1. Gene Pool

2. A change in the genetic make-up of a population over time.
What is Evolution?
A change in the genetic make-up of a population over time.

3. How Does Evolution Occur?
There were two hypotheses

4. Evolution by acquired traits by Jean Baptiste de Lamarck

5. Do we acquire traits? Eating Show affection Defend yourself Act nutty
Climbing
Eating
Show affection
Defend yourself
Act nutty

6. These traits are not genetic so evolution does not occur

7. How Does Evolution Occur?
NATURAL SELECTION !!! (major mechanism of evolution)
Darwin’s hypothesis (now a theory):
Survival of the fittest…..how is fitness measured?
By reproductive success
Inheritable variations occur in individuals in a population. Due to competition for limited resources, individuals with more favorable variations or phenotypes are more likely to survive & produce more offspring, thus passing traits to future generations.

8. Darwin’s View of History
Like a Tree with multiple branches.
Common trunk
Tips of twigs = diversity of organisms living in the present.
Forks = most recent common ancestor

9. Natural Selection Summary
A process in which individuals that have certain heritable traits survive & reproduce at a higher rate than others because of those traits.
Over time, natural selection can increase the match between organisms & their environment.
If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species.

10. Natural Selection acts on phenotypic variations in populations
Environments change and act as selective mechanism on populations.

11. Phenotypic variations are not directed by the environment but occur through random changes in the DNA and through new gene combinations.

12. Some phenotypic variations significantly increase or decrease fitness of the organism and the population.

13. Explain 2 examples of Evolution in response to environmental change; 1 must be antibiotic resistance in bacteria

14. Examples of Natural Selection
Antibiotic resistance in bacteria
Develops in several steps:
Person is sick from a bacterial infection
Takes antibiotics
Gets better
One bacteria is not killed by the antibiotics, due to genetic modification & reproduces
Person gets sick again & goes to the doctor again
Same antibiotic is prescribed but there’s no effect
Doctor prescribes a different antibiotic which hopefully works.
If bacterium continues to change it could become resistant to more antibiotics

15. Examples of Natural Selection
Pesticide resistance in rats
Apply pesticide…most rats killed
Due to natural variations, a few rats are not affected by the poison.
They reproduce passing on the trait to some if not all of their offspring
Seeing the rats, you apply the pesticide again with worse results.
A new pesticide must be used.

16. Artificial Selection
Darwin used these examples to help him derive another piece of his theory.
Humans impact the gene variation.

17. What Evidence is there that Evolution by Natural Selection occurs?
Direct observations
Peppered moths
Drug resistant bacteria
Analysis of similarities among different organisms.
Homologous structures
Vestigial structures
Fossil Record
Documents the pattern of evolution
Shed light on origin of new groups of organisms
Biogeography
Geographical distribution of species
Continental drift (slow movement of the continents over time)
Help make predictions of where fossils of groups of organisms can be found

18. Direct observations

19. Analysis of similarities among different organisms
Homologous structures: represent variations on a structural theme that was present in their common ancestor.
Vestigial structures: remnants of features that served important functions in the organism’s ancestors.

20. Convergent Evolution: independent evolution of similar features in different lineages.
Species that share features because of convergent evolution are said to be analogous. Analogous features share similar function but not common ancestry.

21. Fossil Record
Fossils can be dated, this helps us provide evidence of evolution by dating rocks where fossils are found, it helps indicate the relationships within phylogenetic trees, as well as chemical properties &/or geographical data.
Allow us to take a look at how new groups came about & when characteristics showed up.
EX: Cetaceans are closely related to even-toed ungulates.

22. Biogeography
We can use our understanding of evolution and continental drift to predict where fossils of different groups of organisms might be found.
EX: Horses
Fossil dating indicates horses originated in North America 5 million years ago.
Since North & South America were not yet connected it was predicted that the oldest horse fossils would be located in North America.
So far the prediction has been upheld

23. The environment does not direct the changes in DNA, but acts upon phenotypes that occur through random changes in DNA
These changes can involve alterations in DNA sequences, changes in gene combinations, and/or the formation of new gene combinations.

24. Environments are always changing
No “perfect” genome (entirety of an organism's hereditary information).
Diverse gene pool = long term survival in a changing environment.
Mutations contribute to diversity
Some are silent
Some result in phenotypic difference
Interaction of the environment & phenotype determines fitness.

25. What does “survival of the fittest” mean?
The species that are most adapted in their environment by reproducing more successfully will survive.

26. Mutation
Change in the nucleotide sequence (are rare; change from gen. to gen. is very small.
In multicellular organisms, only mutations occurring in gametes will be passed on to offspring
Most occur in somatic cells.
Some are “silent” changes
Point mutation

27. Genes duplicating Due to errors in meiosis During DNA replication
Activities of transposable elements
(wandering DNA segments)
Large chromosome segment duplications are usually harmful
Smaller pieces of DNA may not be.
Gene duplications that don’t have severe effects can persist & accumulate = potential new genes with new functions.

28. Example of Beneficial Increases in Gene Numbers
A remote ancestor had a single gene for detecting odors & have duplicated over time. Today we have about 1,000 olfactory receptor genes.

29. Evolving Populations What is a population?
A group of individuals of the same species that live in the same area & interbreed, producing fertile offspring.

30. We can characterize a population’s genetic make-up by describing its gene pool.
What is a gene pool?
The total number of genes of every individual in an interbreeding population.
The size of the gene pool affects the rate of mutation

31. Why is it vital to have diversity in the gene pool?
Environmental conditions change
What kills one would kill them all.

32. Clearing Potential Misunderstandings
Natural selection acts on ___________
Ex: pepper moths
_____________not individuals evolve.
Organisms that are _______________ fit will pass on their _________.
PHENOTYPE
POPULATIONS
REPRODUCTIVELY
GENES

33. G.H. Hardy & W. Weinberg (1908)
Both men independently suggested a scheme whereby evolution could be viewed as changes in the frequency of alleles in a population of organisms.

34. Calculating changes in allele frequency
Hardy-Weinberg
For populations to be at equilibrium (remain constant) the following conditions must be met.
Population must be large
Absence of migration
No net mutations
Random mating
Absence of selection
These conditions are seldom if ever met.

35. Of what value is this?
Provides a yardstick by which changes in allele frequency, & therefore evolution, can be measured.

36. The Hardy-Weinberg Equation
Tests whether a population is evolving.

37. The Hardy-Weinberg Principle
The equation determines what the genetic make-up of a population would be if it were not evolving at that locus.
Those results are compared to data from an actual population
If there are no differences, it can be concluded that the “real” population is not evolving
It is also used in medical applications:
Est. the % of a population that carries the allele for an inherited disease.

38. Knowing the frequency of the phenotype, you can calculate the frequency of the genotypes and alleles in the population.
Because there are only two alleles, the sum of p and q must always equal 1.
This equation finds the allele frequency
p + q = 1
= frequency of the dominant
allele
=frequency of the recessive
allele

39. The Hardy-Weinberg equilibrium can be written as an equationp2 q2 1
2pq + = +
% of Individuals homozygous for allele bb written as a decimal
% of Individuals homozygous for allele BB written as a decimal
% of Individuals heterozygous for alleles Bb written as a decimal
By convention
The more common allele (B) is designated p
The less common allele (b) is designated q
This equation lets us calculate genotypic/phenotypic frequencies in a very simple way.

40. 142/546 = .26 which represents q2 or gg
Let’s say we have a population of 546 frogs. 142 of these frogs have dark spots on them. The plain green frogs are completely dominant to the spotted frogs. Determine the genotypic frequencies within this population.
142/546 = .26 which represents q2 or gg
In order to get the homozygous dominant & heterozygous we need to use the p + q = 1 equation.
q2 = .26  take the square root of each side to get q which is .51
p2 = .24
p + q = 1 p= 1- q p=  p = .49 
2pq = 2(.51 x .49) = .50
So, 26% of the frogs are recessive; 50% are heterozygous; 24% are homozygous dominant.

41. Which means 51% of the population carries at least one g allele.
To determine the frequency of gametes carrying the dominant allele. Meaning the percent of the population carrying at least one dominant allele:
You would take half of the 2pq frequency and add it to the p2 frequency.
= .49
Which means, 49% of the frog population carry at least one dominant allele.
To determine the recessive frequency take half of the 2pq & add to q2
= .51
Which means 51% of the population carries at least one g allele.

42. Cystic fibrosis is caused by the recessive allele b.
CALCULATING THE FREQUENCY OF CYSTIC FIBROSIS
Cystic fibrosis is caused by the recessive allele b.
Calculate the frequency of the recessive allele
If q2, the frequency of recessive homozygotes, is , then q is , or √
Calculate the frequency for the dominant allele B:
p + q = 1 , p = 1-q SO
p = 1 – 0.022, OR
Determine the frequency of heterozygotes
2pq = x x =
Meaning: 43 of every 1,000 Caucasian North Americans are predicted to carry the cystic fibrosis allele unexpressed.

43. TONGUE CURLING!!! How would we determine q2? How do you determine q?
What percentage of the class are carriers for the tongue curling trait? (Tongue curling is a dominant trait.)
Try to curl your tongue upwards.
How would we determine q2?
Divide the total number of non-curler students by the total number of students.
How do you determine q?
Calculate the square root of q2.
Since p + q= 1; determine p.
Now plug in numbers for 2pq.

44. Time for a simulation!!!
Let’s Get It On!!!!

45. Genotypes
# of Students
# of A’s
# of a’s AA Aa aa
Total
Genotypes
# of Students
# of A’s
# of a’s AA Aa aa
Total
Genotypes
# of Students
# of A’s
# of a’s AA Aa aa
Total

46. Case Studies p= q= Genotype Frequency: TOTAL number of A alleles
TOTAL number of alleles in the population
TOTAL number of a alleles q=
TOTAL number of alleles in the population

47. Number of alleles present after several generations
Number of offspring with AA _____X 2= _________ A alleles
Number of offspring with Aa _____X 1= __________A alleles
Total= __________A alleles
TOTAL number of A alleles
p =
TOTAL number of alleles in the population
(number of students X 2)

48. Altering Allele Frequencies in Populations Directly & cause most Evolutionary Change
Natural Selection
Genetic drift
Gene Flow

49. Genetic Drift Random fluctuation of alleles due to chance events
More likely to occur in smaller population
Founder effect
Small group of individuals establishes a population in a new location
Bottleneck effect
A sudden decrease in population size to natural forces

50. Case Study: Genetic Drift
The land was being converted to farmland and other uses.
Led to significant loss of genetic variation & an increase in the frequency of harmful alleles.
A reduction of genetic variation within a given population can increase the differences between populations of the same species.

51. Gene Flow
The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.
If there is gene flow between two populations there is a tendency for the amount of genetic variation between the populations to decrease.

52. Natural Selection is the only mechanism that consistently causes adaptive evolution

53. Increase in the frequency of the intermediate phenotype
Stabilizing Selection
Increase in the frequency of the intermediate phenotype
Fig
In humans, infants with intermediate weight at birth have the highest survival rate
In chicken, eggs of intermediate weight have the highest hatching success

54. Disruptive Selection
In the African seed-cracker finch, large- and small-beaked birds predominate
Can open tough shells of large seeds
Intermediate-beaked birds are at a disadvantage
Unable to open large seeds
Too clumsy to open small seeds
More adept at handling small seeds

55. Directional Selection
Drosophila flies that flew toward light were eliminated from the population
The remaining flies were mated and the experiment repeated for 20 generations
Common when environment changes or members of a population migrate out.
Phototropic flies are far less frequent in the population

56. Sexual Selection
Sexual selection acts on an organism's ability to obtain (often by any means necessary!) or successfully copulate with a mate.
Sexual dimorphism- a difference in the 2 sexes
Sexual selection is often powerful enough to produce features that are harmful to the individual’s survival.
Australian Peacock Spiders

57. Operations of Sexual Selection
Intrasexual selection:
Intersexual selection:
Individuals of one sex compete for mates of the opposite sex. Mostly males compete but there are some species where females compete (ring-tailed lemurs and broad-nosed pipefish)
“mate choice” – individuals of one sex (usually females) are choosy in selecting their mates of opposite sex. Many cases it falls to the male’s showiness or behavior that wins the female.

58. Why natural selection cannot fashion perfect organisms
Limited by species ancestors
Birds ancestors are reptiles & only had 4 legs. Wings were opted for flight so that left only 2 legs left.
Adaptations are often compromises
Seals spend a lot of time on rocks so legs would be a better trait than flippers but then they would not swim as well.
Chance & natural selection interact
Snakes are carried to different islands on seaweed rafts but the snakes that are carried are not necessarily the snakes best suited to the environment.
Selection can edit out only existing variations
New alleles do not arise on demand

59. The biological species concept
Emphasizes reproductive isolation

60. Belonging to the same biological species
Means you are reproductively compatible, potentially.
But, it all hinges on…
Reproductive barriers:
Impede members of two species from producing viable, hybrids.
One barrier may not impede but a combination of several can isolate a species gene pool.

61. Prezygotic & Postzygotic Barriers
Impede mating or hinder the fertilization.
POSTZYGOTIC:
If the sperm is able to overcome the prezygotic barriers then the zygote may be prevented from developing.

62. Two main ways by which new species form

63. Speciation can take place with or without geographic separation
Reproductive barrier must be present.
-allopolyploidy
-reproductive isolation
-habitat, food source, or
other source not used
by parent pop.
-temporal or behavioral
isolation
Geographic isolation
-reproductive isolation may occur; preventing interbreeding

64. Example of sympatric speciation

65. Adaptive Radiation

66. Tempo of Speciation

68. The study of the evolutionary past of a species.
Phylogeny
The study of the evolutionary past of a species.

69. Systematics
An approach to looking at the diversity & relationships between organisms living & extinct.
Morphology
Biochemical resemblances
Molecular comparisons (ex: DNA)
If similar with any they are likely to be closely related
It’s also good to look at fossils- they reveal ancestral characteristics that may have been lost over time.

70. Sorting Analogy from Homology
How can you tell if the structure is similar because of a common ancestor or due to convergent evolution?
Search for corroborating similarities between the species
Fossil evidence
Look at the complexity of the characters & note points of similarities.

71. Molecular comparisons of Nucleic Acids
Species 1 & 2 DNA are identical
Begin to diverge
Mutations shift the matching sequences
Homologous regions (in yellow) no longer align
Using a computer program homologous regions now align because appropriate gaps were created.

72. Connecting Classification with Evolutionary History

73. Binomial nomenclature
Two part naming system
genus and specific epithet
Canis lupus or

74. 1. Cyanocitta cristata 2. Iris cristata 3. Cyanocitta stelleri
WHICH OF THE FOLLOWING ORGANISMS ARE MORE CLOSELY RELATED & EXPLAIN WHY.
1. Cyanocitta cristata
2. Iris cristata
3. Cyanocitta stelleri

75. Iris cristata
Cyanocitta cristata
Cyanocitta stelleri

76. Hierarchy of Classification

77. Fig. 14.3

80. Using & making a dichotomous key

81. Key:
1. Has light blue colored body… go to 2
Has dark blue colored body… go to 4
2. Has 4 legs… go to 3
Has 8 legs… Deerus octagis
3. Has a tail… Deerus pestis
Does not have a tail… Deerus magnus
4. Has a pointy hump… Deerus humpis
Does not have a pointy hump… go to 5
5. Has ears… Deerus darkus
Does not have ears… Deerus deafus

82. Don’t worry, this won’t hurt
Now it’s your turn 
Don’t worry, this won’t hurt

83. ANIMALS
4 legs
2 legs or less
Has fur
Has no fur
Has 4 wings
Has 2 wings
Has no yellow coloring
Has yellow coloring
a) has 4 legs……………………3
b) has 2 or less legs…………..2
a) has 4 wings……………Dragi purplus
b) has 2 wings……….….Flamo pinketti
a) has fur……………………….4
b) no fur………………..Frogata hoppus
a) no yellow coloring……...Ella phantus
b) yellow coloring……………..5
a) long neck………………..Girafit neket
b) no long neck………....Lionus mainto
Has a long neck
Does not have a long neck

84. Phylogenetic trees & cladograms are graphical representations (models) of evolutionary history that can be tested

85. Phylogenetic Tree
Each branch point represents the divergence of two species from a common ancestor

86. Cladogram – depicts patterns of shared characteristics
Does not imply evolutionary history.
If characteristics are homologous the cladogram can serve as a basis for a part of the phylogenetic tree.
Outgroup?
Ingroup?

87. Making cladograms Organism Multicellular Vertebral column Hair
Placenta
Total of yeses
Sponge
Yes No 1
Sailfish 2
Wombat 3
Elephant 4
elephant
sponge
sailfish
wombat
placenta
hair
Vertebral column
multicellular

88. Constructing a cladogram
Using the following animals, list as many characteristics which each organism possesses .
Create & fill in a chart with the animals & the characteristics you have come up with.
Build your cladogram
Rhesus monkey Snapping Turtle
Kangaroo Human
Bull frog
Tuna

89. Rhesus Monkey
Human
Snapping Turtle
Kangaroo
Bull Frog
Short canine teeth
Tuna
Placenta
Mammary glands
Amniotic sac
Paired legs

90. Using Amino Acid Sequences To Determine Evolutionary Relationships
Homework answers

91. Number of Differences in the Amino Acids Sequences

92. One possible answer

93. Questions from the Worksheet
Species X and Y have 25 amino acid differences. Species X and B have 10 amino acid differences in the same protein. Species Y and B have 27 amino acid differences.
a) Which organism (X, Y, or B) diverged from the common ancestor first? ____________ Explain your reasoning. Y
Species Y has the most differences between the other 2 species. With species X it has 25 differences and with species B it has 27 differences. This indicates that it split off from the common ancestor very early.

94. Species X and Y have 25 amino acid differences
Species X and Y have 25 amino acid differences. Species X and B have 10 amino acid differences in the same protein. Species Y and B have 27 amino acid differences.
b) Which pair of organisms--X & Y, X & B, or Y & B--are likely to share more characteristics than the other two pairs. ______________ Again, explain your reasoning.
X & B
X and B have the fewest amino acid sequence differences between the 3 species. Having the fewest differences indicates a closer relationship.

95. Structural evidence supports the relatedness to all eukaryotes
Cytoskeleton
Membrane-bound organelles
Linear chromosomes
Endomembrane systems, including nuclear envelope.

96. Sometimes the most obvious evidence isn’t the best
Which of these is most likely in your opinion?
Sometimes the most obvious evidence isn’t the best

97. Molecular & genetic evidence from existing and extinct organisms indicates all organisms on Earth share a common ancestral origin of life
Molecular building blocks are common to all life forms
Common genetic code are shared by all modern organisms.
Metabolic pathways are conserved across all currently recognized domains (bacteria, archea, & eukarya)

98. The Universal Tree of Life
1. Last common ancestor of all living things.
2. Possible fusion of bacterium with archea making eukaryotes
3. Symbiosis of mitochondrial ancestor with ancestor of eukaryotes
4. Symbiosis of chloroplast ancestor with ancestor of green plants

99. The History of Life on Earth
Earth formed approximately 4.6 billion years ago. The earliest fossil is dated 3.5 billion years old.

100. Primitive Earth
Provided inorganic precursors from which organic molecules could have been synthesized due to the presence of available free energy & the absence of a significant quantity of oxygen.
These molecules served as monomers of building blocks for the formation of more complex molecules, including amino acids & nucleotides.
Joining of the monomers produced polymers with the ability to replicate, store & transfer information.
The RNA World hypothesis proposes that RNA could have been the earliest genetic material.

101. Miller/Urey Experiment
This experiment showed it was possible to form complex organic molecules from inorganic molecules in the absence of life.

102. How are rocks & fossils dated?
Radiometric dating

103. Fossils have been found linking all the major groups
Fig Whale “missing links”
Fossils have been found linking all the major groups
The forms linking mammals to reptiles are particularly well known

104. Radiometric Dating
Certain atoms are known to decay (break down) at a specific rate. Scientists can look at these atoms to determine how old an organic object is.
Radioactive isotope 14C- gradually decays over time back to 14N (known as Carbon Dating)
It takes ~5600 years for half of the 14C present in a sample to be converted to 14N.
This length of time is called the half-life.
Half life (t1/2): the time needed for half of the atoms of the isotope to decay
For fossils older than 50,000 yrs scientists use other isotopes such as, potassium isotope
t1/2 of 40K = 1.3 billion years to turn to argon (40Ar)

105. Mass Extinctions Are rapid during times of ecological stress.
Fossil records chronicles mass extinctions

106. 1st single-celled organism
Prokaryotes
1st Eukaryotes
About 2.1 billion years old.
The endosymbiosis theory