General Biology BI101Spring 2007

Answer Key Study Questions Chapter 15 & 16

  1. Answer: b
  2. Answer: d
  3. Answer: d
  4. Answer: c
  5. Answer: a
  6. Answer: b
  7. Answer: c
  8. Answer: a
  9. Answer: c
  10. Answer: a
  11. Answer: A gene pool is all the genes that are present in a population. Allelic frequencies are determined by Answer: badding all the alleles for a trait in a population and determining their relative proportions.
  1. Answer: An equilibrium population is one in which the allelic frequencies and the distribution of genotypes remain constant in succeeding generations. This can occur only if (1) there are no mutations, (2) there is no gene flow between populations, (3) the population is very large, (4) all mating must be random, and (5) there is no natural selection.
  1. Answer: Chance alone can change allelic frequencies in small populations, but not in very large populations. Genetic drift can alter allelic frequencies, but only in small populations.
  1. Answer: Natural selection can affect a population through directional selection, stabilizing selection, and disruptive selection. Stabilizing selection is most likely to occur in stable environments, and directional selection is most likely to occur in rapidly changing environments.
  1. Answer: Sexual selection involves the mate choices of females. Sexual selection often seems to work in opposition to other forms of natural selection.
  1. Answer:e
  2. Answer: e
  3. Answer: e
  4. Answer: b
  5. Answer: b
  6. Answer: b
  7. Answer: d
  8. Answer: e
  9. Answer: population bottleneck
  10. Answer: genotype
  11. Answer: genetic drift
  12. Answer: A
  13. Answer: B
  14. Answer: B
  15. Answer: B
  16. Answer: B
  17. Answer: D
  18. Answer: d
  19. Answer:Label A: stabilizingLabel B: directionalLabel C: disruptive
  20. Answer: a
  21. population
  22. allele frequency
  23. gene pool
  24. disruptive selection
  25. directional selection
  26. stabilizing selection
  27. stabilizing selection
  28. Label A: will survive and potentially reproduce
    Label B: will potentially succumb to malaria, therefore not living to reproduce
    Label C: will develop sickle cell anemia, potentially dying prior to reaching reproductive years
  29. Answer: D
  30. Answer: D
  31. Answer: C
  32. Answer: A
  33. Answer: A
  34. Answer: E
  35. Possibilities include: continental drift, climate changes (especially glacial advances) that cause habitat fragmentation, formation of islands by volcanic activity or rising sea level, movements of organisms to existing islands (including “islands” of isolated habitats such as lakes, mountaintops, deep-ocean vents), formation of barriers to movement (e.g., new mountain ranges, deserts, rivers). These processes are indeed sufficiently common and widespread to account for a multitude of speciation events over the history of life.
  36. The key question is whether the two populations (apple and hawthorn) interbreed. Tests might involve careful observation of flies under natural conditions, lab experiments in which captive flies of the two types are provided with opportunities to interbreed, or genetic comparisons to determine the degree of gene flow between the two types of flies.
  37. Presumably sympatric. The species in Lake Malawi are found only there and are all more closely related to one another than to any species from outside the lake. This pattern suggests that the species all arose from a single common ancestor that was present in the lake, and that all the speciation events that led to the current array of species took place in a single geographic location, Lake Malawi.
  38. Natural selection cannot look forward and ensure that the only traits that evolve are those that ensure survival of the species as a whole. Instead, natural selection ensures only the preservation of traits that help individuals survive and reproduce more successfully than individuals lacking the trait. So if, in a particular species, highly specialized individuals survive and reproduce better than less-specialized individuals, the specialized phenotype will come to predominate, even if it ultimately puts the species at greater risk of extinction.
  39. Although this is a somewhat subjective question, Mayr's biological-species concept of interbreeding populations is a good one. You need to be able to defend their answer if it differs from this.
  40. If two groups are physically similar but do not interbreed, they would be "biological" species but not "morphological" species. Also, if two populations diverge physically but can still interbreed, they would not be "biological" species but might be classified as "morphological" species.
  41. Species designated by the biological-species concept are real in a biological sense, because they represent a potentially common gene pool. In theory, all populations of the same species could exchange genes and together contribute to the future evolution of the species.
  42. Answer: D
  43. Answer: B
  44. Answer: A
  45. Answer: E
  46. Answer: A
  47. Answer: A
  48. Answer: B
  49. Answer: C
  50. Answer: C
  51. Answer: E
  52. Answer: D
  53. Answer: B
  54. Answer: E
  55. Answer: B
  56. Answer: A
  57. Answer: a
  58. Answer: b
  59. Answer: c
  60. Answer: d
  61. Label A: original population
    Label B: reproductive isolation
    Label C: genetic divergence
    Label D: isolation, either geographical or ecological
  62. Label A: extinct species
    Label B: speciation event
    Label C: rapid phenotypic change
    Label D: slow phenotypic change
    Label E: extant species

Hint: See Figure 16-6 in the text.

Feedback:

A:

B: Every vertical branch on the tree represents a species. Where a new branch develops, a new species has arisen.
C: Rapid changes in phenotype are indicated by nearly horizontal lines (large change in form with little change in time).
D: Slow phenotypic change is indicated by nearly vertical lines (little change in form over long periods of time).
E: Extant means "living."

B:

A: Extinct species have ceased in their ability to change form with time; therefore, the line ends with the last of the species.
C: Rapid changes in phenotype are indicated by nearly horizontal lines (large change in form with little change in time).
D: Slow phenotypic change is indicated by nearly vertical lines (little change in form over long periods of time).
E: Extant means "living."

C:

A: Extinct species have ceased in their ability to change form with time; therefore, the line ends with the last of the species.
B: Every vertical branch on the tree represents a species. Where a new branch develops, a new species has arisen.
D: Slow phenotypic change is indicated by nearly vertical lines (little change in form over long periods of time).
E: Extant means "living."

D:

A: Extinct species have ceased in their ability to change form with time; therefore, the line ends with the last of the species.
B: Every vertical branch on the tree represents a species. Where a new branch develops, a new species has arisen.
C: Rapid changes in phenotype are indicated by nearly horizontal lines (large change in form with little change in time).
E: Extant means "living."

E:

A: Extinct species have ceased in their ability to change form with time; therefore, the line ends with the last of the species.
B: Every vertical branch on the tree represents a species. Where a new branch develops, a new species has arisen.
C: Rapid changes in phenotype are indicated by nearly horizontal lines (large change in form with little change in time).
D: Slow phenotypic change is indicated by nearly vertical lines (little change in form over long periods of time).

BI101 SQ Key Ch15-16110/21/2018