LE4.3-Snail & Elodea Investigation – Biology EOC Scenario, Bethel SD
LE4.3-Snail & Elodea Investigation – Biology EOC
Developed by Bethel School District – April 2012
LE4.3-Snail & Elodea Investigation – Biology EOC Scenario, Bethel SD
Description: Students investigate the exchange of gases between seaweed and aquatic snails.
Note: Strictly speaking, this investigation is actually a “systematic observation,” not a controlled
experiment. [A controlled experiment would allow multiple values for a single manipulated variable.
For example, manipulating the population of snails from 1 to 2 to 3, etc. In this investigation, several
variables (one at a time) are systematically present or absent  first “snails,” then “Elodea,” then
“snails + Elodea.”]
Item Description (Performance Expectation statement from the 2009 WA Item
Science Std
Type
Biology EOC Item Specifications)
& P.E.
Describe the regulatory inputs and/or outputs of a given positive feedback
system (e.g., after a cut, a clotting process cascades to form a scab;
increased CO2 and methane inputs results in higher temperatures,
decreased light reflected to space, ice caps melting, and sea levels rising).
Identify the components, boundaries, flows, and/or feedbacks of a given
system.
1
2
Describe a plan for a scientific investigation using a model, simulation, or
3 systematic observation.
4
5
6
7
8
Describe the transfers and transformations of matter and/or energy in an
ecosystem (e.g., sunlight transforms to chemical energy during
photosynthesis, chemical energy and matter are transferred when animals
eat plants or other animals, carbon dioxide produced by animals by
respiration is used by plants and transformed to glucose during
photosynthesis).
Generate a logical conclusion that is supported by evidence from the
investigation and/or provide a scientific reason to explain the trend in
data given a description of and the results from a scientific investigation.
Describe the cycle of carbon through ecosystems (e.g., carbon dioxide in
air becomes large carbon-containing molecules in the tissues of plants
through photosynthesis, these molecules can be cycled to animals that
consume the plants, then returned as carbon dioxide to the atmosphere
through cellular respiration, combustion, and decomposition).
Describe the transfers and transformations of matter and/or energy in an
ecosystem (e.g., sunlight transforms to chemical energy during
photosynthesis, chemical energy and matter are transferred when animals
eat plants or other animals, carbon dioxide produced by animals by
respiration is used by plants and transformed to glucose during
photosynthesis).
Describe that large molecules in food are broken down into smaller
molecules by cells to provide energy or building blocks (i.e., proteins into
amino acids, carbohydrates into simple sugars, fats into fatty acids, DNA
into nucleotides).
Describe the cycle of nitrogen through ecosystems (e.g., nitrogen in air is
taken in by bacteria in soil, then made directly available to plants through
the soil, and returned to the soil and atmosphere when the plants
decompose).
Developed by Bethel School District – April 2012
Answer
D – (photosynthesis -
SYS-A(3)
MC
SYS-B(2)
MC
INQ-B(4)
MC
LS2-A(4)
SA
(concept map rubric)
INQ-C(1)
SA
(see SA rubric)
LS2-A(1)
MC
LS2-A(4)
MC
LS1-F(1)
B – (limit CO2
sources)
B – (systematic
observation)
C – (yellow from CO2
from respiration)
C – (decomposition)
(location of nitrogen)
SA
LS2-A(3)
respiration)
(molecular form of
nitrogen)
LE4.3-Snail & Elodea Investigation – Biology EOC Scenario, Bethel SD
Togetherness: Animals & Plants
Directions: Use the following information to answer questions 1 through 8.
Michaela wondered whether molecular exchanges between aquatic animals and plants is similar to the molecular
exchange of gases through the air between land-based organisms. She designed an investigation to detect an
exchange between the seaweed, Elodea, and the water snail, Pomacea.
Question: Which molecular gases, if any, are exchanged between aquatic animals and plants?
Hypothesis: Seaweed and aquatic snails will exchange carbon dioxide and oxygen through the water, just as
other animals and plants exchange those gases through the air.
Materials:
Seaweed, Elodea, and the water snail, Pomacea
Screw-cap test tubes
Bromothymol Blue indicator
Water and air
Investigation Setup Diagram:
Procedure:
1. Label four tubes—1, 2, 3, 4—as shown in the
Investigation Setup diagram.
2. Add water and Bromothymol Blue indicator to each
tube.
3. Create four different combinations of seaweed and
aquatic snails, and close all tubes with the screwcap:
Tube #1 – only the water + Bromothymol Blue
Tube #2 – aquatic snail
Tube #3 – seaweed
Tube #4 – aquatic snail + seaweed
4. Observe the tubes each day for 7 days:
a. Color change from blue  green/yellow
(presence of acid)
b. Health of snails and seaweed
5. Record observations each day.
6. Repeat Steps 1-5 at least two more times.
Data:
Organism Combinations vs. Health & Color Change (after 7 days)
Tube Contents
Tube #
Water
1
+
+
+
+
2
3
4
Snail
Seaweed
+
+
+
+
Developed by Bethel School District – April 2012
Bromothymol
Blue
Health Notes
Blue
No changes
Yellow
Snails dead
Blue
Seaweed less green, a bit brown
Green/
Yellow
Snails healthy, seaweed green
LE4.3-Snail & Elodea Investigation – Biology EOC Scenario, Bethel SD
1 Describe an example of positive feedback in Tube #4.
o
o
o
o
A. Decrease of light  decrease in snail respiration
B. Increase of carbon dioxide  decrease in oxygen
C. Decrease of seaweed respiration  increase in snail respiration
D. Increase of seaweed photosynthesis  increase in snail respiration
2 Why are all of the tubes set up as closed systems?
o
o
o
o
SYS-B(2)
A. To control the evaporation of water
B. To limit the sources of CO2 inside the tube
C. To capture the oxygen produced by the seaweed
D. To see if limiting the amount of air affects the acidity of the water
3 What type of investigation is this?
o
o
o
o
SYS-A(3)
INQ-B(4)
A. Field study
B. Systematic observation
C. Controlled investigation
D. Model-based investigation
4 Use a concept map to diagram the flow of gases in Tube #4. Describe evidence from the
investigation that supports how you know about each gas.
Draw your map in this box:
Developed by Bethel School District – April 2012
LS2-A(4)
LE4.3-Snail & Elodea Investigation – Biology EOC Scenario, Bethel SD
5 Write a conclusion for this investigation.
INQ-C(1)
In your conclusion, be sure to:
 Answer the investigative question.
 Include supporting data from the Organism Combinations vs. Health & Color Change table.
 Explain how these data support your conclusion.
 Provide a scientific explanation for the pattern in the data.
Question:
Which molecular gases, if any, are exchanged between aquatic animals and plants?
Conclusion:
Developed by Bethel School District – April 2012
LE4.3-Snail & Elodea Investigation – Biology EOC Scenario, Bethel SD
6 What would happen to the blue color in Tube #1 if we added decomposing organic matter?
o
o
o
o
A. Blue color will stay, because decomposition produces CO2 and consumes O2
B. Blue color will stay, because decomposition consumes CO2 and produces O2
C. Blue color will change to yellow, because decomposition produces CO2 and consumes O2
D. Blue color will change to yellow, because decomposition consumes CO2 and produces O2
7 Describe a pond ecosystem process that is not being modeled in Tube #4.
o
o
o
o
LS2-A(1)
LS2-A(4)
A. Respiration
B. Photosynthesis
C. Decomposition
D. Energy transformation
8 Describe two places where nitrogen can be found in Tube #4.
In your description, be sure to:
 Describe two locations of nitrogen.
 Describe the molecular form of nitrogen in each location.
1st Location of nitrogen:
1st molecular form of nitrogen:
2nd Location of nitrogen:
2nd molecular form of nitrogen:
Developed by Bethel School District – April 2012
LS1-F(1)
LS2-A(3)