Atmosphere
AND liquid water
AND temperature range in which large organic structures can exist.
earth 6 kingdoms of living things
There is no known life on any planet other than Earth.
.How do you know that earth isn't the other planet?
Earth, Apart from ours no other planets been proved to have living things !
1 . Earth is the only planet where life is known to exist..there is no other planet where life can exist !!2. Earth is the third planet which nearest to the sun and it has an atmosphere which consists of hydrogen ,oxygen and carbon dioxide which are required for the existence of human life whereas other planets do not have any such gases!!!
Life/land forms and water
Other planets do have oxygen, but not in as high of concentration as we have here on Earth.
Earth, even though there are life forms on Earth which can use any of the gasses found on other planets.
Eart's status of being the only planet with living things must be made conditional with a "that we know of now". In the immensity of the Universe there are other planets which we will eventually discover, that have life.,
Earth's atmosphere contain significant amounts of oxygen, no other planet in the solar system has it - it may well be that other planets in the galaxy do have oxygen. It's not just oxygen though; if the atmosphere was pure oxygen it would kill us very quickly. It's the combination of gases; oxygen, nitrogen, hydrogen, etc, etc know as AIR, together with its pressure of around 15 psi that enables us to live here on earth.
No planet that we know of other than Earth is capable of supporting life.
The only planet that can't be seen from earth is earth itself. Other than earth itself other planet can be seen, however sometimes it might requires use of high technology!