Skills Worksheet Directed Reading B Section: Eras of the Geologic Time Scale 1. What are the four biggest eras in geologic history? a. Precambrian, Paleozoic, Mesozoic, and Cenozoic b. Precambrian, Prehistoric, Mesozoic, and Cenozoic c. Prehistoric, Mesozoic, and Cenozoic, and Modern d. Prehistoric, Paleozoic, Mesozoic, and Modern PRECAMBRIAN TIME 2. What first appeared on Earth during Precambrian time? a. dinosaurs b. mammals c. life d. humans How Did Life Begin? 3. What do scientists think the earliest living things grew from? a. oxygen b. a nucleus c. simple chemicals d. photosynthesis 4. How many cells did the first living things, prokaryotes, have? a. none b. one c. hundreds d. thousands Holt Science and Technology 15 The History of Life on Earth
Photosynthesis and Oxygen Read the description. Then, draw a line from the dot next to each description to the matching word. 5. living things that first made food from sunlight 6. gas that cyanobacteria sent into oceans and air 7. a layer of gas around the earth that keeps out radiation Multicellular Organisms a. cyanobacteria b. ozone c. oxygen 8. A billion years after Earth formed, what kind of living thingsappeared? a. smaller, less complex b. gas c. larger, more complex d. fossil 9. What may eukaryotic cells have evolved into? a. organisms made of many cells b. organisms made of one cell c. prokaryotes d. fossils THE PALEOZOIC ERA 10. What geologic era came after the Precambrian era? a. Mesozoic b. Paleozoic c. Modern d. Prehistoric Holt Science and Technology 16 The History of Life on Earth
11. What do Paleozoic era rocks have a lot of? a. sand b. fossils c. dinosaurs d. dirt 12. What were the first animals to have a backbone? a. sponges b. humans c. fish d. mammals 13. What does the word Paleozoic mean? a. new life b. ancient life c. animal life d. no life Life on Land 14. During the Paleozoic era, plants and animals slowly moved where? a. into the air b. onto the land c. into the oceans d. into shelter 15. What were some of the first animals to live on land? a. salamanders b. reptiles c. crawling insects d. winged insects Holt Science and Technology 17 The History of Life on Earth
16. What happened to almost all living things from the Paleozoic era? a. They came to land. b. They moved to the oceans. c. They died out. d. They were eaten. THE MESOZOIC ERA 17. What era came after the Paleozoic Era? a. the Prehistoric era b. the Precambrian era c. the Mesozoic era d. the Modern era 18. What is the Mesozoic Era known as? a. The Age of Fossils b. The Age of Reptiles c. The Age of Fishes d. The Age of Plants Life in the Mesozoic Era 19. What are the best-known reptiles of the Mesozoic era? a. salamanders b. fish c. dinosaurs d. plants Holt Science and Technology 18 The History of Life on Earth
The Extinction of Dinosaurs 20. What is one theory about why of the dinosaurs died out? a. A meteorite caused changes. b. There was too much sunlight. c. The dinosaurs got sick. d. Earth s temperatures got higher. THE CENOZOIC ERA Read the description. Then, draw a line from the dot next to each description to the matching word. 21. the geologic era that followed the Mesozoic 22. what Cenozoic means in Greek 23. type of animals the Cenozoicera is famous for The Cenozoic Era Today 24. What happened during the Cenozoic Era? a. Dinosaurs appeared. b. Mammals disappeared. c. Dinosaurs disappeared. d. Modern humans appeared. a. mammals b. recent life c. Cenozoic Holt Science and Technology 19 The History of Life on Earth