Earth's History and dating of the Earth Modified True/False Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true. ____ 1. The geologic species scale has units based on changes in rocks and fossils. _____________ ____ 2. If all Earth’s history took place in one year starting on January 1, humans would have appeared in March. _____________ ____ 3. If a very large asteroid impacts Earth, the dust and debris thrown into the atmosphere will act like a blanket and trap the heat from the Sun, causing global warming. _____________ Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 1. Geologic time is divided into units based upon types of _____. a. sedimentary rocks c. organisms b. climatic changes d. igneous rocks ____ 2. The longest subdivision in geologic time is a(n) _____. a. epoch c. century b. period d. eon ____ 3. A life-form in the Precambrian time was _____. a. cyanobacteria c. reptiles b. humans d. dinosaurs ____ 4. A life-form that evolved during the _____ Era was the dinosaur. a. Cenozoic c. Precambrian b. Mesozoic d. none of the above ____ 5. Little is known about much of Earth’s early history because _____. a. Precambrian rocks have been deeply buried b. Precambrian rocks have been changed by heat and pressure c. Precambrian soft-bodied life-forms weren’t often preserved as fossils d. all of the above ____ 6. The division of Earth’s history into smaller units makes up the _____. a. eras c. periods b. geologic time scale d. sequence of events ____ 7. Humans first appeared during the _____ Era. a. Precambrian b. Paleozoic c. Mesozoic d. Cenozoic ____ 8. Geologists organized the geologic time scale based on _____. a. superposition c. fossils in the rock layers b. evenly spaced time segments d. both a and c ____ 9. The divisions on the geologic time scale are most like which of the following? a. b. c. d. a calendar with evenly divided weeks sand pouring steadily through an hourglass marking your life by the major events marking your life by years ____ 10. Imagine all of Earth’s history taking place within 1 year, starting January 1. When did humans appear? a. January 1 c. November 20 b. February 10 d. December 31 Completion Complete each statement. 1. Radioactive elements decay at a _______________ rate. 2. As you move from left to right on the chart, each circle shows _______________ as many parent atoms as the circle preceding it. 3. The geologic time scale is always drawn vertically with the _______________ rocks at the bottom.