Examples of homeostasis include the regulation of body temperature, the pH of extracellular fluid, or the concentrations of sodium, potassium and calcium ions as well as that of glucose in the blood plasma, despite changes in the environment, diet, or level of activity.
Blue-collar workers perform labor jobs and typically work with their hands. The skills necessary for blue-collar work vary by occupation. Some blue-collar occupations require highly skilled personnel who are formally trained and certified.
Blue-collar work may involve skilled or unskilled manufacturing, mining, sanitation, custodian work, oil field, construction, mechanical maintenance, warehousing, firefighting, technical installation and many other types of physical work. Often something is physically being built or maintained.