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

Grade 9 Science Worksheet

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 after Earth formed did the Pilbara stromatolites form, by Bo's math?

   • About 8 billion years
   • About 1 billion years
   • About 3.5 billion years
   • About 0.1 billion years
3. 2.

   NASA: Earth is about 4.5 billion years old, and life may date to about 4 billion years ago. About what share of Earth's history might life span, by Esme's math?

   • About 11%
   • About 50%
   • About 89%
   • About 113%
4. 3.

   Using the timeline, about how many years passed from Miller's 1953 paper to 2026, by Jun's math?

   • About 1,953 years
   • About 73 years
   • About 3,979 years
   • About 37 years

5. 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.

6. 4.

   Using the table, how many times as many amino acids did the 2008 re-analysis find as Miller identified in 1953, by Milo's math?

   • About 27 times
   • About 0.23 times
   • About 17 times
   • About 4.4 times
7. 5.

   RNA, DNA and a protein, with the jobs each can do. Why is RNA a good candidate for the first genetic molecule, by Noah's reading (NASA)?

   • It makes up most of a cell's water
   • It needs both DNA and proteins before it can ever form
   • It can carry genetic data and act as an enzyme
   • It has vanished from cells today
8. 6.

   A pond, a tide pool, a hot spring and a seafloor vent chimney. NASA: tests with vent-like minerals made RNA strings up to four units long at room temperature. What is a concern, by Pia's reading?

   • The test settled how life began
   • Room temperature is hotter than vents
   • The strings were far too long to count as real RNA molecules
   • Real vents are much hotter, and heat could destroy RNA
9. 7.

   RNA, DNA and a protein, with the jobs each can do. What question does the RNA world idea leave open, by Ren's reading (NASA)?

   • Whether RNA exists in living cells
   • Whether DNA stores genetic data
   • Whether stromatolites are layered rocks made by microbes
   • How RNA itself first formed from simpler molecules

10. 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.

11. 8.

    What are stromatolites, by Tala's reading (NASA)?

    • Crystals grown in hot springs with no life
    • Ripples left by waves on sand
    • Layered rocks built by mats of microbes growing layer by layer
    • Bones of the first animals
12. 9.

    Why do scientists look for stromatolite-like mounds on Mars, by Zee's reading (NASA)?

    • Such mounds could be a sign of ancient microbial mats
    • They form where liquid oceans exist today
    • They show that plants once grew on Mars
    • They mark where meteorites landed
13. 10.

    Model data: each stromatolite layer records a period of microbial growth (NASA). A stromatolite has 600 layers, each about 0.5 mm thick. How tall is it, by Ari's math?

    • About 1,200 mm
    • About 600.5 mm
    • About 30 mm
    • About 300 mm (30 cm)