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.
The blue collar worker is perceived to make less than the white collar worker. The white collar worker might work behind a desk in the service industry, while the blue collar worker gets his hands dirty doing manual labor or working in a division of manufacturing. Perhaps the white collar worker has a more well-rounded education than the blue collar worker.