The existing natural ecosystem is often confronted with negative impacts of modern technology. These often cause stress, especially by altering the fundamental stability of an ecosystem.
Apart from this we know that various environmental factors like light, temperature, humidity, wind speed, availability of food, nutrients etc., keep changing. These changes affect the well being and survival of the organisms in an ecosystem as they can thrive only if all the factors essential for life are available. For example, a plant may have adequate nutrition, light, water and space but just one essential nutrient, say phosphorus, is lacking. The plant will not be able to survive. This essential nutrient then becomes a limiting factor for the plant’s survival. We need to consider two laws to explain the organisms’ response to these environmental changes.
The law of minimum which states that the growth and well-being of an organism is ultimately limited by that essential resource that is in its lowest supply relative to what is required. The most deficient resource is, therefore, called the limiting factor.
The law of tolerance states that for each physical factor in the environment a minimum and maximum limit exists called the tolerance limit beyond which the organism does not thrive or survive. For example, an insufficient amount of vitamin A leads to drying of skin, night blindness and abnormal bone formation, whereas an excess of vitamin A will produce gastrointestinal upsets, loss of hair, dermatitis and pain in bones. Either too little or too much of any required factor like food, energy, heat, vitamins, minerals, water or oxygen threatens the survival of organisms and even entire species.