| A | B |
|---|
| half-life | the number of years it takes for 50% of an isotope to decay |
| magnetic reversals | reversal of the polarity of Earth's magnetic field |
| genetic annealing | production of a new genome through the transfer of part of the genome of one organism to another. |
| stromatolites | rocks made of branded domes of sediment where most forms of ancient prokaryotic life are found |
| snowball Earth hypothesis | hypothesis that glaciers covered the planet 750-570 million years ago, confining life to limited places |
| serial endosymbiosis | model of the origin of eukaryotes consisting of a sequence of endosymbiotic events in which cellular structures were derived form small prokaryotes that had been engulfed by larger cells |
| Pangea | supercontinent formed at the end of the Paleozoic era when plate movements brought all the land masses together |
| protobionts | aggregate of biologically produced molecules surrounded by a membrane or membrane-like structure |
| geologic record | division of Earth's history into time periods |
| three domain system | system of taxonomic classification based on three superkingdoms: Bacteria, Archaea, and Eukarya |
| radiometric dating | method used to determine ages of rocks and fossils on a scale of absolute time, based on the half-life of radioactive isotopes |
| ribozyme | an enzyme-like RNA molecule that catalyzes reactions during RNA splicing |
