Where life lives in oceans, lakes and rivers
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Algae need at least 1 percent of surface light. Ari compares the two waters. How does the depth of the photic zone in clear ocean water compare with the bay's?
- 27 m deeper, the gap between 30 m and 3 m
- The same depth, since light halves in both
- About 10 times as deep, roughly 200 m against 20 m
- About 100 times as deep, since 1 percent is 1 in 100
Read this first
Net sugar made by layer of a 40 m column (model data)
layer thickness (m) net sugar per meter of layer (units) 0 to 10 m 10 8 10 to 20 m 10 5 20 to 30 m 10 2 30 to 40 m 10 −1 Bo adds up the net sugar made in the whole column. What is the total?
- 150 units, treating the bottom layer as zero
- 14 units, adding the four rates without the thickness
- 140 units
- 80 units, the top layer alone where light is strongest
Trout need water at 15 °C or colder with at least 5 mg per L. A hot summer warms every layer by 3 °C and cuts oxygen by 1 mg per L at each depth. Esme rechecks the lake. How much trout habitat is left?
- 6 m, since its oxygen is still 5.1 mg per L
- None: 6 m is 17 °C and 9 m has only 1.0 mg per L
- 9 m, since 12 °C is cool enough
- The same band as before, since the two changes cancel out
Nitrate is a nutrient; µM is how much of it is dissolved in the water. Jun reads a tropical ocean profile. Which explanation best fits the chlorophyll peak at 75 m?
- Nitrate is plentiful at 75 m, so that is where cells peak, as nitrate feeds growth
- Light is bright enough at 75 m, so that is where cells peak, as light feeds growth
- At 75 m there is enough of both: above, nitrate runs low; below, light fades
- Deep water holds more oxygen, so cells peak at 75 m
These bacteria grow best at about 20 to 45 °C. Kira reads a vent profile. Which explanation best fits the bacteria peak at 5 m rather than at the vent mouth?
- At 5 m the water is cool enough and still rich in hydrogen sulfide
- Hydrogen sulfide is highest at 0 m, so the count at 0 m must be a mistake
- More sunlight reaches the water at 5 m, so the bacteria grow better there
- Bacteria prefer the coldest water, so the peak at 5 m is a counting error
Streams brought the same load all year. A writer blames pollution for the low oxygen at 12 m in August. Luz looks for data that favor summer layering. Which feature is strongest?
- Oxygen stayed low in October, close to the August value of 0.8
- The August value of 0.8 is very low for any fish in the lake
- Oxygen jumped from 0.9 to 7.5 once the layers mixed, with inputs unchanged
- Oxygen fell from 8.0 in April to 0.8 in August, as the lake layered and warmed
Use this
Notebook, 4 lines. Line 1: A station had 40 snails in a low-tide sample and 3 in a high-tide sample. Line 2: The water was 8 ppt and 14 °C at low tide, and 26 ppt and 21 °C at high tide. Line 3: So salinity was the only thing that changed between the samples. Line 4: So snails may do better at low salinity, and a test that holds temperature steady would settle it.
Noah reads a classmate's notebook about snails in an estuary. Which line has the flaw?
- Line 3: temperature also changed, so salinity was not the only difference
- Line 2: water cannot be measured in ppt and °C at once
- Line 1: 40 and 3 are very different sizes, so the samples cannot be compared at all
- Line 4: no test could ever separate salinity from temperature
Use this
Card (from NOAA Ocean Exploration), in words. Photosynthesis: carbon dioxide, water and light go in; sugar and oxygen come out. Vent chemosynthesis: carbon dioxide, hydrogen sulfide and oxygen go in; sugar, sulfur and water come out. Notebook, 4 lines. Line 1: Photosynthesis needs light and gives off oxygen. Line 2: Vent chemosynthesis uses hydrogen sulfide in place of light. Line 3: So vent chemosynthesis also gives off oxygen. Line 4: Both ways make sugar from carbon dioxide.
Pia reads a classmate's notebook comparing photosynthesis with vent chemosynthesis. Which line has the flaw?
- Line 1: photosynthesis uses up oxygen
- Line 2: vent bacteria use light, so hydrogen sulfide is not needed
- Line 3: in vent chemosynthesis oxygen goes in; it is used, not made
- Line 4: chemosynthesis cannot make sugar
A pond at dawn after a hot night (model data)
measure value water temperature (°C) 30 oxygen measured (mg per L) 2.1 most oxygen fresh water holds at 30 °C (mg per L) 7.6 fish need at least (mg per L) 4 A classmate says pollution caused the fish loss, since clean water would hold plenty of oxygen. Ren checks the card. Which reply is best?
- Agree: 2.1 is far below 7.6, so pollution alone could explain a gap that large
- Disagree: warm water holds no oxygen, so fish cannot live at 30 °C
- Not shown: water at 30 °C holds at most 7.6, and night respiration can lower it
- Agree: warm water holds more oxygen than cool water, so 2.1 is far too low
Spring in a cold ocean (model data)
month daylight (hours) surface water (°C) nitrate (µM) chlorophyll (µg per L) February 10 4 12 0.5 March 12 4 12 0.8 April 14 6 10 6.0 May 15 9 3 3.5 June 16 13 0.5 1.0 A classmate says the spring bloom starts because the water warms. Zee checks the table. Which reply is best?
- Not supported: temperature cannot affect phytoplankton at all
- Supported: chlorophyll peaks in April, right after the water warms from 4 to 6 °C, so warmth is the cause
- Not supported: chlorophyll jumped in April at only 6 °C; June was warmest, nitrate nearly gone
- Not supported: only daylight matters, since nitrate and temperature changed very little