_____________Time Scale Geologic Time Scale● Began when Earth was ________________and continues to

_________________day● At the end of Each era a ______________ ___________________occurred

○ Mass Extinction - The extinction of a large number of species within a relatively ________________period of geological time, thought to be due to factors such as a catastrophic _______________ _____________or widespread _______________________change that occurs too rapidly for most species to__________________.

○ Other extinctions also occurred during each period of geologic time

● Using the fossil record, paleontologists have created an idea of the different types of common organisms in each Geologic period

Geologic Time scale (largest to smallest)

● Eon● Era● Period● Epoch

Present Day-We are currently in:Phanerozoic EonCenozoic Era Quaternary PeriodHolocene Epoch

Precambrian Era● Earth’s _______________era of time ● Began with the creation of earth around

_____________________years ago● 5 Major events during this era:

1. The formation of the Sun and light2. The creation of the ____________3. The creation of the atmosphere through volcanic

out-gassing4. The creation of the oceans5. The creation of life

Precambrian Era (continued)● Began with ________________ life forms such as

__________________and _________________● There was a rise of simple organisms such as jellyfish

and sea worms by the end of this era● Few ________________because the life forms were

soft-bodied and had no hard skeleton

Paleozoic Era● Began with the early invertebrates, such as

___________________and brachiopods; continued to develop early vertebrate fish, then arachnids and insects; later came the first amphibians, and near the era’s end the __________________ became dominant.

● Early land __________________included simple mosses, ferns, and then cone-bearing plants.

● By the end of the era, seed plants were common. ● The mass extinction that ended the era caused most

___________________invertebrates as well as amphibians to__________________.

Mesozoic Era● __________________were the dominant animals of this

era, including the various __________________. ● Small ________________and _________________also

appeared. ● Toward the end of the era, flowering plants appeared

and the kinds of mammals increased. ● The ____________ ________________that ended the era

caused the ___________________to become extinct.

Cenozoic Era● New _________________appeared while others

became_________________. ● The _________________of life forms___________________. ● Flowering plants became most common. ● _________________are also part of the most recent

period of this era (we are currently in the Cenozoic Era)

So… What do we see change throughout time?● _________________of life-forms

_____________________○ This means that there are a lot

more species of living things now than long ago

● __________________of the life-forms ____________________○ It is believed that earliest life

forms may have been microscopic organisms (simple single celled organisms). Today, we have much more complex organisms (made of many cells).