1. Plants and animals are pH sensitive. Living organisms can survive\xa0only in narrow range of pH change.2. pH of the soil. Plants require a specific pH range for their healthy\xa0growth.3. pH in our digestive system. Our stomach produces hydrochloric acid\xa0that helps in the digestion of food. During in digestion the stomach\xa0produces too much acid that cause pain and irritation.4. Change in pH causes tooth decay. Tooth decay start when the pH of\xa0the mouth is lower than 5.5. Tooth enamel gets corroded when the pH\xa0in the mouth is below 5.5.5. Self-defense by plants and animals through chemical warfare. Bee–sting leaves and acid causing pain and irritation. Applying a mild base\xa0like baking soda on the stung area provides relief.