For photosynthetic organisms to evolve and become more abundant than chemosynthetic organisms, what variable must have changed in the environment of ancient earth? carbon dioxide must have become more abundant. nitrogen must have become more abundant in the atmosphere. oxygen must have become more abundant. endosymbiosis needed to occur between a smaller prokaryote and a larger prokaryote.

step 1: replication fork formation.

step 2: primer binding.

step 3: elongation.

step 4: termination.

explanation:

hope this !

correct answer is option a.

tropopause, stratopause and mesopause have all in common aspect that is point of maximum temperature in its layer of the atmosphere. all layers of atmosphere observe abrupt change in temperature. tropopause is the boundary between troposphere and stratosphere. stratopause is the boundary between stratosphere and mesosphere. mesopause is the boundary between mesosphere and thermosphere. these all boundaries are ranges between altitude of 0 to 80 km.