Divisions of earth’s history are seen on the scale.
geologic time scale
longest subdivision based on the abundance of certain fossils
eon
Worldwide changes in fossils, Mass extinction, Divided into periods
era
units of geologic time characterized by the types of of life existing at the time
periods
characterized by differences in life-forms
epoch
a change through time that shows that species had changed over time
organic evolution
a group of organisms that normally reproduce only with other members of their group
species
a process in which organisms with characteristics that are suited to a certain enviorment have a better chance of surviving a reproducing than organisms that do not have these characteristics
natural selection
an organism with a three-lobed exoskeleton that was abundant in Paleozoic oceans and is considered to be an index fossil
trilobite
when the continents were all connected
Pangea