Observed evolution (antibiotic resistance, pesticide resistance) Knowledge-Based Download PDF

Questions

1. 1.

   Why does treating an infection or pest infestation with a combination of two distinct chemical agents with different biological targets significantly delay the evolution of resistance compared to using a single agent?

   • A) The combination of chemicals neutralizes their selective action, preventing the substances from inducing targeted adaptive mutations.
   • B) An organism must simultaneously possess two independent, rare genetic variations to survive, which drastically lowers the probability of a resistant lineage emerging.
   • C) Simultaneous exposure to multiple toxins forces surviving cells to shed their plasmids and revert to an ancestral wild-type genome.
   • D) Applying two distinct toxins eliminates phenotypic variation entirely by preventing all viable genetic mutations from being passed to offspring.
2. 2.

   When the application of a particular antibiotic or pesticide is completely discontinued, what evolutionary change is most frequently observed in the target population over subsequent generations?

   • A) Resistant individuals immediately undergo reverse mutations to restore their original wild-type genotypes within a single generation.
   • B) The frequency of resistant individuals gradually declines because the resistance trait often carries a fitness cost in the absence of the chemical.
   • C) The proportion of resistant individuals remains fixed permanently because evolutionary adaptations cannot be lost once established.
   • D) Susceptible individuals rapidly downregulate their metabolic enzymes to match the physiological state of the resistant variants.
3. 3.

   Which observation provides the strongest evidence that the emergence of antibiotic resistance in bacteria represents an evolutionary process rather than individual physiological acclimatization?

   • A) Individual bacterial cells gradually thicken their cell walls during their lifespan in response to increasing drug concentrations.
   • B) Exposure to the antibiotic directly stimulates non-resistant cells to synthesize novel protective enzymes on demand.
   • C) The frequency of pre-existing resistance alleles increases across successive generations within the exposed population.
   • D) Susceptible bacterial cells temporarily downregulate their metabolic pathways until the chemical agent is removed.
4. 4.

   Which statement accurately describes the role of an antibiotic in the observed evolution of resistance within a bacterial population?

   • A) It stimulates directed genetic mutations that actively neutralize the antibacterial chemical.
   • B) It triggers physiological acclimatization that individual bacteria subsequently transmit to their offspring.
   • C) It acts as a selective agent that favors the survival and reproduction of individuals with pre-existing resistance traits.
   • D) It prompts bacterial cells to synthesize specific antibodies that confer inherited immunity.
5. 5.

   Which statement best explains how the widespread application of a chemical pesticide leads to the evolution of pesticide resistance in an insect population?

   • A) Individual insects gradually develop physiological tolerance during their lifespan and pass this acquired trait directly to their offspring.
   • B) Chemical exposure directly induces targeted protective mutations in susceptible insects to prevent cellular damage.
   • C) Pre-existing genetic variants with higher detoxification capacity survive pesticide exposure and pass their resistance alleles to subsequent generations.
   • D) The pesticide forces all insects in the treated area to upregulate metabolic enzymes that permanently alter the germline genome.