Where life lives in oceans, lakes and rivers

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Light in clear ocean water (model rule)

   depth (m)	share of surface light left (%)
   0	100
   30	50
   60	25

   Rule: light halves every 30 m.

2. 1.

   Ari reads the rule for clear ocean water. What share of surface light is left at 90 m?

   • 6.25 percent, after four halvings
   • 25 percent, the share read at 60 m
   • 12.5 percent, after three halvings
   • 0 percent, since three steps of 50 percent remove the light
3. 2.

   Bo knows the photic zone ends where 1 percent of surface light is left. About how deep is that in clear water?

   • About 200 m, between 180 m and 210 m
   • About 100 m, where about 10 percent is left
   • About 300 m, after ten halvings
   • About 60 m, where two steps of 50 percent take the light away
4. 3.

   Esme checks a coral at 120 m in clear water. Its algae need at least 5 percent of surface light. Do they get enough?

   • No: four steps of 50 percent remove the light
   • Yes: 120 m is four halvings, which leaves 6.25 percent
   • No: four halvings leave 4 percent
   • Yes: photosynthesis works at any depth in the ocean

5. Most oxygen that fresh water can hold (real data, from USGS DOTABLES)

   temperature (°C)	oxygen (mg per L)
   0	14.6
   10	11.3
   20	9.1
   25	8.3
   30	7.6

6. 4.

   Jun reads the oxygen table. A pond warms from 10 °C to 30 °C. How does the most oxygen it can hold change?

   • It falls by 3.7 mg per L
   • It rises by 3.7 mg per L
   • It falls by 2.2 mg per L
   • It falls by 7.6 mg per L
7. 5.

   At dawn, Luz measures 4.5 mg per L in a 20 °C pond. About what share of the most oxygen it could hold is that?

   • About half, since 4.5 is close to half of 9.1
   • About 5 percent, reading 4.5 mg as 4.5 percent
   • About 200 percent, since 9.1 is about twice 4.5
   • About 20 percent, from the 20 in 20 °C

8. Salt in some waters (model data)

   place	salt (ppt)
   cell fluid of a river fish	9
   river water	0.5
   ocean water	35
   estuary water at mid-tide	9. ppt means parts of salt per thousand parts of water

9. 6.

   Milo puts a river fish cell in river water. Water crosses the cell membrane by osmosis. Which way does the net movement go?

   • Both ways equally, so the cell stays the same size
   • Neither way, because the cell is built to stop water
   • Out of the cell, toward the fresher river water
   • Into the cell, toward the saltier cell fluid
10. 7.

    Noah moves the same cell into ocean water. Which way does the net movement of water go?

    • Neither way, because both sides hold salt
    • Out of the cell, toward the saltier ocean water
    • Both ways equally, so the cell stays the same size
    • Into the cell, toward the fresher cell fluid
11. 8.

    Pia places the same fish cell in estuary water at mid-tide. What does the table say about water movement?

    • Water moves out, because estuary water counts as the fresher side
    • No net movement, since both sides hold 9 ppt
    • Salt moves in until the cell holds 35 ppt
    • Water moves in, because estuary water is fresher than the sea

12. Vent bacteria in four sealed bottles (model data)

    bottle	light	hydrogen sulfide	sugar made (units)
    A	no	yes	14
    B	yes	yes	15
    C	no	no	0
    D	yes	no	0

13. 9.

    Ren tests vent bacteria in four sealed bottles. Which condition do the bacteria need in order to make sugar?

    • Neither one, since sugar appeared in dark bottle A
    • Both together: the bottle with both made the most sugar
    • Light: the bottle with light made the most sugar
    • Hydrogen sulfide: bottles A and B made sugar, with or without light
14. 10.

    Tala wants to see whether light helps when hydrogen sulfide is present. Which two bottles should be compared?

    • C and D, since only the light differs, but neither has hydrogen sulfide
    • B and C, since both conditions differ
    • A and C, since only the hydrogen sulfide differs
    • A and B, since only the light differs