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Chapter 12 Vocabular


Fossil A trace of an organism from the past
Relative Dating An estimate of the age of a fossil based on the location of fossils in strata.
Radiometric Dating Technique that uses the natural decay rate of isotopes to calculate the age of material.
Isotope A form of an element that has the same number of protons but a different number of neutrons as another element
Half-Life The amount of time it takes to for half of the isotopes in a sample to decay into its product isotope
Index Fossil A fossil of an organism that existed during only specific spans of geologic time across large geographic areas.
Era The second largest unit of geologic time, lasting tens to hundreds of millions of years and consisting of two or more periods
Period Unit of geologic time that lasts tens of millions of years and is associated with a particular type of rock system.
Epoch The smallest unit of geologic time, lasting several million years
Ribozyme RNA molecule that can catalyze specific chemical reactions
Cyanobacteria Bacteria that can carry out photosynthesis
Endosymbiosis Ecological relationship in which once organism lives within the body of another
Cambrian Explosion The earliest part of the Paleozoic era, when a huge diversity of animal species evolved
Created by: pategirl10