Question

the greater prairie chicken of illinois was once one of the most prevalent birds in the great plains and across north america. with habitat destruction and overhunting, a decline in the bird population occurred. the graph shows the number of male birds from the 1970s through the 1990s. an arrow indicates the year 1993, after which the population began to rebound. what explanation best describes the data from the graph? a prior to 1993, there was abundant habitat for the birds. in 1993, large portions of their habitat were converted into farmland, further decreasing the population. b prior to 1993, male prairie chickens were aggressive and killed each other to determine who would mate. after 1993, farmers domesticated the birds and controlled which males would mate to increase the population. c prior to 1993, chemical pollution in the air and water killed hatchlings of the prairie chicken. in 1973, the regulation banning the release of chemicals in the air prevented all atmospheric and water pollution. d prior to 1993, there was too little genetic diversity in the population, and the population declined. in 1993, prairie chickens that were captive bred were introduced to increase genetic diversity, increasing the population size of the birds.

Explanation:

• Option A: If habitat was converted to farmland in 1993, the population should decrease, but the graph shows an increase after 1993. So this option is incorrect.
• Option B: Aggression - related population decline and domestication - based increase is not a scientific explanation for the population trend shown in the graph. There is no indication of such behavior - based population changes from the graph.
• Option C: If a regulation in 1973 prevented all chemical pollution, the population should not have a significant decline after 1973. But the graph shows a decline over the years. So this option is incorrect.
• Option D: Low genetic diversity can lead to a population decline. Introducing captive - bred birds (which can increase genetic diversity) can lead to a population rebound. This aligns with the graph's trend of decline before 1993 and increase after 1993.

Answer:

D