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.
In the Roman Catholic Church, the clerical collar is worn by all ranks of clergy, thus: bishops, priests, and deacons, and often by seminarians who have been admitted to candidacy for the priesthood as well as with their cassock during liturgical celebrations.