Early Earth History

Complex organisms with gills and lungs were major life forms that existed in the_____________.

90 % of marine organisms and 70% of land organisms died off due to environmental and/or climate changes during the Paleozoic Era.

Cyanobacteria, unusual worm like life-forms and marine organisms did not exist in Precambrian Time.

Species developed harder shelled eggs to raise them on land, this is to adapt to the changes in the environment during the Cenozoic era.

Early land animals had gills as well as lungs.

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

The formation of the moon may have caused the Paleozoic extinction.

Cyanobacteria increased the levels of carbon dioxide in the atmosphere.

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

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