After a copper smelter begins operation, local downwind populations of plants begin to adapt to the resulting air pollution. Scientists document, for example, that the acid tolerance of several plant species has increased significantly in the polluted area. This is an example of

Adaptation.

Explanation:

Adaptation occurs when the acid tolerance of several plant species has increased significantly in the polluted area. The main reason for this tolerance is the change in the genetic makeup or mutation occurs in the cell due to the exposure of DNA to the chemicals of the environment that cause pollution. The plant adopt the environment by producing certain chemicals that cancel the effects of pollutants and as a result, the plant survive.

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.