1. EVOLUITON Selection & Genetic drift
working on variation in the population cause
EVOLUITON

2. SELECTION

3. Artificial Selection = genetic changes within a population which occur because human beings intentionally select for certain characteristics either by choosing which organisms to breed or eliminating undesirable individuals.
Natural Selection = genetic changes within a natural (wild) population which occur because of differences in the reproductive success of some individuals over other individuals.

4. Artificial Selection

5. Why doesn’t selection work anymore on running speed?
There are probably diseases involved.
Too much inbreeding causes genetic defects.
There is no more genetic variation in the alleles determining running speed.
Epistatic effects are now in play.
Artificial insemination programs inadvertently select for defective (weaker) sperm.

6. In order for Evolution to Occur there must be variation in the population

7. Which is not a cause of allele variation in a population?
Homology
Mutation
Genetic recombination (crossover)
Sexual reproduction
Migration (gene flow) 30

8. How Effective Is Selection? Consider Artificial Selection

9. All of these plants come from wild mustard !

10. Artificial Selection Farm animals (e.g. chicken egg production)
126 eggs/hen/year
Today 365 eggs/hen/year

11. Milk Production

12. Artificial Selection in Dogs

13. Dogs mtDNA indicates that all dogs are derived from a species of
wolf ~10,000 BC
in Eurasia.
The Romans (2,000 yrs. ago
had 6 only breeds
In 1837 the book British Quadrupeds listed < 20 breeds
Now, ~200 breeds
Most developed in the last 150 yrs.

16. EVOLUTION CAN BE FAST !
Over 200 breeds

17. Domestication of silver foxes
Dmitri Belyaev
Artificial Selection

18. Domestication of silver foxes

19. Pleiotropy

20. Domestication of silver foxes

21. NATURAL SELECTION
Differences in mortality & reproduction lead to differences in the proportion of alleles passing to the next generation.
Positive selection= a selective advantage for one allele and that favored allele increases in the population.
Negative selection= a selective disadvantage
for a allele and that tends to disappear from the population.

22. NATURAL SELECTION IN BACTERIA
Development of antibiotic
resistance in bacteria

23. e.g. NATURAL SELECTION IN BACTERIA Resistance to antibiotics

24. e.g. NATURAL SELECTION IN BACTERIA Resistance to antibiotics

25. The Plague
Deaths

27. e.g. NATURAL SELECTION IN INSECTS Resistance to pesticides
Foliate
insecticide

28. NATURAL SELECTION OF PLANTS TO Herbicides

29. NATURAL SELECTION IN PLANTS FOR COPPER TOLERENCE
Please look at the video.

30. WHAT PRODUCES SELECTION?
Internal Environment
e.g. genetic environment (society of genes)
e.g. physiological/developmental environment
External Environment
Physical Environment (water, temp., 02,)
Biological Environment
Competition
Predation
Parasitism
Food supply
Mate selection (Sexual Selection)

31. Success must be judged in 2 ways:
Absolute Terms= Will the genome work?
Relative Terms= Is the genome the best
available model?

32. Small selective advantages Suppose there were a selective advantage to having a long nose and suppose that advantage produced a trend so the average nose length increased inch/ year. How many inches will the nose will have grown in 100,000 years?
One
Ten
100
1,000
None of the above

33. Slight advantages over long time
= Enormous changes!

34. SELECTION IN 2 ALLELE TRAITS
Selection against a dominant trait
Genotypes: AA Aa aa
Rapid elimination of the trait should occur.
Speed depends on how deleterious the allele is.

35. Fitness & Natural Selection
How to calculate relative fitness
Compare the success of the favored allele to that of the unfavored allele.
W= number of children produced by 100 unfavored genotype
number of children produced by 100 favored genotype

36. W= 20/100= 0.20 = fitness coefficient
e.g. Achondroplastic Dwarfism
Due to a dominant allele
DD and Dd = dwarf condition
dd = normal
Number of children per 100 dwarf parents = 20
Number of children per normal parents = 100
W= 20/100= = fitness coefficient

37. If the w= 20/100 = 0.2 the fittness value of the unfavored allele, what is the fittness value for the “favored allele”?
Zero
0.2
0.5
1.0
None of the above

38. Selection in two allele systems Continued
Selection against the recessive
Genotypes: AA Aa aa
Selection will be slow to remove the “a” allele in complete dominance because it is hidden in the heterozygous condition “Aa.” These are carriers.

39. Cystic Fibrosis Caused by recessive trait, cc
Normal allele C causes channels in the cell membranes (lung, gut) to allow Cl- out of cells
and H20 follows.
If both alleles are cc, then this doesn’t happen
& thick sticky mucus clogs lungs & gut & these tissues are breeding ground for bacteria

40. Cystic Fibrosis Most common genetic disorder in Caucasians;
affects 1 out of 2,500 white babies
5% of Caucasians are carriers
CC is normal
Cc is normal, but carrier
cc has cystic fibrosis

41. If two carriers have children, what are the chances that their child will have cystic fibrosis?
100%
75%
50%
25%
Zero %

42. Cystic Fibrosis Cc x Cc = 25% of kids are cc & have cystic fibrosis
Why aren’t they eliminated from the pop?
Because Cc have protection against diarrhea ?

43. Selection in two allele systems Continued
Selection favoring heterozygotes “Aa”
Can only occur if incomplete or co-dominance
because the trait is expressed.
e.g. Sickle-cell anemia

44. Sickle Cell Co-dominance
Normal Mild Anemia Severe Anemia
HbN HbN HbN HbS HbS HbS
In the
USA: W = W = W = 0.14 In
Africa: W = W = W = 0.14
Heterozygotes are favored in Africa because they are more resistant to malaria!
The environment determines what is fit!

45. Natural Selection in Polygene Traits Directional Selection

46. Natural Selection in Polygene Traits Stabilizing Selection

47. Natural Selection in Polygene Traits Disruptive Selection

48. What kind of selection is this?
Directional
Stabilizing
Disruptive
Eliminative
No way to tell

49. This is negative selection— elimination of “unfit” genotypes.