Passage 1

ECOSYSTEM refers to all the things that form the environment we live in and their relations. Itincludes the followings:AtmosphereThe atmosphere covers the Earth. It is a thin layer of mixed gases that make up the air webreathe. This thin layer also helps the Earth from becoming too hot or too cold, much like clothing does for us. Weather systems, such as clouds, rain, and winds, which develop in the lower atmosphere, are driven by heat from the sun, the rotation of the Earth, and variations in the Earth's suce.WaterThe biggest bodies of water on Earth are the oceans, covering about 70 percent of Earth's suce.Millions of living things live in the oceans. Fresh water, on the other hand, is very important for animals, plants and humanity on the land. Water on the Earth also plays an important role in adjusting the temperature. The atmosphere and ocean constantly exchange energy and matter during the cycle of the waters. For example, water evaporates(蒸发))from the oceans into the atmosphere. This moisture( 湿气)then falls back to the Earth as precipitation---rain, snow sleet, and even the morning dew(露水) on the grassLandLand covers 27 percent of Earth's suce. It is where we live and most of our food comes.

What does ecosystem refer to?