1. The division of Earth’s history into smaller units makes up the ____.

eras
geologic time scale***
periods
sequence of events

2. Today, some scientists think that ____.

birds evolved from dinosaurs
dinosaurs evolved from fish
birds evolved from amphibians
both a and b***

3. A life-form in the Precambrian time was ____.

cyanobacteria***
humans
reptiles
dinosaurs

4. Which trilobite characteristic did not change through time?

shape of eyes
three-lobed body***
number of body segments
number of spines

5. ____ existed during the Mesozoic era.

Angiosperms
Humans
Birds
both a and c***