Interval of time when the earth's magnetic field is oriented so that magnetic north pole is approximately in the same positions as the geographic south pole strata singular: Understanding the ages of related fossil species helps scientists piece together the evolutionary history of a group of organisms. The assemblage of protons and neutrons at the core of an atom, containing almost all of the mass of the atom and its positive charge daughter isotope: The empty spaces within an organism spaces filled with liquid or gas during life become filled with mineral-rich groundwater. Fossil wood is wood that is preserved in the fossil record. This scheme has application over a wide range of geologic dates.
A review". New York: A fossil can be studied to determine what kind of organism it represents, how the organism lived, and how it was preserved. The scheme worked all round the world, without fail.