How life and Earth have changed each other

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Microbes made oxygen for a long time before it built up in the air. Noah looks for the best explanation of the delay. Which fits?

   • Early oxygen reacted with dissolved iron and volcanic gases before it could build up in the air
   • Ozone destroyed the oxygen as fast as the microbes made it
   • Microbes made no oxygen until the delay ended, so nothing built up
   • Oxygen escaped to space, so very little remained in the air
2. 2.

   A, warmer climate, faster weathering, less CO₂, cooler climate; B, warmer climate, less snow, darker ground, more warming. Bo compares the loops. Which statement about their feedback fits?

   • Both loops amplify the warming, since each starts with a warmer climate
   • Neither loop is a feedback, since each ends in a different system
   • Loop A damps the warming, while loop B amplifies it
   • Loop A amplifies the warming, while loop B damps it

3. Read this first

   Card

   Reef-building corals live in sunlit water, mostly shallower than about 50 m. A drill core through an island's limestone cap shows shallow-water coral fossils from the top down to 1,400 m.

4. 3.

   Luz reads the core. What does it show about the reef and the island?

   • The corals lived at 1,400 m depth, deep in the dark sea where they were found
   • Currents carried the corals down to 1,400 m after the reef formed there
   • The sea once stood 1,400 m higher, so the corals grew at the surface
   • The reef grew upward as the island sank, so life and Earth changed together
5. 4.

   A student says oxygen has been 21% of the air since microbes first made it. Jun replies using what is known. Which reply is best?

   • No: oxygen stayed far below today's level for a very long time after it first rose
   • Yes: the first microbes set the air at 21%, and it has not changed since
   • No: the air held no oxygen until land plants appeared
   • Yes: oxygen jumped to 21% within a few thousand years of the first microbes
6. 5.

   Mineral grains, 45; Water, 25; Air, 25; Roots, microbes and humus, 5. A student says soil is just crushed rock. Kira uses the table. Which reply is best?

   • No: organic matter is the largest part, at 45% of the volume of the soil
   • No: roots, microbes and humus are 50%, as much as water and air
   • Yes: minerals are the largest part at 45%, so the water, air and roots do not matter
   • No: minerals are only 45%; the 5% organic part comes from living things
7. 6.

   Squeeze Earth's 4.54 billion years into one 24-hour day. Oxygen rose 2.4 billion years ago and land life spread 0.43 billion years ago. How many hours apart, by Ren's math?

   • About 21.7 hours
   • About 2.3 hours
   • About 12.7 hours
   • About 10.4 hours

8. Card

   Burying 12 g of plant carbon leaves 32 g of oxygen in the air. (C + O₂ is CO₂ running backward.)

9. 7.

   A coal swamp buries 1 million tonnes of plant carbon. How much oxygen does Tala say is left in the air?

   • About 0.38 million tonnes
   • About 2.7 million tonnes
   • About 3.7 million tonnes
   • About 1 million tonnes

10. Card

    Volcanoes add 250 million tonnes of CO₂ a year and weathering removes 240 million (example data). The air holds about 3 trillion tonnes of CO₂ now.

11. 8.

    Zee adds up the gap for 1 million years with no other change. About how much CO₂ builds up in the air?

    • About 10 trillion tonnes, three times today's total, so feedbacks must balance
    • About 0 tonnes, since a feedback loop cancels any imbalance as soon as it appears
    • About 250 trillion tonnes, about eighty times today's total
    • About 10 billion tonnes, a small fraction of today's total

12. Parts of the long carbon cycle (example)

    Step	Where	Time it takes
    Weathering and shell-building	surface and sea	thousands to millions of years
    Burial of limestone	sea floor	millions of years
    Subduction and volcanic release	deep Earth	tens to hundreds of millions of years

13. 9.

    Esme reads the table. Which summary of the long carbon cycle fits?

    • Shells turn carbon into rock in a few years, and volcanoes return it the same year
    • Carbon locked in rock does not return to the air
    • Carbon moves from air to rock by weathering and shells, then returns by volcanoes over hundreds of millions of years
    • Carbon returns from rock to the air within days, by erosion

14. Rates of change (example data)

    Process	Rate (mm per year)
    Coral reef growth	5
    Soil formation	0.1

15. 10.

    Milo turns the rates into change per 1,000 years. Which summary of the pace of life's changes to Earth fits?

    • Reefs and soils both add about 5 m per 1,000 years, so they run at one speed
    • Reefs add about 5 m and soils about 10 cm per 1,000 years, so the processes run at very different speeds
    • Reefs add about 10 cm and soils about 5 m per 1,000 years, so soils are faster
    • Reefs add about 50 m and soils about 1 m per 1,000 years, so both are fast