Where life lives in oceans, lakes and rivers
Grade 9 Science Worksheet - Building Confidence
Circle the best answer.
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.
Bo knows the photic zone ends where 1 percent of surface light is left. About how deep is that in clear water?
- About 100 m, where about 10 percent is left
- About 200 m, between 180 m and 210 m
- About 300 m, after ten halvings
- About 60 m, where two steps of 50 percent take the light away
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 halvings leave 4 percent
- Yes: photosynthesis works at any depth in the ocean
- Yes: 120 m is four halvings, which leaves 6.25 percent
- No: four steps of 50 percent remove the light
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 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 2.2 mg per L
- It falls by 7.6 mg per L
- It falls by 3.7 mg per L
- It rises by 3.7 mg per L
Kira reads that a trout needs at least 8.5 mg per L of oxygen. What is the warmest temperature in the table that can still supply that?
- 30 °C, since warmer water holds more oxygen
- 20 °C, which holds 9.1 mg per L
- 25 °C, since 8.3 is close to 8.5
- 10 °C, because colder water holds more oxygen
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 200 percent, since 9.1 is about twice 4.5
- About half, since 4.5 is close to half of 9.1
- About 5 percent, reading 4.5 mg as 4.5 percent
- About 20 percent, from the 20 in 20 °C
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 Milo puts a river fish cell in river water. Water crosses the cell membrane by osmosis. Which way does the net movement go?
- Out of the cell, toward the fresher river water
- Neither way, because the cell is built to stop water
- Into the cell, toward the saltier cell fluid
- Both ways equally, so the cell stays the same size
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
- Into the cell, toward the fresher cell fluid
- Both ways equally, so the cell stays the same size
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
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 Tala wants to see whether light helps when hydrogen sulfide is present. Which two bottles should be compared?
- A and B, since only the light differs
- B and C, since both conditions differ
- A and C, since only the hydrogen sulfide differs
- C and D, since only the light differs, but neither has hydrogen sulfide
Zee reads the bottle results. What is the best conclusion about where these bacteria could live?
- Anywhere with water, since no bottle was ever dry
- In sunlit water alone, since bottle B made the most sugar
- Anywhere hydrogen sulfide is supplied, even in total darkness
- Where both light and hydrogen sulfide are present