Scientifically, the term buffalo is incorrect for the North American species; its proper Latin name is Bison bison. However, common usage has made the term buffalo an acceptable synonym for the American bison. (from The American Buffalo in Transition, by J. Albert Rorabacher.).
Life cycle. Life cycle, in biology, the series of changes that the members of a species undergo as they pass from the beginning of a given developmental stage to the inception of that same developmental stage in a subsequent generation.
Mathematically, life expectancy is the mean number of years of life remaining at a given age, assuming age-specific mortality rates remain at their most recently measured levels. It is denoted by , which means the mean number of subsequent years of life for someone now aged , according to a particular mortality experience.