The large size of insects and amphibians during the Pennsylvanian period has been suggested to be due to ______.
A) a lack of predators for early land forms
B) an excess of sunlight and water during that time
C) a decrease in methane in the atmosphere during that time
D) an excess of oxygen during that time
E) the emergence of a super continent that allowed greater areas for animals to evolve

Question

Quizplus · Accepted Answer

The large size of insects and amphibians during the Pennsylvanian period has been attributed to high oxygen levels in the atmosphere. The atmospheric oxygen concentration during the Pennsylvanian period is estimated to have been around 35%, compared to the current 21%, which allowed for more efficient respiration and growth in these animals.

The Large Size of Insects and Amphibians During the Pennsylvanian