Bioindicators are useful because they are telltale signs of impending environmental problems. Early effects of pollution begin to occur at the lower levels of biological organization. Changes in genes, cells, tissues, body chemical processes, and basic body functions appear before more severe disturbances occur in populations and ecosystems. These biochemical and molecular effects can be detected as changes in enzyme levels, in structure of cell membranes, and in genetic material, or DNA.
Changes at these sub cellular levels induce a series of structural and functional responses at the next level of biological organization. Complex processes such as hormonal regulation, metabolism, and immune system responses can be impaired. These effects may eventually alter the organism's ability to grow, reproduce, or even survive. All these measurable changes serve as bioindicators of pollutant stress. They provide early warnings of environmental damage.
Penguins without acid rain
Penguins living with acid rain
Smog has a direct affect on humans health. Smog is an indicator of acid rain.