Chapter 12 Flashcards
Estimate of the age of a fossil based on the location of fossils in the rock strata (top-younger and bottom-older)
Relative dating
Technique that measures age based the natural decay rate of isotopes; compares the relative dating percentages of a radioactive (parent) isotope and a stable (daughter) isotope
Radiometric dating
Form of an element that has the same number of protons but a different number of neutrons as another element
Isotope
The time in which half the atoms in a radioactive isotope decay into its daughter isotope (ex: potassium–> argon)
Half-life
Fossil of an organism that existed during only specific spans of geologic time across large geographic areas; used to establish rage of a rock layer
Index fossil
Time scale representing the geological history of earth
Geologic time scale
Second largest unit Of geologic time, consisting of two or more periods
Era
A unit of geologic time that is longer than an epoch but shorter than an era
Period
Smallest unit of geologic time, shorter than a period
Epoch
Bacteria that can carry out photosynthesis; blue-grew algae
Cyanobacteria
Mutually beneficial relationship in which one organism lives within the body of another; theory for origin of eukaryotes
Endosymbiosis
The geologic era that followed Pre-Cambrian time
Paleozoic
Earliest part of the Paleozoic era, when a huge diversity of animal phyla appeared
Cambrian explosion
The geologic era that lasted from 251 million to 65.5 million years ago; also called the Age of Reptiles
Mesozoic
The current geologic era, which began 65.5 million years ago; also called the Age of Manmals
Cenozoic
