because there is presence of water and ait

Earth is unique in the Solar System as being the only planet which is able to support life in all its forms: from basic living micro-organisms to highly sophisticated and intelligent human beings. There are many reasons why this happens.

REASON ONE: ATMOSPHERE

Earth has a breathable atmosphere. Oxygen is the gas that is required for the life of most creatures. This is present in Earth's atmosphere and also in water. Oxygen is constantly put into the atmosphere by plants and trees. Earth's atmosphere also contains a small amount of carbon dioxide. This is a poisonous gas which makes up most of the atmosphere of planets likeVenusandMarsand makes them unable to support human life. However, its smaller presence on Earth is useful as it helps to moderate the planet's temperature and is absorbed by plants during photosynthesis to produce oxygen. Earth's atmosphere is kept on the planet by its pull of gravity.MarsandMercuryare too small to keep atmosphere. As a result,Mercuryhas no atmosphere, andMars' atmosphere is very thin, containing gases which have not managed to escape into space yet. Earth's atmosphere is thick enough to prevent poisonous rays of radiation from getting through it (this is what has happened onMars).

REASON TWO: CLIMATE

life is only possible on the earth because there is air,water and trees are present