How life and Earth have changed each other
Grade 9 Science Worksheet - Building Confidence
Circle the best answer.
Read this first
Four events (approximate)
Event Billions of years ago Earth forms 4.5 Microbes raise oxygen in the air 2.4 Animals with hard shells appear 0.54 Land plants appear 0.47 Ari reads the table. Which pair shows life changing the air first, and the changed air then allowing new life?
- Microbes raise oxygen (2.4); animals that use oxygen appear (0.54)
- Earth forms (4.5); microbes alone then raise oxygen (2.4)
- Animals appear (0.54); microbes then raise oxygen (2.4)
- Land plants appear (0.47); microbes then raise oxygen afterward (2.4)
Lower, 2.8, dissolved iron, no rust; Middle, 2.4, red-brown iron rust bands; Upper, 2.0, rust and red soils on land. Bo reads the layers. Which explanation fits the rust that appears at 2.4 billion years?
- Iron in the sea rusted by itself, with no help from living things
- The air lost its oxygen, so iron rusted less than before
- Iron in the sea made microbes release oxygen, which formed the rust bands
- Oxygen from living microbes reacted with iron in the sea and made rust
Earth is 4.54 billion years old, and oxygen began to rise in the air 2.4 billion years ago. What share of Earth's history has had oxygen in the air, by Kira's math?
- About 190%, more than the whole of Earth's history
- About 5%, a small slice at the end
- About 2.4%, the number of billions
- About 53%, a little more than half
Card
Ultraviolet light splits O₂ into 2 oxygen atoms. Each atom joins an O₂ to make ozone (O₃). Overall: 3 O₂ make 2 O₃.
Jun follows the card. How many ozone molecules can 6 oxygen molecules (O₂) make?
- 9 ozone molecules
- 4 ozone molecules
- 6 ozone molecules
- 2 ozone molecules
Luz asks why land life had to wait for the ozone layer. Which reason fits?
- Ozone absorbs ultraviolet light, which would damage cells on land
- Ozone warms the surface, so land was too cold before it formed
- Ozone formed first and made the oxygen that later filled the air
- Ozone supplies the oxygen that land animals breathe
Milo puts three events in order: oxygen in the air, the ozone layer, and life on land. Which order is right?
- Oxygen, then life on land, then ozone
- Life on land, then ozone, then oxygen
- Ozone, then oxygen, then life on land
- Oxygen, then ozone, then life on land
Granite plots after 10 years (example data)
Plot Rock surface lost (mm) Bare rock 0.1 Rock under lichens 0.5 Noah compares the plots. What does the experiment show about living things and rock?
- Lichens make no difference, since both plots lose a little rock
- Lichens protect rock, so it wears 5 times slower under them
- Lichens speed up the breakdown, but just 0.4 times as fast here
- Lichens speed up the breakdown of rock, 5 times as fast here
Organic matter in soil (example data)
Site Organic matter (%) Bare rock debris 0.1 Forest floor 5 Pia compares the sites. What do the data show about where soil's organic matter comes from?
- Weathering adds it: the bare rock debris holds 50 times as much as the forest
- Living things add it: the forest holds 50 times as much as bare rock debris
- Rock itself makes it: both sites hold about the same amount
- Living things add it: the forest holds 5 times as much as bare rock debris
New soil forms at about 0.05 mm a year (example data). How long does Ren say a 30 cm layer of soil takes to form?
- About 6,000 years
- About 15 years
- About 60,000 years
- About 600 years
A rock sample (example)
Test Result Weak acid fizzes Under a hand lens shell fragments Crystals of cooled lava none Tala tests a rock. Which source does the evidence point to?
- Lava that cooled quickly and hardened
- Salt left behind as a lake dried out
- Sand grains that were cemented together
- Shells and hard parts of sea life that settled and hardened