ON EARTH, cont45

46. VIII. HISTORY OF LIFE ON EARTH, cont

47. VIII. HISTORY OF LIFE ON EARTH, cont
Mass Extinctions

48. VIII. 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

49. IX. PHYLOGENY

50. IX. PHYLOGENY, cont Taxonomy Naming and classifying of organisms
Binomial nomenclature
Molded by phylogeny

51. IX. PHYLOGENY, cont Phylogeny, cont
Evolutionary history of an organism
Represented with a phylogenetic tree
A lineage is comprised of ancestor and descendant populations
A taxon is any group represented with a name
Sister taxa are groups of organisms that share an immediate common ancestor that is not shared by the other groups represented
Basal taxon is group that diverges early in the group’s history
Each branch point represents the common ancestor of two evolutionary lineages that have diverged

52. IX. PHYLOGENY, cont
Trees
Root
Node
Extant versus Extinct

53. IX. PHYLOGENY, cont Taxa are sub-categorized as
Monophyletic – Includes ancestral group and all descendants
Clade
Paraphyletic – Includes ancestral group and some, but not all descendants
Polyphyletic – Includes taxa with multiple ancestors

54. IX. PHYLOGENY, cont

55. IX. PHYLOGENY, cont Tree Construction Homology
Heritable traits shared by 2 or more ancestors
Example: backbone in all vertebrates
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
Analogies are also known as homoplasies
May also be done at a molecular level 55

56. IX. PHYLOGENY, cont Tree Construction, cont Ancestral Trait
Derived Traits
Synapomorphies
May see evolutionary reversals
Relative term
Ingroup
Groups of organisms being considered, phylogenetically organized
Outgroup
Group chosen as point of reference for tree
Closely related but diverged before the ingroups

57. IX. PHYLOGENY, cont Tree Construction, cont Parsimony
Also known as Occam’s Razor
Principle that if multiple trees are possible, the correct one is most often the one with the fewest evolutionary changes

58. IX. PHYLOGENY, cont 58

59. IX. PHYLOGENY, cont - + Derived Trait Taxon Fur Gizzard Claws/ Nails
Taxon
Derived Trait
Fur
Gizzard
Claws/
Nails
Lungs
Feathers
Jaws
Mammary Glands
Keratinous Scales
Lamprey -
Chimp +
Crocodile
Lizard
Mouse
Perch
Pigeon
Salamander

60. IX. PHYLOGENY, cont
Ring of Life

61. IX. PHYLOGENY, cont
PhyloCode

62. X. KINGDOM ANIMALIA PHYLOGENY