Name: -- Date: --
In "Dung Detective" (pp. 8-9), you read that Karen Chin studies fossilized dinosaur dung from the Mesozoic era. Scientists who study rocks and fossils divide Earth's history into long eras and shorter periods. This timeline is called the Geologic Time Scale. The time scale below shows some of the major events that occurred in the past 600 million years. Study the time scale, then answer the questions.
Geologic Time Scale Era Period Major Events Cenozonic Neogene First humans appear. Paleogene Mesozoic Cretaceous Dinosaurs go extinct. First primates appear. Jurassic First birds appear. Triassic First mammals appear. First dinosaurs appear. Paleozonic Permian 90 percent of species become extinct. Carboniferous First reptiles appear. Devonian First amphibians appear. Silurian Ordovician Cambrian First fish appear. Precambrian First traces of animals appear. SOURCE: GEOLOGICAL SOCIETY OF AMERICA
1. Which period are we in now?
2. During which period did the first reptiles appear?
3. Which of the following life-forms appeared first?
4. About how many years did the Mesozoic era last?
5. Imagine you found an animal fossil in rock that formed during the Carboniferous period. What types of species could it have come from? Use the Geologic Time Scale to explain your answer.
1. c 2. Carboniferous period 3. c 4. Answers may vary slightly but should be close to 180 million years. 5. The fossil could have come from a reptile, an amphibian, or a fish, because those species existed by that time. The fossil could not have come from a mammal, a bird, a dinosaur, or a human because they appeared later.