定義： Egg-shaped; a spheroid quality inhering in a bearer by virtue of the bearer's exhibiting a continuous convex surface with an axis of symmetry and one axis longer than the other.
定義： A shallow stretch of a river or stream, where the current is above the average stream velocity and where the water forms small rippled waves as a result. It often consists of a rocky bed of gravels or other small stones.
定義： This organism produces this material or substance, either during its life or after death. A produces B if some process that occurs in A has output B.
定義： 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)
