Brody studied the geologic time scale and became interested in the sorts of life that existed in each era. What kind of life characterized Precambrian time?

A.
invertebrates with hard shells

B.
early reptiles and amphibians

C.
animals with shells and outer skeletons

D.
single- and simple multi-celled organisms

D. single- and simple multi-celled organisms

Although more complex animals like invertebrates and multi-celled organisms began to appear, it was very late compared to the original, simpler organisms for which the Precambrian time is characterized by.

which elements do geologists measure to determine the age of an organism’s remains? check all that apply.

carbon-14

nitrogen

carbon-12