Aquatic
Respiration in a Microcosm Lab
Name: Audrey Smith
Title of
lesson: Aquatic Respiration in a
Microcosm Lab
Length
of lesson:
Two 50 minute periods extended
over two days.
Description
of the class:
Course
Title: What is the trophic state of
Grade
level: 9-12
Source of the lesson: http://waterontheweb.org/curricula/bs/teacher/aquatic/teaching.html
TEKS
addressed:
Biology:
(1) Scientific processes. The student, for at least 40% of instructional time, conducts field and laboratory investigations using safe, environmentally appropriate, and ethical practices.
The student is expected to:
(A) demonstrate
safe practices during field and laboratory
investigations
2) Scientific processes. The student uses scientific methods during field and laboratory investigations.
The student is expected to:
(A)
plan and implement investigative
procedures including
asking questions, formulating testable hypotheses, and selecting
equipment and
technology;
(B)
collect data and make measurements
with precision;
(C) organize, analyze, evaluate, make inferences, and
predict
trends from data; and
(D) communicate valid conclusions.
9) Science concepts. The student knows metabolic processes and energy transfers that occur in living organisms. The student is expected to:
(D)
analyze the flow of matter and energy
through different
trophic levels and between organisms and the physical environment.
12) Science concepts. The student knows that interdependence and interactions occur within an ecosystem. The student is expected to:
(A)
analyze the flow of energy through
various cycles
including the carbon, oxygen, nitrogen, and water cycles.
The
Lesson:
I. Overview
Students will investigate the effects of respiration on water chemistry by studying a microcosm of a lake ecosystem.
II. Performance or learner outcomes
Students will use laboratory microcosms and Water on the Web data (http://waterontheweb.org) to explore the affects of respiration on the water chemistry of lakes. In this lesson students learn that the simple act of respiration can have profound effects on an ecosystem.
Students will:
1. Develop a laboratory experiment which will allow then to measure parameters that correlate to aquatic respiration.
2. Analyze the data they generate in a lab report format.
III. Resources, materials and supplies needed
Water Quality Testing Equipment and Materials (per student group)
- Hach or Lamotte water quality testing materials or
meters for each group's workstation (for analyzing DO and pH). Each
group will make up to 5 pH and DO analyses with a meter or two analyses
with chemical reagent kits.
- 250 ml bottle with a cap
- 4 - two-inch minnows (fathead minnows
are readily available and tolerant of low oxygen levels)
- 75 -100 ml of sandy sediment
- 75 -100 ml of organic/mucky sediment
- Thermometers (if water temperature is
the selected measure for the student inquiry lesson)
- Conductivity pens (if conductivity is the selected measure for the student inquiry lesson)
- Worksheet for each group (worksheet follows lesson plan).
IV. Supplementary materials, handouts.
This
lesson assumes
that the students already have an initial lesson on water chemistry and
how
water is analyzed and they are familiar with the concept of communities
and
food webs.
Five-E
Organization
Teacher Does Student Does
|
Engage: Present this scenario to the
students: A lake association curious
about the effects of aquatic respiration on its lake has hired you as a
consulting biologist. The lake association has asked you to answer the
following questions: Can you demonstrate how respiration occurs in
aquatic organisms? Can aquatic respiration be quantified? How does aquatic respiration affect water
chemistry?
Questions Where does the oxygen in water come from? What organisms use the oxygen? Discuss students’ observations of events such as aquaria that have been overfed or left untended for prolonged periods of time, or minnow buckets that have been left without fresh water for a prolonged period. What happens? Why do the animals often die in these situations? What water quality measures might correlate to this situation? Why do students think similar situations might, or might not, occur in lakes? What water quality measures might correlate to aquatic respiration? |
Student Activity Students come up with reasons why aquatic respiration might be an issue for the lake association. Discuss uses of a lake for humans and other organisms. Student Response Students may know that the oxygen comes from plants and algae. Some may think that because water is part hydrogen and part oxygen, this fulfills the oxygen requirements of aquatic organisms. Some students have probably seen these things. Overfeeding will cause an algal bloom, and
minnows left in a bucket with too little water will die. Students might
think that the minnows die because they get too hot, which might also
be a factor in some cases. |
Evaluate
|
Explore: Learning Experience(s) Students work in groups of 3. Students are given the materials listed above as they are needed.
Questions What is detritus? Why should the bottles have lids? Do we need a control? What are you going to use as a control? What do you think will happen to the fish? |
Student Activity Students examine Water on the Web site to see what kind of data is taken. Students will design an experiment in which aquatic respiration can occur and measure the effects it has on water chemistry. Based on their internet research, they can analyze parameters that correlate to aquatic respiration (dissolved oxygen and pH, possibly temperature). Students should measure all materials before adding them to the microcosm and they should set up a variety of microcosms. Example: fish and sand fish and organic matter sand and organic matter fish organic matter sand Students will take data during first class period and second class period.
Student
Response Detritus is the organic matter that falls into a lake and decomposes. Bottles have lids so that oxygen from the air doesn’t enter the water. Students should design a control into their experiment. Students might think some of the fish will die – have them make predictions and support their hypotheses. On Day 2, students measure their D.O. and pH
levels and record their data and observations. Data should be graphed. |
Evaluate
|
Explain: Learning Experience(s) Notes: Respiration by visible organisms (minnows or aquaria fish) and by "invisible" organisms — bacteria — uses oxygen to oxidize organic materials and releases energy, water, and carbon dioxide. In a system where respiration exceeds the input of oxygen (through photosynthesis or aeration), there will be a measurable decline in dissolved oxygen and a corresponding decline in pH due to the addition of CO2 to the system. A lack of dissolved oxygen or a significant decline in pH can kill aquatic life.
Questions How did your microcosms change? Describe the change and provide a reason for its occurrence. What do the results show? How does this compare with the results of other class projects (if students have taken data in the field) |
Student Activity Identify any possible flaws in the experiment setup. Take data and record observations. Begin lab report (students will have to finish lab report outside of class or the following class period).
Student Response Students should be prepared to present their changes informally the class. |
Evaluate
|
Extend / Elaborate: Learning Experience(s) This can be measured on a larger scale on lakes with a more complex food web. Present data from larger scale studies. Present the role of tertiary predators, and how a change at the top of the food chain can cause a change at the bottom and vice versa.
Questions How does this compare to the results found on the Water on the Web website? What can we infer about this experiment that would apply to a lake? Why does dissolved oxygen change by the hour? |
Student Activity Look at lake data on the internet. Compare with data taken by class in the field (if this lesson has occurred)
Student Response They will find more complex data when
looking at lakes, including hour by hour changes on dissolved oxygen. |
Evaluate
|
Respiration
in a Microcosm |
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