The primary use of pH indicators in biology is to determine the acidity or alkalinity of a solution. These indicators are chemical compounds that change color in response to specific pH levels, allowing researchers to visually assess the acidity of various biological samples, such as bodily fluids or growth media. pH levels can affect numerous biological processes, including enzyme activity, respiration, and metabolic pathways. Understanding pH is crucial for experimentation, clinical diagnoses, and monitoring environmental conditions in aquatic ecosystems. Common pH indicators include litmus, phenolphthalein, and universal indicator.