What general pattern is shown from 1900 to 2000?

What general pattern is shown from 1900 to 2000?

• A. A steady increase in the number of resistant species
• B. A decline in resistance after 1950
• C. Fluctuations with no overall trend
• D. A sudden spike and then a return to baseline

Answer: (A)

This question tests how evolutionary pressure shapes resistance over time. When a population faces ongoing selective pressure—such as widespread use of antibiotics or pesticides—traits that confer resistance become more common. Mutations arise and resistance genes spread between organisms, so each passing decade tends to add more species that are resistant. That cumulative effect yields a steady rise in the number of resistant species from 1900 to 2000. The other patterns would require the selective pressure to vanish or act only briefly, or for resistance to spike and then revert, which doesn’t align with the long, persistent exposure that drives resistance upward across the century.

This question tests how evolutionary pressure shapes resistance over time. When a population faces ongoing selective pressure—such as widespread use of antibiotics or pesticides—traits that confer resistance become more common. Mutations arise and resistance genes spread between organisms, so each passing decade tends to add more species that are resistant. That cumulative effect yields a steady rise in the number of resistant species from 1900 to 2000. The other patterns would require the selective pressure to vanish or act only briefly, or for resistance to spike and then revert, which doesn’t align with the long, persistent exposure that drives resistance upward across the century.