From Envirowiki

Earth is the third planet in orbit around the Sun (Sol), a star in the milkyway galaxy. so far, no life has been discovered outside earth's biosphere by humans.

the earth consists of a huge molten core, made up of iron and other metals, surrounded by molten magma, and a solid "crust" (lithosphere) made of various types of minerals. on top of these rocks lie soil and water. these bodies are the lower limit of the biosphere. the soil and sea are the base for plants and flightless animals and other forms of life, which grow in abundance nearly everywhere. some animals, such as birds and insects, also inhabit the lower reaches of the gas layer (atmosphere), the troposphere