T. Dobzhansky (geneticist)

1. T. Dobzhansky (geneticist) “Nothing in biology makes sense except in the light of evolution”

2. Adaptation A genetically determined characteristic that influences an organism's ability to survive and reproduce in a particular environment. Characteristics can be morphological, behavioral, or physiological.

3. Evolution • Is a genetic change in a population (not an individual) over time • Ecologists look at phenotypic (physical changes), in most cases, because that is how we recognize populations. • It is, in fact, changes in the genotype, or more specifically, the gene pool.

5. Allele Frequencies The frequency of occurrence of alleles in a population. If we use the simple one dominant and one recessive allele model, this can be demonstrated by: p = frequency of the dominant allele q = frequency of the recessive allele

6. Example AA - 30 individuals Aa - 20 individuals aa - 50 individuals p = 2(# individuals AA) + # individuals Aa 2(Total # individuals in population) p + q = 1; therefore q = 1 - p

7. Example p = 2(30) + 20 200 = 0.4 p + q = 1; therefore q = 1 - 0.4 = 0.6 With these values, we can calculate the probability of what genotypes would be present in the next generation if this population were to mate randomly

8. Genotypic Frequencies p2 = probability of AA q2 = probability of aa 2pq = probability of Aa p2 + 2pq + q2 = 1

9. Mechanisms for Evolutionary Change • Mutation • Genetic Drift (small population size) • Gene Flow (immigration and emigration) • Non-Random Mating • Natural Selection

10. Basic Tenet of Natural Selection The most fit organisms (survivors) will reproduce and pass their genes on to the next generation.

11. Hardy-Weinberg Equilibrium In diploid, sexually reproducing organisms, phenotypes, genotypes and genes all tend to come to equilibrium in populations in certain conditions are met

12. Hardy-Weinberg Equilibrium • No Mutation • Large Population Size • No immigration or emigration • Random Mating • No Selection for Traits

13. Genetic Drift • Random or chance events lead to a change in the genetic makeup of a population • Limited to small populations • “Bottleneck”

14. p = 0.33 p = 0.7 Random event leads to loss of individuals Population will come to reflect surviving population

16. Effective Population Size (Ne) The number of individuals actually participating in random mating. This number is always smaller than the actual population size - number of old - number too young - small number of one sex

17. Gene Flow • Change in gene pool of a population from immigration or emigration. • Founder Effect

18. Identification of Human Migration from Mitochondrial DNA

19. Steps for Natural Selection • Variation occurs in every group of living organisms. Individuals are not identical in any population. • Every population produces an excess of offspring. • Competition will occur among these offspring for the resources they need to live.

20. Steps for Natural Selection • The most fit offspring will survive. • If the characteristics of the most fit organisms are inherited, these favored traits will be passed on to the next generation.

22. Common Types of Individual Selection • Stabilizing selection • Direction selection • Disruptive selection

24. figure 21-12.jpg Figure 21.12 Figure 21.12

27. Figure 21.13 Figure 21.13

28. Figure 21.14

29. Similarities in Adaptive Strategies • Convergent Evolution – similar responses to similar environmental situations BUT not related evolutionarily • Example – Fig. 2.9

30. !!!!!!!!!!VARIATION!!!!!!!!!!!

31. Properties of Fitness • Fitness is a property of a genotype, not an individual or population. • Fitness is specific to a particular environment. As the environment changes, so does the fitness of genotypes. • Fitness is measured over one generation or more.

32. Outcomes of Selection • Changes in Genetic Make-up of a Population • Rise of new species – IF certain conditions met

33. Allopatric Speciation Distribution of a Species

34. Geographic Barrier Splits Distribution

35. No longer interbreeding; therefore, no exchange of genes and could be undergoing different selection pressures

36. Over time, the gene pool of each group can become quit different

37. If two groups are brought back together and do not interbreed, they are now two separate species

38. Parapatric Speciation Distribution of a Species

39. Individuals move into a new habitat

40. If no interbreeding occurs between individuals in new habitat and those in the old, reproductive isolating mechanisms can develop.

41. Sympatric Speciation Isolating mechanism develops within the existing distribution of a species

42. Sympatric Speciation Isolating mechanism develops within the existing distribution of a species

43. Reproductive Isolating Mechanisms • Prezygotic mechanisms prevent fertilization or zygote formation. • Temporal shifts - do not become reproductively active at the same time. • Behavioral shifts - do not recognize courtship behaviors (female bird doesn't recognize the dance of a male). • Mechanical shift - change in reproductive structure making it physically impossible to mate. • Habitat shifts – populations live in the same regions but occupy different habitats/microhabitats.

44. Reproductive Isolating Mechanisms • Postzygotic mechanisms zygote forms but • Does not complete development • Develops into a weak, unhealthy individual • Is sterile in either the F1 or F2 generation

45. Evolution of Interactions Among Species

46. Mimicry • Batesian mimicry - a benign species resembles a noxious or dangerous species. • Müllerian mimicry - both the mimics and the model are noxious or dangerous.

49. Coevolution • Evolutionary change in one species results in a reciprocal response of another species • Many examples – excellent one is diversification of flowering plants and insect pollinators

50. Parasitism • Predator-Prey Interactions (including herbivory) • Competition • Other topics of note • Sexual selection • Kin Selection