Dichloro-diphenyl-trichloroethane, commonly called DDT, was a widely used pesticide in the United States from 1943 to the 1970s. By 1972, increasing awareness of the harmful effects on human health and wildlife resulted in the pesticide being banned from use in the United States. However, the environmental impact of DDT use did not end with the ban. Due to its chemical properties, DDT is known to remain in soil and animal tissues for 2–15 years and can pollute aquatic ecosystems for up to 150 years. One of the environmental issues caused by DDT directly affects birds in the ecosystems where the pesticide was applied. The image shows the relationship between concentrations of DDT in the environment and the thickness of bird eggshells.
What predictions can be made about the population of birds when DDT is present in the ecosystem?
A. The population of birds will increase when there is a higher concentration of DDT because the eggs develop over a longer period of time.
B. The populations of birds will increase when there are higher concentrations of DDT to increase the strength of the eggshells.
C. The population of birds will decrease when there is a higher concentration of DDT because thin eggshells will break more easily than normal eggshells during incubation.
D. The population of birds will decrease when there are lower concentrations of DDT to decrease the strength of the eggshells.
