Solar System
As far as scientists know, Earth is the only planet in the solar system that has the combination of factors needed to support life. Life as we know it requires liquid water and an energy source. Earth has both. Earth’s atmosphere contains the oxygen that animals need to breathe. Matter is continuously cycled between the environment and living things. And a number of ecosystems exist on Earth that different organisms can inhabit. Earths vast liquid-water oceans and moderate temperatures provided by the ideal conditions for life to emerge in flourish. Today the total number of species of organisms that inhabit Earth is thought to be anywhere between 5 million and 30 million