11.   He estimated that half the local population had become sensitive to the pollen from one or both of those trees.

12.   If chinch bug populations become a real threat to the lawn, apply an appropriate insecticide.

13.   If through inattention, or haphazard control efforts, a flea population becomes thoroughly established, pet owners may choose to turn to a professional pest control service.

14.   In those states, the populations are becoming more ethnically diverse and entrepreneurial.

15.   Our population is also becoming increasingly urban, and many hunters are having a difficult time finding a place to hunt.

16.   One reason for this is that bacteria that survive the antibiotics reproduce until the entire population becomes resistant.

17.   Plant populations have become isolated from one another, turning a once-robust gene pool into a series of shallow gene puddles.

18.   Relief agencies in Kansas City, where the refugee population is becoming increasingly Muslim, face a similar situation when trying to acquaint refugees with new customs.

19.   Since World War II, the US Roman Catholic population has become better educated, and Catholic colleges have played a central role in opening academic doors to Catholics.

20.   The American population is steadily becoming more kaleidoscopic.