6th Grade Strand 4: Great Salt Lake Ecosystem

Transcription

1 Curriculum written by Megan Black in partnership with The Great Salt Lake Institute at Westminster College. 6th Grade Strand 4: Great Salt Lake Ecosystem Lesson Description: In the following lesson students will use the Great Salt Lake ecosystem to explore food webs and how changes in living and nonliving factors affect populations in an ecosystem. Standard(s): Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem. Emphasize food webs and the role of producers, consumers, and decomposers in various ecosystems. Examples could include Utah ecosystems such as mountains, Great Salt Lake, wetlands, and deserts Construct an argument supported by evidence that the stability of populations is affected by changes to an ecosystem. Emphasize how changes to living and nonliving components in an ecosystem affect populations in that ecosystem. Examples could include Utah ecosystems such as mountains, Great Salt Lake, wetlands, and deserts. Practice(s) Describe how students are engaged in one or two practices. Develop and/or revise a model to show the relationships among variables. Construct an argument supported by evidence and scientific reasoning to support or refute an explanation. Crosscutting Concept(s) Explain how crosscutting concept(s) provide a lens for the students Stability and Change Small changes in one part of a system might cause large changes in another part. Energy and Matter Energy may take different forms (e.g. energy in fields, thermal energy, energy of motion). The transfer of energy can be tracked as energy flows through a natural system. Disciplinary Core Idea(s) State the big ideas students will use to explain the phenomenon. Food webs are models that demonstrate how matter and energy is transferred between producers, consumers, and decomposers as the three groups interact within an ecosystem. Transfers of matter into and out of the physical environment occur at every level. Decomposers recycle nutrients from dead plant or animal matter back to the soil in terrestrial environments or to the water in aquatic environments. The atoms that make up the organisms in an ecosystem are cycled repeatedly between the living and nonliving parts of the ecosystem. Ecosystems are dynamic in nature; their characteristics can vary over time. Disruptions to any physical or biological component of an ecosystem can lead to shifts in all its populations.

2 Lesson Time Frame This lesson will take several class periods. Suggested scheduling is as follows. Day 1 & 2 - Engage with images of Great Salt Lake and Explore with GSL ecosystem stations Day 3 & 4 - Explain 1 with GSL food web Day 5 & 6 - Elaborate 1 with brine shrimp investigation Day 7 - Elaborate 2 with salinity changes argument Day 8 - Evaluate with GSL letter Lesson Materials Per Class: Salt water with 3%, 15%, and 30% salinity & droppers GSL Station Cards & access to Internet Per Student: Food web organism cards Food web reading #1 Food web reading #2 Brine Shrimp Experiment: Per Class: 1 tsp hydrated brine shrimp cysts (place cysts in freshwater for 2 hours before investigation)* Non-iodized salt Water 5-6 beakers Digital kitchen scale Per Group: 1 petri dish 1 paper towel 1 pipette Hand lens (ideally with 10X magnification) * Brine shrimp cysts can be purchased locally from Great Salt Lake Artemia (801) or from science supply companies such as Carolina Biological.

3 Great Salt Lake Ecosystem Storyline Driving Question / Anchoring Phenomenon Does anything live in Great Salt Lake? Phenomenon-driven question* Engage: Why is Great Salt Lake so unique? Explore: What do we find at Great Salt Lake? Explain: How do the organisms at Great Salt Lake interact? Elaborate 1: How does the salinity level of the lake affect the hatch rate of brine shrimp? Elaborate 2: How does the salinity level of the lake affect other populations? How students will make sense of phenomenon through practices Asking questions about Great Salt Lake, including the environment and what lives in its waters. Obtain information about the Great Salt Lake ecosystem. Develop a model of a food web for the Great Salt Lake ecosystem. Plan and conduct an investigation to show relationship between salinity levels and hatch rate for brine shrimp. Construct an argument based on evidence for how a change in lake salinity affects the Great Salt Lake food web. Conceptual understanding(s) Great Salt Lake is an extreme environment because it is a salt lake, with salinity concentrations that are 5 to 10 times higher than the ocean. An ecosystem describes both the living and nonliving factors in a particular location. The Great Salt Lake ecosystem includes salt water surrounded by wetlands and mountains as well as organisms that live in the lake and the shoreline. A food web describes interactions between organisms in an ecosystem. It shows how energy flows from the sun to producers, consumers, and decomposers. Environmental conditions affect whether or not brine shrimp cysts will hatch. Brine shrimp will not hatch in water with very low or very high salinity. Changes to the nonliving components of an ecosystem can affect many of the populations of organisms living in that ecosystem. Evaluate: Does anything live in Great Salt Lake? Construct an explanation for why Great Salt Lake is a thriving environment that supports many different types of organisms. Great Salt Lake is a unique environment. Energy and matter flows from organisms in the lake, such as algae, microbes, and brine shrimp, to organisms on land, such as brine flies and birds. Changes in nonliving factors in the lake, such as salinity, affect the organisms that live in this ecosystem. * Note: These questions may need to be modified based on the questions students develop throughout the unit.

4 Great Salt Lake Ecosystem 5E Lesson Engage: Why is Great Salt Lake so unique? Provide students with images of Great Salt Lake, both aerial photos, and photos of the landscape surrounding the lake (available in lesson folder). Have students share experiences that they have with the lake, observations of the lake based on the provided images, and questions they have about the lake. If students do not mention it, explain that Great Salt Lake is like an inland sea - its water is salty. Invite students to taste Great Salt Lake water and compare it to ocean water. To do this place water of varying salinities in dropper bottles or cups with eye droppers in them. For ocean water, make a 3% solution (3 g salt / 100 ml of water). For south arm water, make a 15% solution (15 g salt / 100 ml of water). For north arm water, make a 30% solution (30 g salt / 100 ml of water). Let students place a drop of each type of water on their fingers and taste the water. This works best if students taste the ocean water, lowest concentration, first. Tell students that we know many organisms live in the ocean, but do you think organisms can survive in waters with salinity that is as high as 300 ppt or 30% salinity? Have students share their reasoning for whether they think organisms live in Great Salt Lake or do not live there. Then share the driving question for the lesson: Does anything live in Great Salt Lake? (Teacher note: If you have access to a refractometer, students can use the tool to measure the salinity of the water you have provided in parts per thousand (ppt). Have students place a drop of the ocean water on the refractometer. If you have made a 3% solution, which is 3 parts per 100, the refractometer should read about 30 ppt. Some refractometers only go up to about 100 ppt. If that is the case, students can use a one to one dilution (one drop of fresh water and one drop of saltwater) to figure out the salinity of the north arm water. Have students dilute the water until they can read it on the refractometer and then multiply the reading by the number of times they diluted the water. Explore: What do we find at Great Salt Lake? The goal of this learning activity is for students to begin to recognize both the nonliving and living components of the Great Salt Lake ecosystem. Ideally, you would bring students to the lake to explore this question, but if that is not an option, use images, videos, and objects to bring the lake to the students. Tell students that they will be learning about the Great Salt Lake ecosystem by visiting a series of stations. After gathering information from the stations, they will be using what they learned to create a model that shows the important components of the Great Salt Lake ecosystem. Set up your classroom as a Great Salt Lake Museum. Below are suggestions for the stations. In the lesson folder are stations cards. 1. Brine Shrimp Station: Hatch brine shrimp in a jar of 5% salt water (5 g of salt to 100 ml of water). It should take about 24 to hatch the shrimp and they should live for about 24 hours after hatching. To extend their life you can add a sprinkle of crushed algae pellets (from a pet store) to the water each day. Alternately, show a video of brine shrimp swimming: 2. Salinity Station: Provide students with maps of GSL. Have the students identify where water enters and leaves the lake. Then have students read about where the salt in the lake comes from. Finally, let students explore the relationship between water level and salinity:

5 3. Climate Station: Print a copy of the temperature and precipitation graph from the GSL stations packet in the lesson folder. The graphs show the average temperature and % of precipitation that falls each month on Antelope Island. Temperature and precipitation varies by location, but will give students a basic idea that climate is an important non-living factor in describing an ecosystem. 4. Brine Fly Station: Have the following video ready for students to view: The station card lets students know that the dark wave like movements in the video are not water, but rather swarms of brine flies along the shoreline. 5. Bird Station: GSL is an important stop for migratory birds. The wetlands on the edge of the lake provide an important source of food for the birds. Eared grebes feed on thousands of brine shrimp each day. At this station students observe some of the birds found at GSL and view a radar video showing the huge number of birds that migrate to the lake 6. Landscape Station: At this station, students view images of the lake to identify the mountains and salt flats that define the lake s shoreline. 7. Microbe Station: Have students view aerial photos of GSL. From these photos they should see that the north arm has a pinkish color and the south arm of the lake has a green color. Then have students watch a timelapse video of the lake: (Note: This video flashes rapidly, and may bother students sensitive to flashing light.) A short reading will teach students that the pink color comes from salt tolerant microbes that live in the north arm. The green color comes from phytoplankton that are able to live in the less saline waters of the south arm. 8. Optional (station card not included): If you visit the lake on your own, or with students, you can make winogradsky columns. These are basically an ecosystem in a jar made by filling a large jar ⅓ full of wet sediment from the lake bottom, ⅓ full of lake water, and leaving the last ⅓ with only air. Place a lid on the jar and keep it in a windowsill. Full directions for making winogradsky columns is included in the lesson folder. Have small groups of students spend about 4 to 5 minutes at each station. Give students time to view images, read articles, and watch videos. At each station have students record one or two key points from the station. These key points should focus on what the station tells us about Great Salt Lake. After groups have visited all of the stations, invite the class to share some of the things they observed. Record these observations on the board as terms and phrases that describe Great Salt Lake. Then invite small groups to organize these phrases by grouping them. Ideally students will group the information by living and nonliving factors, but they may find other organizational schemes as well. Give students a chance to share how they organized the phrases and then share the idea that ecosystems can be described by the living and nonliving factors that interact in an area. As a class identify the key living and nonliving components of the Great Salt Lake ecosystem. The chart below provides an example of components of the GSL ecosystem.

6 Great Salt Lake Ecosystem Living Components Nonliving Components Brine shrimp Saltwater (south arm - 15% & north arm - 28%) Brine flies 15 inches of rain annually Many different species of birds Average temperature range of 22 F - 91 F Pink microbes in north arm Green microbes in south arm Surrounded by wetlands and mountains Freshwater from mountain rivers Evaporation only outlet for lake water Check for student understanding by asking students to describe the Great Salt Lake ecosystem in a few sentences. Students should use both living and nonliving components to describe the ecosystem. Note: If students are interested in learning more about why GSL is so salty, they can listen to the first five minutes of the Science Friday podcast: Great Salt Lake is No Dead Sea - Explain 1: How do the organisms at Great Salt Lake interact? In this section of the lesson students will develop and continually revise a model to show how energy flows and matter cycles between organisms living at Great Salt Lake. The organism cards and articles are available in the lesson folder in the document called food web models. The initial model students develop will be a kinesthetic model. For this model, divide the class into groups of 6 students. Pass out the organism cards (available in lesson folder). For groups without 6 students, one student can take more than one card. These initial cards only describe where the organisms are found. Have students arrange the cards to show how they think the organisms may interact in the environment. Then have each group share some of their interactions with the class. Use this initial modeling activity to discuss how understanding feeding relationships in an ecosystem is important to understanding how changes in populations affect entire ecosystems. Provide students with the same set of organism cards. Have the students cut out the cards, or list the names of the organisms on sticky notes, and then arrange the cards to show feeding relationships. At this point in the activity, you may want to tell students that to show feeding relationships they can use arrows. The arrows show the direction of energy flow, meaning that the arrow points from the prey to the predator. Let students create a revised model of interactions based on the earlier kinesthetic model and information on representing feeding relationships with arrows. Students could develop this model on a 11 X 17 piece of paper or a small whiteboard. While students can work together and discuss ideas, have each student create his/her own model. This model will act as students initial model. They will gather

7 more information to improve the model by reading two articles about Great Salt Lake food webs. In the next part of the activity students will use a short reading about the Great Salt Lake ecosystem to further revise their food web model. Have partners read the article and then make revisions to their models. You could have students use a close read with the article, or underline key phrases that they are useful for revising their model. As students revise their work, encourage them to describe the changes that they have made and to explain why they made these revisions after gaining more information. Students may need to move organisms to show different feeding relationships. Students may add high level consumers such as coyotes and bald eagles. In this second revision of the model, they should also identify the producers consumers, and decomposers in their food web. Next, provide students with the second reading, which describes how energy flows through the food web as it relates to the GSL food web. After reading this, discuss as a class, why only 5% - 20% of the available energy moves to the next level (because most of the available energy is used by the organisms to move and grow before they are eaten). Ask students why there are so many more brine shrimp than eared grebes at GSL (because each eared grebe needs to eat many brine shrimp each day in order to gain enough energy to migrate after stopping at GSL. In fact scientists estimate that adult eared grebes need to consume 25,000 30,000 brine shrimp per day to build up fat stores for migration!). Have students revise their model one more time. Be sure that students add the Sun as the source of energy for the food web to their model. And add information, either through drawings or captions to explain how energy moves from one level to the next in a food web. After these iterations students should have a revised model of the Great Salt Lake food web that includes information about the organisms involved in the GSL food web, identifies producers, consumers, and decomposers, shows the feeding relationships between these organisms, and describes how energy moves through the ecosystem. Adding one more step to this process will help students to refine their ideas and models. Have students create a final model that represents a final draft of the model they have been adding to throughout this section of the lesson. As students develop a final model, encourage them to add additional information to their model through drawings or captions. Check for student understanding by reviewing students final models. A sample student model and rubric for the GSL food web model is provided below. Student Response

8 Rubric Criteria GSL Food Web Model Food web shows relationships, however relationships may not be accurate or organisms may be missing. Organisms are named. Model does not state or define the roles that organisms play in the food web. Food web model shows most of the feeding relationships. Organisms are named, some are labeled with their role in the food web. Model defines producer, consumer, and decomposer. The flow of energy and/or cycling of matter is not explained in the model. Food web model accurately shows feeding relationships. Organisms are labeled with their role in the food web. Model explains roles of the sun, producers, consumers, and decomposers in the flow of energy and cycling of matter in the ecosystem. Model states that energy is lost as it moves through food web. Food web model accurately shows all feeding relationships including decomposers. Organisms are labeled with their role and level (primary, secondary, etc.) in the food web. Model explains roles of the sun, producers, consumers, and decomposers in the flow of energy and cycling of matter in the ecosystem. Model explains how available energy and biomass changes at different levels of the food web. Elaborate 1: How does the salinity of the lake affect brine shrimp? In the first elaborate section of the lesson, students will conduct an investigation to determine how salinity affects the hatch rate of brine shrimp cysts. This investigation is based on the Hatch-A-Cyst activity developed by the Great Salt Lake Institute. For a full description of the investigation visit the Extreme Environments: Great Salt Lake teacher page: Have students return to their models of the Great Salt Lake food web. Ask them which populations of organisms would be directly affected by changing salinity levels in the lake. Students may recognize

9 that brine shrimp, brine fly larvae, phytoplankton, and cyanobacteria could all be directly affected by changing salinity levels. Then ask students what would cause the salinity level of the lake to change? Help students to recognize that if more water evaporates than comes into the lake the salinity will be higher. If more water comes into the lake than evaporates the salinity level will be lower. Tell the students that in this investigation they will be determining how changing salinity levels affect the hatch rate of brine shrimp cysts. To help students understand what a brine shrimp cyst is, review the following interactive: Before you begin the experiment, you will need to hydrate the cysts. Do this by placing cysts in a beaker of room temperature freshwater for about 2 hours. If your tap water has a lot of chlorine, use bottled or distilled water from the store. Students will use this beaker of hydrated cysts to get cysts for their investigation. Guide students in setting up the investigation by modeling how to set up the control. For this experiment, the control will be water with a salinity of 3%. Make the 3% salinity water by measuring 3 grams of salt into a beaker and then adding 100 ml of fresh water. Take a paper towel piece and fold it three or four times to make a small square that will fit in the bottom of a petri dish. Using a pipette, gently swirl the hydrated cysts. Then use the pipette to pull a sample of the cysts from the bottom of the beaker. The cysts floating on top of the beaker are empty cyst cases; you do not want these. Squeeze these cysts on the paper towel. You are aiming for 30 to 50 cysts on your towel; this is a very small amount! Then use another pipette to soak the paper towel with 3% solution. Add enough water to soak the towel, but not for the cysts to float away. Label the top of the petri dish with 3% solution and gently close the petri dish. Use a hand lens to count the number of cysts on your paper towel. Record this number. Have student groups set up their own experiments using different water salinities, up to 30% salinity. One group, or the teacher, should set up a freshwater sample. The materials needed per group include: 1 paper towel, 1 petri dish, access to hydrated cysts, beaker, water, salt, access to scale, masking tape, hand lens. Be sure students record information in their science notebooks, including a question, diagram or written procedures, and their initial cyst count. The cysts should hatch within hours. Return the next day and have students count the number of hatched cysts, see image. Again, students will need to use a hand lens. Have students calculate the percentage of cysts that hatched and share their data with the class. Using the entire class data, students should be able to construct a simple C-E-R (claim - evidence - reasoning) conclusion about the ideal salinity range for brine shrimp cysts. The claim should answer the question, how does the salinity level affect brine shrimp hatch rates? The evidence should be based on the class data. Students reasoning could return to what they know about brine shrimp from either the interactive brine shrimp life cycle: or from the information they learned while developing the GSL food web. Check for student understanding by reading students C-E-R explanations. Students claims should be supported by data gathered in the class experiment. Ideally, you will find that the brine shrimp cysts hatch in salinities ranging from 3% - 10%. The reason the shrimp hatch at those salinities is that they hatch in the spring when freshwater enters the lake and floats on top of the denser salt water. The cysts hatch in the layer between the fresh and saltwater. Students can find this information in Reading #1 for the Food Web activity. The class results may show a slightly different range for hatching cysts, which is fine. It is more important to assess students ability to support a claim using

10 evidence and to use reasoning to try to explain why the evidence supports the claim. Elaborate 2: How does the salinity level of the lake affect other populations? The second elaborate section of this lesson focuses on stability and change. Students will use what they have learned throughout the lesson to construct an argument, based on evidence, for what might happen to organisms at Great Salt Lake during years with heavy flooding and during droughts. You could choose to have small groups of students work on arguments for both flooded and drought conditions, or divide the class in half, with one half working on floods, and other on droughts. Provide the following prompts to students: Use the information in the prompts and data table to construct an argument for: How would a flood or drought affect the organisms in the Great Salt Lake ecosystem? Flood Scenario: Above average snowfall during the winter has led to heavy spring runoff. Great Salt Lake receives much more freshwater than usual. The salinity in the south arm of the lake is about 8%, less than the usual 15%. Drought Scenario: Several years of droughts have caused the lake level to drop by 10 feet. Great Salt Lake receives much less freshwater than usual. Also, warm temperatures during the summer increase evaporation. The salinity in the south arm of the lake is about 20%, more than the usual 15%. Organism Estimated Salinity Tolerance Free Floating Microbes / Phytoplankton 6% - 15% Free Floating Microbes / Archaea 20% - 30%

11 Bottom Dwelling Microbes / Cyanobacteria Less than 20% Brine Fly Larvae Can tolerate high salinity, but food dies at levels greater than 20% Brine Shrimp Cysts 3% - 10% Adult Brine Shrimp 10% - 30% Ask students to construct an argument for the following question: What would happen to two or three organisms in the Great Salt Lake ecosystem if there were a drought or if there were a flood? Have students construct an argument by using the C-E-R framework. Students should use their claim to describe what will happen to two or three organisms in the food web if the salinity of the lake changes. They should use evidence from the data table above to support their claim. For their reasoning, encourage students to explain why the evidence supports their claim by using the GSL food web to explain how changes to one population will affect another population. Have students to share their C-E-R arguments, either through a whole class discussion, or by having small groups of students come together to discuss their claims, evidence, and reasoning. After sharing, provide students time to revise their C-E-R argument. A sample student response and rubric for a written argument is provided below: Student Response If drought conditions caused the salinity in the south arm of Great Salt Lake to reach 20% populations of bottom dwelling microbes, brine flies and shorebirds would decrease. Bottom dwelling microbes cannot tolerate salinity levels that are above 20%. With fewer microbes, the brine fly larvae will not have enough to eat. These larvae will not become brine flies. With fewer brine flies, there will be less food available for shorebirds. Shorebirds will either starve or need to move to new locations to search for food.

12 Rubric Criteria Flood or Drought Scenario Written Argument The claim does not state what would happen in drought or flood conditions. Evidence from the data chart is not used to support the claim. Reasoning is insufficient and does not connect the claim and evidence. The claim states what would happen in drought or flood conditions, but is not clearly stated or only discusses 1 organism. Evidence is based on data from the chart, but does not clearly support the claim. Reasoning does not clearly connect the claim and evidence, or does not use an understanding of the GSL food web. The claim clearly states what would happen in drought or flooding conditions to at least 2 organisms. Evidence to support the claim is based on data from the chart. Reasoning connects the claim and evidence by using an understanding of the GSL food web. The claim clearly states what would happen in drought or flooding conditions to at least 3 organisms, including an organism that is not listed in the data chart. Evidence to support the claim is based on data from the chart. Reasoning is thorough and connects the claim and evidence by using an understanding of the GSL food web. Evaluate: Does anything live in Great Salt Lake? The evaluate section of the lesson gives students a chance to pull together what they have learned about the GSL ecosystem in an informal letter. From assessment perspective this allows the teacher to see what students have learned, without prompting them for specific information. Encourage students to add examples and details from their science notebooks as they write a letter based on the following prompt. You are a journalist for a local paper. In one of your columns, you answer readers questions about the environment. A reader of your column writes the following: I flew over Great Salt Lake when I was returning from vacation. All I could see was a big body of water surrounded by brown hills. I have heard people call Great Salt Lake a dead sea, and from what I saw there didn t seem to be very much life in or around the lake. Is Great Salt Lake a dead sea? Sincerely, Curious About the Lake Based on what you now know about Great Salt Lake write a letter response to your reader. Would you describe Great Salt Lake as a dead sea? Why or why not? In your response be sure to include details about the nonliving and living components of the lake ecosystem, the interactions that occur in this ecosystem and how changes affect the ecosystem.

13 Student Response Dear Curious About the Lake, Great Salt Lake my look like a dead sea from the air, however the Great Salt Lake ecosystem supports many plants and animals. Great Salt Lake s name comes from its salty waters. In the south arm of the lake the salinity is about 15%; in the north arm the salinity is almost 30%. For comparison, the salinity of the ocean is about 3%. The reason Great Salt Lake has such high salinity is because it has no outlets. Freshwater carrying minerals enters the lake from spring snowmelt. Water leaves the lake through evaporation. The minerals area left behind, making the lake a salt lake. Since Great Salt Lake is so salty it cannot support fish. However, many small plants and animals live in the water including phytoplankton, microbes, brine fly larvae, and brine shrimp. These organisms are important in the Great Salt Lake food web. They provide shorebirds with food. Phytoplankton use energy from the Sun to produce food, brine flies and brine shrimp consume phytoplankton and other microorganisms living in the lake for energy. Then the millions of shorebirds that migrate through the area consume the brine shrimp and brine flies for energy. Other microbes in the lake are decomposers. They break down dead plants and animals and return the nutrients to the lake environment. Environmental changes can have a large impact on the organisms living in and around Great Salt Lake. For example, during a drought, less freshwater makes it to the lake. With less freshwater, the salinity levels increase. Brine shrimp cysts cannot hatch if the salinity is too high. Without brine shrimp there would not be enough food for the many migratory birds that visit Great Salt Lake. Birds that visited the lake would either need to leave to search for food, or may die because they do not have enough food reserves to complete their long migration. Great Salt Lake is no dead sea. It is an important ecosystem for the organisms that live in the lake and on the land surrounding the lake. Sincerely, A 6th Grade Science Student

14 Rubric Criteria Letter Describing the Great Salt Lake ecosystem Does not describe the nonliving components of the GSL ecosystem. Describes the nonliving components of the GSL ecosystem. Describes the nonliving components of the GSL ecosystem. Explains in detail the GSL environment, including why GSL is a salt lake. Names two or three organisms found in and around the lake. Does not name a change that would affect the stability of the ecosystem. Names the organisms found in and around the lake. Describes one or two interactions between these organisms (i.e. what eats what). Names a change that would affect the stability of the ecosystem, does not use an example to support an explanation for the change. Describes the organisms found in and around the lake and emphasizes the roles (producer, consumer, and decomposer) the organisms play in the GSL food web. Explains how changes to the ecosystem affect the stability of the ecosystem, uses a basic example to support the explanation. Describes the organisms found in and around the lake. Provides a clear explanation for how energy flows and matter cycles between these organisms and the environment. Explains how changes to the ecosystem affect the stability of the ecosystem, uses relevant examples that include changes to nonliving and living components to support the explanation.