Information for the Term Paper

1. Information for the Term Paper • Goal – about 10 pages long, will need at least 10 references • Use the primary literature for your references – reports of original research and ideas • Primary literature is usually published as research or review papers in scholarly journals, or in scientific books • Example journals – Science, Nature, Conservation Biology, Environmental Management, Ecology, Applied Ecology, Annual Review of Ecology and Systematics, etc. • Do not use secondary literature – general works based on primary literature

2. Use of Webpages as Sources • You may need to use webpages for most up-to-date material but: • No more than 3 webpages for paper • Main value of webpages is they may provide very current information – but reader beware: • Webpages are not archived • Webpages are not peer-reviewed

3. :VirtualSalt Evaluating Internet Research Sources Robert Harris Version Date: November 22, 2010Previous Version: June 15, 2007 "The central work of life is interpretation." --Proverb http://www.virtualsalt.com/evalu8it.htm

4. Genetic Diversity

5. Measuring Genetic Diversity • Among and within populations we often measure genetic diversity by measuring polymorphism - the percentage of genes that are polymorphic (have several alleles) within a population • Polymorphism is sometimes also considered to be a process - the maintenance of genetic diversity within a population • We can also measure genetic diversity by measuring heterozygosity - the percentage of genes at which the average individual is heterozygous

6. Importance of Genetic Diversity • Beginning with Darwin, most evolutionary biologists have thought that rather small heritable changes provide most of the variation on which natural selection acts • These small changes are most obvious when using measurable characters such as size or yield - typically they result in continuous variation seen when graphing size as a bell curve

7. Continuous variation: Selection for white spotting in Dutch Rabbits

8. Cause of Continuous Variation • The genetic cause for these changes are genes with small phenotypic effect called multiple factors or polygenes – • Polygenes are where several genes interact to produce a quantitative phenotypic effect on a character

9. Mutation is the source of genetic variation

10. Common mutation – black color in grey squirrels

11. Mutation Rates

12. Genetic Polymorphism • Polymorphism is the maintenance of genetic variability within a population • Polymorphism has been widely observed in many species

13. Polymorphism in Grackles

15. Direct Observation of Genetic Variation • Originally done by protein gel electrophoresis • DNA hybridization was another early method • Now mostly done by directly sequencing DNA – either in small fragments or entire genomes

16. Protein Gel Electrophoresis

17. Hominid relationships – based on gel electrophoresis

18. DNA Hybridization

19. Hominid relationships – based on DNA hybridization

20. DNA Sequencing

21. Hominid relationships – based on mitochondrial DNA sequencing

22. Extent of Polymorphism • Electrophoretic studies have generally found about 25% of all loci tested to be polymorphic - humans 28%, chimps 5%, drosophila - 43% • It is generally thought that only one-third of genetic differences are detected by electrophoresis – this is due to the presence of silent substitutions – for example: GGU, GGC, GGA, and GGG all code for Glycine • Thus it is possible that two-thirds to three-fourths of all loci are polymorphic in a species and that an average individual is heterozygous at about 25% of its loci

23. DDT resistance in mosquitoes

25. DDT Resistance Mechanisms • an increase in lipid content that lets fat-soluble DDT separate from other parts of the organism • presence of enzymes that break down DDT into relatively less toxic products • reduced toxic response of the nervous system to DDT • differences in permeability of insect cuticle to DDT absorption • behavioral response that limits contact with DDT

26. Comparing Heterozygosity • When comparing heterozygosity of different species we usually look at total genetic diversity - symbolized Ht • Ht is composed of two aspects of heterozygosity – • Hs - genetic diversity within the populations that compose the species • and Dst - genetic diversity due to variability among the populations • thus Ht = Hs + Dst

27. Some heterozygosity

28. What do Hs and Dst tell us? • Species with widely scattered populations that don’t exchange genes (like desert pup fish in ponds in Death Valley) tend to have very high Dst • Species with populations that do exchange a lot of genes (like pines) tend to have high Hs – Humans also have high Hs

29. Fitness • evolutionary fitness is a measure of the number of offspring an individual produces

30. Loss of Fitness • Another important aspect of polymorphism is that it tends to maintain fitness - • populations of animals in zoos, which are typically low in genetic diversity, often have low fitness - low fertility and high mortality among offspring

31. Fitness of Zoo Animals

32. Reasons for Loss of Fitness 1. increased incidence of deleterious recessive homozygous individuals 2. lack of heterosis – heterosis (hybrid vigor) is the phenomenon where heterozygous individuals have higher fitness than do homozygotes - often heterozygotes are more resistant to disease 3. lack of evolutionary potential - with all homozygotes there is lack of variation and thus limited ability to respond to environmental changes

33. Inbreeding Depression • Inbreeding depression is the loss of fitness resulting from the breeding of closely related individuals - it occurs due to the three reasons listed before

34. Ngorongoro Crater

35. Lions at Ngorongoro Crater

36. Vipera berus - adder

37. Glanville Fritillary Butterfly

38. Outbreeding Depression • The loss of fitness that occurs when distantly related individuals breed – • This occurs because certain populations may have been selected for traits that are successful in their environment, so that introducing novel traits may reduce fitness for that environment

40. Austrian Ibex – Capra ibex ibex

41. Turkish Ibex – Capra ibex aegagrus

42. Nubian Ibex – Capra ibex nubiana

43. Optimum outbreeding in Japanese Quail

44. Fitness • evolutionary fitness is a measure of the number of offspring an individual produces

45. Maintenance of Polymorphism without natural selection - • random mating tends to maintain polymorphism – due to the benefits of sexual reproduction – recombination, independent assortment, and crossing over

46. Maintenance of Polymorphism • The effects of nonrandom mating are variable - species may either mate assortatively (like with like) or disassortatively (like with unlike) • assortative mating results in many homozygous individuals • disassortative with many polymorphic, heterozygous individuals

47. Assortative Mating - Three spined stickleback

49. Disassortative Mating – Nonbreeding Ruff

50. Disassortative Mating - Breeding male ruff and variant on head pattern