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Biology Chapter 19
Terms to do with the History of Life
Term | Definition |
---|---|
Extinct | A species that has died out |
Paleontologists | Researchers who study fossils to learn about ancient life such as the structure of ancient organisms, their environment, and the way they lived |
Relative Dating | Determines the relative age of a rock layer or fossil by comparing its placement with that of fossils in other rock layers. |
Index Fossils | Used when scientists need to correlate the relative ages of the rock layers that carry them distant places |
Radiometric Dating | Relies on radioactive elements which decay or breakdown into nonradioactive elements at a steady rate |
Half-life | The time required for half of the radioactive atoms in a sample to decay |
Geologic Time Scale | A timeline of Earth that geologists and paleontologists have built |
Eras | What eons are divided into |
Periods | What eras are divided into (ranging in length from hundreds of millions of years to just 2 million years) |
Plate Tectonics | Huge plates that move in the past and continue to move on in the Earth's outermost layer |