1. Population Dynamics
Humans and malaria

2. Science (2010), v.328:841

3. Global Map of Malaria
“…a far more urgent task: reducing the horrific toll of malaria
in central Africa, where five countries account for 50% of all
global deaths from the disease and elimination is not possible.”
Science (2010), v.328:849

4. Malaria

5. Malaria life cycle http://www.who.int/topics/malaria/en/

6. But some human populations show resistance to the disease. How??
Malaria is large threat to human health in equatorial regions of the Earth
But some human populations show resistance to the disease.
How??

7. Natural Selection Overproduction Environmental pressure/competition
Pre-existing individual variation
Heritable traits
Happens over generations (time)
Happens in populations (not single individuals)
Offspring must be viable and fertile

8. Darwin’s Inescapable Conclusion
Evidence for humans?
Fact 1: Potential for overproduction
and competition for existence
Fact 2: Individual variation
The inescapable conclusion:
Unequal reproductive success
Darwin called this process natural selection.
The result of natural selection is evolution when a population has adapted to its environment. 8

9. Human Population Growth The History of Global Population Growth

10. Darwin’s Inescapable Conclusion
Fact 1: Potential for overproduction and
competition for existence
Fact 2: Individual variation
The inescapable conclusion:
Unequal reproductive success
Darwin called this process natural selection.
The result of natural selection is evolution when a population has adapted to its environment.
Evidence for humans? 10

11. The Modern Synthesis: Darwinism Meets Genetics
The modern synthesis is the fusion of genetics with evolutionary biology.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

12. Populations as the Units of Evolution
A population
Is a group of individuals of the same species living in the same place at the same time.
Is the smallest biological unit that can evolve.

13. Population genetics Focuses on populations as the evolutionary units.
Tracks the genetic makeup of populations over time.

14. Genetic Variation in Populations
Individual variation abounds in populations.
Not all of this variation is heritable.
Only the genetic component of variation is relevant to natural selection.

15. Sources of Genetic Variation in sexually reproducing organisms
Mutations
Are changes in the DNA of an organism.
Sexual recombination
Crossing over
Independent assortment of chromosomes
Random fertilization

16. Hemophilia
Is a blood-clotting disease.

17. Intergenerational Mutation Rate
By how many mutations does your genome differ from your parents genome?
Roach et al (2010) found about 60 mutations, 30 from each parent, that occurred during the formation of egg and sperm (meiosis).

19. Sickle-cell allele: genotype, phenotype, and resistance to malaria
Malaria infection causes
cells to sickle. Sickled cells,
along with parasite, are killed.
from The Human Evolution Coloring Book, 2nd Ed.

20. Sickle-cell Allele

21. Biochemistry of sickle-cell disease
from Steinberg, M.H., (2006),
Trends Pharm. Sci., 27(4):

22. Sources of Genetic Variation in sexually reproducing organisms
Mutations
Are changes in the DNA of an organism.
Sexual recombination
Crossing over
Independent assortment of chromosomes
Random fertilization

23. Meiosis, The Basis of Sexual Reproduction
Sexual reproduction depends on
Production of gametes through Meiosis.
Fertilization.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

24. Gametes and the Life Cycle of a Sexual Organism
The life cycle of a multicellular organism is the sequence of stages leading from the adults of one generation to the adults of the next.

25. Humans are diploid organisms.
Their cells contain two sets of chromosomes
Their gametes are haploid, having only one set of chromosomes
Figure 8.14

26. Fertilization
Is the fusion of sperm and egg.
Creates a zygote, or fertilized egg.
Sexual life cycles involve an alternation of diploid and haploid stages.

27. Eukaryotic Chromosomes
Each eukaryotic chromosome contains one very long DNA molecule,
Typically bearing thousands of genes.
The number of chromosomes in a eukaryotic cell
Depends on the species.

28. Homologous Chromosomes
Homologous chromosomes are matching pairs of chromosomes.
Humans have
Two different sex chromosomes, X and Y.
A female has XX
A male has XY
Twenty-two pairs of matching chromosomes, called autosomes.

29. Meiosis is the process where the two sets of homologous
chromosomes are separated into different cells - egg or sperm.
Start with one cell with
2 sets of homologous chromosomes
End with 4 cells with
1 set of homologous chromosomes
How does this happen?

30. Meiosis is the process where the two sets of homologous
chromosomes are separated into different cells - egg or sperm.

31. The Process of Meiosis In meiosis, From movie folder play:
Haploid daughter cells are produced in diploid organisms.
Two consecutive divisions occur, meiosis I and meiosis II, preceded by interphase.
Crossing over occurs.
From movie folder play:
MeiosisOverview.html TelophaseICytokin.html
Interphase.html ProphaseII.html
ProphaseI.html MetaphaseII.html
MetaphaseI.html AnaphaseII.html
AnaphaseI.html TelophaseIICytokin.html

32. Figure

33. Figure

34. Figure

35. Review: Comparing Mitosis and Meiosis
All the events unique to meiosis occur during meiosis I.

36. Figure 8.17

37. The Origins of Genetic Variation
Offspring of sexual reproduction are genetically different from their parents and from one another.
Independent assortment of chromosomes
Random fertilization
Crossing over
Random mutations

38. Independent Assortment of Chromosomes
In independent assortment, every chromosome pair orients independently of the others during meiosis.

39. Random Fertilization
The human egg cell is fertilized randomly by one sperm, leading to genetic variety in the zygote.

40. Crossing Over In crossing over,
Homologous chromosomes exchange genetic information.
Genetic recombination occurs.
From the movie folder play:
- CrossingOver.html

41. When Meiosis Goes Awry
What happens when errors occur in meiosis?

42. How Accidents During Meiosis Can Alter Chromosome Number
In nondisjunction,
The members of a chromosome pair fail to separate during anaphase.
Gametes with an incorrect number of chromosomes are produced.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

43. Figure 8.20

44. The result of nondisjunction

45. Down Syndrome: An Extra Chromosome 21
Is a condition where an individual has an extra chromosome 21.
Is also called trisomy 21.

46. The incidence of Down Syndrome increases with the age of the mother.

47. Abnormal Numbers of Sex Chromosomes
Nondisjunction
Also affects the sex chromosomes.