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.
White collar work used to mean a high level of education and a cushy job with perks. That distinction today is blurred by the fact that white collar employment has become the dominant working class in the U.S. and other advanced nations.