| A | B |
|---|
| What do paleontologists do? | They are scientists who study fossils. |
| What is a fossil record? | It's information about past life, the order in which they lived, structures of organisms, their environment, and the "food" they ate and what ate them. (mnemonic: POSE F: past, order, structure, environment, "food") |
| Of what help is the fossil record? | It provides evidence of Earth's history, and shows how different groups of organisms and species have changed over time. |
| How many of the species that have ever lived on Earth are extinct? | More than 99% are extinct. |
| Where are most fossils formed? | They're formed in sedimentary rock. |
| Why is the fossil record an incomplete record of life's history? | Many organisms die without leaving fossils, as fossils require a precise combination of conditions to form. |
| What is relative dating? | It is a process of dating the age of a fossil; it's determined by comparing the fossil's placement with that of fossils in other layers of rock. (See pictures on pg. 418-19) |
| What is radioactive dating? | Scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains. |
| Carbon-14 is used to date fossils that are how old? | Scientists compare the amount of Carbon-12 and Carbon-14 in a fossil; the most carbon-12 there is compared to the carbon-14, the older the sample. Carbon-14's short half-life dates fossils younger than about 60,000 years. |
| What is a half-life? | It's the length of time rquired for half of the radioactive atoms in a sample to decay. |
| What are the 3 eras in which geologic time is divided after the Precambrian Time? | Paleozoic; Mesozoic; Cenozoic |
| Which era was known as the Age of the Dinosaurs? | The Mesozoic age. Mammals began to evolve then. |
| What's the Age of Mammals? | It's the Cenozoic Age. |
| What types of animals lived during the Paleozoic Era? | Many vertebrates & invertebrates lived then. |
| How long does a period in the geologic scale last? | Periods in the geologic scale last from tens of millions of years to less than 2 million years. |
