The Earth we live is a part of our solar system and there are numerous solar systems in our Galaxy. There are many billions of planets and countless numbers of Stars. So thinking life only exists on Earth is not acceptable. It would be probable for Life to exist somewhere other than Earth. There are possibilities that life in some other planets may be more intelligent and have developed high technology and may have well developed in scientific and all other areas compared to us. But in some planets there might be life at the level of micro organisms.
Earth is the home of millions of species including Humans. And environmental factors and physical properties of Earth have allowed Life to persist. Earth is the only planet in our solar system where life is known to exist. It is debate these days that Life may exist in planets of other solar systems. Scientists have speculated about the possibility of Life on planets other than Earth. But it is an open question whether life currently exists other than Earth. Before 100 years it was true that scientists believed that Life could not be possible in other planets. Even now there are scientists against the theory that Life exists in other planets.