Hey there!
The changes that were (necessary) in the Earth's atmosphere to allow complex organisms to evolve was a collision from above such as a meteor and an increase in volcanic activity.
Your correct answer . . .
. . .
Hope this helps.
~Jurgen
The changes that were (necessary) in the Earth's atmosphere to allow complex organisms to evolve was a collision from above such as a meteor and an increase in volcanic activity.
Your correct answer . . .
Hope this helps.
~Jurgen