Earth is called a unique planet due to its several exceptional features that make it different from other planets in the solar system. The following are some of the reasons for Earth being a unique planet:

The Presence of Life
- Earth is the only planet in the solar system that supports life.
- It has a diverse range of living organisms, from microorganisms to complex beings like humans.
- The presence of life on Earth is due to its location in the habitable zone, where the conditions are suitable for life to exist.

The Atmosphere
- Earth has a unique atmosphere that is composed of various gases, such as nitrogen, oxygen, and carbon dioxide, which are essential for life.
- The Earth's atmosphere also protects the planet from harmful radiation and meteoroids from space.

The Water Cycle
- Earth is the only planet in the solar system that has a significant amount of liquid water on its surface.
- The water cycle on Earth helps to regulate the planet's temperature and supports the growth of living organisms.

Plate Tectonics
- Earth is the only planet in the solar system that has plate tectonics, which causes the movement of the Earth's crust and creates landforms such as mountains, valleys, and oceans.
- Plate tectonics also plays a significant role in the Earth's climate by regulating the amount of carbon dioxide in the atmosphere.

Conclusion
In conclusion, Earth is a unique planet in the solar system due to its exceptional features, such as the presence of life, the atmosphere, the water cycle, and plate tectonics. These features have made Earth a habitable planet and a suitable place for life to thrive.

Earth is called a unique planet because life exists only on earth. It has conditions for supporting life. Earth is neither too hot nor too cold and it has life supporting gasses like oxygen. Hence Earth is called a unique planet.