conditions alter this minimum exposure.Further adding to the complexity several additional factors come into play with the effect and response of an organism from a pollutant. One such factor is age. Although we think of youngsters of all species as resilient creatures, young, growing organisms are generally more susceptible to toxic chemicals than adults (Chiras, 127). Health Status is determined by many factors, among them one's nutrition, level of stress, and personal habits such as smoking. As a rule, the poorer one's health, the more susceptible he or she is to a toxin (Freeman, 214). Toxins may also interact with each other producing several different responses. Some chemical substances for example, team up to produce an additive response that is, an effect that is simply the sum of the individual responses. Others may produce a synergistic response that is, a response stronger than the sum of the two individual ones. A pollutant can also synergize for instance, sulphur dioxide gas and particulates (minute airborne particles) inhaled together can reduce airflow through the lungs' tiny passages. The combined response is much greater than the sum of the individual responses.Plants have three strategies in response to a disturbance - this wassuggested by Grimes. These strategies are:C - selection - having high competitive abilityS - selection - having a high endurance for stressR - selection - having a good ability to colonize disturbed areas.Plant response to a disturbance was suggested by Connell and Slatyer (1977) using models. Model I (the "facilitation" model assumes that only certain species that come early in the succession are capable of colonizing the site. In contrast the other two models both assume that any individual of any species that happens to arrive at the site is capable of colonizing it, although all models accept that certain species will tend to appear first because of their colonizing abilities. All models als...
