7.2a In ecosystems, balance is the result of interactions between community members

and their environment.

7.2b The environment may be altered through the activities of organisms. Alterations

are sometimes abrupt. Some species may replace others over time, resulting in long-

term gradual changes (ecological succession).

7.2c Overpopulation by any species impacts the environment due to the increased use

of resources. Human activities can bring about environmental degradation through

resource acquisition, urban growth, land-use decisions, waste disposal, etc.

7.2d Since the Industrial Revolution, human activities have resulted in major pollution

of air, water, and soil. Pollution has cumulative ecological effects such as acid rain,

global warming, or ozone depletion. The survival of living things on our planet depends

on the conservation and protection of Earth’s resources.