Question

A woman treated her home with a pesticide that kills spiders. The first application killed 78% of the spiders. Two months later she applied the pesticide again, but it only killed 45% of the spiders. What would best explain the decrease in the effectiveness of the pesticide?

Answer 1

The spiders that survived the first pesticide spraying were resistant to the pesticide and when they reproduced most of their offsprings got the gene of pesticide resistance.

Answer 2

If the pesticide killed 78% at first and now kills only 45% dat means the effectiveness if the pesticide has reduced by 33%. This could happen only if the pesticide was left open or in non favourable condition