The Earth is a unique planet because of the following reasons:
1. It is at optimum distance from the Sun; that is it is neither too far nor too close to the Sun. Hence, it supports several forms of life.
2. Seasonal and daily variations are maintained as by the rotation and revolution of the Earth which prevent any extremity.
3. The atmosphere of the Earth protects its surface from harmful ultraviolet rays of the Sun.
4. Oxygen is the essential component of the atmosphere on the Earth having a share of 21%, as it helps in supporting life on this planet.