**Optional.** Scientific ideas about how life began

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Table, Early Earth timeline (NASA), with columns Event, When

   Earth forms, about 4.5 billion years ago; Possible earliest signs of life, about 4 billion years ago; Pilbara stromatolites, Australia, about 3.5 billion years ago; Miller–Urey paper in Science, May 15, 1953.

2. 1.

   Using the timeline, about how long ago might life have been on Earth, by Bo's reading (NASA)?

   • About 40 billion years ago
   • About 4 billion years ago
   • About 4 million years ago
   • About 400 years ago

3. Table, The Miller–Urey experiment (NASA), with columns Part, What it stood for or gave

   Flask of water, an early ocean; Methane, ammonia, hydrogen and water vapor, an early atmosphere, as Urey proposed; Electric sparks, lightning; Result in 1953, 5 amino acids identified; Re-analysis in 2008 of a sibling experiment, 22 amino acids.

4. 2.

   Using the table, what did the electric sparks in the Miller–Urey flask stand for, by Jun's reading (NASA)?

   • Lightning
   • Sunlight on a pond
   • Heat from a volcano
   • Living cells
5. 3.

   Which gases did Miller and Urey use for the early atmosphere, by Luz's reading (NASA)?

   • Methane, ammonia, hydrogen and water vapor
   • Helium and neon
   • Oxygen and nitrogen, like the air we breathe today
   • Carbon dioxide and nothing else
6. 4.

   What did the 1953 Miller–Urey experiment make, by Milo's reading (NASA)?

   • Amino acids
   • Living bacteria
   • Complete cells with DNA
   • Stromatolites

7. Use this

   RNA, DNA and a protein, with the jobs each can do.

8. 5.

   What can RNA do that makes the RNA world idea possible, by Noah's reading (NASA)?

   • Store genetic data and speed up reactions like an enzyme
   • Build cell walls around itself
   • Store genetic data but speed up no reactions
   • Turn sunlight into sugar
9. 6.

   What chicken-and-egg problem does the RNA world idea try to solve, by Pia's reading (NASA)?

   • Cells need oxygen to grow, and oxygen needs cells to form
   • Fossils need cells, and cells need fossils
   • Water needs life, and life needs rock
   • DNA needs proteins to form, and proteins need DNA
10. 7.

    In the RNA world idea, what later took over RNA's main jobs, by Ren's reading (NASA)?

    • Methane and ammonia
    • DNA and proteins
    • Amino acids by themselves
    • Stromatolites

11. Use this

    A pond, a tide pool, a hot spring and a seafloor vent chimney.

12. 8.

    Which places do NASA scientists study as possible sites for life's origin, by Tala's reading?

    • A single known site, already confirmed
    • The center of the Sun
    • Ponds, tide pools, hot springs, sea ice and hydrothermal vents
    • Deep caves on the Moon
13. 9.

    Is how life began a settled question, by Zee's reading (NASA)?

    • Yes; RNA has been shown to arise on its own
    • Yes; the 1953 experiment settled it
    • Yes; fossils record the first cell forming
    • No; many aspects of early life are still unknown
14. 10.

    What are alkaline hydrothermal vents, by Esme's reading (NASA)?

    • Holes in the ozone layer
    • Volcanoes on the Moon
    • Seafloor vents with chimney-like structures rich in iron and sulfur
    • Fossil microbial mats