定义：Living in the fluid medium (water or air) but unable to maintain their position or distribution independently of the movement of the water/air mass (adapted from Lincoln et al., 1998).
定义：directly or indirectly modulating the availability of resources to other species, by causing physical state changes in biotic or abiotic materials; modifying, maintaining and/or creating habitats
定义：Diameter of the egg life stage of this organism. An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, it is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing embryo can survive on its own.
定义：Drag swimmers use a cyclic motion where they push water back in a power stroke, and return their limb forward in the return or recovery stroke. When they push water directly backwards, this moves their body forward, but as they return their limbs to the starting position, they push water forward, which will thus pull them back to some degree, and so opposes the direction that the body is heading. This opposing force is called drag. The return-stroke drag causes drag swimmers to employ different strategies than lift swimmers. Reducing drag on the return stroke is essential for optimizing efficiency.
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)
