Curricular Units
Aquarium Unit
Introduction to Modeling
Unit 1
Overview
Prior to beginning the main portion of the aquatic ecosystems unit, the students will engage in a broad discussion about ecosystems. The discussion will serve to activate prior knowledge and/or introduce some foundational concepts. The students will then engage in a content-light modeling activity to help build their understanding of the role of models in scientific reasoning. In the activity, Intro to Models, the students are presented with a set of representations and asked to discuss which representations are examples of scientific models. Next the students are presented with pairs of models and asked which model is better and why. This activity serves as scaffold toward forming a list of model criteria by which models can be evaluated. In Lesson 1, students will design an aquarium and begin to engage in scientific modeling based on the driving question “How many fish can fit in an aquarium and why?”
Objectives
Modeling
Students may not have had any experience with scientific models prior to this lesson. The preparatory activities in this unit can serve as a supplement to build students’ modeling knowledge base in preparation for the unit itself.
Time 2- 3 forty minute periods
Materials and Preparation
- Copies of other resources for introductory discussion as per teacher’s discretion
- 1 copy of Handout 1.1
Intro to Models for each student
Activities
1. Introduction to Ecosystems Discussion – Prior to beginning the unit itself, the teacher will guide the students in a discussion introducing basic ecosystem concepts, activating prior knowledge regarding ecosystems, and drawing connections to prior lessons regarding the characteristics of life and ecosystems. The teacher may use other classroom resources (including textbook materials) as (s)he deems appropriate. The nature of this discussion will vary widely between classrooms; however, the teacher should strive to include the basic concepts outlined below. To connect this discussion to the next activity, the teacher should explain that ecologists often use scientific models to explain phenomena they observe in ecosystems, therefore the class will be taking some time to look at different models to learn about what makes a good scientific model.
a. Defining an ecosystem and giving examples of aquatic and terrestrial ecosystems.
b. Explaining basic (1) life processes – eating, reproduction, death, growth – this discussion can be tied to characteristics of living things (2) ecosystem processes –photosynthesis, cellular respiration, nitrification, carbon cycling, and carrying capacity.
c. Abiotic v. biotic factors and examples
d. Ecologists build and revise models to explain observations in ecosystems
This is a good stopping point for the 1st period
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2. Intro to Modeling (this activity should take no more than 2 periods to complete, although some classes may be able to complete it in a single period)
a. Hand out one copy of Handout 1.1 Intro to Models for each student. Go over the information about models on the top of the first page. Ask the students to work in groups of 2-4 students to discuss the 6 images and decide which ones are scientific models that explain how plants get energy.
b. Have a class discussion about each image in turn. They have been labeled A to F for your convenience. The focus should be on getting students to explain their understanding; rather than focusing on a single correct answer. Here are some potential explanations:
i. Image A is not a model of because it just shows what is happening not why it is happening.
ii. Image E is a model because it explains what is happening even though it does so in words, not pictures.
The take-home message from this conversation should be that scientific models can be expressed in many different ways, but they should be explanatory i.e., they show underlying causes (mechanisms).
c. Ask each group to discuss each pair of models on the following pages and answer the questions on each page.
d. Have a class discussion about each page in turn. Try to push the students towards more scientific reasons why one model might be better than another. Examples of characteristics of good models that might emerge from this discussion include:
i. Scientific models should explain how things happen
ii. Scientific models should include all relevant details
iii. Scientific models should be consistent with accepted scientific knowledge
iv. Scientific models may include diagrams for clarity, when included, diagrams should be clearly labeled and easy to understand
e. Ask each group to brainstorm and rank their list of characteristics of a good model. (Note: if this activity takes 2 periods to complete, the students can be asked to make their own list of model criteria for homework after the first day of the activity).
f. Have a class discussion about model criteria. Try to come to a class consensus list of model criteria. These model criteria can then serve as a starting place for the model criteria discussion in lesson 2 of the actual unit.
This is the probable stopping point for the 2nd period
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Assessment
Students should be assessed based on their participation during class discussion, as well as during group work. Handout 1.1 Intro to Model can be collected and assessed for completion.
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Understanding Aquatic Ecosystems through the Study of Eutrophication
Unit 2
Lesson 2 – Designing an Aquarium, Fish Spawn and Carrying Capacity
Overview
In this lesson, the teacher will lead a discussion about how scientists use aquaria to test ideas about ecosystems. The students will construct a classroom aquarium and begin monitoring the water quality. The students will draw preliminary models (on paper), explaining how many fish can survive in an aquarium and why. The students will apply the model criteria they established in Lesson 1 to their models. Then the students will be introduced to the PMC2E terminology, hypermedia and Ecomodeler. The students will transfer their paper models into Ecomodeler. At this point, students will be invited to visit the hypermedia before finalizing their models in Ecomodeler. Next, the students will use a Fish Spawn NetLogo simulation to learn about carrying capacity in an aquarium. The driving question for this lesson will be ‘what determines how many fish can survive in an aquarium?’ The teacher will engage the students in short discussion on carrying capacity. The students will refer to the Aquarium Hypermedia and revise their models based on the Fish Spawn NetLogo and the hypermedia. An optional lesson has been provide that could be used before Lesson 3, which covers nitrification. In Lesson 3, the students will begin to explore the fish kill phenomena that serves as a project context for the remainder of the unit.
Objectives
Modeling
Students are expected to have had some experience with scientific models prior to this lesson. At the minimum, the Intro to Models activity in Lesson 1 should have familiarized students with a general notion of the forms and purposes of scientific models.
Time 5-6 forty minute periods
Materials and Preparation ·
Teachers should review the Pond Aquarium Unit Backbone prior to lesson.
2 Aquarium kits (1 tank setup per classroom for monitoring and testing, and 1 smaller tank setup to act as a control/“rescue” tank to move fish to in Lesson 5)
o 10-20 gallon aquarium
o Lighted hood
o Water conditioner
o Assorted tropical fish
o Filter with pump and filter cartridge
o Aquarium gravel
o Algae sponge
o Fish food
o Net
o Heater
o Thermometer
o Optional: plants, decorative rocks
o Materials for monitoring the following aspects of water quality
§ pH level
§ dissolved oxygen level
§ nitrite level
§ nitrate level
§ ammonia level
§ biological oxygen demand
§ amount of algae – using travel spectrophotometer
· Poster paper (1 piece per group plus 8 pieces for data tables)
· Markers (1 set per group)
· One computer for every group (2-4 students) with access to Ecomodeler
· One copy of Handout 2.1 NetLogo Fish Spawn for each student
Activities
1. Constructing an Aquarium (40 minutes)
a. Tell the students that they will soon be studying a serious problem that occurred in a pond, and to help them with their investigation of this problem they will set up an aquarium that they will explore later.
b. Ask the students to work in groups to come up with a list of biotic and abiotic factors that would be included in an aquarium. Using a whiteboard to make the list public, the teacher will then conduct a brief discussion about the aquarium’s components and why they are needed. The teacher may need to prompt the class for anything that may be missing from the materials list.
Note: Ask the students how many fish they think the aquarium will be able to support and why? It is important that they do not discover the rule of thumb for the number of fish an aquarium can sustain until later in the lesson.
c. (Optional) The teacher may want to have the class set up the aquarium during this period. Otherwise it should be set up before class during prep time. Depending on class size, some students may work on the tank setup while others create poster-size tables to record the following information:
· pH level
· dissolved oxygen level
· nitrite level
· nitrate level
· ammonia level
· biological oxygen demand
· amount of algae
· fish activity/behavior
d. Once the aquarium is set up and all of the tables are created (and posted publicly), students will need to take their initial measurements. Each class will need their own set of tables, and readings will continue daily for the remainder of the unit. (Tip: The teacher may want to “hide” the tables from other classes so there is no bias introduced. Use of a Smart Board or other technology may be helpful.)
This is a good stopping point for the 1st period
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2. Preliminary Models (40 minutes)
a. The teacher will divide the class into groups of 2-4 students who will work together throughout the unit. The groups should be diverse in learning preferences and achievement level.
b. The teacher should give each group a set of markers and construction paper and ask them to draw a model (diagram) explaining how many fish can survive in an aquarium and why. At this point, due to students’ possible lack of experience with modeling, they may be more likely to draw pictorial models. At this stage, let the students choose the format and do not place too much emphasis on the right explanation or a particular format.
This is a good stopping point for the 2nd period
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3. Refining Model Criteria (developed in lesson 1):
a. Optional warm-up activity (5 minutes): Students individually answer the question “What characteristics make a good model?” Remind the students of the model criteria they established in lesson 1.
b. Model Gallery Walk (10 minutes): Place the models around the room and give students approximately 10 minutes to walk around and look at all the models. On a piece of paper or index card, each student should record one positive aspect of each model and one area each model could be improved. Emphasize that comments should refer not only to the visual appearance of model; rather, also the ideas contained in the model. If students don’t get to see every model, that’s okay. They just need enough of a sense of the variety of models in the classroom. Also make sure at least one group starts at each model so that all models are viewed. Another option for the gallery walk is for the students to rate all the models that they visit for each of the model criteria (i.e., have them note the presence or absence of each criteria). This could be accomplished by creating a checklist for students to use as they walk among the models.
c. Model Criteria Discussion (15 minutes): The teacher will guide the students in a discussion of the differences between their models, both in terms of visual representation and underlying explanation. Students will discuss what characteristics constitute a good model. The teacher may bring up the list of model criteria created in Lesson 1 to use as a starting point for this discussion. This discussion will lead to a list of model criteria, which will be posted on the classroom wall and revised throughout the unit. Model criteria could include, but are not limited to:
Good models:
· are clear and understandable, with an appropriate level of detail (for example, having organisms, like snails, in the model that do not relate to the problem is not necessary)
· show an underlying explanation, rather than a description of what is already known
· Should be supported with evidence, and are testable (ask students what data will be needed to see if the model holds true)
· are realistic and sensible given prior knowledge (for example, a fish killing a shark is not realistic)
Assign each model criteria a color (making sure you have adhesive notes in those colors). In Lesson 4 students will use color-coded adhesive notes to assess their peer’s models using these criteria.
4. Introducing PMC2E
a. Benchmark lecture (10 minutes): The teacher will give a benchmark lecture presenting the PMC2E modeling framework as a way of reasoning about systems. In this framework, explanations include components, mechanisms (processes), and phenomena (outcomes). See Handout 2.0 for definitions and examples.
b. Optional Homework: The teacher may choose to give a homework assignment for students to define components, mechanisms, and phenomena and/or describe an everyday example of a system (factory, computer, house) in PMC2E terms. Alternatively the teacher can ask the students to start making a list of the components, mechanisms, and phenomena that they had included in their models.
This is the probable stopping point for the 3rd period
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c. Labeling PMC2E in models (10 minutes): Students will then return to their models and identify the components, mechanisms, and phenomena in their model by labeling them on the original model.
d. Incorporating PMC2E into model criteria (5-10 minutes): Briefly the class will discuss examples of PMC2E in their model. This discussion should lead to adding a model criterion that every component should have a mechanism associated with it, and that explanatory models are tied to explaining a central phenomenon. This criterion should be added to the posted list.
e. Translating models into PMC2E (20 minutes): The students will transfer their models into Ecomodeler. The teacher will probably need to briefly demonstrate how to use the software. When the teacher introduces the student to the Ecomodeler software, the teacher should invite the students to begin to investigate the aquarium hypermedia, and revise their models as they feel in appropriate.
f. Optional Classwork /Homework: The teacher should give each student a printout of another group’s PMC2E model and a list of the model criteria. The students should then assess how well the model fits the model criteria.
This is the probable stopping point for the 4th period
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5. NetLogo Simulation – Fish Spawn (40 minutes)
a. The teacher will remind the students of the models they have been working on. After a brief discussion the teacher should tell them that they will now use a NetLogo simulation to explore the factors that affect fish population size in an aquarium.
b. Handout one copy of Handout 2.1 NetLogo Fish Spawn to each student to complete as they are manipulating the simulation. Students will work in groups of 2-4 and will manipulate the following variables:
· Number of male and female fish
· Spawning probability
· Filtration level
· Amount of food
c. Students will run the simulation and observe the results by monitoring the water quality level as well as the various levels of fish mortalities and spawning numbers.
d. The teacher should help students by pointing out that by changing each input individually, he or she will see the effect it has on the population of fish in the tank.
e. The teacher should be looking for students to try different variable settings, working towards an equilibrium in which the simulation continues on indefinitely. Some students may discover this on their own, at which time they should be guided to watching the levels of water quality, number spawned and mortality levels change to get a feel for the carrying capacity of the aquarium.
f. Optional Homework- At this point (no earlier) you can introduce the rule of thumb often used for calculating how many fish an aquarium can sustain. The students can then calculate the appropriate number for homework.
This is a good stopping point for the 5th period
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6. Revising Models in Ecomodeler (40 minutes)
a. Teacher will give a brief explanation of the purpose of the “notes” section of Ecomodeler. The notes section is a place for students’ thinking and explanations to become visible, and all students should be strongly encouraged to make use of it.
b. Students will work in their groups to revise their models from Ecomodeler to explain the factors that limit fish population size in an aquarium. Revisions must be documented in the notes section and should include what was changed and the evidence that caused the students to make the change. Revised models should try to account for the new evidence from the NetLogo simulation.
This is the probable stopping point for the 6th period
Assessment
Students should be assessed based on their participation during class discussion, as well as during group work. The teacher can also use the NetLogo Simulation worksheet as an assessment.
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Pond Unit
Pond Unit backbone
Overview
In this unit, students will be engaged with learning about PMC2E modeling and aquatic ecosystems through a problem context centered on a eutrophic pond.
In Lesson 1, the students will participate in a broad discussion about ecosystems. The students will be then introduced to the concept of scientific modeling as a tool scientists use to explain phenomena they observe in ecosystems, through a handout showing examples of models and asking student to compare models. The teacher will work with the class to characterize what makes a good scientific model. Model criteria should be established—they should be clear, accurate, provide explanation.
In Lesson 2, the teacher will lead a discussion about how scientists use aquaria to test ideas about ecosystems. The students will construct a classroom aquarium and begin monitoring the water quality. The students will be asked to draw preliminary models (on paper), explaining how many fish can survive in an aquarium and why. The students will apply the model criteria they established in Lesson 1 to their models. The students will be then introduced to the PMC2E terminology, hypermedia and Ecomodeler. The students will transfer their paper models into Ecomodeler. At this point, students will be invited to visit the hypermedia before finalizing their models in Ecomodeler. Next, the students will use a Fish Spawn NetLogo simulation to learn about carrying capacity in an aquarium. The driving question for this lesson will be “what determines how many fish can survive in an aquarium ecosystem?” The teacher will engage the students in a short discussion on carrying capacity. The students will refer to the Aquarium Hypermedia and revise their models based on the Fish Spawn NetLogo and the hypermedia.
In Lesson 3, the students will watch a two minute film, which highlights the problem of eutrophication (and resulting fish kills) without explaining the cause. The students will revisit the modeling criteria. The students will be asked to draw preliminary models in the Ecomodeler explaining what they think is causing the fish to die. The students will be given data from a representative pond to analyze to determine if it supports or contradicts their models. Students will then revise their models from Ecomodeler.
In Lesson 4, the students will manipulate two carbon/oxygen NetLogo simulations to try to determine what factors might be causing the decrease in dissolved oxygen observed in the pond data. The first simulation will show the phenomenon at the macroscopic level, the second simulation focuses on the functions and behaviors of the structures at the microscopic level. Students will also be introduced to the Pond Hypermedia that provides information helpful in understanding what is happening in the simulations. Using this new information, students will revise their models from Ecomodeler and construct a class consensus model.
In Lesson 5, students will add fertilizer to small containers in order to simulate the conditions they hypothesize led to the fish kill. Finally the class will view a eutrophication animation animation (at: http://new.coolclassroom.org/adventures/explore/plume/39), followed by discussion of possible natural sources of nitrates.
Lesson 1- Intro to modeling (3 periods)
The students will engage in a broad discussion about ecosystems. The teacher will scaffold the conversation around factors that afford life and those that constraint (limit) life within that system. The students will then engage in a content-light modeling activity to help build their understanding of the role of models in scientific reasoning. In the activity, Intro to Models, the students are presented with a set of representations and asked to discuss which representations are examples of scientific models. Next the students are presented with pairs of models and asked which model is better and why. This activity serves as scaffold toward forming a list of model criteria by which models can be evaluated.
Lesson 2 – Designing an Aquarium, Fish Spawn and Carrying Capacity (5-6 periods)
In this lesson the students will design an aquarium that they will later be able to use as a tool to test hypotheses when they students a particular natural aquatic phenomenon (eutrophication). The teachers will begin this activity by discussing how scientists use aquaria to test ideas about ecosystems. The class will brainstorm what components should be included in the aquarium.
The students will be asked to work in small groups and draw preliminary models (on paper), explaining how many fish can survive in an aquarium and why. The teacher will give a benchmark lecture presenting the PMC2E modeling framework. Students will draw these preliminary models on large sheets of paper using colored markers. The students will then be introduced to the aquarium hypermedia and Ecomodeler. The students will then transfer their paper models into Ecomodeler by using PMC2E and the aquarium hypermedia.
The teacher will bring up the issue of how many fish can an aquarium support. The class will investigate this issue using a Fish Spawn NetLogo simulation. From the simulation, the students will conclude that there is a limit (carrying capacity) to the population a tank can sustain. The teacher will lead a discussion on carrying capacity and explain to the students that the notion of stuffing as much as we can in a tank may not be the essence of building a healthy aquarium. The students will be given a chance to revise their models by using the hypermedia and the evidence from the Fish Spawn simulation.
Lesson 3 – Introducing the Problem of the Eutrophic Pond (5-7 periods)
Students will be shown a brief 3-minute news clip, which highlights a problem facing many ponds nationwide. In the early spring/summer, the ponds become filled with an unidentified green muck. As the problem worsens, the pond water turns brown and dead fish are even found floating in many of the ponds. The students will be charged with the task of evaluating solution to this important problem. In order to do so they must understand what is causing the fish to die. The students will visit modeling criteria. The students will then create preliminary models in Ecomodeler trying to explain why the fish died.
The teacher will guide the students in a discussion of the differences between their models, both in terms of visual representation and underlying explanation. Students will discuss what characteristics constitute a good model. This discussion will lead to a revised list of model criteria, which will be posted on the classroom wall and revised throughout the unit.
The teacher will look through the models and group them into categories of similar explanations. Three general categories of explanations should emerge:
1. Heat/Temperature is the culprit: the increased sunlight allows the green muck to grow and the increased temperature kills the fish. In this explanation, the green muck and dead fish have a common cause but are not related to each other.
2. Pollution/toxins: the green muck may be poisonous or be a sign of pollution and it is the poison/pollution that kills the fish. In this explanation, the green muck may be considered non-living.
3. Lack of essential life elements (oxygen/food): In this explanation, the students hypothesize that the fish are missing something needed for survival, which could be oxygen or food.
If needed a 4th category can be added. The teacher should post an example of each category of model for reference in the future lessons. The students will discuss what predictions come out of each model and what data needs to be collected to test those predictions.
Now that 3 categories of explanations for the fish deaths have emerged, students will analyze additional data from the pond to determine if any of the models are supported or refuted. Students will be given a packet that includes 7 pieces of data with question prompts to help scaffold their understanding of the data. The 7 pieces of data will include:
· Temperature range of tolerance graph for a species of fish in the pond
· Graph of pond water temperature over the course of the year
· Graph showing the concentration of chlorophyll-a in the pond water over the course of the year (this is a method of measuring the amount of algae in the water)
· Necropsy data table showing fish died due to suffocation, no toxins, normal weight
· Dissolved oxygen range of tolerance table for fish
· Graph showing the level of dissolved oxygen in the pond over the course of the year
· Water quality graph showing the concentrations of ammonia and nitrates
Students will use that data to make revised models in Ecomodeler that explain the cause of the fish deaths. The students should record, in notes section of Ecomodeler, what changes they made to their models and what evidence caused them to make those changes. In the same notes section, students should also write a list of questions that they still need answered to complete their models. At this point there will still be some variation among student models; however, all models could include the idea that the green muck increases with increasing temperatures in the spring and summer, the fish die when the dissolved oxygen in the pond water gets to low, and the fish deaths are preceded by a rise nitrates in the water. In this way, elements of all 3 categories of preliminary models appear to be correct. The students will be given a copy of each group’s model and asked to sort those models into categories based on their explanations. The class will discuss how the groups sorted the models and why. At the end of this lesson, students will be left with the open questions of (1) what causes the decrease in dissolved oxygen? and (2) what are these nitrates and why are they important?
Lesson 4 - Simulating the Role of Carbon and Oxygen in NetLogo (5-6 periods)
In this lesson, students will manipulate two carbon/oxygen NetLogo simulations to try to determine what factors might be causing the decrease in dissolved oxygen. Two questions were left at the end of lesson two, and this lesson addresses the first question, because we thought the students would find that question more pressing. The first simulation will show the phenomenon at the macroscopic level. The simulation will include the following visible components, inputs, outputs, and behaviors:
· Visible components: Fish, fish food, algae (amorphous green blobs), nutrients
o Note: Fish/algae disappear when they die
· Inputs: add fish, add fish food, add algae, add plant nutrients
· Outputs: graph showing concentrations of O2 and CO2, graph showing the mass of living fish, dead fish, living algae, dead algae
o Note: to simplify the second graph, maybe we can try having the dead fish can be a lighter shade of the color of the living fish and the dead algae can be a lighter shade of the color of the living algae
· Behaviors:
o If the algae population is balanced with the fish population, the system will be in a state of equilibrium with stable amounts of fish and algae and dissolved gases.
o If the fish population is too high in comparison to the algae population, the amount of dissolved oxygen will rapidly decrease, killing the fish, but the algae will survive.
o If excess nutrients are added to the system, the algae population will exceed carrying capacity and crash. As the dead algae are decomposed (by bacteria, which are not visible at the macroscopic level), the amount of dissolved oxygen will decrease rapidly causing the fish to die.
This simulation will allow students to conclude that as the algae die in large numbers, the dissolved oxygen decreases, killing the fish. The teacher should give students 10 minutes or so to manipulate the simulation and jot down observations, without worrying about precise data collection. The class should then discuss what they noticed and what testable hypotheses they would want to investigate more systematically. The students will then return to the simulation and collect data more systematically filling out a data worksheet. There may be several alternations between observational runs of the simulation and more systematic experimental runs. When the students have finished with the simulation, the class should discuss their conclusions and what they think might be causing the oxygen levels to decrease when all the algae die.
Next, the students will look at a NetLogo simulation that allows them to peak into the microscopic processes that underlie what they observed in the macroscopic level simulation. The simulation will include the following visible components, inputs, outputs, and behaviors:
· Visible components: Living algal cells (green circle in the same shade as the algae from the previous simulation), dead algal cells (appear brown), decomposing bacteria, O2 and CO2
· Inputs: add algae, add plant nutrients, add bacteria
· Outputs: graph showing concentrations of O2 and CO2, graph showing the mass of bacteria, living algae, dead algae
· Behaviors:
o Adding plant nutrients will increase the growth of the algal cells. However, if excess amounts of nutrients are added, the algae population will decrease rapidly, causing a rapid increase in the decomposing bacteria, causing a rapid decrease in dissolved oxygen.
o At non-excessive nutrient levels, the bacteria and algae population will fluctuate in a predator-prey relationship.
After the students have manipulated the microscopic level NetLogo, the teacher should stop the class to discuss what they learned from the macroscopic NetLogo model and what they see in the microscopic NetLogo that was not visible in the first simulation. The teacher should make sure the students understand that the algal cells in the second NetLogo are what ones sees when they zoom in on the green muck visible in the macroscopic level simulation. Looking at wet mounts of algal cells under the microscope can facilitate this understanding. Algal samples can be collected from a local pond or ordered from a lab supply company. At this point (if they have not done so already), the class should agree that the green muck is made of living cells.
With this knowledge, the students should be given additional time to manipulate the microscopic NetLogo simulation. They may then also consult any sections of the hypermedia they consider relevant. The class should discuss their observations and reach a consensus on what conclusions they can draw from the data. Students will use that data to make revised models in Ecomodeler that explain the cause of the fish deaths. The students should record in Notes section of Ecomodeler what changes they made to their models and what evidence caused them to make those changes. In the same notes section, students will also write a list of questions that they still need answered to complete their models. At this point there will still be some variation among student models; however, all models could include the idea that if there is too much nutrient input, the algal population rises rapidly and crashes, when the algae population crashes, the bacteria population increases rapidly, and the dissolved oxygen decreases rapidly, causing the fish to die.
In groups the students will revisit the model criteria and discuss any changes they think should be made. As a class, the students will reach a consensus on a revised set of model criteria. Next, the class will construct a consensus model using all their information to date and making sure the class model fits all the model criteria. Students will be left with the open questions of (1) What are these plant nutrients and where do they come from? and (2) do these plant nutrients have anything to do with the nitrates that were in the pond data in Lesson 2?
Lesson 5 – Replicating Eutrophication in an Aquarium Posing Environmental Solutions (3 periods)
In Lesson 5, students will add fertilizer to small containers in order to simulate the conditions they hypothesize led to the fish kill. Finally the class will view a eutrophication animation animation (at: http://new.coolclassroom.org/adventures/explore/plume/39), followed by discussion of possible natural sources of nitrates. Next students will investigate possible solutions for a eutrophic pond.
Possible solutions:
1. Aeration systems (fountains/bubblers) to speed decomposition and increase dissolved oxygen
2. Copper algaecide- can be harmful for other organisms
3. Dyes- to decrease the sunlight in the water, can be toxic to some fish
4. Barley straw- created peroxides as it decomposes which prevent algae growth
5. Wait for seasons to change
Students will model each of these solutions in the small containers and predict what effects they would expect each solution to have. They will then create a final class consensus model and discuss the implications of their mitigation solutions on their own future actions as citizens.
Understanding Aquatic Ecosystems through the Study of Eutrophication
Unit 3
Lesson 3 – Introducing the Eutrophic Pond Problem
Overview
In the previous lesson, the students analyzed the issue of carrying capacity in an aquarium. This lesson serves to introduce the students to the main problem context of the aquatic ecosystem unit and provide them with a need to know the content material. The students will be shown a brief news clip, which highlights the problem of eutrophication (and resulting fish kills) without explaining the cause. The students will be asked to work in small groups and draw preliminary models in Ecomodeler explaining what they think is causing the fish to die. The teacher will group the models into categories based on their explanations and the students will discuss the predictions that arise from the models. Next, the students will be given data from a representative pond to analyze. They will complete arrow diagrams (Handout 3.1) and discuss how the information learned from the activity may be incorporated into their models. Students will then revise their models from Ecomodeler. A second Gallery Walk will allow students to evaluate their peer’s revised models using the model criteria. During this lesson, students should conclude that the toxin and temperature models are not supported by the data. That conclusion leaves the oxygen deprivation model and a question about the role of nitrates. The lesson will end with two open questions based on the data students’ analyzed: 1) What caused the decrease in the dissolved oxygen and 2) What are nitrates and why are they important? In Lesson 4, students will investigate the oxygen deprivation model by using two different NetLogo simulations to manipulate fish, fish food, algae and other factors to observe the effects on oxygen and carbon dioxide concentrations as well as living organisms such as algae and bacteria. They will revisit their models from Ecomodeler and make further revisions.
Modeling
Time 5-7 forty minute periods Materials and Preparation · 1 computer for every group (2-4 students)
· access to a printer
· colored post-it notes for critiquing models
· 1 copy of Handout 3.1 (Pond Data) for each student
· 1 copy of Handout 3.2 (Aquarium Design Assessment) for each student
Activities 1) Opening Video Clip (5 minutes)
a. Class will begin with the teacher showing a brief 5-minute news clip, which highlights a problem facing many ponds nationwide. In the early spring/summer, the ponds become filled with an unidentified green muck. As the problem worsens, the pond water turns brown and dead fish may be found floating in many of the ponds. The students will be charged with the task of evaluating solutions to this important problem. In order to do so, they must first understand what is causing the fish to die.
b. Ask students to write observations to create a sequence/time line while watching the video a second time.
2) Preliminary Models (35 minutes) - The students will work in groups to use Ecomodeler to construct preliminary models of what they think is causing the green muck and fish deaths in the pond.
This is a good stopping point for the 1st period
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3) Categorizing Models (20 minutes)
a. Prior to this lesson, the teacher will look through the models and group them into categories of similar explanations. Three general categories of explanations should emerge:
· Heat/Temperature is the culprit: the increased sunlight allows the green muck to grow and the increased temperature kills the fish. In this explanation, the green muck and dead fish have a common cause but are not related to each other.
· Pollution/toxins: the green muck may be poisonous or be a sign of pollution and it is the poison/pollution that kills the fish. In this explanation, the green muck may be considered non-living.
· Lack of essential life elements (oxygen/food): In this explanation, the students hypothesize that the fish are missing something needed for survival, which could be oxygen or food.
If needed a 4th category can be added.
b. The teacher will explain to the students what the three categories of models are. The teacher should post an example of each category of model for reference during the remainder of this lesson.
c. The students will discuss what predictions come out of each model and what data needs to be collected to test those predictions. This discussion can be facilitated by filling out a table with 3 columns labeled (a) Model, (b) Cause of Death, (c) Possible evidence. For example:
Model
Cause of Death
Possible Evidence
Heat/temperature
The temperature of water led to fish deaths.
Temperature of pond water is high
Pollutions/toxins
The pollution/toxins caused the fish to die.
Presence of pollutants/toxins.
Lack of essential life elements
Lack of essential life elements caused the fish to die.
Information about the health of the fish.
4) Arrow Diagrams (60 minutes)
a. Teacher will distribute Handout 3.1 to all students and ask them to get into their groups.
b. Students will be asked to complete the questions associated with the first 2 pieces of evidence (Temperature range of tolerance graph, Water temperature of pond), complete an arrows diagram connecting these pieces of evidence to the 3 models, and finally students will be asked to eliminate 1 of the models based on this evidence.
c. Once the students have completed the first section of the handout (until the stop sign). Discuss the evidence and arrows diagram as a class. At this point a class discussion should be done to reach a consensus that, although there may be valid aspects of the temperature model, it does not directly explain the fish deaths.
This is a good stopping point for the 2nd period
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d. Students will be asked to complete the questions associated with the remaining 5 pieces of evidence (Chlorophyll-a concentration, Necropsy data, Dissolved oxygen range tolerance and Dissolved oxygen level and water quality graph) and two arrows diagrams.
e. The class will discuss the last two diagrams as well, and how those 5 pieces of evidence can be incorporated into their models from Ecomodeler. Based on the data, the class should reach a consensus on the following issues:
· temperature was not the cause of the fish death
· the fish did not die of illness or starvation
· for unknown reasons, there was not enough oxygen in the water for the fish to survive
· The nitrate level is high. The nitrate isn’t toxic because the fish didn’t die of nitrate poisoning (important point to clarify here), but we don’t know how or if the nitrates play an indirect role in the cause of the fish death.
· The data also shows lots of chlorophyll, which means lots of plants (algae is what makes the green muck).
· The revised model should attempt to explain these 3 factors- lack of oxygen, excess nitrate, and lots of algae.
This is a good stopping point for the 3rd period
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5) Revising Ecomodeler Models (40 minutes)
a. Teacher will give a brief explanation of the purpose of the “notes” section of Ecomodeler. The notes section is a place for students’ thinking and explanations to become visible, and all students should be strongly encouraged to make use of it.
b. The teacher should make sure to remind students that they may consult the pond hypermedia while they are revising their models.
c. Students will work in their groups to revise their models from Ecomodeler to explain the cause of fish deaths. Revisions must be documented in the notes section and should include what was changed and the evidence that caused the students to make the change. Revised models should try to account for the new evidence from the studies (lack of oxygen, lots of nitrate, lots of plants)
d. Additionally, students should list any questions that they still need answered to complete their models.
This is the probable stopping point for the 4th period
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6) Critiquing Ecomodeler Models (40 minutes)
a. Preparing Models for Gallery Walk: The teacher should print a copy of the notes page and model from Ecomodeler for each group. Each group should then use a colored writing utensil to annotate their model to include the evidence that they used to decide on each component, mechanism, and phenomenon. Students can do this by drawing an arrow to the behavior, function, or structure and then writing a note as to what evidence cause them to decide on that behavior, function, or structure.
b. Model Gallery Walk: The teacher should post the annotated printouts of each group’s models around the room and give students approximately 10 minutes to walk around and look at all the models. Each student should be given post-it notes that correspond to the assigned color for each model criteria. For each model criteria, each student must score at least 3 models by placing a post-it note of the appropriate color on the model and writing a rating from 1 to 10 for each criterion. Emphasize that students should critique each other’s models as objectively as possible and they will be asked to defend their critiques. If students don’t get to see every model, that’s okay. They just need enough of a sense of the variety of models in the classroom. Also make sure a group of students starts at each model, so that all models are viewed.
c. Based on the model ratings, the teacher should select 3 models that received top scores in different areas. The class should discuss what makes each model a particularly good example of each criterion, and what areas each model could use more work on. The goal here is for students to understand that a model may be excellent in one area, but require work in another area. Also, students who are struggling with modeling will have an opportunity to see examples of models that they can aspire to.
d. The class should then discuss what all the models have in common, and what questions remain unanswered by their models. Teacher should expect some variation among student models, however students should understand the following:
· The green “muck” (chlorophyll) increases with increasing temperatures in the spring and summer
· The fish die when the dissolved oxygen in the pond water gets too low
· The fish deaths are preceded by a rise in nitrates in the water
Students will be left with the following two open questions:
· What causes the decrease in dissolved oxygen?
· What are these nitrates and why are they important?
This is the probable stopping point for the 5th period
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7) Aquarium Design Assessment (20 minutes)
a. Distribute 1 copy of Handout 3.2 Aquarium Design Assessment to each student
b. Tell the students that will now apply what they have learned from the pond data to draw a diagram showing their design for a healthy aquarium. Remind the students that they will be assessed based on the class model criteria and how well they incorporated the information from the pond data.
c. This design assessment should be completed silently and individually
Note: In Lesson 4, the students will be revising their aquarium designs, so make sure to photocopy them before grading,
Assessment
Students should be assessed based on their participation during class discussion, as well as during group work. The teacher can individually assess Handout 3.1 and assess the group models from Ecomodeler based on the model criteria.
The Aquarium Design Assessment can be assessed using Resource 3.1 Aquarium Design Rubric and a model criteria rubric, which will have to be created by the teacher based on the model criteria that the class has agreed on. Resource 3.2 shows a model criteria rubric that was created by a teacher working on another educational research project. This rubric can be modified to reflect the model criteria that the class has agreed on.
Lesson 4 – Simulating the Role of Carbon and Oxygen in NetLogo
Overview
In Lesson 3, the students analyzed data from the pond to determine which of the generalized models were supported by the evidence. After completing arrows diagrams, revising their models from Ecomodeler, and engaging in a guided classroom discussion, the students realized that low dissolved oxygen level and a rise in nitrates level were associated with fish death. Two questions should arise at the end of Lesson 3 related to the decrease in oxygen and increase in nitrate, and this lesson addresses the first one about the oxygen (which is simpler and needs to be addressed first). The other second will be addressed in Lesson 5.
In this lesson, the students will manipulate two carbon/oxygen NetLogo simulations to try to determine what factors might be causing the decrease in dissolved oxygen. The first simulation will show the phenomenon at the macroscopic level, the second simulation will focus on the microscopic level. Using this new information, students will revise their models from Ecomodeler, and record reasons for their changes. Again, any additions and/or changes in the classroom list of model criteria can be made based on their evolving understanding of modeling. In the next lesson, the class will add fertilizer to their classroom aquarium to replicate eutrophication, and will discover the relationship between fertilizer and water nitrate levels. Objectives Modeling
Students will be able to explain the relationships between components of an ecosystem.
· Students will be able to explain how changes in populations can cause changes in dissolved gases (such as O2 and CO2) and particulate matter, which are indicators of water quality.
Relevant Student Assumptions Students are expected to have developed a good understanding for the criteria of scientific models prior to this lesson. They should be able to use evidence to support or refute an explanatory model. They should also be familiar with the components of a pond ecosystem and their mechanisms and phenomena.
Time approximately 6 forty minute periods
Materials and Preparation · One computer for every group (2-4 students) with Ecomodeler
· Projector and screen to demonstrate NetLogo use
· 1 copy of Handout 4.1 NetLogo Carbon Macro Questions for each student
· 1 copy of Handout 4.2 Net Logo Carbon Micro questions for each student
· Photocopies of Students Aquarium Design Assessments from Lesson 3
· Access to a printer for printing out models and notes from Ecomodeler
· Optional Activity 4: microscopes, algae and bacteria specimens, lab investigation worksheet or Journal for observation notes
· In Lesson 5, the class will be adding fertilizer to the classroom aquarium to observe the effects on water quality. It may be preferable for the teacher to add the fertilizer (without telling the students) at some point during this lesson, so that the process will already be underway when the class gets to lesson 5.
Activities 1) Macro-level NetLogo Simulations (one 45 minute period)
a. Re-cap/warm-up: Class should begin with a recap of yesterday’s findings, and a reiteration of the pressing questions left unanswered (low dissolved O2 condition) (The teacher can create a warm-up based on this.)
b. Teacher will introduce the NetLogo macroscopic level simulation, as a way to investigate what affects oxygen levels in pond water, using a projected image to give a general demonstration of its use. Keep this demonstration as brief as possible.
c. Instruct students to work in groups of 2-4 and to make sure every member has an opportunity to manipulate the simulation. Students will master how to use the simulation at varying rates, but the teacher should continually circulate to provide needed help. Encourage students to make observations about the components and their behaviors. (Discuss: are these components in their models?)
d. After about 5 minutes of manipulating the simulation, facilitate a class discussion on general observations and clarify what is represented by each of the visible components.
e. Distribute Handout 4.1 questions for each group to discuss and then individually write answers, as they continue manipulating the NetLogo simulation. These questions will help to guide students into recognizing the specific behaviors that are occurring and the relationships between the inputs and outputs. They will be asked to create more systematic experimental runs to view outcomes.
f. With 10 minutes left into class, engage in class discussion to share responses to the questions. Brainstorm statements/conclusions that can be made based on the results of the simulation.
g. Optional homework assignment: Discuss what conclusions about the behaviors/relationships of the components can be supported by the simulation evidence.
This is a good stopping point for the 1st period
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2) Micro-level Net Logo Simulations (one 45-minute period)
a. Re-cap/warm-up: Create a common list of conclusions that can be made based on the Macro NetLogo simulation and questions that have emerged.
Examples:
o Conclusion: “When the algae population increases and then dies, the oxygen level decreases.”
o Question: “What causes the oxygen level to decrease as the algae dies?”
b. Briefly introduce the Microscopic level Net Logo simulation using projector and screen. Have students manipulate the simulation for 5 minutes, and make observations as to how it compares and contrasts with the previous simulation. Engage in class discussion to share observations.
Key points to emphasize:
- this simulation models the components on a microscopic level
- the model represents the same algae, but on a microscopic level, it represents algal cells
- a new component has been added: orange patches (bacteria- don’t tell the students the orange patches are bacteria. Encourage them to use the hypermedia to find out.)
See Teacher Notes above for key ideas to emphasize about NetLogo simulations in general.
c. Distribute Handout 4.2 questions for each group to discuss and then individually write answers, as they continue manipulating the NetLogo simulation. Again, these questions will help to guide and focus the student’s recognition and understanding of the specific behaviors that are occurring and the relationships between the inputs and outputs.
d. Engage in class discussion to share responses to the questions. Particularly, visit the questions that had the least consensus within each group. Create a common list of statements/conclusions that can be made based on the results of the simulation. Add unanswered questions to the list.
This is the probable stopping point for the 2nd period
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3) OPTIONAL: Microscopic Investigations (one 45-minute period)
a. In groups of 2-4, have students observe algal cells and bacteria through a microscope. Specimens can be either purchased from a lab company or collected from local ponds. You may use a formal lab worksheet, or have students draw and record observations in a Journal. Books and websites can be supplied for students to get help in identification of the specimens and finding out about their natural history.
b. Following observations, discuss similarities and differences between the specimens. Clarify whether they are living organisms or not. What are their needs and behaviors? What is their food source? Are they autotrophic or heterotrophic? How are they classified?
c. Time permitting, students may return to the microscopic NetLogo simulation to continue to manipulate the components and enhance understanding given the new information retrieved from specimen observation.
This is a good stopping point for the 3rd period
4) Benchmark Lesson on Photosynthesis and Respiration
a. Recap-warm up: Class should discuss their observations and reach a consensus on what conclusions they can draw from their observations of the simulation data and the actual specimens.
· Recall/emphasize that in the simulation, as dead matter increased, O2 decreased enough to cause death of the fish. There were also orange patches that appeared as the dead matter mass increased. Some students may have figured out that those orange patches are bacteria.
· Discuss that these gases are byproducts of cell processes, and since both the algae and fish are composed of cells, we need to look at these processes in more detail.
b. Returning to the Ecomodeler tool to help understand the relationship between the process of photosynthesis and respiration. To gather what they already know, have them create a new PMC2E model that shows the two processes, then share ideas as a class creating a class model.
c. Next have students consult any sections of the hypermedia that provide more detailed information about photosynthesis and respiration. New information should be added or used to revise the PMC2E model.
d. As a brief benchmark lecture, the teacher can then provide accurate information about each of the processes, clearing up any misunderstandings. A class consensus model should be finalized.
e. Some type of formative assessment can be included at this point or the following period: an exit card, a mini-quiz, a printout of model for each student with written explanation.
f. OPTIONAL: Various 1-period labs could be performed to provide evidence of the gases being given off (i.e. plants also give off CO2 through the process of respiration).
This is a good stopping point for the 4th period
5) Ecomodeler Model Revisions
a. Recap-warm-up: Recall the processes of photosynthesis and respiration and and their importance in the aquatic ecosystem.
b. Students will now revise their PMC2E models explain the case of the fish kill. They should use the data and information that they have gathered through simulations, hypermedia, and specimen observations to make and support their revisions. Important: As the students make revisions, have them record in the “Notes” section of Ecomodeler what changes they made to their models and what evidence caused them to make those changes. In the same “Notes” section, the students should also write a list of questions that they still need answered to complete their models.
Note: At this point there will still be some variation among student models; however, all models could include the idea that if there is too much nutrient input, the algal population rises rapidly and crashes, when the algae population crashes, the bacteria population increases rapidly because they decompose the dead algae, and the dissolved oxygen decreases rapidly because bacteria use it, causing the fish to die.
c. The teacher should print a copy of the notes page and Ecomodeler model for each group. Each group should then use a colored writing utensil to annotate their model to include the evidence that they used to decide on each component, mechanism, or phenomenon. Students can do this by drawing an arrow to the component, mechanism, or phenomenon and then writing a note as to what evidence cause them to decide on that component, mechanism, or phenomenon.
d. Groups will now exchange models with another group, who will use the established model criteria to critique each other’s models. Students should give a score from 1 to 10 for each model criteria and a justification for each score.
e. Within the groups, students will revisit the “model criteria” (that were posted at the beginning of the Unit) and discuss any changes they think should be made. As a class, guide the students to reach a consensus on a revised set of model criteria.
Note: At this stage they may remove criteria like labeling as they should be doing that automatically. They can add criteria like account for ALL evidence, and provide mechanism (use more scientific language and add nuance to the criteria) or omit irrelevant details. The changes here do not have to be very large, if the criteria they started out with are relatively complete. The goal here is to add clarification and accuracy.
This is a good stopping point for the 5th period
f. Next, the class will construct a consensus SBF model using all their information to date and making sure the class model fits all the model criteria. The teacher should draw this model on the board and facilitate a discussion about what should be included and how, and what should not be included. The criteria can be used to help students decide what to include and what not to include. Make sure this “consensus class model” fits all the updated model criteria that were agreed upon by the class.
Note: As the classroom consensus model is created, emphasize that the students should not feel that their model must match it. A conversation can ensue regarding how scientists often have different hypotheses and models may look different, yet have the same overarching ideas represented. Each group may have details that will not be agreed upon to place in the classroom consensus model. These details can be noted by using different colors to show less agreed upon elements of the model and reflect this natural level of uncertainty.
g. At the end of consensus model discussions, students will still be left with the open questions of (1) What are these plant nutrients and where do they come from and (2) do these plant nutrients have anything to do with the nitrates that were in the pond data in Lesson 3?
6) Aquarium Design Assessment (20 minutes)
a. Distribute photocopies Handout 3.2 Aquarium Design Assessment that each student completed during Lesson 3
b. Tell the students that will now apply what they have learned from the pond data to revise their diagram showing their design for a healthy aquarium. Remind the students that they will be assessed based on the class model criteria and how well they incorporated the information from the pond data, hypermedia, and NetLogo simulations. The students should revise their drawings in colored pen.
c. This design assessment should be completed silently and individually
Note: In Lesson 5, the students will be revising their aquarium designs again, so make sure to photocopy them before grading
Assessment
This lesson contains both class discussion and group work components and is therefore conversation-based. Students should be assessed based on their participation during class discussion, as well as during group work. The teacher can individually assess the optional warm up and homework activities, if desired. He/She can also use the NetLogo Simulation worksheet questions and the Microscopic Investigation lab observations as an assessment. Checking that revisions to their SBF models have been made and appropriate reasoning is explained in their notes is an important formative assessment.
The Aquarium Design Assessment can be assessed using a model criteria rubric, which will have to be created by the teacher based on the model criteria that the class has agreed on. Resource 3.2 shows a model criteria rubric that was created by a teacher working on another educational research project. This rubric can be modified to include the model criteria that the class has agreed on.
Lesson 5 – Replicating Eutrophication in an Aquarium & Estuary Solutions
Overview
In Lesson 4, students manipulated two carbon/oxygen NetLogo simulations to try to determine what factors might be causing the decrease in dissolved oxygen observed in the pond data. The first simulation showed the phenomenon at the macroscopic level, and the second simulation focused on the functions and behaviors of the structures at the microscopic level. Using this new information, students revised their models from Ecomodeler, and recorded reasons for their changes. At this point students should realize that bacteria consuming the dead algae are using up all the oxygen and depleting the water.
In Lesson 5, students will add fertilizer to small containers in order to simulate the conditions they hypothesize led to the fish kill. This will help them determine the relationship between fertilizer and nitrate level and the role nitrate has in the plant populations of an aquatic system. Left with the question of how nitrate levels increase in natural ecosystems, the class views an eutrophication animation, followed by discussion of possible natural sources of nitrates.
Next students will investigate possible solutions for a eutrophic pond. The investigations can be used as assessment for understanding and mastery of the content material covered in this unit.
Objectives Modeling
· Students will be able to explain the relationships between components of an aquatic ecosystem and their effects on populations
· Students will be able to identify the role of nitrogen in an aquatic system
· Students will demonstrate their understanding of key ecosystem concepts through a well supported argument supporting specific solutions to an ecosystem problem.
Relevant Student Assumptions By this point, students are expected to recognize the major components of a natural aquatic system, living and non-living. They should also have a good understanding of how the levels of certain dissolved substances, such as CO2 and O2, affect the quality of the water to the point of being detrimental to populations.
Time approximately 3 forty minute periods
Materials and Preparation ·
1 computer for every group (2-4 students) with Ecomodeler
· Projector for showing the eutrophication experiment picture and eutrophication simulation
· Photocopies of Handout 3.2 Aquarium Design Assessment as revised in Lesson 4
· Computer File of Resource 5.2 Eutrophication Animation Video
· Web address for the eutrophication simulation: http://new.coolclassroom.org/adventures/explore/plume/39
· 1 copy of Handout 6.1 solution proposal per student
· Aeration system, copper algaecide, blue sapphire dye, barley straw, and/or net to implement the chosen solution in the classroom aquarium.
Activities 1) You have been given 20 dirt containers several months prior.
Steps:
(i) You have 20 dirt containers.
(ii) Fill pond water in 12 of these containers.
(iii) In 9 containers add ½ teaspoon 20:20:20 fertilizer.
(iv) Leave these for several months.
(v) About 2 weeks prior to teaching this unit, add the following to the containers that have fertilizers: Barley straw to 1, Copperalgacide to 1, Aerator to 1, Dye color to 1 and put 1 in the refrigerator.
2) Recall Discussion (5 minutes)
a. Recall the ideas from the last lesson. The class concluded that adding nutrients to a pond leads to an increase in algal mass and when those algae died, the decomposing bacteria use up too much oxygen, causing the fish to die. Ask the students what they think (in real life) corresponds to plant nutrients; i.e. what might I add to make a plant grow better? They should come to the conclusion that somehow fertilizer got into the pond. The teacher will then tell the students that they are going to eutrophy their classroom tank to see the effects of eutrophication in a biological system.
3) Whole class discussion of Aquarium Data (15 minutes)
a. The students should discuss the aquarium water quality data that has been collected over the course of the unit. Sample data is available in Resource 5.1. The students should conclude that when the fertilizer was added, the nitrate level increased. They may also notice the levels of ammonia and nitrate varied when the tank was first set up. At the teacher’s discretion, the class may briefly discuss the evidence of the nitrogen cycle that is visible in the aquarium data. Optional concepts to discuss include:
· As ammonia increases, it begins to get converted to nitrite, then nitrate.
· There are organisms (bacteria) that facilitate that conversion of nitrogen between different forms.
· The final form of nitrogen (nitrate) is used by plants such as algae for growth.
4) Pond Hypermedia (10 min)- The teacher should ask students to look at pond hypermedia with the goal of trying to identify the connection between nitrates (a form of nitrogen) and their class consensus model of this fish kill. The students should come to the conclusion that nitrates are normally a limited resource that keeps algal populations small. So, when nitrates are added, algae population increase dramatically. Optional: Teachers can use the nitrification simulation as well.
5) Eutrophication Experiment Picture (5 min) – to
Introduction to Modeling
Unit 1
Overview
Prior to beginning the main portion of the aquatic ecosystems unit, the students will engage in a broad discussion about ecosystems. The discussion will serve to activate prior knowledge and/or introduce some foundational concepts. The students will then engage in a content-light modeling activity to help build their understanding of the role of models in scientific reasoning. In the activity, Intro to Models, the students are presented with a set of representations and asked to discuss which representations are examples of scientific models. Next the students are presented with pairs of models and asked which model is better and why. This activity serves as scaffold toward forming a list of model criteria by which models can be evaluated. In Lesson 1, students will design an aquarium and begin to engage in scientific modeling based on the driving question “How many fish can fit in an aquarium and why?”
Objectives
Modeling
- Students will be able to explain that there are different types of models and give examples of different kinds of models
- Students will use evidence when evaluating models
- Students will be able to develop and apply criteria for model evaluation
Students may not have had any experience with scientific models prior to this lesson. The preparatory activities in this unit can serve as a supplement to build students’ modeling knowledge base in preparation for the unit itself.
Time 2- 3 forty minute periods
Materials and Preparation
- Copies of other resources for introductory discussion as per teacher’s discretion
- 1 copy of Handout 1.1
Intro to Models for each student
Activities
1. Introduction to Ecosystems Discussion – Prior to beginning the unit itself, the teacher will guide the students in a discussion introducing basic ecosystem concepts, activating prior knowledge regarding ecosystems, and drawing connections to prior lessons regarding the characteristics of life and ecosystems. The teacher may use other classroom resources (including textbook materials) as (s)he deems appropriate. The nature of this discussion will vary widely between classrooms; however, the teacher should strive to include the basic concepts outlined below. To connect this discussion to the next activity, the teacher should explain that ecologists often use scientific models to explain phenomena they observe in ecosystems, therefore the class will be taking some time to look at different models to learn about what makes a good scientific model.
a. Defining an ecosystem and giving examples of aquatic and terrestrial ecosystems.
b. Explaining basic (1) life processes – eating, reproduction, death, growth – this discussion can be tied to characteristics of living things (2) ecosystem processes –photosynthesis, cellular respiration, nitrification, carbon cycling, and carrying capacity.
c. Abiotic v. biotic factors and examples
d. Ecologists build and revise models to explain observations in ecosystems
This is a good stopping point for the 1st period
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2. Intro to Modeling (this activity should take no more than 2 periods to complete, although some classes may be able to complete it in a single period)
a. Hand out one copy of Handout 1.1 Intro to Models for each student. Go over the information about models on the top of the first page. Ask the students to work in groups of 2-4 students to discuss the 6 images and decide which ones are scientific models that explain how plants get energy.
b. Have a class discussion about each image in turn. They have been labeled A to F for your convenience. The focus should be on getting students to explain their understanding; rather than focusing on a single correct answer. Here are some potential explanations:
i. Image A is not a model of because it just shows what is happening not why it is happening.
ii. Image E is a model because it explains what is happening even though it does so in words, not pictures.
The take-home message from this conversation should be that scientific models can be expressed in many different ways, but they should be explanatory i.e., they show underlying causes (mechanisms).
c. Ask each group to discuss each pair of models on the following pages and answer the questions on each page.
d. Have a class discussion about each page in turn. Try to push the students towards more scientific reasons why one model might be better than another. Examples of characteristics of good models that might emerge from this discussion include:
i. Scientific models should explain how things happen
ii. Scientific models should include all relevant details
iii. Scientific models should be consistent with accepted scientific knowledge
iv. Scientific models may include diagrams for clarity, when included, diagrams should be clearly labeled and easy to understand
e. Ask each group to brainstorm and rank their list of characteristics of a good model. (Note: if this activity takes 2 periods to complete, the students can be asked to make their own list of model criteria for homework after the first day of the activity).
f. Have a class discussion about model criteria. Try to come to a class consensus list of model criteria. These model criteria can then serve as a starting place for the model criteria discussion in lesson 2 of the actual unit.
This is the probable stopping point for the 2nd period
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Assessment
Students should be assessed based on their participation during class discussion, as well as during group work. Handout 1.1 Intro to Model can be collected and assessed for completion.
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Understanding Aquatic Ecosystems through the Study of Eutrophication
Unit 2
Lesson 2 – Designing an Aquarium, Fish Spawn and Carrying Capacity
Overview
In this lesson, the teacher will lead a discussion about how scientists use aquaria to test ideas about ecosystems. The students will construct a classroom aquarium and begin monitoring the water quality. The students will draw preliminary models (on paper), explaining how many fish can survive in an aquarium and why. The students will apply the model criteria they established in Lesson 1 to their models. Then the students will be introduced to the PMC2E terminology, hypermedia and Ecomodeler. The students will transfer their paper models into Ecomodeler. At this point, students will be invited to visit the hypermedia before finalizing their models in Ecomodeler. Next, the students will use a Fish Spawn NetLogo simulation to learn about carrying capacity in an aquarium. The driving question for this lesson will be ‘what determines how many fish can survive in an aquarium?’ The teacher will engage the students in short discussion on carrying capacity. The students will refer to the Aquarium Hypermedia and revise their models based on the Fish Spawn NetLogo and the hypermedia. An optional lesson has been provide that could be used before Lesson 3, which covers nitrification. In Lesson 3, the students will begin to explore the fish kill phenomena that serves as a project context for the remainder of the unit.
Objectives
Modeling
- Students will construct an explanatory model
- Students will be able to evaluate alternative models of processes within an ecosystem
- Students will emphasize the importance of evidence when evaluating models and also use evidence to construct their models
- Students will use evidence when evaluating models
- Students will be able to develop and apply criteria for model evaluation
- Students will be able to identify biotic and abiotic factors in an aquarium
- Students will be able to explain the factors that limit population growth contributing to a carrying capacity
Students are expected to have had some experience with scientific models prior to this lesson. At the minimum, the Intro to Models activity in Lesson 1 should have familiarized students with a general notion of the forms and purposes of scientific models.
Time 5-6 forty minute periods
Materials and Preparation ·
Teachers should review the Pond Aquarium Unit Backbone prior to lesson.
2 Aquarium kits (1 tank setup per classroom for monitoring and testing, and 1 smaller tank setup to act as a control/“rescue” tank to move fish to in Lesson 5)
o 10-20 gallon aquarium
o Lighted hood
o Water conditioner
o Assorted tropical fish
o Filter with pump and filter cartridge
o Aquarium gravel
o Algae sponge
o Fish food
o Net
o Heater
o Thermometer
o Optional: plants, decorative rocks
o Materials for monitoring the following aspects of water quality
§ pH level
§ dissolved oxygen level
§ nitrite level
§ nitrate level
§ ammonia level
§ biological oxygen demand
§ amount of algae – using travel spectrophotometer
· Poster paper (1 piece per group plus 8 pieces for data tables)
· Markers (1 set per group)
· One computer for every group (2-4 students) with access to Ecomodeler
· One copy of Handout 2.1 NetLogo Fish Spawn for each student
Activities
1. Constructing an Aquarium (40 minutes)
a. Tell the students that they will soon be studying a serious problem that occurred in a pond, and to help them with their investigation of this problem they will set up an aquarium that they will explore later.
b. Ask the students to work in groups to come up with a list of biotic and abiotic factors that would be included in an aquarium. Using a whiteboard to make the list public, the teacher will then conduct a brief discussion about the aquarium’s components and why they are needed. The teacher may need to prompt the class for anything that may be missing from the materials list.
Note: Ask the students how many fish they think the aquarium will be able to support and why? It is important that they do not discover the rule of thumb for the number of fish an aquarium can sustain until later in the lesson.
c. (Optional) The teacher may want to have the class set up the aquarium during this period. Otherwise it should be set up before class during prep time. Depending on class size, some students may work on the tank setup while others create poster-size tables to record the following information:
· pH level
· dissolved oxygen level
· nitrite level
· nitrate level
· ammonia level
· biological oxygen demand
· amount of algae
· fish activity/behavior
d. Once the aquarium is set up and all of the tables are created (and posted publicly), students will need to take their initial measurements. Each class will need their own set of tables, and readings will continue daily for the remainder of the unit. (Tip: The teacher may want to “hide” the tables from other classes so there is no bias introduced. Use of a Smart Board or other technology may be helpful.)
This is a good stopping point for the 1st period
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2. Preliminary Models (40 minutes)
a. The teacher will divide the class into groups of 2-4 students who will work together throughout the unit. The groups should be diverse in learning preferences and achievement level.
b. The teacher should give each group a set of markers and construction paper and ask them to draw a model (diagram) explaining how many fish can survive in an aquarium and why. At this point, due to students’ possible lack of experience with modeling, they may be more likely to draw pictorial models. At this stage, let the students choose the format and do not place too much emphasis on the right explanation or a particular format.
This is a good stopping point for the 2nd period
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3. Refining Model Criteria (developed in lesson 1):
a. Optional warm-up activity (5 minutes): Students individually answer the question “What characteristics make a good model?” Remind the students of the model criteria they established in lesson 1.
b. Model Gallery Walk (10 minutes): Place the models around the room and give students approximately 10 minutes to walk around and look at all the models. On a piece of paper or index card, each student should record one positive aspect of each model and one area each model could be improved. Emphasize that comments should refer not only to the visual appearance of model; rather, also the ideas contained in the model. If students don’t get to see every model, that’s okay. They just need enough of a sense of the variety of models in the classroom. Also make sure at least one group starts at each model so that all models are viewed. Another option for the gallery walk is for the students to rate all the models that they visit for each of the model criteria (i.e., have them note the presence or absence of each criteria). This could be accomplished by creating a checklist for students to use as they walk among the models.
c. Model Criteria Discussion (15 minutes): The teacher will guide the students in a discussion of the differences between their models, both in terms of visual representation and underlying explanation. Students will discuss what characteristics constitute a good model. The teacher may bring up the list of model criteria created in Lesson 1 to use as a starting point for this discussion. This discussion will lead to a list of model criteria, which will be posted on the classroom wall and revised throughout the unit. Model criteria could include, but are not limited to:
Good models:
· are clear and understandable, with an appropriate level of detail (for example, having organisms, like snails, in the model that do not relate to the problem is not necessary)
· show an underlying explanation, rather than a description of what is already known
· Should be supported with evidence, and are testable (ask students what data will be needed to see if the model holds true)
· are realistic and sensible given prior knowledge (for example, a fish killing a shark is not realistic)
Assign each model criteria a color (making sure you have adhesive notes in those colors). In Lesson 4 students will use color-coded adhesive notes to assess their peer’s models using these criteria.
4. Introducing PMC2E
a. Benchmark lecture (10 minutes): The teacher will give a benchmark lecture presenting the PMC2E modeling framework as a way of reasoning about systems. In this framework, explanations include components, mechanisms (processes), and phenomena (outcomes). See Handout 2.0 for definitions and examples.
b. Optional Homework: The teacher may choose to give a homework assignment for students to define components, mechanisms, and phenomena and/or describe an everyday example of a system (factory, computer, house) in PMC2E terms. Alternatively the teacher can ask the students to start making a list of the components, mechanisms, and phenomena that they had included in their models.
This is the probable stopping point for the 3rd period
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c. Labeling PMC2E in models (10 minutes): Students will then return to their models and identify the components, mechanisms, and phenomena in their model by labeling them on the original model.
d. Incorporating PMC2E into model criteria (5-10 minutes): Briefly the class will discuss examples of PMC2E in their model. This discussion should lead to adding a model criterion that every component should have a mechanism associated with it, and that explanatory models are tied to explaining a central phenomenon. This criterion should be added to the posted list.
e. Translating models into PMC2E (20 minutes): The students will transfer their models into Ecomodeler. The teacher will probably need to briefly demonstrate how to use the software. When the teacher introduces the student to the Ecomodeler software, the teacher should invite the students to begin to investigate the aquarium hypermedia, and revise their models as they feel in appropriate.
f. Optional Classwork /Homework: The teacher should give each student a printout of another group’s PMC2E model and a list of the model criteria. The students should then assess how well the model fits the model criteria.
This is the probable stopping point for the 4th period
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5. NetLogo Simulation – Fish Spawn (40 minutes)
a. The teacher will remind the students of the models they have been working on. After a brief discussion the teacher should tell them that they will now use a NetLogo simulation to explore the factors that affect fish population size in an aquarium.
b. Handout one copy of Handout 2.1 NetLogo Fish Spawn to each student to complete as they are manipulating the simulation. Students will work in groups of 2-4 and will manipulate the following variables:
· Number of male and female fish
· Spawning probability
· Filtration level
· Amount of food
c. Students will run the simulation and observe the results by monitoring the water quality level as well as the various levels of fish mortalities and spawning numbers.
d. The teacher should help students by pointing out that by changing each input individually, he or she will see the effect it has on the population of fish in the tank.
e. The teacher should be looking for students to try different variable settings, working towards an equilibrium in which the simulation continues on indefinitely. Some students may discover this on their own, at which time they should be guided to watching the levels of water quality, number spawned and mortality levels change to get a feel for the carrying capacity of the aquarium.
f. Optional Homework- At this point (no earlier) you can introduce the rule of thumb often used for calculating how many fish an aquarium can sustain. The students can then calculate the appropriate number for homework.
This is a good stopping point for the 5th period
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6. Revising Models in Ecomodeler (40 minutes)
a. Teacher will give a brief explanation of the purpose of the “notes” section of Ecomodeler. The notes section is a place for students’ thinking and explanations to become visible, and all students should be strongly encouraged to make use of it.
b. Students will work in their groups to revise their models from Ecomodeler to explain the factors that limit fish population size in an aquarium. Revisions must be documented in the notes section and should include what was changed and the evidence that caused the students to make the change. Revised models should try to account for the new evidence from the NetLogo simulation.
This is the probable stopping point for the 6th period
Assessment
Students should be assessed based on their participation during class discussion, as well as during group work. The teacher can also use the NetLogo Simulation worksheet as an assessment.
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Pond Unit
Pond Unit backbone
Overview
In this unit, students will be engaged with learning about PMC2E modeling and aquatic ecosystems through a problem context centered on a eutrophic pond.
In Lesson 1, the students will participate in a broad discussion about ecosystems. The students will be then introduced to the concept of scientific modeling as a tool scientists use to explain phenomena they observe in ecosystems, through a handout showing examples of models and asking student to compare models. The teacher will work with the class to characterize what makes a good scientific model. Model criteria should be established—they should be clear, accurate, provide explanation.
In Lesson 2, the teacher will lead a discussion about how scientists use aquaria to test ideas about ecosystems. The students will construct a classroom aquarium and begin monitoring the water quality. The students will be asked to draw preliminary models (on paper), explaining how many fish can survive in an aquarium and why. The students will apply the model criteria they established in Lesson 1 to their models. The students will be then introduced to the PMC2E terminology, hypermedia and Ecomodeler. The students will transfer their paper models into Ecomodeler. At this point, students will be invited to visit the hypermedia before finalizing their models in Ecomodeler. Next, the students will use a Fish Spawn NetLogo simulation to learn about carrying capacity in an aquarium. The driving question for this lesson will be “what determines how many fish can survive in an aquarium ecosystem?” The teacher will engage the students in a short discussion on carrying capacity. The students will refer to the Aquarium Hypermedia and revise their models based on the Fish Spawn NetLogo and the hypermedia.
In Lesson 3, the students will watch a two minute film, which highlights the problem of eutrophication (and resulting fish kills) without explaining the cause. The students will revisit the modeling criteria. The students will be asked to draw preliminary models in the Ecomodeler explaining what they think is causing the fish to die. The students will be given data from a representative pond to analyze to determine if it supports or contradicts their models. Students will then revise their models from Ecomodeler.
In Lesson 4, the students will manipulate two carbon/oxygen NetLogo simulations to try to determine what factors might be causing the decrease in dissolved oxygen observed in the pond data. The first simulation will show the phenomenon at the macroscopic level, the second simulation focuses on the functions and behaviors of the structures at the microscopic level. Students will also be introduced to the Pond Hypermedia that provides information helpful in understanding what is happening in the simulations. Using this new information, students will revise their models from Ecomodeler and construct a class consensus model.
In Lesson 5, students will add fertilizer to small containers in order to simulate the conditions they hypothesize led to the fish kill. Finally the class will view a eutrophication animation animation (at: http://new.coolclassroom.org/adventures/explore/plume/39), followed by discussion of possible natural sources of nitrates.
Lesson 1- Intro to modeling (3 periods)
The students will engage in a broad discussion about ecosystems. The teacher will scaffold the conversation around factors that afford life and those that constraint (limit) life within that system. The students will then engage in a content-light modeling activity to help build their understanding of the role of models in scientific reasoning. In the activity, Intro to Models, the students are presented with a set of representations and asked to discuss which representations are examples of scientific models. Next the students are presented with pairs of models and asked which model is better and why. This activity serves as scaffold toward forming a list of model criteria by which models can be evaluated.
Lesson 2 – Designing an Aquarium, Fish Spawn and Carrying Capacity (5-6 periods)
In this lesson the students will design an aquarium that they will later be able to use as a tool to test hypotheses when they students a particular natural aquatic phenomenon (eutrophication). The teachers will begin this activity by discussing how scientists use aquaria to test ideas about ecosystems. The class will brainstorm what components should be included in the aquarium.
The students will be asked to work in small groups and draw preliminary models (on paper), explaining how many fish can survive in an aquarium and why. The teacher will give a benchmark lecture presenting the PMC2E modeling framework. Students will draw these preliminary models on large sheets of paper using colored markers. The students will then be introduced to the aquarium hypermedia and Ecomodeler. The students will then transfer their paper models into Ecomodeler by using PMC2E and the aquarium hypermedia.
The teacher will bring up the issue of how many fish can an aquarium support. The class will investigate this issue using a Fish Spawn NetLogo simulation. From the simulation, the students will conclude that there is a limit (carrying capacity) to the population a tank can sustain. The teacher will lead a discussion on carrying capacity and explain to the students that the notion of stuffing as much as we can in a tank may not be the essence of building a healthy aquarium. The students will be given a chance to revise their models by using the hypermedia and the evidence from the Fish Spawn simulation.
Lesson 3 – Introducing the Problem of the Eutrophic Pond (5-7 periods)
Students will be shown a brief 3-minute news clip, which highlights a problem facing many ponds nationwide. In the early spring/summer, the ponds become filled with an unidentified green muck. As the problem worsens, the pond water turns brown and dead fish are even found floating in many of the ponds. The students will be charged with the task of evaluating solution to this important problem. In order to do so they must understand what is causing the fish to die. The students will visit modeling criteria. The students will then create preliminary models in Ecomodeler trying to explain why the fish died.
The teacher will guide the students in a discussion of the differences between their models, both in terms of visual representation and underlying explanation. Students will discuss what characteristics constitute a good model. This discussion will lead to a revised list of model criteria, which will be posted on the classroom wall and revised throughout the unit.
The teacher will look through the models and group them into categories of similar explanations. Three general categories of explanations should emerge:
1. Heat/Temperature is the culprit: the increased sunlight allows the green muck to grow and the increased temperature kills the fish. In this explanation, the green muck and dead fish have a common cause but are not related to each other.
2. Pollution/toxins: the green muck may be poisonous or be a sign of pollution and it is the poison/pollution that kills the fish. In this explanation, the green muck may be considered non-living.
3. Lack of essential life elements (oxygen/food): In this explanation, the students hypothesize that the fish are missing something needed for survival, which could be oxygen or food.
If needed a 4th category can be added. The teacher should post an example of each category of model for reference in the future lessons. The students will discuss what predictions come out of each model and what data needs to be collected to test those predictions.
Now that 3 categories of explanations for the fish deaths have emerged, students will analyze additional data from the pond to determine if any of the models are supported or refuted. Students will be given a packet that includes 7 pieces of data with question prompts to help scaffold their understanding of the data. The 7 pieces of data will include:
· Temperature range of tolerance graph for a species of fish in the pond
· Graph of pond water temperature over the course of the year
· Graph showing the concentration of chlorophyll-a in the pond water over the course of the year (this is a method of measuring the amount of algae in the water)
· Necropsy data table showing fish died due to suffocation, no toxins, normal weight
· Dissolved oxygen range of tolerance table for fish
· Graph showing the level of dissolved oxygen in the pond over the course of the year
· Water quality graph showing the concentrations of ammonia and nitrates
Students will use that data to make revised models in Ecomodeler that explain the cause of the fish deaths. The students should record, in notes section of Ecomodeler, what changes they made to their models and what evidence caused them to make those changes. In the same notes section, students should also write a list of questions that they still need answered to complete their models. At this point there will still be some variation among student models; however, all models could include the idea that the green muck increases with increasing temperatures in the spring and summer, the fish die when the dissolved oxygen in the pond water gets to low, and the fish deaths are preceded by a rise nitrates in the water. In this way, elements of all 3 categories of preliminary models appear to be correct. The students will be given a copy of each group’s model and asked to sort those models into categories based on their explanations. The class will discuss how the groups sorted the models and why. At the end of this lesson, students will be left with the open questions of (1) what causes the decrease in dissolved oxygen? and (2) what are these nitrates and why are they important?
Lesson 4 - Simulating the Role of Carbon and Oxygen in NetLogo (5-6 periods)
In this lesson, students will manipulate two carbon/oxygen NetLogo simulations to try to determine what factors might be causing the decrease in dissolved oxygen. Two questions were left at the end of lesson two, and this lesson addresses the first question, because we thought the students would find that question more pressing. The first simulation will show the phenomenon at the macroscopic level. The simulation will include the following visible components, inputs, outputs, and behaviors:
· Visible components: Fish, fish food, algae (amorphous green blobs), nutrients
o Note: Fish/algae disappear when they die
· Inputs: add fish, add fish food, add algae, add plant nutrients
· Outputs: graph showing concentrations of O2 and CO2, graph showing the mass of living fish, dead fish, living algae, dead algae
o Note: to simplify the second graph, maybe we can try having the dead fish can be a lighter shade of the color of the living fish and the dead algae can be a lighter shade of the color of the living algae
· Behaviors:
o If the algae population is balanced with the fish population, the system will be in a state of equilibrium with stable amounts of fish and algae and dissolved gases.
o If the fish population is too high in comparison to the algae population, the amount of dissolved oxygen will rapidly decrease, killing the fish, but the algae will survive.
o If excess nutrients are added to the system, the algae population will exceed carrying capacity and crash. As the dead algae are decomposed (by bacteria, which are not visible at the macroscopic level), the amount of dissolved oxygen will decrease rapidly causing the fish to die.
This simulation will allow students to conclude that as the algae die in large numbers, the dissolved oxygen decreases, killing the fish. The teacher should give students 10 minutes or so to manipulate the simulation and jot down observations, without worrying about precise data collection. The class should then discuss what they noticed and what testable hypotheses they would want to investigate more systematically. The students will then return to the simulation and collect data more systematically filling out a data worksheet. There may be several alternations between observational runs of the simulation and more systematic experimental runs. When the students have finished with the simulation, the class should discuss their conclusions and what they think might be causing the oxygen levels to decrease when all the algae die.
Next, the students will look at a NetLogo simulation that allows them to peak into the microscopic processes that underlie what they observed in the macroscopic level simulation. The simulation will include the following visible components, inputs, outputs, and behaviors:
· Visible components: Living algal cells (green circle in the same shade as the algae from the previous simulation), dead algal cells (appear brown), decomposing bacteria, O2 and CO2
· Inputs: add algae, add plant nutrients, add bacteria
· Outputs: graph showing concentrations of O2 and CO2, graph showing the mass of bacteria, living algae, dead algae
· Behaviors:
o Adding plant nutrients will increase the growth of the algal cells. However, if excess amounts of nutrients are added, the algae population will decrease rapidly, causing a rapid increase in the decomposing bacteria, causing a rapid decrease in dissolved oxygen.
o At non-excessive nutrient levels, the bacteria and algae population will fluctuate in a predator-prey relationship.
After the students have manipulated the microscopic level NetLogo, the teacher should stop the class to discuss what they learned from the macroscopic NetLogo model and what they see in the microscopic NetLogo that was not visible in the first simulation. The teacher should make sure the students understand that the algal cells in the second NetLogo are what ones sees when they zoom in on the green muck visible in the macroscopic level simulation. Looking at wet mounts of algal cells under the microscope can facilitate this understanding. Algal samples can be collected from a local pond or ordered from a lab supply company. At this point (if they have not done so already), the class should agree that the green muck is made of living cells.
With this knowledge, the students should be given additional time to manipulate the microscopic NetLogo simulation. They may then also consult any sections of the hypermedia they consider relevant. The class should discuss their observations and reach a consensus on what conclusions they can draw from the data. Students will use that data to make revised models in Ecomodeler that explain the cause of the fish deaths. The students should record in Notes section of Ecomodeler what changes they made to their models and what evidence caused them to make those changes. In the same notes section, students will also write a list of questions that they still need answered to complete their models. At this point there will still be some variation among student models; however, all models could include the idea that if there is too much nutrient input, the algal population rises rapidly and crashes, when the algae population crashes, the bacteria population increases rapidly, and the dissolved oxygen decreases rapidly, causing the fish to die.
In groups the students will revisit the model criteria and discuss any changes they think should be made. As a class, the students will reach a consensus on a revised set of model criteria. Next, the class will construct a consensus model using all their information to date and making sure the class model fits all the model criteria. Students will be left with the open questions of (1) What are these plant nutrients and where do they come from? and (2) do these plant nutrients have anything to do with the nitrates that were in the pond data in Lesson 2?
Lesson 5 – Replicating Eutrophication in an Aquarium Posing Environmental Solutions (3 periods)
In Lesson 5, students will add fertilizer to small containers in order to simulate the conditions they hypothesize led to the fish kill. Finally the class will view a eutrophication animation animation (at: http://new.coolclassroom.org/adventures/explore/plume/39), followed by discussion of possible natural sources of nitrates. Next students will investigate possible solutions for a eutrophic pond.
Possible solutions:
1. Aeration systems (fountains/bubblers) to speed decomposition and increase dissolved oxygen
2. Copper algaecide- can be harmful for other organisms
3. Dyes- to decrease the sunlight in the water, can be toxic to some fish
4. Barley straw- created peroxides as it decomposes which prevent algae growth
5. Wait for seasons to change
Students will model each of these solutions in the small containers and predict what effects they would expect each solution to have. They will then create a final class consensus model and discuss the implications of their mitigation solutions on their own future actions as citizens.
Understanding Aquatic Ecosystems through the Study of Eutrophication
Unit 3
Lesson 3 – Introducing the Eutrophic Pond Problem
Overview
In the previous lesson, the students analyzed the issue of carrying capacity in an aquarium. This lesson serves to introduce the students to the main problem context of the aquatic ecosystem unit and provide them with a need to know the content material. The students will be shown a brief news clip, which highlights the problem of eutrophication (and resulting fish kills) without explaining the cause. The students will be asked to work in small groups and draw preliminary models in Ecomodeler explaining what they think is causing the fish to die. The teacher will group the models into categories based on their explanations and the students will discuss the predictions that arise from the models. Next, the students will be given data from a representative pond to analyze. They will complete arrow diagrams (Handout 3.1) and discuss how the information learned from the activity may be incorporated into their models. Students will then revise their models from Ecomodeler. A second Gallery Walk will allow students to evaluate their peer’s revised models using the model criteria. During this lesson, students should conclude that the toxin and temperature models are not supported by the data. That conclusion leaves the oxygen deprivation model and a question about the role of nitrates. The lesson will end with two open questions based on the data students’ analyzed: 1) What caused the decrease in the dissolved oxygen and 2) What are nitrates and why are they important? In Lesson 4, students will investigate the oxygen deprivation model by using two different NetLogo simulations to manipulate fish, fish food, algae and other factors to observe the effects on oxygen and carbon dioxide concentrations as well as living organisms such as algae and bacteria. They will revisit their models from Ecomodeler and make further revisions.
Modeling
- Students will be able to evaluate alternative models of processes within an ecosystem
- Students will emphasize the importance of evidence when evaluating models and also use evidence to construct their models
Time 5-7 forty minute periods Materials and Preparation · 1 computer for every group (2-4 students)
· access to a printer
· colored post-it notes for critiquing models
· 1 copy of Handout 3.1 (Pond Data) for each student
· 1 copy of Handout 3.2 (Aquarium Design Assessment) for each student
Activities 1) Opening Video Clip (5 minutes)
a. Class will begin with the teacher showing a brief 5-minute news clip, which highlights a problem facing many ponds nationwide. In the early spring/summer, the ponds become filled with an unidentified green muck. As the problem worsens, the pond water turns brown and dead fish may be found floating in many of the ponds. The students will be charged with the task of evaluating solutions to this important problem. In order to do so, they must first understand what is causing the fish to die.
b. Ask students to write observations to create a sequence/time line while watching the video a second time.
2) Preliminary Models (35 minutes) - The students will work in groups to use Ecomodeler to construct preliminary models of what they think is causing the green muck and fish deaths in the pond.
This is a good stopping point for the 1st period
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3) Categorizing Models (20 minutes)
a. Prior to this lesson, the teacher will look through the models and group them into categories of similar explanations. Three general categories of explanations should emerge:
· Heat/Temperature is the culprit: the increased sunlight allows the green muck to grow and the increased temperature kills the fish. In this explanation, the green muck and dead fish have a common cause but are not related to each other.
· Pollution/toxins: the green muck may be poisonous or be a sign of pollution and it is the poison/pollution that kills the fish. In this explanation, the green muck may be considered non-living.
· Lack of essential life elements (oxygen/food): In this explanation, the students hypothesize that the fish are missing something needed for survival, which could be oxygen or food.
If needed a 4th category can be added.
b. The teacher will explain to the students what the three categories of models are. The teacher should post an example of each category of model for reference during the remainder of this lesson.
c. The students will discuss what predictions come out of each model and what data needs to be collected to test those predictions. This discussion can be facilitated by filling out a table with 3 columns labeled (a) Model, (b) Cause of Death, (c) Possible evidence. For example:
Model
Cause of Death
Possible Evidence
Heat/temperature
The temperature of water led to fish deaths.
Temperature of pond water is high
Pollutions/toxins
The pollution/toxins caused the fish to die.
Presence of pollutants/toxins.
Lack of essential life elements
Lack of essential life elements caused the fish to die.
Information about the health of the fish.
4) Arrow Diagrams (60 minutes)
a. Teacher will distribute Handout 3.1 to all students and ask them to get into their groups.
b. Students will be asked to complete the questions associated with the first 2 pieces of evidence (Temperature range of tolerance graph, Water temperature of pond), complete an arrows diagram connecting these pieces of evidence to the 3 models, and finally students will be asked to eliminate 1 of the models based on this evidence.
c. Once the students have completed the first section of the handout (until the stop sign). Discuss the evidence and arrows diagram as a class. At this point a class discussion should be done to reach a consensus that, although there may be valid aspects of the temperature model, it does not directly explain the fish deaths.
This is a good stopping point for the 2nd period
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d. Students will be asked to complete the questions associated with the remaining 5 pieces of evidence (Chlorophyll-a concentration, Necropsy data, Dissolved oxygen range tolerance and Dissolved oxygen level and water quality graph) and two arrows diagrams.
e. The class will discuss the last two diagrams as well, and how those 5 pieces of evidence can be incorporated into their models from Ecomodeler. Based on the data, the class should reach a consensus on the following issues:
· temperature was not the cause of the fish death
· the fish did not die of illness or starvation
· for unknown reasons, there was not enough oxygen in the water for the fish to survive
· The nitrate level is high. The nitrate isn’t toxic because the fish didn’t die of nitrate poisoning (important point to clarify here), but we don’t know how or if the nitrates play an indirect role in the cause of the fish death.
· The data also shows lots of chlorophyll, which means lots of plants (algae is what makes the green muck).
· The revised model should attempt to explain these 3 factors- lack of oxygen, excess nitrate, and lots of algae.
This is a good stopping point for the 3rd period
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5) Revising Ecomodeler Models (40 minutes)
a. Teacher will give a brief explanation of the purpose of the “notes” section of Ecomodeler. The notes section is a place for students’ thinking and explanations to become visible, and all students should be strongly encouraged to make use of it.
b. The teacher should make sure to remind students that they may consult the pond hypermedia while they are revising their models.
c. Students will work in their groups to revise their models from Ecomodeler to explain the cause of fish deaths. Revisions must be documented in the notes section and should include what was changed and the evidence that caused the students to make the change. Revised models should try to account for the new evidence from the studies (lack of oxygen, lots of nitrate, lots of plants)
d. Additionally, students should list any questions that they still need answered to complete their models.
This is the probable stopping point for the 4th period
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6) Critiquing Ecomodeler Models (40 minutes)
a. Preparing Models for Gallery Walk: The teacher should print a copy of the notes page and model from Ecomodeler for each group. Each group should then use a colored writing utensil to annotate their model to include the evidence that they used to decide on each component, mechanism, and phenomenon. Students can do this by drawing an arrow to the behavior, function, or structure and then writing a note as to what evidence cause them to decide on that behavior, function, or structure.
b. Model Gallery Walk: The teacher should post the annotated printouts of each group’s models around the room and give students approximately 10 minutes to walk around and look at all the models. Each student should be given post-it notes that correspond to the assigned color for each model criteria. For each model criteria, each student must score at least 3 models by placing a post-it note of the appropriate color on the model and writing a rating from 1 to 10 for each criterion. Emphasize that students should critique each other’s models as objectively as possible and they will be asked to defend their critiques. If students don’t get to see every model, that’s okay. They just need enough of a sense of the variety of models in the classroom. Also make sure a group of students starts at each model, so that all models are viewed.
c. Based on the model ratings, the teacher should select 3 models that received top scores in different areas. The class should discuss what makes each model a particularly good example of each criterion, and what areas each model could use more work on. The goal here is for students to understand that a model may be excellent in one area, but require work in another area. Also, students who are struggling with modeling will have an opportunity to see examples of models that they can aspire to.
d. The class should then discuss what all the models have in common, and what questions remain unanswered by their models. Teacher should expect some variation among student models, however students should understand the following:
· The green “muck” (chlorophyll) increases with increasing temperatures in the spring and summer
· The fish die when the dissolved oxygen in the pond water gets too low
· The fish deaths are preceded by a rise in nitrates in the water
Students will be left with the following two open questions:
· What causes the decrease in dissolved oxygen?
· What are these nitrates and why are they important?
This is the probable stopping point for the 5th period
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7) Aquarium Design Assessment (20 minutes)
a. Distribute 1 copy of Handout 3.2 Aquarium Design Assessment to each student
b. Tell the students that will now apply what they have learned from the pond data to draw a diagram showing their design for a healthy aquarium. Remind the students that they will be assessed based on the class model criteria and how well they incorporated the information from the pond data.
c. This design assessment should be completed silently and individually
Note: In Lesson 4, the students will be revising their aquarium designs, so make sure to photocopy them before grading,
Assessment
Students should be assessed based on their participation during class discussion, as well as during group work. The teacher can individually assess Handout 3.1 and assess the group models from Ecomodeler based on the model criteria.
The Aquarium Design Assessment can be assessed using Resource 3.1 Aquarium Design Rubric and a model criteria rubric, which will have to be created by the teacher based on the model criteria that the class has agreed on. Resource 3.2 shows a model criteria rubric that was created by a teacher working on another educational research project. This rubric can be modified to reflect the model criteria that the class has agreed on.
Lesson 4 – Simulating the Role of Carbon and Oxygen in NetLogo
Overview
In Lesson 3, the students analyzed data from the pond to determine which of the generalized models were supported by the evidence. After completing arrows diagrams, revising their models from Ecomodeler, and engaging in a guided classroom discussion, the students realized that low dissolved oxygen level and a rise in nitrates level were associated with fish death. Two questions should arise at the end of Lesson 3 related to the decrease in oxygen and increase in nitrate, and this lesson addresses the first one about the oxygen (which is simpler and needs to be addressed first). The other second will be addressed in Lesson 5.
In this lesson, the students will manipulate two carbon/oxygen NetLogo simulations to try to determine what factors might be causing the decrease in dissolved oxygen. The first simulation will show the phenomenon at the macroscopic level, the second simulation will focus on the microscopic level. Using this new information, students will revise their models from Ecomodeler, and record reasons for their changes. Again, any additions and/or changes in the classroom list of model criteria can be made based on their evolving understanding of modeling. In the next lesson, the class will add fertilizer to their classroom aquarium to replicate eutrophication, and will discover the relationship between fertilizer and water nitrate levels. Objectives Modeling
- Students will be able to explain an event by producing an explanatory model that is supported by scientific data
- Students will be able to graphically represent and interpret the relationships between components in an ecosystem
- Students will emphasize the importance of evidence when evaluating models and also use evidence to construct their models
Students will be able to explain the relationships between components of an ecosystem.
· Students will be able to explain how changes in populations can cause changes in dissolved gases (such as O2 and CO2) and particulate matter, which are indicators of water quality.
Relevant Student Assumptions Students are expected to have developed a good understanding for the criteria of scientific models prior to this lesson. They should be able to use evidence to support or refute an explanatory model. They should also be familiar with the components of a pond ecosystem and their mechanisms and phenomena.
Time approximately 6 forty minute periods
Materials and Preparation · One computer for every group (2-4 students) with Ecomodeler
· Projector and screen to demonstrate NetLogo use
· 1 copy of Handout 4.1 NetLogo Carbon Macro Questions for each student
· 1 copy of Handout 4.2 Net Logo Carbon Micro questions for each student
· Photocopies of Students Aquarium Design Assessments from Lesson 3
· Access to a printer for printing out models and notes from Ecomodeler
· Optional Activity 4: microscopes, algae and bacteria specimens, lab investigation worksheet or Journal for observation notes
· In Lesson 5, the class will be adding fertilizer to the classroom aquarium to observe the effects on water quality. It may be preferable for the teacher to add the fertilizer (without telling the students) at some point during this lesson, so that the process will already be underway when the class gets to lesson 5.
Activities 1) Macro-level NetLogo Simulations (one 45 minute period)
a. Re-cap/warm-up: Class should begin with a recap of yesterday’s findings, and a reiteration of the pressing questions left unanswered (low dissolved O2 condition) (The teacher can create a warm-up based on this.)
b. Teacher will introduce the NetLogo macroscopic level simulation, as a way to investigate what affects oxygen levels in pond water, using a projected image to give a general demonstration of its use. Keep this demonstration as brief as possible.
c. Instruct students to work in groups of 2-4 and to make sure every member has an opportunity to manipulate the simulation. Students will master how to use the simulation at varying rates, but the teacher should continually circulate to provide needed help. Encourage students to make observations about the components and their behaviors. (Discuss: are these components in their models?)
d. After about 5 minutes of manipulating the simulation, facilitate a class discussion on general observations and clarify what is represented by each of the visible components.
e. Distribute Handout 4.1 questions for each group to discuss and then individually write answers, as they continue manipulating the NetLogo simulation. These questions will help to guide students into recognizing the specific behaviors that are occurring and the relationships between the inputs and outputs. They will be asked to create more systematic experimental runs to view outcomes.
f. With 10 minutes left into class, engage in class discussion to share responses to the questions. Brainstorm statements/conclusions that can be made based on the results of the simulation.
g. Optional homework assignment: Discuss what conclusions about the behaviors/relationships of the components can be supported by the simulation evidence.
This is a good stopping point for the 1st period
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2) Micro-level Net Logo Simulations (one 45-minute period)
a. Re-cap/warm-up: Create a common list of conclusions that can be made based on the Macro NetLogo simulation and questions that have emerged.
Examples:
o Conclusion: “When the algae population increases and then dies, the oxygen level decreases.”
o Question: “What causes the oxygen level to decrease as the algae dies?”
b. Briefly introduce the Microscopic level Net Logo simulation using projector and screen. Have students manipulate the simulation for 5 minutes, and make observations as to how it compares and contrasts with the previous simulation. Engage in class discussion to share observations.
Key points to emphasize:
- this simulation models the components on a microscopic level
- the model represents the same algae, but on a microscopic level, it represents algal cells
- a new component has been added: orange patches (bacteria- don’t tell the students the orange patches are bacteria. Encourage them to use the hypermedia to find out.)
See Teacher Notes above for key ideas to emphasize about NetLogo simulations in general.
c. Distribute Handout 4.2 questions for each group to discuss and then individually write answers, as they continue manipulating the NetLogo simulation. Again, these questions will help to guide and focus the student’s recognition and understanding of the specific behaviors that are occurring and the relationships between the inputs and outputs.
d. Engage in class discussion to share responses to the questions. Particularly, visit the questions that had the least consensus within each group. Create a common list of statements/conclusions that can be made based on the results of the simulation. Add unanswered questions to the list.
This is the probable stopping point for the 2nd period
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3) OPTIONAL: Microscopic Investigations (one 45-minute period)
a. In groups of 2-4, have students observe algal cells and bacteria through a microscope. Specimens can be either purchased from a lab company or collected from local ponds. You may use a formal lab worksheet, or have students draw and record observations in a Journal. Books and websites can be supplied for students to get help in identification of the specimens and finding out about their natural history.
b. Following observations, discuss similarities and differences between the specimens. Clarify whether they are living organisms or not. What are their needs and behaviors? What is their food source? Are they autotrophic or heterotrophic? How are they classified?
c. Time permitting, students may return to the microscopic NetLogo simulation to continue to manipulate the components and enhance understanding given the new information retrieved from specimen observation.
This is a good stopping point for the 3rd period
4) Benchmark Lesson on Photosynthesis and Respiration
a. Recap-warm up: Class should discuss their observations and reach a consensus on what conclusions they can draw from their observations of the simulation data and the actual specimens.
· Recall/emphasize that in the simulation, as dead matter increased, O2 decreased enough to cause death of the fish. There were also orange patches that appeared as the dead matter mass increased. Some students may have figured out that those orange patches are bacteria.
· Discuss that these gases are byproducts of cell processes, and since both the algae and fish are composed of cells, we need to look at these processes in more detail.
b. Returning to the Ecomodeler tool to help understand the relationship between the process of photosynthesis and respiration. To gather what they already know, have them create a new PMC2E model that shows the two processes, then share ideas as a class creating a class model.
c. Next have students consult any sections of the hypermedia that provide more detailed information about photosynthesis and respiration. New information should be added or used to revise the PMC2E model.
d. As a brief benchmark lecture, the teacher can then provide accurate information about each of the processes, clearing up any misunderstandings. A class consensus model should be finalized.
e. Some type of formative assessment can be included at this point or the following period: an exit card, a mini-quiz, a printout of model for each student with written explanation.
f. OPTIONAL: Various 1-period labs could be performed to provide evidence of the gases being given off (i.e. plants also give off CO2 through the process of respiration).
This is a good stopping point for the 4th period
5) Ecomodeler Model Revisions
a. Recap-warm-up: Recall the processes of photosynthesis and respiration and and their importance in the aquatic ecosystem.
b. Students will now revise their PMC2E models explain the case of the fish kill. They should use the data and information that they have gathered through simulations, hypermedia, and specimen observations to make and support their revisions. Important: As the students make revisions, have them record in the “Notes” section of Ecomodeler what changes they made to their models and what evidence caused them to make those changes. In the same “Notes” section, the students should also write a list of questions that they still need answered to complete their models.
Note: At this point there will still be some variation among student models; however, all models could include the idea that if there is too much nutrient input, the algal population rises rapidly and crashes, when the algae population crashes, the bacteria population increases rapidly because they decompose the dead algae, and the dissolved oxygen decreases rapidly because bacteria use it, causing the fish to die.
c. The teacher should print a copy of the notes page and Ecomodeler model for each group. Each group should then use a colored writing utensil to annotate their model to include the evidence that they used to decide on each component, mechanism, or phenomenon. Students can do this by drawing an arrow to the component, mechanism, or phenomenon and then writing a note as to what evidence cause them to decide on that component, mechanism, or phenomenon.
d. Groups will now exchange models with another group, who will use the established model criteria to critique each other’s models. Students should give a score from 1 to 10 for each model criteria and a justification for each score.
e. Within the groups, students will revisit the “model criteria” (that were posted at the beginning of the Unit) and discuss any changes they think should be made. As a class, guide the students to reach a consensus on a revised set of model criteria.
Note: At this stage they may remove criteria like labeling as they should be doing that automatically. They can add criteria like account for ALL evidence, and provide mechanism (use more scientific language and add nuance to the criteria) or omit irrelevant details. The changes here do not have to be very large, if the criteria they started out with are relatively complete. The goal here is to add clarification and accuracy.
This is a good stopping point for the 5th period
f. Next, the class will construct a consensus SBF model using all their information to date and making sure the class model fits all the model criteria. The teacher should draw this model on the board and facilitate a discussion about what should be included and how, and what should not be included. The criteria can be used to help students decide what to include and what not to include. Make sure this “consensus class model” fits all the updated model criteria that were agreed upon by the class.
Note: As the classroom consensus model is created, emphasize that the students should not feel that their model must match it. A conversation can ensue regarding how scientists often have different hypotheses and models may look different, yet have the same overarching ideas represented. Each group may have details that will not be agreed upon to place in the classroom consensus model. These details can be noted by using different colors to show less agreed upon elements of the model and reflect this natural level of uncertainty.
g. At the end of consensus model discussions, students will still be left with the open questions of (1) What are these plant nutrients and where do they come from and (2) do these plant nutrients have anything to do with the nitrates that were in the pond data in Lesson 3?
6) Aquarium Design Assessment (20 minutes)
a. Distribute photocopies Handout 3.2 Aquarium Design Assessment that each student completed during Lesson 3
b. Tell the students that will now apply what they have learned from the pond data to revise their diagram showing their design for a healthy aquarium. Remind the students that they will be assessed based on the class model criteria and how well they incorporated the information from the pond data, hypermedia, and NetLogo simulations. The students should revise their drawings in colored pen.
c. This design assessment should be completed silently and individually
Note: In Lesson 5, the students will be revising their aquarium designs again, so make sure to photocopy them before grading
Assessment
This lesson contains both class discussion and group work components and is therefore conversation-based. Students should be assessed based on their participation during class discussion, as well as during group work. The teacher can individually assess the optional warm up and homework activities, if desired. He/She can also use the NetLogo Simulation worksheet questions and the Microscopic Investigation lab observations as an assessment. Checking that revisions to their SBF models have been made and appropriate reasoning is explained in their notes is an important formative assessment.
The Aquarium Design Assessment can be assessed using a model criteria rubric, which will have to be created by the teacher based on the model criteria that the class has agreed on. Resource 3.2 shows a model criteria rubric that was created by a teacher working on another educational research project. This rubric can be modified to include the model criteria that the class has agreed on.
Lesson 5 – Replicating Eutrophication in an Aquarium & Estuary Solutions
Overview
In Lesson 4, students manipulated two carbon/oxygen NetLogo simulations to try to determine what factors might be causing the decrease in dissolved oxygen observed in the pond data. The first simulation showed the phenomenon at the macroscopic level, and the second simulation focused on the functions and behaviors of the structures at the microscopic level. Using this new information, students revised their models from Ecomodeler, and recorded reasons for their changes. At this point students should realize that bacteria consuming the dead algae are using up all the oxygen and depleting the water.
In Lesson 5, students will add fertilizer to small containers in order to simulate the conditions they hypothesize led to the fish kill. This will help them determine the relationship between fertilizer and nitrate level and the role nitrate has in the plant populations of an aquatic system. Left with the question of how nitrate levels increase in natural ecosystems, the class views an eutrophication animation, followed by discussion of possible natural sources of nitrates.
Next students will investigate possible solutions for a eutrophic pond. The investigations can be used as assessment for understanding and mastery of the content material covered in this unit.
Objectives Modeling
- Students will be able to evaluate alternative models of processes within an ecosystem
- Students will be able to develop criteria for model evaluation
- Students will emphasize the importance of evidence when evaluating models and also use evidence to construct their models
· Students will be able to explain the relationships between components of an aquatic ecosystem and their effects on populations
· Students will be able to identify the role of nitrogen in an aquatic system
· Students will demonstrate their understanding of key ecosystem concepts through a well supported argument supporting specific solutions to an ecosystem problem.
Relevant Student Assumptions By this point, students are expected to recognize the major components of a natural aquatic system, living and non-living. They should also have a good understanding of how the levels of certain dissolved substances, such as CO2 and O2, affect the quality of the water to the point of being detrimental to populations.
Time approximately 3 forty minute periods
Materials and Preparation ·
1 computer for every group (2-4 students) with Ecomodeler
· Projector for showing the eutrophication experiment picture and eutrophication simulation
· Photocopies of Handout 3.2 Aquarium Design Assessment as revised in Lesson 4
· Computer File of Resource 5.2 Eutrophication Animation Video
· Web address for the eutrophication simulation: http://new.coolclassroom.org/adventures/explore/plume/39
· 1 copy of Handout 6.1 solution proposal per student
· Aeration system, copper algaecide, blue sapphire dye, barley straw, and/or net to implement the chosen solution in the classroom aquarium.
Activities 1) You have been given 20 dirt containers several months prior.
Steps:
(i) You have 20 dirt containers.
(ii) Fill pond water in 12 of these containers.
(iii) In 9 containers add ½ teaspoon 20:20:20 fertilizer.
(iv) Leave these for several months.
(v) About 2 weeks prior to teaching this unit, add the following to the containers that have fertilizers: Barley straw to 1, Copperalgacide to 1, Aerator to 1, Dye color to 1 and put 1 in the refrigerator.
2) Recall Discussion (5 minutes)
a. Recall the ideas from the last lesson. The class concluded that adding nutrients to a pond leads to an increase in algal mass and when those algae died, the decomposing bacteria use up too much oxygen, causing the fish to die. Ask the students what they think (in real life) corresponds to plant nutrients; i.e. what might I add to make a plant grow better? They should come to the conclusion that somehow fertilizer got into the pond. The teacher will then tell the students that they are going to eutrophy their classroom tank to see the effects of eutrophication in a biological system.
3) Whole class discussion of Aquarium Data (15 minutes)
a. The students should discuss the aquarium water quality data that has been collected over the course of the unit. Sample data is available in Resource 5.1. The students should conclude that when the fertilizer was added, the nitrate level increased. They may also notice the levels of ammonia and nitrate varied when the tank was first set up. At the teacher’s discretion, the class may briefly discuss the evidence of the nitrogen cycle that is visible in the aquarium data. Optional concepts to discuss include:
· As ammonia increases, it begins to get converted to nitrite, then nitrate.
· There are organisms (bacteria) that facilitate that conversion of nitrogen between different forms.
· The final form of nitrogen (nitrate) is used by plants such as algae for growth.
4) Pond Hypermedia (10 min)- The teacher should ask students to look at pond hypermedia with the goal of trying to identify the connection between nitrates (a form of nitrogen) and their class consensus model of this fish kill. The students should come to the conclusion that nitrates are normally a limited resource that keeps algal populations small. So, when nitrates are added, algae population increase dramatically. Optional: Teachers can use the nitrification simulation as well.
5) Eutrophication Experiment Picture (5 min) – to