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
A keystone species is one that plays a unique and crucial role in the way an ecosystem functions. It has a disproportionally large effect on its environment relative to is abundance. There are two hallmarks of a keystone species.irst, the presence of a keystone species is crucial in maintaining the integrity of its ecosystem through species diversity and organization. Second, these species are relatively more important in structuring their ecosystem when compared to most other species of equal biomass found within their community.