Humans can survive indefinitely in the desert if they have a water source and food and shelter. Millions of people survive in desert cities and towns for years. Look at Cairo, Egypt, or Las Vegas in Nevada. Myself? I have lived over 40 years in the Chihuahuan Desert and have running water and all the other utilities as well as a Wal*Mart a half mile from my home. I have had no problem surviving.
Yup....they do
Yes, many live in the Gobi
An ecosystem is a place where plants and animals ( maybe humans ) live and animals and plants live in the desert so … 
In the desert Mojave Desert
garts
yes, scientists live there
A person can live indefinitely in the desert as long as they have sufficient water and nutritious food and, depending upon the particular desert, shelter.
There are saguaro cacti that live in the desert but there is no Saguaro Desert.
not really, but if they did they would have to have a big supply of water
Bears do live in the desert. I live in the Chihuahuan Desert and bears occasionally come down from the local mountains to the desert floor. As long as they have a water source they survive quite well.
It will live for at least as long as you let it live for. If you take really good care of your desert iguana, it will live for up to 15 to 20 years old. If you take bad care for your desert iguana it will live for a shorter time.
a long time