1.
The age of a rock compared to the ages of other rocks.________________________
2.
The age of a rock given as the number of years since the rock formed.________________________
3.
The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.________________________
4.
The preserved remains or traces of an organism that lived in the past.________________________
5.
A gap in the geologic record that shows where rock layers have been lost due to erosion.________________________
6.
The process in which the nuclei of radioactive elements break down, releasing fast-moving particles and energy.________________________
7.
The process of determining the age of an object using the half-life of one or more radioactive isotopes.________________________
8.
A record of the geologic events and life forms in Earth's history.________________________
9.
An animal without a backbone.________________________
10.
An animal with a backbone.________________________
11.
A vertebrate whose body temperature is determined by the temperature of its environment, and that lives its early life in water and its adult life on land.________________________
12.
A vertebrate whose temperature is determined by the temperature of its environment, that has lungs and scaly skin, and that lays eggs on land.________________________
13.
When entire species of living things die off at the same time.________________________
14.
A vertebrate whose body temperature is regulated by its internal heat, and that has skin covered with hair or fur and glands that produce milk to feed its young.________________________
15.
A major division of geological time, subdivided into eras, characterized by an immeasurably long period of time. It is 1 billion of years long.________________________
16.
A major division of time that is a subdivision of an eon and is itself subdivided into periods. It is several hundred million years long.________________________
17.
A major division of geological time that is a subdivision of an era and is itself subdivided into epochs. It is tens to several hundred of million years long.________________________
18.
A division of time that is a subdivision of a period and is itself subdivided into ages. It is tens of millions of years long.________________________
