Smooth muscle, such as in the digestive system, is also controlled by the autonomic nervous system. Like heart muscle, it is not under our conscious control. The SNS is responsible for controlling voluntary body movements, such as movement of the arms and legs.
The oceans cover 71 percent of the Earth's surface and contain 97 percent of the Earth's water. Less than 1 percent of the Earth's water is fresh water, and 2-3 percent is contained in glaciers and ice caps. The oceans contain 99 percent of the living space on the planet. If the ocean's total salt content were dried, it would cover the continents to a depth of 5 feet.
Water is distributed across earth. Most water in the Earth's atmosphere and crust comes from the world ocean's saline seawater, while freshwater accounts for only 2.5% of the total. Because the oceans that cover roughly 78% of the area of the Earth reflect blue light, the Earth appears blue from space, and is often referred to as the blue planet and the Pale Blue Dot. An estimated 1.5 to 11 times the amount of water in the oceans may be found hundreds of miles deep within the Earth's interior, a