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Nile Perch from Lake Victoria PowerPoint Presentation
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Nile Perch from Lake Victoria

Nile Perch from Lake Victoria

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Nile Perch from Lake Victoria

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  1. Nile Perch from Lake Victoria

  2. Genetic Diversity

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

  4. 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

  5. Fitness of Zoo Animals

  6. 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 all individuals will be susceptible to the same problems

  7. 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

  8. Ngorongoro Crater

  9. Lions at Ngorongoro Crater

  10. Vipera berus - adder

  11. Glanville Fritillary Butterfly

  12. 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

  13. Austrian Ibex – Capra ibex ibex

  14. Turkish Ibex – Capra ibex aegagrus

  15. Nubian Ibex – Capra ibex nubiana

  16. Optimum outbreeding in Japanese Quail

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

  18. 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

  19. 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

  20. Assortative Mating - Three spined stickleback

  21. Disassortative Mating – Nonbreeding Ruff

  22. Disassortative Mating - Breeding male ruff and variations on head pattern

  23. Maintenance of Polymorphism • environmental variance - the environment may affect development of different genotypes so that which genotype dominates changes with the environment - if the environment varies or different habitats exist within the species range, then different genotypes will exist

  24. Backswimmers – winged or wingless forms

  25. Maintenance of Polymorphism With Natural Selection with selection, we would expect the most fit genotype to come to dominate the population, but polymorphism may still occur: 1. selection acts to maintain stable polymorphism so that different genotypes are most fit under different situations 2. fixation of a particular genotype is counteracted by mutation 3. fixation of a particular genotype in one population is counteracted by gene flow from another population

  26. Polymorphism under selection –in the Grove Snail - Cepaea

  27. Clines • in many species, local populations have little variation, but the entire species exhibits much variation as local populations are adapted to different conditions - if these changes in genes change in response to certain environmental variables, we may see a cline - a gradual change along a geographic transect

  28. Clines with Body Size • Bergmann's rule - many animals get larger in size as the species range approaches the poles - it is related to ability to keep warm - larger bodies maintain warmth better • Allen’s Rule – size of extremities decreases towards the poles – heat is lost through things like large ears

  29. Bergman’s Rule in same aged White-tailed Deer

  30. Allen’s Rule in Foxes Arctic Fox Desert (Kit) Fox

  31. Allen’s Rule in Hares

  32. Cline in Cyanide Production in White Clover

  33. Cline in cyanide production by white clover

  34. Greater Racquet-tailed Drongocline in crest size

  35. Reductions in Polymorphism • Gene Flow - the movement of alleles from one population to another tends to maintain genetic similarity among populations

  36. African Wild Dog

  37. Rates of Gene Flow – Ne (effective population size) = 120

  38. Minimum Viable Population • The smallest population for a species which can be expected to survive for a long time • Many factors effect MVP – the study of those factors is often called Population Viability Analysis – or Population Vulnerability Analysis – or PVA

  39. Factors that make populations vulnerable to extinction • Environmental fluctuations • Catastrophes • Demographic uncertainties • Genetic problems • Habitat fragmentation

  40. Environmental Fluctuations

  41. Kirtland’s Warbler

  42. Cheetah

  43. Habitat Fragmentation • Fragmentation is the transformation of large expanse of habitat into a number of smaller patches of smaller total area isolated from each other by a matrix of habitat unlike the original