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 its most basic usage, to say that one person is working a white collar job and another is working a blue collar job carries the significance of salary size. The blue collar worker might not earn a salary at all, he might be working for hourly wages, or he may get paid for every item produced or assembled.