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Earth week 9

name: ______________________________
Across
Divisions of geologic time less than a period and greater than an age.
A condition or factor which is affected by another factor or factors.
The death of an entire species.
The period that begins about 800 million years after Earth formed and lasted for about 1.4 billion years.
The condition or factor which can be manipulated in an experiment and which influences another factor.
The first period in Earth's history, so named because it was thought to be like Hades.
A gradual process in which something changes into a different and usually more complex or better form.
Large divisions of geologic time usually shorter than an eon.
Divisions of geologic time that are longer than an epoch and included in an era.
The preserved remains or traces of organisms that lived in the geologic past.
The geologic era that spans from the formation of Earth around 4.5 b.y.a. to about 544 m.y.a.
The study of the origin, history, and structure of Earth.
Down
A series of steps that scientists use to guide their reasoning while conducting science.
Period from 1.8 million years ago to present day.
When a large percentage of all known living species die out in a relatively short amount of geologic time.
A timeline that describes the timing and relationships of events in Earth's history.
A group in a lab experiment that is exposed to the tested variable.
A group of organisms of the same species living in a given area.
The third, and last, period in the Precambrian, that lasted nearly 2 billion years.
The modern species of humans.
The most recent era on the geologic time scale.
The second most recent era on the geologic time scale, spanning from 245 m.y.a. to 65 m.y.a; often called the "Age of Dinosaurs."
Period from 65 to 1.8 million years ago.