Many of the earth's systems are similar to human systems they have similar functions. I picked the two that I knew really could be seen by anyone that they are similar in the earth and in the human body. The two pairs I am going to compare are the water cycle to the circulatory system and skin to the layers of the earth.
The water cycle is made up of Hydrogen, Oxygen, and other minerals. The earth has hydrogen and oxygen but also carbon, nitrogen, phosphate and a lot of other minerals. They both are made up of H2O because they are both primarily water.
The water cycle has been in circulation for the entire life span of earth and a humans circulatory system is in circulation for their entire life span. People can not live with out their circulatory system and the earth can not function with out its water cycle. .
The water cycle starts when the sun's heat evaporates water from the oceans into the atmosphere and form clouds. When the conditions are right the clouds release water as rain or snow. Most of the rain falls back into the ocean but the rest is onto the land. Rivers and streams collect water from the ground and return it to the ocean and the cycle starts again. The water cycle began at the beginning of the earth's development. .
The circulatory is the blood traveling through your body to your lungs. From your lungs the blood is pumped back to the heart. After the oxygen rich blood reenters the heart it is then pumped to all parts of the body through the arteries. Circulation begins early in fetal life.
The water cycle is similar to the circulatory system because with out either of them life would not exist. If we did not have the main element to all life ,water, then no one would be able to live. If we did not have one of the main elements in our bodies, blood, then how would we survive. The water cycle is important because it keeps the water flowing.