Cyanobacteria increased the levels of carbon dioxide in the atmosphere.
Geologic events that occurred during the Paleozoic Era include mountain building and volcanic activity.
The development of ____ factored in the development of complex organisms.
d. all of the above
A life-form in the Precambrian time was ____.
a. cyanobacteria
What time period lasted for more than half of the hypothesized history of the Earth?
d. Precambrian
Animal life in the Paleozoic Era included all of the following EXCEPT ____.
b. humans
Little is known about much of Earth's early history because ____.
d. all of the above
Life-forms that existed during the Paleozoic Era included ____.
d. all of the above
Early land animals had gills as well as lungs.
The Precambrian time period is the largest on the geological time scale.