A biosphere is a place where organisms live. You wouldn't want to travel beyond the earth's biosphere, unless of course you are an astronaut.
From the Greek bios, "life," and sphaira, "sphere," biosphere came into English use in the 19th century. It means the life that occurs within a certain sphere or region around a planet. If you're reading this from Mars you probably have a biosphere all your own. You and other living things on Earth need oxygen and other substances to survive, and the biosphere fulfills those needs.
