Question

over geologic time, the concentration of o2 in earths atmosphere has increased. however, at the end of the period, the o2 concentration decreased significantly and was associated with.
carboniferous; mass extinctions
permian; mass extinctions
cretaceous; mass extinctions
cretaceous; rapid evolution of lineages
devonian; rapid evolution of lineages

Explanation:

The Permian - Triassic extinction event, also known as the Great Dying, occurred at the end of the Permian period. It was the most severe mass - extinction event in Earth's history. During this time, there were significant environmental changes including a drop in oxygen levels in the atmosphere.

Answer:

B. Permian; mass extinctions