How life and Earth have changed each other
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
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
- Microbes made no oxygen until the delay ended, so nothing built up
- Oxygen escaped to space, so very little remained in the air
- Ozone destroyed the oxygen as fast as the microbes made it
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?
- Loop A amplifies the warming, while loop B damps it
- Loop A damps the warming, while loop B amplifies it
- Both loops amplify the warming, since each starts with a warmer climate
- Neither loop is a feedback, since each ends in a different system
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.
Luz reads the core. What does it show about the reef and the island?
- The sea once stood 1,400 m higher, so the corals grew at the surface
- Currents carried the corals down to 1,400 m after the reef formed there
- The reef grew upward as the island sank, so life and Earth changed together
- The corals lived at 1,400 m depth, deep in the dark sea where they were found
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?
- 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
- No: oxygen stayed far below today's level for a very long time after it first rose
- Yes: oxygen jumped to 21% within a few thousand years of the first microbes
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?
- 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
- 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
Three planets' air (NASA)
Planet CO₂ (%) O₂ (%) Earth 0.04 21 Mars 95 0.17 Venus 96.5 0 A student says life only lives on Earth and never changes it. Pia uses the table. Which reply is best?
- No: Earth's air is 21% oxygen and 0.04% CO₂, unlike its neighbors, because of life
- Yes: the three airs are alike, so life cannot have changed any of them
- No: Mars has the most oxygen, so life made its air
- Yes: Earth's air differs from its neighbors just because it is closer to the Sun than Mars
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 10.4 hours
- About 21.7 hours
- About 12.7 hours
- About 2.3 hours
Events (approximate, millions of years ago)
Event Millions of years ago Microbes' oxygen fills the air 2,400 Land plants spread 470 Roots form deep soil and forests 385 Buried swamp plants form coal 300 Ari reads the table. Which summary of how life and Earth changed together fits all four events?
- The four events happened within a few thousand years of each other
- Soil formed from rock alone, so roots changed nothing about Earth
- Life changed the air; the air opened land to life; plants then changed soil and rock
- Earth changed first, and life just responded to it; life did not change Earth in return
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 Esme reads the table. Which summary of the long carbon cycle fits?
- Carbon returns from rock to the air within days, by erosion
- Carbon locked in rock does not return to the air
- Shells turn carbon into rock in a few years, and volcanoes return it the same year
- Carbon moves from air to rock by weathering and shells, then returns by volcanoes over hundreds of millions of years
Rates of change (example data)
Process Rate (mm per year) Coral reef growth 5 Soil formation 0.1 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 10 cm and soils about 5 m per 1,000 years, so soils are faster
- 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 50 m and soils about 1 m per 1,000 years, so both are fast
