... leave their climatic zone, and in a zone that is divided by landmasses the animals are prevented from passing to other bodies of water in the same zone. The environmental conditions in deep waters are markedly different at each level of depth. The water temperature decreases and pressure increases with increasing depth. Feeding conditions, which depend on the number and types of plants and animals present, also vary greatly with depth. The depth of the ocean floor is much more variable than is the elevation of land. Consequently, the few widely distributed saltwater forms are those that live at or near the surface. An aquatic animal that can live only at depths of 6,000 to 7,500 m (20,000 to 25,000 ft) cannot cross a ridge in the ocean floor if the crest of the ridge is only 3,000 m (10,000 ft) below the surface.Assuming relative uniformity of temperature, pressure, and feeding ...

See this essay or coursework document in full right now