定义：Single birth offspring quantity. The proportion or number of offspring produced from a single pregnancy (mammals) or ovulation (fish) or nesting (birds).
定义：A forest biome is a terrestrial biome which includes, across its entire spatial extent, densely packed vegetation which strongly limits light penetration to the forest floor.
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)
