Describe Earth during Early Paleozoic Era and during Late Paleozoic Era. Drscribe one organism of each era(early and late Paleozoic)

Astudent poured a solution of bromothymol blue indicator into three test tubes. then he placed an aquatic plant in two of the test tubes, as shown below. he placed a stopper on each test tube and placed them all in the dark for 24 hours. bromothymol blue turns from blue to yellow in the presence of co2