Light-colored lizards move toan area where there is dark-colored sand. after many years, most of the lizards are dark-colored. why do you think this happened?

I believe that the lizards had adapted to the environment in order to survive and thrive. Using camouflage, the lizards are able to hide. They may have changed, through natural selection, or something like that. I know this isn't a deep answer, and it's only barely touching the surface of the topic, but I still hope that it helps you :D.

The higher you go up the less oxygen there is 

No because the eaeht is on a 23.5 degree axis tilt and so when it is winter the northern hemisphere is pointing away from the sun and the soutubern hemisphere is pointing toward the sun