Unit: Ecological networks Part 1- Network Interactions
Lesson Title: Lesson 8- Revisiting the GSL network
Important Note: Activity 2 is very important to link the data from the halobacteria investigation back to the GSL ecosystem and network concepts from the entire unit. Depending upon how foodwebs, matter cycles, and ecosystem concepts were taught, teachers may choose to do the entire activities or only activity 2 and certain parts of Activity 1.
ACTIVITY 1 (OPTIONAL): Creating a Food Web Network of the Great Salt Lake Ecosystem
Say to the students “Now that we have explored extremophiles and specifically investigated the effect of salinity on the growth of Halobacterium we will now focus on the entire Great Salt Lake ecosystem. We will focus on the abiotic and biotic factors within the network and exploring how humans have impacted the entire system."
- For a class of 30, divide students into 6 groups with 5 students each.
- The teacher should ask students to recall the cell phone activity and review what a network is, what the components of a network are, and why networks are useful visualization tools. Explain networks are really important to visualizing systems in Biology and today they will be creating a biological network, a food web!
- Review with students about food webs. Distribute the student activity sheet (GSLfoodwebworksheet.doc) and read through the introduction as a class. Have the students complete the pre-activity questions individually of with a small group.
- Read through the first two procedure steps as a class (below).
- You will be working with your assigned group to learn about some of the organisms that live in the Great Salt Lake.
- As a group you will need to answer the following four questions about each of your assigned organisms. Each group member must write down the answers to the questions in the table provided below.
- On the Smartboard or overhead using the table from student sheet 2b, model one organism with which students are familiar such as a fox.
Ask the students what the fox eats. The students can use the food web in the example to determine that a fox eats snakes, raccoons, mice, etc. Ask the students what waste is produced? The students should determine that carbon dioxide is one of the waste products. Ask the students what abiotic or environmental factors the fox needs to survive. Possible student responses may include oxygen, water, sunlight, etc. Finally, ask the students to explain the process by which the fox obtains its energy and whether the fox is a heterotroph or an autotroph? Students should say the fox is a heterotroph because it consumes food and obtains its energy from consuming other organisms.
- Explain that each group will be responsible for researching 2-3 organisms living in the Great Salt Lake. Give the students time (15- 20 minutes) in their groups to research their organism and complete the table provided on the student sheet.
Assign each group 3-4 of the following organisms (you may assign more than one group the same organism):
- Migrating Birds
- Marsh Hawk
- Brine Shrimp
- Brine Flies
- Meadow Vole
- Salt Grasses
- After students have gathered their information, have them number off 1-5. Go over the remainder of the procedures with the class (below).
- Next, you will be assigned to a different group in which you will share your information. Together you will create a food web network showing the relationships existing in this ecosystem. Use circles (nodes) to represent the organisms and any abiotic factors and arrows (edges) to represent the relationship between the organisms. Remember the arrow always points toward the consumer!
- Use your food web to answer the following questions.
Alternative approach to step 7:
- Rather than hand drawing the network you could have students create a network using Cytoscape. Show the students how to use Cytoscape using the prepared PowerPoint.
- Have the students create a sif file and then use this to create a network in Cytoscape.
- Have all the 1’s meet together, all the 2’s meet together, etc to create a food web network and answer the associated questions.
ACTIVITY 2: Salinity Effect on Halobacterium PowerPoint
- Say to students: Now that we have explored the effect of salinity on the growth of Halobacterium and designed a food web network with our Great Salt Lake organisms, we will now use all of this knowledge to explore a detailed PowerPoint simulation of the Great Salt Lake Ecological Network. In this network we will consider how an ecological disturbance could affect an entire ecosystem (both abiotic and biotic factors).
- Start PowerPoint (salinity_effect_on_halobacterium.ppt) Description slides below to conduct a class discussion. Do not rush through the slides, encourage all students to participate. You may want to have printed copies of the effect of salinity on the growth of Halobacterium graphs for students to refer to.
- Slide 1: This is the static network of the GSL. You have discovered a relationship between salinity and Halobacterium growth. We will now see how that relationship will be visualized in the network. Please note: students have data only for effect of salinity on Halobacterium growth and they do not have knowledge about other quantitative relationships. Please be sure to distinguish hypothesis from fact.
- Slide 2: First you started with a salinity of 2.5M –what was the effect on growth of halo?
- Slide 3: Students should observe that Halo did not grow at all
- Slide 4: At a salinity of 3.0M –what was the effect on growth of halo?
- Slide 5: Students should observe that Halo showed moderate growth
- Slide 6: At a salinity of 3.5M –what was the effect on growth of halo?
- Slide 7: Students should observe that Halo grew even better
- Slide 8: At a salinity of 4.0M –what was the effect on growth of halo?
- Slide 9: Students should observe that Halo grew extremely well
- Slide 10: At a salinity of 4.5M –what was the effect on growth of halo?
- Slide 11: As a reminder form lab activities ask the students: What overall observation about Halobacterium growth can we make regarding the different salinities? Observation: Halo growth was less relative to growth at 4.0M; 4.5M is approximately the salinity of the North arm of the lake.
- Slide 12: Great Salt Lake Food networks in North and South Arms
Students Hypothesize about the Great Salt Lake Network in the North arm
- Slide 13: Observation: Halo growth was less relative to growth at 4.0M; 4.5M is approximately the salinity of the North arm of the lake.
Students should HYPOTHESIZE what will happen to rest of the network in the North arm of the lake (remind them of salinity-4.5M). Students can write their hypotheses in journals, or they can be discussed in small groups and then shared with the whole class. Students should draw a sketch of how salinity affects the network.
- Before going to slide 14, ask students which nodes are directly affected by salinity. Students should respond by saying that the algae, brine shrimp, and salt grasses nodes will decrease in size. This hypothesis should be based on the information learned about in the PowerPoint before the Halobacterium lab about how most organisms can not thrive/live in a salt environment.
- Slide 14: Observation: Halo growth was less relative to growth at 4.0M; 4.5M is approximately the salinity of the North arm of the lake. Salt grasses, algae, and brine shrimp population nodes have decreased in size due to the increase in salinity.
- Before going to slide 15 ask students which nodes are indirectly affected by salinity. Students should respond with the migrating bird, meadow vole, and marsh hawk nodes (populations) will decrease because their energy source (brine shrimp and salt grasses) is depleted.
- Slide 15: Observation: Halo growth was less relative to growth at 4.0M; 4.5M is approximately the salinity of the North arm of the lake. Migrating birds and meadow vole populations have decreased because their food source populations have decreased.
- Slide 16: Observation: Halo growth was less relative to growth at 4.0M; 4.5M is approximately the salinity of the North arm of the lake. The Marsh Hawk node has decreased in size because its energy source (meadow voles and migrating birds) is depleted.
Students draw conclusions about how ecological disturbance affected the Great Salt Lake Network in its entirety.
- Show slide 17 and ask students to think about the Great Salt Lake network in its entirety. Thinking back to the lesson objectives ask students what is the ecological disturbance that we are referring to here? (Human impact by building the causeway in the 1952) Ask students to summarize how this ecological disturbance affected the entire ecosystem. Students should either draw the GSL showing how the causeway resulted in different ecological networks for the north and the south arm, or they can write about it in paragraph form.
Ask for students to share their conclusions with the entire class.
- Use slide 18 to support student conclusions about how the building of the causeway resulted in an ecological network in the north arm that is different than the network in the south arm.
- Students’ summary conclusions of how the building of the causeway affected the entire Great Salt Lake Network.
- Oral responses by students during discussion.
Move slowly through the slides and take time to go back and forth between slides for students who may have a difficult time processing the numerous changes within the network diagram.
Have students discuss the benefits and risks for trying to undo this alteration to the Great Salt Lake. Are there any solutions? Should there be a solution?
Have the students explore a problem or situation in their local environment, such as the removal of a dam, in order to describe the process as well as the advantages and disadvantages of using a systems approach to solving the problem.