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
It is now known that all different types of species can be considered keystone. Anything from plants to microorganisms can have the important role of keystone species in different ecosystems. Examples of Keystone Species. One example of a keystone species is the prairie dog. They dig tunnels that form prairie dog towns, which can be hundreds of acres in size. The towns help the prairie by providing homes for animals like black-footed ferrets, burrowing owls, and snakes.