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form when flowing water removes all of the original bone or tissue, leaving just an impression in sediment.
record the activity of an organism; they include nests, burrows, imprints of leaves, & footprints.
organisms that become trapped in tree resin that hardens to amber after the tree gets buried underground.
form when an entire organism becomes encased in material such as ice or volcanic ash or immersed in bogs.
_______ _______ estimates the time during which an organism lived by comparing the placement of fossils of that organism with the placement of fossils in other layers of rock.
_______ _______ is a technique that uses the natural decay rate of unstable isotopes found in materials in order to calculate the age of that material
________ are atoms of an element that have the same number of protons but a different number of neutrons.
______ is the amount of time it takes for half of the isotope in a sample to decay into a different element or its produce isotope.
fossils of organisms that existed only during specific spans of time over large geographic areas.
_______ are the most commonly used units of time on the geologic time scale, lasting tens of of years; each ______ is associated with a particular type of rock system (same word).
a relationship in which one organism lives within the body of another, and both benefit from the relationship.
The earliest part of the Paleozoic era when a huge diversity of animal species evolved.
_____ make up a category of mammals with flexible hands and feet, forward looking eyes, and enlarged brains relative to body size.
the humanlike primates; are further subdivided into the New World monkeys, Old World monkeys, and hominoids.
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