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scientist who studies fossils

fossil record

information about past life, including the structure of organisms, what they ate, what ate them, in what environment they lived, and the order in which they lived


term used to refer to a species that has died out

relative dating

method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock

index fossil

distinctive fossil used to compare the relative ages of fossils


length of time required for half of the radioactive atoms in a sample to decay

radioactive dating

technique in which scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains

geologic time scale

scale used by paleontologists to represent evolutionary time


one of several subdivisions of the time between the Precambrian and the present


unit of time into which eras are subdivided

proteinoid microsphere

tiny bubble, formed of large organic molecules, that has some characteristics of a cell


microscopic fossil

endosymbiotic theory

theory that eukaryotic cells formed from a symbiosis among several different prokaryotic organisms

mass extinction

event in which many types of living things become extinct at the same time


large-scale evolutionary changes that take place over long periods of time

adaptive radiation

process by which a single species or small group of species evolves into several different forms that live in different ways; rapid growth in the diversity of a group of organisms

convergent evolution

process by which unrelated organisms independently evolve similarities when adapting to similar environments


process by which two species evolve in response to changes in each other

punctuated equilibrium

pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change

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