定义：Behavior related to the expansion lateral surface of the body with the intention of increasing the wind resistance against the body and hence reducing the speed of falling.
定义：Description of the relationships among individuals within a population of organisms, including reproductive relationships (mating system), relationships within each sex, adult – young interactions, helpers and cooperation (group living).
定义：A group of species that exploit the same food resources, and/or use the same feeding or foraging methods. http://en.wikipedia.org/wiki/Guild_(ecology)
