2. Evolution and Genetics
Biochemical, or Molecular, Genetics
Population Genetics and Mechanisms of Genetic Evolution
The Modern Synthesis

3. Evolution and Genetics
What is evolution, and how does it occur?
How does heredity work, and how is it studied?
What forces contribute to genetic evolution?

4. Why tall parents have tall kids? Does obesity run in the family?
How much do genes influence in our bodies?
Human biology is plastic but only to a certain degree (blood type)
Cultural (medical) solutions exist for genetic disorders

5. Is culture intervening too much with intrinsic biological features?
Hearing impaired community’s fear that hearing aid implants are a threat to the deaf subculture.
Plastic surgery and genetic screening might create a future in which physical perfection might reduce human diversity and increase socioeconomic inequality.

6. How about the long-term plasticity of human genome?
 Evolution: All living organisms come from ancestors that were different in some way.
Evolution is a fact.
The scientific theory of evolution is the organizing principle of modern biology and anthropology.

7. Evolutionary facts
All living forms come from older or previous living forms
Birds arose from nonbirds, humans arose from nonhumans, and neither existed 250 million years ago.
Major ancient life forms are now extinct (dinosaurs).
New life forms (viruses) are evolving right now.
Natural processes help us understand the origins and history of plants and animals (including humans and diseases).

8. Evolution
Humans have uniquely varied ways—cultural and biological—of adapting to environmental stresses
Many scholars became interested in biological diversity and our position within the classification of plants and animals during the 18th century

9. Evolution
Creationism: biological similarities and differences originated at the Creation
Based on Genesis, the first book of Bible
Life forms were seen as immutable, they could not change
Biblical scholars claim to have traced creation to October 23, 4004 BC at 9:00 am.

10. Creationism
Linnaeus (1707–1778) developed the first comprehensive and still influential classification, or taxonomy, of plants and animals
He grouped life forms on the basis of differences and similarities in physical characteristics.
Fossil discoveries during the 18th and 19th centuries raised doubts about creationism

11. If all life originated at the same time, why aren’t ancient species still around?
Why weren’t contemporary plants and animals found in fossil records?

12. Evolution
Catastrophism: a modified version of creationism that accounts for the fossil record by positing divinely authored worldwide disasters that wiped out creatures represented in the fossil record

13. After each destructive event, God had created again, leading to contemporary species.
Some ancient species managed to survive in isolated areas, hence the similarities between fossils and modern animals.

14. Theory and Fact
Evolution (descent with modification): an alternative to creationism and catastrophism was transformism
Species arise from others through a long and gradual process of transformation.
Charles Darwin is the best known of evolutionists

15. Theory and Fact Darwin influenced by
Grandfather, Erasmus Darwin, who proclaimed a common ancestry of all animal species
Lyell’s principle of Uniformitarianism: The present is the key to the past; explanations for past events should be sought in the long-term action of ordinary forces that still operate today.

16. Natural forces (rain, earthquakes, volcanic eruptions) have gradually built and modified geological features (such as mountain ranges).
Cappadocia

17. Uniformitarianism cast doubt on the belief that the world was only 6000 years old. It would take much longer for ordinary forces such as rain and wind to produce major geological changes.
Theory of evolution
Theory: a set of ideas formulated to explain something
Darwin applied uniformitarianism and long-term transformation to living things and argued that all life forms are related and the number of species have increased over time.

18. Theory and Fact
Natural selection: the process by which the forms most suited to survive and reproduce in a given environment do so in greater numbers.
More than survival of the fittest, natural selection is differential reproductive succes.
Competition for strategic resources (food and space)
Finding mates
Variety within that population
Natural selection continues today

19. Giraffe’s neck
When there’s a food shortage, those with longer necks have an advantage
If this feeding advantagepermits longer-necked giraffes to survive and reproduce more effectively, then they will transmit more of their genetic material to future generations than will those with shorter necks.

20. Incorrect alternative to Darwinian explanation
Inheritance of acquired characteristics
In each generation, individual giraffes strain their necks to reach higher and this straining modifies tgeir genetic material.
Over generations of strain , the average giraffe neck gradually gets longer through the accumulation of small increments of neck length acquired during lifetime of each generation of giraffes.

21. This is not how evolution works!!
Physical development of the individual, not species. (babies of weight lifters)
Evolution works as the process of natural selectiontakes advantage of the variety that is already present in a population.

22. Genetics
Genetic science helps us understand the causes of biological variation
Mendelian genetics: studies the ways in which chromosomes transmit genes across generations
Biochemical genetics: examines structure, function, and changes in DNA
Population genetics: investigates natural selection and the causes of genetic variation, stability, and change

23. Mendel’s Experiments
Austrian monk Gregor Mendel began a series of experiments that revealed the basic principle of genetics in 1856
Studied inheritance of seven contrasting traits in pea plants
Discovered that heredity is determined by discrete particles or units

24. Mendel’s Experiments
Concluded that a dominant form could mask another form in hybrid individuals, without destroying the recessive trait
Basic genetic units Mendel described were factors (now called genes or alleles) that are located on chromosomes

25. Mendel’s Experiments
Chromosome: a paired length of DNA, composed of multiple genes
Gene: a place (locus) on a chromosome that determines a particular trait
Allele: a variant to a particular gene

26. Mendel’s Experiments
Heterozygous: dissimilar alleles of a gene in an offspring
Homozygous: two identical alleles of a gene in an offspring
Dominance produces a distinction between genotype (hereditary makeup) and phenotype (expressed physical characteristics)

27. Mendel’s Experiments Independent Assortment and Recombination
Independent Assortment: chromosomes are inherited independently of one another
Recombination: the combination of genetic traits in an offspring; this process creates new types on which natural selection can operate

28. Figure 5.1: Mendel’s Second Set of Experiments with Pea Plants

29. Figure 5.2: Simplified Representation of a Normal Chromosome Pair

30. Figure 5.3: Punnett Squares of a Homozygous Cross and a Heterozygous Cross

31. Figure 5.4: Determinants of Phenotypes (Blood Groups) in the ABO System

32. Biochemical, or Molecular, Genetics
Mutation: changes in the DNA molecules of which genes and chromosomes are built
Gametes: sex cells that make new generations

33. Biochemical, or Molecular, Genetics
The DNA molecule is a double helix
RNA carries DNA’s message to its cytoplasm (outer area)
The structure of RNA, with paired bases, matches DNA
DNA, with RNA’s assistance, initiates and guides the construction of hundreds of proteins necessary for bodily growth, maintenance, and repair

34. Figure 5.5: A Double-Stranded DNA Molecule

35. Cell Division
Mitosis: ordinary cell division, wherein one cell splits to form two identical cells
Meiosis: the special process by which sex cells are produced
Four cells produced from one
Each cell carries half the genetic material of the original cell
Fertilization allows the products of meiosis from one parent to recombine with those from the other parent
Chromosomes sort independently

36. Crossing Over
Crossing over: the process wherein homologous chromosomes exchange segments by breakage and recombination
Can occur with any chromosome pair
An important source of variety

37. Figure 5.6: Crossing Over

38. Mutation
Base substitution mutation: substitution of one base in a triplet by another
If mutation occurs in a sex cell, the new organism will carry mutation in every cell
Chromosomal rearrangement: pieces of a chromosome break off and reattach someplace else on that chromosome

39. Mutation Approximately three mutations will occur in every sex cell
Most mutations are neutral
Evolution depends on mutations
Variants produced through mutation can be especially significant if there is a change in environment

40. Population Genetics and Mechanisms of Genetic Evolution
Population genetics studies stable and changing populations
Gene pool: alleles and genotypes within breeding population
Genetic evolution: the change in allele frequency in a breeding population

41. Natural Selection Genotype: the genetic makeup of an organism
Phenotype: an organism’s evident biological traits
Natural selection acts only on phenotypes
Human biology has considerable plasticity
The environment works on a genotype to build a phenotype

42. Directional Selection
After several generations of selection, gene frequencies change
Adaptive: favored by natural selection
Directional selection continues as long as environmental sources stay the same
Humans do not have to delay adaptation until a favorable mutation occurs

43. Sexual Selection Selection also operates through competition for mates
Sexual selection: based on differential success in mating; a selection of traits that enhances mating success

44. Stabilizing Selection
Balanced polymorphism: the frequencies of two or more alleles of a gene remain constant from generation to generation

45. Appreciating Anthropology
Scientists linked the first European explorers of the New World to the origin of sexually transmitted syphilis
Researchers applied phylogenetics in examining 26 geographically disparate strains in the family of treponema bacteria
Infections in the New World have been traced back at least 7,000 years by studying scars on bones

46. Random Genetic Drift
Random genetic drift: loss of alleles from a population’s gene pool through chance
Lost alleles can reappear in the gene pool only through mutation
Fixation, the replacement, for example, of blue eyes by brown eyes, is more rapid in small populations

47. Gene Flow
Gene flow: exchange of genetic material between populations of the same species
Alleles spread through gene flow even when selection not operating on the allele
Species: group of related organisms whose members can interbreed to produce offspring that live and reproduce
Gene flow tends to prevent speciation: the formation of new species

48. Figure 5.8: Gene Flow Between Local Populations

49. The Modern Synthesis Currently accepted view of evolution:
Microevolution: small-scale changes in allele frequencies over just a few generations
Macroevolution: large-scale changes in allele frequencies in a population over a longer time period that result in the formation of new species.

50. The Modern Synthesis
Punctuated equilibrium: long periods of stasis may be interrupted by evolutionary leaps
Sudden environmental change offers possibility for the pace of evolutions to speed up
Although species can survive radical environmental shifts, extinction is more common