1. Week 5!! Get ready for entrance quiz
Labs—Discussions and graphs need work

2. Evolution evidence: Biogeography
Geographical distribution of species
Examples: Islands vs. Mainland Australia Continents 2

3. Evolution evidence: The Fossil Record
Succession of forms over time
Transitional links
Vertebrate descent 3

4. Fossil Record 4

5. 2006 Fossil Discovery of Early Tetrapod
Tiktaalik
“missing link” from sea to land animals 5

6. Evolution evidence: Comparative Anatomy
Homologous structures (homology)
Descent from a common ancestor 6

7. Homologous structures
Similar structure
Similar development
Different functions
Evidence of close evolutionary relationship
recent common ancestor 7

8. Homologous structures
spines
leaves
succulent leaves
tendrils
needles
colored leaves 8

9. Analogous structures Separate evolution of structures
similar functions
similar external form
different internal structure & development
different origin
no evolutionary relationship
Don’t be fooled by their looks!
Solving a similar problem with a similar solution 9

10. Vestigial organs
Modern animals may have structures that serve little or no function
remnants of structures that were functional in ancestral species
deleterious mutations accumulate in genes for non-critical structures without reducing fitness
snakes & whales — remains of pelvis & leg bones of walking ancestors
eyes on blind cave fish
human tail bone 10

11. Dispatch Compare analogous to homologous structures
What are 3 pieces of evidence that whales evolved from land mammals?
Give 2 examples of vestigial structures.

12. Evolution evidence: Comparative Embryology
Pharyngeal pouches, ‘tails’ as embryos 12

13. Evolution evidence: Molecular Biology
Similarities in DNA, proteins, genes, and gene products
Common genetic code
Closely related species have sequences that are more similar than distantly related species
DNA & proteins are a molecular record of evolutionary relationships 13

14. Building “family” trees
Closely related species (branches) share same line of descent until their divergence from a common ancestor 14

15. Artificial selection
Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties”
“descendants” of wild mustard
“descendants” of the wolf 15

16. Natural selection in action
Insecticide & drug resistance
insecticide didn’t kill all individuals
resistant survivors reproduce
resistance is inherited
insecticide becomes less & less effective
The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action.
The results of application of new insecticide are typically encouraging, killing 99% of the insects.
However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases. 16

17. Final words…...
“Absence of evidence is not evidence of absence.”

18. Evolution on a micro level
Looking at alleles
Looking at the DNA
DARWIN DIDN”T KNOW DNA

19. Get a bottle and colored sticks

20. Microevolution, II: type of genetic drift
The Bottleneck Effect: type of genetic drift resulting from a reduction in population (natural disaster) such that the surviving population is no longer genetically representative of the original population

21. Microevolution, I
A change in the gene pool of a population over a succession of generations
1- Genetic drift: changes in the gene pool of a small population due to chance (usually reduces genetic variability)

22. Chapter 23~
Chapter 23~ The Evolution of Populations

23. Population genetics
Population: a localized group of individuals belonging to the same species
Species: a group of populations whose individuals have the potential to interbreed and produce fertile offspring
Gene pool: the total aggregate of genes in a population at any one time
Population genetics: the study of genetic changes in populations
Modern synthesis/neo-Darwinism
“Individuals are selected, but populations evolve.”

24. Conservation issues
Peregrine Falcon
Bottlenecking is an important concept in conservation biology of endangered species
loss of alleles from gene pool
reduces variation
reduces adaptability
Breeding programs must consciously outcross
Golden Lion Tamarin 24

25. Microevolution, III type of genetic drift
Founder Effect: a cause of genetic drift attributable to colonization by a limited number of individuals from a parent population
just by chance some rare alleles may be at high frequency; others may be missing
skew the gene pool of new population
human populations that started from small group of colonists
example: colonization of New World

26. Dispatch 1) Compare and contrast: -founder effect -genetic drift
-bottle neck effect
2) Give 3 deadlines for October

27. Microevolution, IV
2- Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations)
seed & pollen distribution by wind & insect
migration of animals

28. Microevolution, V
3- Mutations: a change in an organism’s DNA (gametes; many generations); original source of genetic variation (raw material for natural selection)
Mutation creates variation

29. Microevolution, VI 4- Nonrandom mating: Sexual selection
inbreeding and assortive mating (both shift frequencies of different genotypes)

30. Sexual selection
It’s FEMALE CHOICE, baby! 30

32. Microevolution, VII 5.NaturalSelection
differential success in reproduction;
climate change
food source availability
predators, parasites, diseases
toxins
only form of microevolution that adapts a population to its environment
combinations of alleles that provide “fitness” increase in the population

33. Natural Selection
Selection acts on any trait that affects survival or reproduction
predation selection
physiological selection
sexual selection

34. Variation & natural selection
Variation is the raw material for natural selection
there have to be differences within population
some individuals must be more fit than others 34

35. Where does Variation come from?
Mean beak depth of parents (mm)
Medium ground finch 8 9 10 11
1977
1980
1982
1984
Dry year
Wet year
Beak depth
Beak depth of
offspring (mm)
Mutation
random changes to DNA
errors in mitosis & meiosis
environmental damage
Sex
mixing of alleles
recombination of alleles
new arrangements in every offspring
new combinations = new phenotypes
spreads variation
offspring inherit traits from parent 35

37. Population variation
Polymorphism: coexistence of 2 or more distinct forms of individuals (morphs) within the same population
Geographical variation: differences in genetic structure between populations (cline)

38. Variation preservation
Prevention of natural selection’s reduction of variation
Diploidy nd set of chromosomes hides variation in the heterozygote
Balanced polymorphism heterozygote advantage (hybrid vigor; i.e., malaria/sickle-cell anemia); frequency dependent selection (survival & reproduction of any 1 morph declines if it becomes too common; i.e., parasite/host)

39. Natural selection
Fitness: contribution an individual makes to the gene pool of the next generation
3 types:
A. Directional
B. Diversifying
C. Stabilizing

41. Effects of Selection Changes in the average trait of a population
DIRECTIONAL SELECTION
STABILIZING SELECTION
DISRUPTIVE SELECTION
giraffe neck
horse size
human birth weight
rock pocket mice 41

42. Sexual selection
Sexual dimorphism: secondary sex characteristic distinction
Sexual selection: selection towards secondary sex characteristics that leads to sexual dimorphism

43. Any Questions??

44. Hardy-Weinberg Theorem
Serves as a model for the genetic structure of a nonevolving population (equilibrium)
Evolution = change in allele frequencies in a population
hypothetical: what conditions not would cause allele frequencies to change?
non-evolving population
REMOVE all agents of evolutionary change
very large population size (no genetic drift)
no migration (no gene flow in or out)
no mutation (no genetic change)
random mating (no sexual selection)
no natural selection (everyone is equally fit)

45. Hardy-Weinberg Equation
p=frequency of one allele (A); q=frequency of the other allele (a); p+q= (p=1-q & q=1-p)
p2=frequency of AA genotype; 2pq=frequency of Aa genotype; q2=frequency of aa genotype;
frequencies of all individuals must add to 1 (100%), so:
p2 + 2pq + q2 = 1
G.H. Hardy
mathematician
W. Weinberg
physician

46. Using Hardy-Weinberg equation
population: 100 cats
84 black, 16 white
How many of each genotype?
q2 (bb): 16/100 = .16
q (b): √.16 = 0.4
p (B): = 0.6
p2=.36
2pq=.48
q2=.16 BB Bb bb
What are the genotype frequencies?
Must assume population is in H-W equilibrium! 46

47. Hardy Problem
Calculate q2 Count the individuals that are homozygous recessive in the illustration above. Calculate the percent of the total population they represent. This is q2.
Calculate q
Q2=4/16=0.25
Q=0.5
p + q = l. You know q, so what is p, the frequency of the dominant allele?
P=0.5
Find 2pq
2pq = 2(0.5) (0.5) = 0.5 , so 50% of the population is heterozygous.

48. Problem 1
In a certain population of 1000 fruit flies, 640 have red eyes while the remainder have sepia eyes. The sepia eye trait is recessive to red eyes. How many individuals would you expect to be homozygous for red eye color? Hint: The first step is always to calculate q2! Start by determining the number of fruit flies that are homozygous recessive. If you need help doing the calculation, look back at the Hardy-Weinberg equation.

49. Problem 2
The Hardy-Weinberg equation is useful for predicting the percent of a human population that may be heterozygous carriers of recessive alleles for certain genetic diseases. Phenylketonuria (PKU) is a human metabolic disorder that results in mental retardation if it is untreated in infancy. In the United States, one out of approximately 10,000 babies is born with the disorder. Approximately what percent of the population are heterozygous carriers of the recessive PKU allele?