ATR 250
Chapter 8: Fossils and Their Place in Time and Nature

Amino acid dating     an absolute dating method for organic remains such as bone or shell, in which the amount of change in the amino acid structure is measured.
biostratigraphic dating    A relative dating method that uses the associations of fossils in strata to determine each layer's approximate age. 
C3 plants    Plants that take in carbon through C3 photosynthesis, which changes carbon dioxide into a compound having three carbon atoms. Tending to be from more temperate regions, these plants include wheat, sugar beets, peas, and a range of hardwood trees.
C4 plants     Plants that take in carbon through C4 photosynthesis, which changes carbon dioxide into a compound with four carbon atoms. These plants tend to be from warmer regions with low humidity and include corn, sugarcane, millet, and prickly pear.
Cenozoic    The era lasting from 65 mya until the present, encompassing the radiation and proliferation of mammals such as humans and other primates.
chemical dating       Dating methods that use predictable chemical changes that occur over time.
cultural dating    Relative dating methods that are based on material remains' time spans.
dendrochronology    A chronometric dating method that uses a tree-ring count to determine numerical age.
electron spin resonance dating   An absolute dating method that uses microwave   spectroscopy   to measure electrons' spins in various materials.
epochs    Divisions of periods (which are the major divisions of eras) in geologic time
 eras    Major divisions of geologic time that are divided into periods and further subdivided into epochs. 
fission track dating   An absolute dating method based on the measurement of the number of tracks left by the decay of uranium-238.
fluorine dating   A relative (chemical) dating method that compares the accumulation of fluorine in animal and human bones from the same site.
foraminifera   Marine protozoans that have variably shaped shells with small holes.
half-life    The time it takes for half of the radioisotopes in a substance to decay; used in various radiometric dating methods.
igneous    Rock formed from the crystallization of molten magma, which contains the radioisotope 40K; used in potassium-argon dating.
 index fossils Fossils that are from specified time ranges, are found in multiple locations, and can be used to determine the age of associated strata.
isotopes    Two or more forms of a chemical element that vary in the number of neutrons in the nucleus and by the atomic weight.
luminescence dating    A relative dating method  in which the energy trapped in a material is measured when the object is heated.
Mesozoic    The second major era of geologic time, 230-65 mya, characterized by the emergence and extinction of dinosaurs.
paleomagnetic dating  An absolute dating method based on the random reversals of Earth's magnetic field.
Paleozoic    The first major era of geologic time, 570-230 mya, during which fish, reptiles, and insects first appeared.
Pangaea    A hypothetical landmass in which all the continents were joined, approximately 300—200 mya.
pebble tools  The earliest stone tools, in which simple flakes were knocked off to produce an edge used for cutting and scraping.
phylogeny   the evolutionary relationships of a group of organisms.
polarized light  A kind of light used in amino acid dating because it allows amino acid changes to be observed and measured.
racemization    The chemical reaction resulting in the conversion of L amino acids to D amino acids for amino acid dating. 
radiocarbon dating   The radiometric dating method in which the ratio of 14C to 12C is measured to provide an absolute date for a material younger than 50,000 years.
radiopotassium dating    The radiometric dating method in which the ratio of 40K to 40Ar is measured to provide an absolute date for a material older than 200,000 years.
sedimentary    Rock formed when the deposition of sediments creates distinct layers, or strata.
Steno's law of superposition   The principle that the lower the stratum or layer, the older its age; the oldest layers are at the bottom, and the youngest are at the top.
strata    Layers of rock, representing various periods of deposition.
stratigraphic correlation    The process of matching up strata from several sites through the analysis of chemical, physical, and other properties.
taphonomy    The study of the deposition of plant or animal remains and the environmental conditions affecting their preservation.
tectonic    Refers to various structures on Earth's surface, such as the continental plates.