Early Earth History Answers

The Precambrian time period is segmented into very few parts because:a.the fossil record is scarcec.cyanobacteria were the only life formb.life did not existd.volcanic activity ruined the fossil record

Cyanobacteria increased the levels of carbon dioxide in the atmosphere.

Life-forms that existed during the Paleozoic Era included ____.a.fishc.reptilesb.trilobitesd.all of the above

The Precambrian time period is the largest on the geological time scale.

Early land animals had to return to the water to reproduce.

A life-form in the Precambrian time was ____.a.cyanobacteriac.reptilesb.humansd.dinosaurs

Early land animals had gills as well as lungs.

Geologic events that occurred during the Paleozoic Era include mountain building and volcanic activity.

The geological time scale is divided up and organized according to what life forms existed on earth.

The development of ____ factored in the development of complex organisms.a.ozonec.cyanobacteriab.oxygend.all of the above