Mary Jones, Richard Fosbery, Dennis Taylor and, Jennifer Gregory Solutions for Chapter: Selection and Evolution, Exercise 8: EXAM-STYLE QUESTIONS

With reference to the evolution of antibiotic resistance in bacteria, explain the meaning of the term directional selection.

List the number of the following statements in the correct order, to explain the evolution of resistance to the antibiotic streptomycin by the bacterium Escherichia coli.

1. Most of the population of E.coli is resistant to streptomycin.
2. A random mutation in a DNA triplet of a plasmid, changing TTT to TTG, gives an E.coli bacterium resistance to streptomycin.
3. The resistant bacterium divides and passes copies of the R plasmid (plasmid with gene for resistance to antibiotic) to its offspring.
4. Sensitive bacteria die in the presence of streptomycin as a selective pressure.
5. The frequency of the mutated allele in the population increases.
6. The resistant bacterium has a selective advantage and survives.

Hybrids produced by crossing two different inbred (homozygous) varieties are often more vigorous in their growth than either of their parents. Copy and complete the table to show how breeders of maize plants that show hybrid vigour.

Inbred Line 1

Inbred Line 2

Hybrid

Copy and complete the table to compare artificial selection with natural selection.