The more commonly used light-year is also presently defined to be equal to precisely 7007315576000000000â 31557600 light-seconds, since the definition of a year is based on a Julian year (not Gregorian year) of exactly 365.25 days, each of exactly 7004864000000000000â 86400 SI seconds.
Keystone resource a component of the environment utilized by individuals in the ecological community without which the individuals would not thrive or without which the ecological community structure would be negatively effected. Kin selection
Primary Industry: Pennsylvania's industry has diversified, though the state still leads the country in the production of specialty steel. Pennsylvania is a leader in the production of chemicals, food, and electrical machinery and produces 10% of the nation's cement. Also important are brick and tiles, glass, limestone, and slate. Pennsylvania State Nickname: The Keystone State. Pennsylvania State Motto: Virtue, liberty and independence.