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BSCS Middle School Science Student Edition levels of organization in the biosphere Life Science Unit: biosphere–the part of Earth that contains life ecosystem–Chesapeake Bay Living Energy community–all organisms in Chesapeake Bay population–all striped bass in Chesapeake Bay organism–striped bass energy energy energy flows to flows to organ system–circulatory systemflows to organ–heart sunflower tissue–muscle pocket mouse bull snake cell Tablecell–blood of Contents large molecule–hemoglobin Chapter 2: Ecosystems and Energy................ LS2-2 molecule–water Engage: Get Out!....................................................................... LS2-4 Explore: Backyard Biology.........................................................LS2-7 Explain: The Web of Life........................................................... LS2-11 Elaborate: Stability and the Web of Life................................... LS2-22 Evaluate: Evaluate: Menu Connections................................... LS2-28 Spanish Vocabulary................................................................. LS2-31 atom–hydrogen LS2-1 BSCS Middle School Science Student Edition Life Science Unit · Living Energy chapter 2: Ecosystems and Energy A re you curious about all the different kinds of living things around you? Dogs, squirrels, trees, butterflies, or maybe even bacteria? All these different living things can be exciting yet overwhelming. But using a few “big ideas” from science can help you start to see patterns in living systems. Some of these patterns relate to energy and matter: (1) energy is not created or destroyed, but instead changes form and (2) the amount of matter that goes into a system is the same as the amount of matter that leaves a system. Two big ideas! In chapter 2, Ecosystems and Energy, you’ll use scientific inquiry and these two powerful ideas to help you understand the living world. You’ll also work on the teamwork skill of making sure that everyone understands. Goals for the Chapter By the end of this chapter, you should be able to n explain how energy transfers in ecosystems affect organisms; n begin to describe how matter cycles in an ecosystem; n summarize the roles different organisms play in an ecosystem; n use food webs to make predictions about changes in ecosystems; and n gather your own data from where you live, contribute your data to a class data set, and develop an explanation of your findings. Fortunately, you have help meeting these goals. Each activity in this chapter gives you experiences to learn about important ideas related to ecosystems and energy. The activities are as follows: Engage—Get Out! Explore—Backyard Biology Explain—The Web of Life Elaborate —Stability and the Web of Life Evaluate—Menu Connections Remember that chapter organizers can help you keep track of where you are in your learning. Look at the chapter organizer every day. LS2-2 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Engage—Get Out! key idea: Finding patterns in the natural world begins with careful observations. Linking Question: How does the mass of animals in an area relate to the mass of plants? Ecosystems and Energy major CONCEPTS • Food webs show the energy relationships in an ecosystem. • Energy pyramids help explain patterns in ecosystems. • Changes to 1 species affect other organisms in a food web. Linking Question: How is my life affected by the web of life? Elaborate—Stability and the Web of Life key idea: Changes in a population affect parts of the web of life. Explore—Backyard Biology key idea: Evidence shows how the mass of plants relates to the mass of animals. Linking Question: How can understanding matter and energy help explain patterns in the world? Evaluate—Menu Connections key idea: Everyday life depends on connections between organisms in the web of life. Explain—The Web of Life Part I: Organizing Life Part II: Matter and Energy in the Web of Life key idea: Food webs track matter and energy in ecosystems. Transfers of energy help explain patterns in the numbers of different kinds of organisms. Linking Question: How can changes in 1 population affect a food chain? LS2-3 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Engage Get Out! How can you start to make sense of the living world? A good place to start is just by looking. In this Engage activity, Get Out!, you’ll make some careful observations of your local area and then some other places in the world. Then you’ll describe the ideas you have that might explain some of the patterns you observe. Many important questions in science got their start with someone simply observing living things. Then the person started to wonder, “How can I explain what I just saw or heard?” These simple and fun steps started the person on the path of scientific inquiry. Start observing! Materials For each student paper clip or sticky note Caution Do not handle any organism you observe, even if you are certain it is harmless. Unnecessary handling may be harmful to the organism and yourself. Process and Procedure 1.Go outside with your classmates. Look around you. In your science notebook, write a brief description of the area. This is a new chapter. Did you start on a new page in your science notebook? Did you label the new chapter? Your description of the area should be specific. Think about the following questions. Are you in a park? Next to a city street? In the country? What time of day is it? What are the weather conditions? Careful observations help you recall what you observed. They also help you reflect on your observations later. LS2-4 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Engage 2.Observe the area for 2 minutes, focusing on observing as many different living things as you can. You may want to make some notes about what you are seeing, but do not let that take too much time out of your 2 minutes. After 2 minutes, sketch and label the organisms you saw. It’s easy to overlook living things that you see all the time. Now is the time to look closely. Make sure to include potted plants, grass in a field, weeds in a parking lot, squirrels in trees, crows perched on a trash can, insects crawling under rocks, and so on. Do not be afraid to dig in the soil! Look at the ground where the plants meet the soil. Each of your drawings should be about a quarter of a page. Put something in each diagram to indicate the size of the organism. 3.Make a quick estimate of the relative number of living plants, animals, and fungi. Use symbols such as greater than (>), much greater than (>>), less than (<), much less than (<<), or equal to (=) to compare the 3 groups. Record your estimates in your science notebook. You may have questions about what counts as an individual. Make sure you write down in your science notebook what you think counts as an individual. Don’t forget that organisms like insects and worms are animals. Also, some plants may lose their leaves during certain parts of the year but are still alive. You may also wonder what counts as fungi. An example of fungi is mushrooms. 4. Return to your classroom. On your own, answer the following questions: Suppose you could collect all the living things in the area. You separate them into plants, animals, and fungi. Which group do you think would have the most matter (or, the most mass)? Why do you think that way? Remember, this is an Engage activity. You’re not expected to know all the right answers. But sharing your best ideas now makes it easier to learn as you go through the chapter. 5.Make a 3-column table. Label the first column “ecosystem.” Label the second column “number of plants compared to the number of animals.” Label the third column “Which group has the most matter?” 6. Look at photos from different ecosystems on Earth. Fill in the table as you see each photo. To fill in the second column, make a quick estimate of the number of individual plants and animals. Is the number of plants greater than (>), less than (<), or equal to (=) the number of animals? Of course there will be animals and plants that are hard to see in the photo. You’ll have to use what you know to make a reasonable guess. To fill in the third column, do the following. Suppose that you collect all the living things in the photo. Which group do you think would have the most matter: plants or animals? Think about weighing each group to determine which you think would have more matter. LS2-5 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Engage 7.Compare your table from Step 5 to your partner’s table. Can you come to a consensus on your answers? A consensus means you both agree. Discuss each row of the table. If you find you had different answers, explain why you chose the answer you did. Then see if you can agree on 1 answer. Reflect and Connect Answer the following questions on your own in your science notebook. As you learned in other chapters, it is important to write down your best ideas during an Engage activity even if you don’t know the complete answer now. Mark this page with a paper clip or sticky note. You will revisit your answers to Questions 3 and 4 later in the chapter. 1.Were the numbers of plants and animals in the different areas (including your local area) similar or different? Explain your answer. 2.You looked at different areas and predicted if animals or plants had the most matter. Was there a pattern in your predictions among these different areas? For example, was one group always larger than the other? Explain your answer. 3.Humans can eat lots of different kinds of organisms. We do not often eat animals that eat other animals, like wolves, lions, or orcas. Why do you think these animals are not a regular part of what humans eat? 4.You often see plants. Think about the number of individual grass plants in a field. It is much less common to see large carnivores like alligators, wolves, or mountain lions. Why do you think this is so? 5.Why do you think bacteria and other microscopic organisms were left out of your analysis? 6. Which do you think are more important to human survival: plants or animals? Why do you think that? LS2-6 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explore Backyard Biology In the Engage activity, you made rough estimates about plants and animals in different areas on Earth. What if you dig a little deeper into your own neighborhood? Could the things you are learning apply to the places you see every day? Work with your class to discover patterns in your own world. Materials For each student 1 yellow plastic bowl (cereal-bowl size) 1 piece of string, 1 m long 1 stake or nail (optional) 1 copy of Backyard Biology Data Collection Protocol handout 1 cup of water 2 tsp of salt liquid dish detergent 1 plastic containers with screw lids 1 pair of scissors 1 plastic grocery bag gallon-sized, resealable plastic bags (optional) 1 paper clip or sticky note For each team of 2 students hand lens or stereomicroscope (dissecting microscope) paper towels different-colored pens or pencils For the class 4–8 electronic balances or triple-beam balances Caution Do not directly touch any organism you observe, even if you are certain it is harmless. Touching organisms may be harmful to them. The Explore activity, Backyard Biology, is adapted with permission from Richardson, M. L., & Hari, J. (2008, April). Teaching students about biodiversity by studying the correlation between plants and arthropods. American Biology Teacher, 70(4), 217–220. LS2-7 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explore Process and Procedure In this activity, you will collect insects, plants, and other organisms from a local area. You will only collect a small number of insects, but they will not survive. If you do not want to participate in this part of the activity, please inform your teacher. Data Collection 1.Write the following focus question in your science notebook. Draw a thick box around it. a Focus Question: “How does the mass of plants in an area compare to the mass of small animals like arthropods?” A simple way to think about mass is that it’s the amount of “stuff,” or matter, that something has. Mass is not the same thing as weight, but they are related. Arthropods are a group of animals. There are many different Corel species of arthropods. Scientists have named over 1 million species. Still, many biologists believe there may be over 10 million b different species! The arthropod group includes insects and spiders. It also includes crustaceans like crabs and pill bugs (figure 2.1). 2.In this activity, you will collect the plants and arthropods from an area near where you live. Use what you know and your experience from the Engage activity to make a prediction. Write the following sentence in your science notebook. Choose the correct phrase from those in the parentheses. Then fill Corel in the blank with your reason. “I think the mass of plants in an area will be (higher than / lower than / the same as) the mass of the small animals because c .” 3.Look again at the focus question from Step 1. How could you test this question? Discuss your ideas with a partner. 4.Contribute your ideas to a class discussion about designing an experiment to test the focus question. 5. Take notes as you learn how you will collect data for this investigation. 6.Get the materials you need, including a copy of the Backyard Biology Data Collection Protocol. Read through the protocol. Ask your teacher to clarify any steps you don’t understand. 7.Take the materials home. Complete all the steps in the protocol. As part of the protocol, you will put the arthropods in a plastic bottle and the plants in a bag. Tomorrow or the next day, bring the plastic bottle back to school. Write a note Corel Figure 2.1: Arthropods. There are many different kinds of arthropods. Pictured here are (a) an insect (rhinoceros beetle), (b) a spider (hunting spider), and (c) a pill bug. You will collect arthropods in this activity. so you don’t forget! LS2-8 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explore After Data Collection 8. Join with a partner to examine the arthropods you collected. Use the following steps. a. Individually, pour a small amount of your sample back into the yellow bowl. b. Use a hand lens or a stereomicroscope to examine the sample. Place any arthropods you find onto a paper towel. It might be helpful to use forceps to remove the smallest insects. c. When you have removed all the organisms from the bowl, dump the remaining fluid down the sink. our more of your sample into the yellow bowl. Repeat Steps d. P 8a–c until you have removed all the organisms. e. Use the paper towel to dry off the organisms as best as you can. 9.Create a 2-column table in your science notebook. Label the first column “mass of small animals.” Label the second column “mass of plants.” 10.Using a balance, find the mass of the arthropods you collected. Then find the mass of the plants you collected. Multiply the mass of the plants by 4. Record these values in the first row of your table. Label this row “my values.” You only collected plants from one-fourth of the circle around the bowl. This is considered your sampling area. Multiply the mass of the plants by 4 to estimate the mass for the whole area in the circle with a 1-meter (m) radius. 11.Contribute your data to a class data set. Record the average mass for small animals and plants in the second row of your table. Label this row “class averages.” 12.Create a bar graph in your science notebook. The y-axis should be “mass (grams).” You should have 4 bars along the x-axis. Two bars will be for your samples. The other 2 bars will be for the class averages. Add a title to your graph. 13.Use the Identify and Interpret (I2) strategy to help make sense of the graph. To use this strategy, follow these steps. a. Look for patterns on your graph. Draw an arrow to all the patterns that you identify. b. Write “What I see” followed by a short phrase describing what you identified. Be concise and write only the highlights of what you see. c. Interpret what you see, 1 observation at a time. Write “What it means” below each “What I see” phrase. Then describe what you think the observation means. d. Write a caption for the graph. Make sure that you describe how the graph helps you answer the focus question, “How does the mass of plants in an area compare to the mass of small animals like arthropods? For more information about this strategy, see I Can Use the Identify and Interpret (I2) Strategy. LS2-9 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explore 14. Exchange graphs with your partner. Look over your partner’s graph. Give your partner feedback on his or her graph. Use the following questions to help you give good feedback. n Is the y-axis properly spaced? n Does the graph have a title? n Are the bars on the graph labeled? n Does the caption answer the focus question? n Does the caption include evidence? n Does the caption include a claim and reasoning? 15. Make revisions to your graph and your I2 phrases. Use feedback from your partner if you found it useful. Use a different-colored pen or pencil for your revisions. You do not have to use all the advice your partner gave if you do not think it is useful. However, you should consider all the advice and make a decision about which pieces to use. Reflect and Connect Answer these questions on your own. Also mark the page with a paper clip or sticky note. You’ll revisit your answers later in the chapter. 1.In Step 2, you made a prediction about how the mass of plants in an area compares to the mass of animals. Did your experimental results match your predictions? 2.Suppose you compare your results with a classmate’s. Your classmate found that the mass of plants in an area was higher than the mass of animals. How could you explain this evidence? 3. The plants and animals you examined are made of matter. What do you think is the source of most of the matter that makes up the animals? 4. Look at the chapter organizer. The key idea from the Engage activity is: “Finding patterns in the natural world begins with careful observations.” The key idea from this Explore activity is: “Evidence shows how the mass of plants relates to the mass of animals.” Write your own linking question to tie these activities together. LS2-10 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain The Web of Life All living things are connected to other living things. What does this mean? For starters, some organisms eat other organisms. Still other organisms—like plants— need the nutrients that come from the decomposed bodies of other organisms. All organisms need energy and matter. We call the connections among living things the web of life. You are a part of the web of life. You depend on a large number of other organisms. Think about how many living things contributed to your breakfast! Also, did you know that thousands of different species of bacteria live in and on you? These bacteria help your body with important tasks! In this Explain activity, The Web of Life, you will investigate the web of life. You will use what you learn to help you answer some of the questions you encountered in the first two activities. Part I—Organizing Life Materials For each student different-colored pens or pencils 1 highlighter Process and Procedure 1. Think of a local park or similar type of area. a. Quickly write down in your science notebook at least 6 living organisms that you would see. b. Write down 4 nonliving things you’d expect to find. 2.Sort your list of organisms into at least 3 different groups based on some characteristics of the organisms. Each organism can only be in 1 group. Draw 1 circle for each group you create and write the names of the organisms in the circle. Do not write the characteristics you used. LS2-11 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain 3. Exchange your circles of living organisms with a partner. Then complete Steps 3a–d. a. Look over the groupings your partner created. b. Try to guess what characteristics your partner used to sort the organisms. c. Go through a few rounds of guessing if you don’t come up with the correct answer. d. D iscuss with your partner the reasons you grouped the organisms together. 4. Work with your partner to answer the following questions. a. Do you think one way of sorting the organisms was better than the other? Explain. b. In what ways do you think sorting the organisms on Earth into different groups is helpful to scientists? In other words, what kinds of problems or questions might this help them solve? 5. In the last few steps, you organized living things in different ways. Read Organizing the Web of Life to help you understand different ways that scientists organize living things. As you read, enter all bold and unfamiliar terms into your personal glossary. Also complete the tasks described in the reading. Reading: Organizing the Web of Life Biologists study all kinds of questions. They use what they learn to solve lots of different kinds of problems. But living systems have many levels of organization (figure 2.2). Let’s take a look at some of the levels, starting with the smallest and least complex. At the smallest level are microscopic things like molecules and cells. As you get to more-complex levels, you start to find structures you can see with just your eyes, such as organs. Your heart is an example of an organ. Even more complex are individual organisms, like you! In chapter 1, you studied populations—that’s another level. A population is all the individuals from one type of organism in an area. A species includes all the populations of one type of organism. An individual from one species usually cannot reproduce with an individual from another species. What if you included all the different living species in an area? Then you have a community. An ecosystem includes both the living community and the nonliving part of the environment. L ook back to the living and nonliving parts of the environment you listed in Step 1 of Process and Procedure. You started describing an ecosystem. continued LS2-12 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain Some scientists even study the whole biosphere. The biosphere is the portion of Earth where life is found. As you go up the levels, they become complex. This represents one way to group different parts of living systems—by levels of organization. levels of organization in the biosphere Figure 2.2: Levels of structure in the biosphere. The living world has increasing levels of organization. Each higher level depends on the one below it. biosphere–the part of Earth that contains life ecosystem–Chesapeake Bay community–all organisms in Chesapeake Bay population–all striped bass in Chesapeake Bay organism–striped bass organ system–circulatory system organ–heart tissue–muscle cell–blood cell large molecule–hemoglobin molecule–water atom–hydrogen Another way scientists organize living things is based on how closely related they are to other species. A crow is more closely related to a pigeon than it is to a dog. All the birds are in one group. Scientists use evidence to figure out which species are more closely related to other species. Another way to organize living things is by how they get the matter and energy they need to live. Think about two big groups. One group includes organisms that make their own food. The other group includes organisms that need to eat other organisms. Producers make their own food. Producers include plants, algae, and some bacteria. Producers use light energy to help them form food, which is a type of chemical energy. Remember photosynthesis? Energy is not turned into food. Instead, energy is used to make new forms of matter from other forms of matter. For example, plants can combine carbon dioxide and water to form sugar. If you’re not sure how plants and other producers make food, review how photosynthesis works using the reading Making More Algae in chapter 1. continued LS2-13 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain Consumers are organisms that rely on other organisms for energy. You are a consumer. Dogs are consumers. Insects are consumers. Consumers generally eat other plants or animals. They break down the matter from the things they eat to get the energy they need to live. Decomposers are a very important group of consumers. They break down the bodies of dead animals, plants, and all other organisms. Some decomposers use waste (like feces) from other organisms as a source of energy. Mushrooms, other fungi, and many bacteria are decomposers. Placing organisms in one of the two groups is usually a good way to begin separating species. Ask yourself, “Do they make their own food?” If so, they are producers. Do they eat other organisms for food? If so, they are consumers. But we can further organize living things. Examine figure 2.3. This diagram represents a food chain. A food chain summarizes the feeding relationships among different groups of organisms in a community. It shows who eats whom. The arrows in a food chain represent the direction of energy transfers. They point from the organism that gets eaten to the one doing the eating. Because energy transfers from the plant to the mouse, the arrow points toward the mouse. energy flows to sunflower energy flows to pocket mouse energy flows to bull snake red-tailed hawk Make a simple food chain that includes at least three organisms. Include different organisms from the ones in figure 2.3. Pay Figure 2.3: A simple food chain. In this food chain, energy gets transferred from the sunflower to the pocket mouse to the bull snake to the red-tailed hawk. Notice the direction of the arrows. sunflower: USDA, Photo by Edward McCain mouse: Photo by Cheryl S. Brehme, USGS snake: U.S. Fish and Wildlife Service hawk: Corel special attention to the direction of the arrows. Biologists use food chains to divide the consumers in a community into more-specific groups. Producers are still just called producers. Herbivores are organisms that only eat plants. Carnivores are consumers that eat the herbivores. Other organisms that eat the carnivores are called secondary carnivores, and so on. These levels for the consumers are called “trophic,” or feeding, levels. Organisms that eat at more than one level are called omnivores. For example, many people eat both plants and animals, making them omnivores. What about decomposers? They are included as consumers, but things can get complicated. Decomposers can function as herbivores when they break down dead plants. The same decomposer can function as a high-level carnivore when it breaks down the bones of a carnivore. To keep their role clear, decomposers usually get their own level in a food web. continued LS2-14 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain Food chains are pretty simple. But real ecosystems are more complicated. There are lots of organisms, and they interact in many ways. For example, red-tailed hawks eat snakes, but they may also prey on mice that eat seeds. Lots of connected food chains form a food web (figure 2.4). A web shows the relationships among different feeding levels. Examine the diagram of a food web for a marine community in figure 2.4. Food webs can be very complex, and this one shows only some of the main players. Figure 2.4: A marine food web. Food webs are a collection of multiple food chains. They summarize the flow of energy in an ecosystem. Are you starting to understand why it is called the web of life? orcas seal Sun king crab sea otters fish seabirds sea urchin zooplankton krill kelp phytoplankton Complete the following tasks related to figure 2.4. • Identify the producers in this food web. • Find three ways to trace the energy transfers from the Sun to an orca. • Find at least four food chains. Food webs help scientists understand how living things interact. The web of life summarizes all the interactions among all living things. One thing that ties all organisms together is the need for nutrients and energy. Understanding the movement of matter and energy in ecosystems is the big idea for this chapter. n LS2-15 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain 6.Review the glossary entries and the food chain developed by your partner. Offer helpful feedback on the entries. Revise your own entries after reviewing the feedback from your partner by using a different-colored pen or pencil. 7.Prepare to observe a demonstration of a food web by making a 2-column table in your science notebook. Label the left-hand column “What I observed.” Label the right-hand column “What it means.” 8. Watch the demonstration. Fill in the table as you watch or play a role in a simulation. If you were a part of the simulation, write down your observations as soon as the demonstration is over. You may need to ask a partner to help you remember all the parts of the demonstration. 9.Copy the analogy map in figure 2.5 into your science notebook. Fill out the table with as many parts of the demonstration as you can remember. Add extra rows if needed. Figure 2.5: An analogy map. Fill in this map so you can better understand the demonstration. Feature of the demonstration is like … Feature of a real food web They are alike because … String is like … the transfer of energy the string showed who eats whom, and that is how energy gets transferred. energy from the Sun A candy bar or hard candy 10.In your science notebook, draw the food web you saw in the demonstration. Use this food web as a base to complete Steps 10a–c. a. Add at least 3 more organisms to your food web. b. Add mushrooms and bacteria to your food web as decomposers. c. Use a highlighter to trace energy transfers leading to the wolf in 2 different ways. Stop and Think—Part I Answer the following questions on your own in your science notebook. 1. Deer are herbivores. Some deer have a parasite called a tapeworm. A parasite lives in or on another organism and uses it as a source of food, but it usually doesn’t kill the host. Where would you place parasites in a food chain? 2.Examine figure 2.4 again. Predict if the following populations would increase or decrease if the number of orcas were much lower. Explain your predictions. a. Sea otters b. Sea urchins c. Kelp LS2-16 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain 3.Food webs are often a simpler version of the large number of interactions that actually exist in a community. Why do you think biologists use food webs to study communities? Part II—Matter and Energy in the Web of Life Materials For each student different-colored pens or pencils You just learned a way to summarize energy relationships in a community. It’s called a food web. Now you can use what you learned to start explaining other patterns in ecosystems—patterns you investigated in the Engage and Explore! Process and Procedure 1.Some unusual questions are below. Write your best ideas about the following questions in your science notebook. Work by yourself as you answer the questions. You’ll learn more about them later and will have a chance to revise your work. a. Much of the matter in living things has the element carbon. Imagine that you eat a steak. The cow that was the source of the meat ate mostly grass. Could some of the carbon in grass end up in the cells of your toe? Why or why not? b. Could carbon that was a part of a long-dead dinosaur be part of a dog living today? Could that carbon be a part of you? Explain your answer. c. Wolves started living with humans about 10,000 years ago. Could you drink a particle of water that a wolf drank 10,000 years ago and eliminated as urine? Explain. 2.Discuss your answers with a partner. Make any revisions to your answers in a different color. 3.To help you answer these questions, read What’s the Matter? As you read, complete the tasks described in the reading. Write your answers in your science notebook. LS2-17 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain Reading: What’s the Matter? Here is a simple rule about matter. The amount of matter going into a system is the same as the amount of matter leaving a system. Under normal circumstances, matter does not usually turn into energy. If we think about the whole Earth as a system, we realize that not much new matter is being added to the system. Well, maybe an occasional meteorite, but that is about it. And matter is not leaving the system. What does this mean? It means that the matter on planet Earth cycles on and on and on. What about living systems? Living things are made up of matter. You may realize that the matter that forms your body comes from the food and liquids you ingest. As a consumer, your food comes from other organisms. But what about producers? How does matter from the nonliving environment enter producers? The matter that makes up producers like plants becomes a part of the plant in different ways. One key process is, again, photosynthesis. Producers use carbon in the air to help them make food and other structures. Other matter producers need, like nitrogen and water, comes from the soil. Plants get this matter through their roots. So producers bring matter into living systems from the nonliving environment. Some of this matter is returned directly to the nonliving world by plants. For example, plants release oxygen to the air. But luckily for you, some of the matter goes to other living things. Draw a picture of a plant in your science notebook. Label this drawing “matter in an ecosystem.” Leave room to add more drawings. In your drawing, show where the matter in the nonliving world comes from to build the plant. Then show some of the matter going back to the nonliving environment from the plant. Matter can also move through a food chain. In figure 2.3, matter moves from the sunflower to the mouse. The mouse returns some matter to the nonliving environment. For example, the mouse breathes out carbon dioxide. But the matter in the mouse can also be eaten by a snake. Are you starting to get the picture? Add an herbivore and a carnivore to the picture of the plant you started. Use arrows to show the direction matter is moving through the food chain. Also indicate where matter gets returned to the nonliving environment. In summary, matter cycles through organisms and the nonliving world. Matter can pass through many different food chains. At other times, it can be part of the nonliving environment. n LS2-18 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain 4.Compare your drawing of matter moving through a food chain to a drawing that your teacher will show you. Make revisions to your drawing as needed. 5.Revisit the answers you gave to the questions in Step 1. Make revisions to your answers based on your new understanding. 6.In the Explore activity, you examined the mass of the plants and the arthropods in an area. You tried to explain this observation in Reflect and Connect Question 2 of that activity. Review your answer to this question to help you get ready for Step 7. 7.Read Energy in Ecosystems. As you read, make a new drawing in your science notebook and label it “energy in an ecosystem.” This drawing should include the following. a. Show the Sun and a food chain. b. Include at least 3 levels and the forms of energy in the system. c. Use arrows to indicate the direction of energy transfers. d. Show how energy enters the food chain. Label this “energy in.” e. Also show how energy leaves the living system. Label this “energy out.” Reading: Energy in Ecosystems You’ve learned that matter cycles in ecosystems. But what about energy? Let’s look at two important ideas about energy. First, energy cannot be created or destroyed. But it can change to other types of energy. This means organisms cannot make their own energy. Second, when energy changes types, some energy always changes into heat. Heat eventually leaves living systems and escapes out into the universe. So if energy always leaves the system, this means that living systems need to replace that energy. In other words, living systems always need a source of energy. So what happens to energy in a food chain? Almost all the producers on Earth change light energy from the Sun into chemical energy. They use this chemical energy to do all the things they need to do to live and grow. The herbivores then eat the food (chemical energy) in the producer. They use this chemical energy to do all the things they need to live. All the energy from the producers is not available to the herbivores. Some parts of the producers may not be eaten by consumers. As a result, these parts are available to decomposers. Also, when plants change energy from one form to another, some energy is converted into heat. The heat leaves the living systems. And don’t forget that some of the energy is used by the producers to grow. In the end, continued LS2-19 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain you should see that there is less energy available to the herbivores than there is to the producers. Next are the carnivores. Do you think they have more or less energy available to them than the herbivores have? Answer this question in your science notebook. Then quickly check with a partner to see if your partner got the same answer. Figure 2.6 is a diagram biologists use to summarize the energy available at different levels in an ecosystem. It is called an energy pyramid. Notice that there is less energy available as you go “up” the food chain. A general rule is that only about 10 percent of the energy from one feeding level is available at the next level. This number varies in different ecosystems. Where does the “lost” energy go? You now know that much of this energy is lost to the universe as heat. Figure 2.6: An energy pyramid. What happens to energy as it passes through a food chain? Notice that there is less energy (measured in kilocalories, or kcal) as you go “up” the food chain. toplevel carnivores carnivores herbivores producers 10 kcal 100 kcal 1,000 kcal 10,000 kcal So what does all this mean? It means that energy gets transferred in living systems. It also means that much of the initial energy gets turned into heat. As a result, ecosystems need a constant source of energy. This is another big idea. Understanding energy and matter also helps us explain a pattern in the living world. What happened when you took the mass of all the producers in an area and compared it to the mass of the animals? continued LS2-20 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Explain You did this in the Explore activity. The mass from the producers was much higher. Why? Because there is less energy available to the herbivores. All organisms need energy to help form their bodies, but herbivores have less energy available compared to plants. Now think about the herbivores compared to the carnivores. The amount of matter in the herbivores is higher than the mass of all the carnivores. Can you figure out why? Decreasing amounts of energy at higher feeding levels helps explain why large predators are relatively uncommon and why they have less total mass. n 8.Compare your drawing of energy transfers in a food chain to a drawing that your teacher will show you. Make revisions to your drawing as needed. 9.Revise your previous explanation from Reflect and Connect Question 2 in the Explore activity. Use what you learned about matter and energy in ecosystems. Reflect and Connect Work by yourself to answer the following questions. Write your answers in your science notebook. 1.Imagine that a fifth grader says to you, “I understand how plants relate to energy. Plants make the energy they need out of nothing.” Do you agree with the student? Answer this question by writing a short dialogue between you and this other student. Your dialogue might look like lines from a play. 2.Look back in your science notebook to your answers to Reflect and Connect Questions 3 and 4 from the Engage activity. Revise your previous answers given your new understanding. Remember, your goal is to have an answer with all the information you now know. 3.Which took more energy to produce—a pound of corn or a pound of chicken? Explain your answer. 4. How can energy be a limiting factor for a population of consumers? LS2-21 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Elaborate Stability and the Web of Life Remember learning about how populations grow? You did this in the previous chapter. You know that a small population of mice in a cage can’t grow forever. Limiting factors can slow the growth of all populations. These factors can be nonliving or living. In this chapter, you’ve explored how different organisms in a community interact. All organisms are dependent on other organisms in one way or another. In this Elaborate activity, Stability and the Web of Life, you’ll put these ideas together as you explore how changing factors in one population affect other species in a food chain. You’ll do this by exploring a simulation about grass, sheep, and wolves. A simulation sure is easier than raising the sheep yourself! Materials For each team of 2 students access to a computer and the Wolf Sheep Predation simulation different-colored pens or pencils Process and Procedure 1.Examine figure 2.7. This figure shows a simple food chain that you will explore by using a simulation. Write the following focus question for this investigation in your science notebook and put a box around it: “How can a variable in one population affect other organisms in a food chain?” Figure 2.7: A simple food chain. In this food chain, grass represents the producers, sheep, the herbivores, and wolves, the carnivores. This is a simple model. In reality, wolves do occasionally prey on sheep, but the main part of their diets is wild herbivores such as deer or elk. The number of domestic sheep lost to wolf predation is usually less than 2 percent. LS2-22 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Elaborate 2.Predict how the organisms in the food web will affect one another. To do this, choose the correct phrase in each set of parentheses, and then finish the following sentences: “When the amount of grass is high, the sheep population will probably (increase / decrease / stay the same) because _____.” “When the amount of grass is high, the wolf population will probably (increase / decrease / stay the same) because _____.” 3.Discuss your predictions with a partner. Make revisions to your predictions if needed. 4.Access the Wolf Sheep Predation simulation. Once you are on the opening page, complete Steps 4a–c. Select Run Wolf Sheep Predation in Your Browser. a. Move the slider in the Grass? box to On. b. Move the speed slider at the top of the black box to the left. You will have to experiment with different speeds to find one that works well for your team. c. Click on the Setup button. Your screen should look like figure 2.8. Press setup after you’ve changed other settings. Press go to both start AND stop the simulation. These numbers at the bottom right show the setting for each variable. Speed slider: moving this bar to the left slows down the simulation. Figure 2.8: Wolf Sheep Predation setup. Make sure to move the slider for Grass? to On. Move the speed slider to the left to find a speed that works for your team. Then click Setup. Look closely at the screen and the descriptions of the different parts of the simulation. Make sure to move this slider to on. You can see the most recent population values here. Note the grass no. is divided by 4. Wilensky, U. (1997). NetLogo Wolf Sheep Predation model. http://ccl.northwestern.edu/netlogo/models/ WolfSheepPredation. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL. A graph showing the populations of the 3 species over time will be shown here. You can put the cursor on the graph and get the x,y values at different points. The teamwork skill you will focus on in this activity is making sure that your partner understands. Especially when using computer simulations, it can be easy for one partner to quickly move through a number of changes on the screen while the other partner sits passively. Throughout the activity, check in to make sure your partner knows what is happening when you change one or more parts of the simulation. 5.Read the Need to Know The Wolf-Sheep-Grass Simulation to yourself to help you understand how the model works. Review each of the variables with your partner to make sure you both understand what they mean. LS2-23 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Elaborate Need to Know: The Wolf-Sheep-Grass Simulation In the Wolf Sheep Predation simulation, you are exploring a simple model of a food chain. The model was written with the following rules in mind: 1.Wolves and sheep wander around the area randomly. Sheep must eat grass as a source of energy. Wolves must eat sheep as a source of energy. 2. Each time a sheep or wolf moves, it costs the animal some energy. 3. If a sheep or a wolf runs out of energy, it dies. 4.Each wolf and sheep that is alive at each time step (or tick) has a certain chance of reproducing. Some will, and some won’t. 5. It takes a certain amount of time for grass that gets eaten to grow back. You have the ability to change certain factors in the model. See figure 2.9 for a summary. n Variable Description Initial-NumberSheep This is the number of sheep at the beginning of the simulation. This number can range from 0 to 250. Sheep-Gainfrom-Food This number tells you how much energy a sheep gets from the grass it eats. This number can range from 0 to 50. SheepReproduce This number is the chance that an individual sheep will reproduce at each time step. A higher number means that more sheep will be born. It takes energy to reproduce. This number can vary from 0% to 20%. Initial-NumberWolves This is the number of wolves at the beginning of the simulation. This number can range from 0 to 250. Wolf-Gainfrom-Food This number tells you how much energy a wolf gets from each sheep it eats. This number can range from 0 to 50. Wolf-Reproduce This number is the chance that an individual wolf will reproduce at each time step. A higher number means the same thing as a higher birthrate. This number can vary from 0% to 20%. Grass? Grass can be removed from the model. If it is, you just monitor how wolves and sheep interact. You should start with the grass on. Grass-RegrowthTime This number is how fast the grass grows back after being eaten by sheep. A higher number means the population grows more quickly. This number can range from 0 to 100. Figure 2.9: A description of the variables in the Wolf Sheep Predation model. LS2-24 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Elaborate 6.This simulation allows you to change many different factors (or variables). Each variable might affect the 3 species in the community. Write down the initial settings for the variables by using a table like the one in figure 2.10 as a guide. Remember to multiply the grass population size by 4. You’ll learn more about what these settings mean in later steps. Variable Initial setting Figure 2.10: Variables in the Wolf Sheep Predation simulation table. Initial-Number-Sheep Sheep-Gain-from-Food Sheep-Reproduce Initial-Number-Wolves Wolf-Gain-from-Food Wolf-Reproduce Grass? (Also include the amount of grass.) On Grass-Regrowth-Time 7.Do the initial settings for population sizes (initial number of sheep, wolves, and grass) seem realistic to you? Explain why or why not. Make sure to refer to the energy pyramid. 8. Try running the simulation by completing Steps 8a–b. a. Run the simulation once with the initial settings (but with grass turned on). Do this by pressing the Go button. Pressing the Go button again will stop the simulation. Run the simulation until at least 700 time steps (called “ticks”) have passed by. b. The simulation may have gone by too quickly. Try sliding the speed slider to the left. Try to get the timing so it takes about 10 seconds to get to 350 ticks. Start the model over by pressing the Setup button. 9.Run the simulation until about 350 ticks have passed by, and then pause it. The person not in control of the computer should try to explain the patterns on the graph to the partner. 10. Switch places so that the other person is in control of the computer. Continue running the simulation until about 700 ticks have passed by. The other partner should explain the patterns on the graph. LS2-25 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Elaborate 11. Record the results from the simulation in your science notebook. If approved by your teacher, you can print the graph by printing the whole web page from within your internet browser. Make sure you paste it in your science notebook. Otherwise, make a sketch of the graph on your own. 12. Use the Identify and Interpret (I2) strategy to help make sense of your graph. As you are observing what you see and deciding what you think certain things mean, consider at least these questions. Are there regular cycles? If so, how long does one cycle take? If there aren’t regular cycles, describe why you think this is so. 13.Exchange graphs with your partner and add constructive comments to your partner’s graph and I2 phrases and caption. Use the following questions to help you give good feedback. id your partner point out when certain populations went up a. D or down? b. Did your partner describe how the sheep population affected the grass population? c. Did your partner describe how the wolf and sheep populations affect each other? 14. Make sure that you each understand one another’s comments. Make revisions based on the feedback you received, using a different color. Remember to at least consider every piece of feedback you got. 15.Explore the effect of 1 factor or variable on interactions in this food chain. Do this using the following steps. ith a partner, decide which variable to test. Be sure to test a. W only 1 variable. b. Come up with a strategy to test a range of values for the variable you decide to change. You should run at least 4 tests. c. Make a prediction about how you think your variable will affect the system. Be specific in your prediction. For example, let’s say you decide to explore how the initial size of the sheep population affects the system. Your prediction would state: “I think a low initial population size of sheep will cause________ because ______. I think a high initial sheep population size will cause ______ because _______.” d. Run the tests. Record the results in a table. Run each variation at least twice to see if the results are the similar. To start the simulation with new values, move the appropriate slider to the position you want. Next, press Setup, and then press Go. LS2-26 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Elaborate 16.Discuss the results with your partner. Then, on your own, make a claim about how your team’s variable affected the 3 species in the food chain. Make sure you tie your claim to specific evidence. Describe how the evidence leads to your claim. Also make sure that you address whether or not the evidence supports your initial prediction. 17.Contribute your results to a class discussion about the impact of different variables. Use this discussion to answer the focus question, “How can a variable in one population affect other organisms in a food chain?” Reflect and Connect Use the information you learned in the simulation to answer the following questions. Write your answers in your science notebook. 1.Were there any changes to the simulation that made some species go extinct? If so, describe what they were. You may use results from your own work or that you learned during the class discussion. 2.You explored a simple model of a food chain. What do you think are some of the limitations of this simple model? In other words, what important factors may not be included in the model? 3. Why are models an important part of scientific inquiry? 4.The teamwork skill that you are working on in this chapter is making sure everyone understands. a. Describe 1 or 2 specific things that you did that helped your partner understand the simulation. b. Describe 1 or 2 specific things you think you could do better to help someone understand in the future. LS2-27 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Evaluate Menu Connections Suppose you go down to the cafeteria for lunch. Today’s menu? Chicken sandwich, salad, and chocolate cake. Yum! Just three menu items. But how many living things are parts of your meal? When you examine this question, you will see your connections to the web of life—and this is just one meal! In this Evaluate activity, Menu Connections, you’ll show what you’ve learned about ecosystems and energy. To show what you’ve learned, you will construct a food web based on your lunch. You will analyze how energy gets transferred in the food web. You’ll also make predictions about the impact of different changes to the food web. Materials For each student 1 large piece of paper 1 set of different-colored pens or pencils, 5 colors 1 copy of Menu Connections Rubric handout 1 copy of What’s for Lunch? handout sticky notes Process and Procedure 1.Examine the Menu Connections Rubric handout. This helps you know how to do your best on this activity. Ask your teacher about any parts of the rubric you don’t understand. 2.On your own, list in your science notebook all the different organisms that you think contributed to your “lunch.” The 3 menu items are n a chicken sandwich with ketchup, pickles, and onions; n a salad with lettuce, mushrooms, red peppers, carrots, olive oil, and balsamic vinegar; and n a piece of chocolate cake. Many foods have ingredients that come from many plants, animals, or fungi. Do the best you can to list as many organisms as you can think of. 3.Compare your list of organisms to those of a partner. Revise your list based on what you learn from your partner. LS2-28 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Evaluate 4.Get a copy of the What’s for Lunch? handout. Read the Main Requirements for Each Food section and then the 2 tables. How many of the organisms are the same as those on your list? 5.Create a table on a new page in your science notebook. The table should have 5 columns. Label the columns “producer,” “herbivore,” “omnivore,” “carnivore,” and “decomposer.” Leave plenty of rows underneath each column heading. Title the table “organisms needed for lunch.” 6.Read the What’s for Lunch? handout again. As you read through the Main Requirements for Each Food section, notice that some of the items are organisms. For example, lettuce is a plant. Add these organisms to your Organisms Needed for Lunch table. Place each organism in the appropriate column. Yeast are fungi that act as decomposers. 7.Many ingredients are products that come from organisms. For example, flour comes from wheat plants. Read the Ingredients and Living Organisms table on the What’s for Lunch? handout. As you read, place the organism that is the source of each ingredient in your table. Again, make sure to put each organism in the correct column. 8.Some of the organisms you listed in Step 7 are animals that have their own diet. Include the organisms that are a part of these animals’ diets in your table, too. 9.Create a food web from the information you have in your Organisms Needed for Lunch table. Use the following directions to help you. a.Get a large piece of paper from your teacher. Fold it to create 5 equal-sized sections. Also get 5 different-colored pens or pencils. Use a different color for each section. b.In the bottom section, list all the names of the plants. Label this section “producers.” c.Write the names of all the herbivores (plant eaters) in the next section, above the plants. Label this section “herbivores.” d.Write all the names of the omnivores (animals that eat plants and animals) in the next section, above the herbivores. Label this section “omnivores.” e.Write all the names of the carnivores (animals that eat only meat) in the section above the omnivore row. Label this section “carnivores.” f.Include the decomposers at the top of the food web. Label this section “decomposers.” g.Write “humans” in the correct row for someone eating this lunch. h.Draw arrows between organisms to create a food web. i.Place the Sun on your diagram and indicate how energy from the Sun affects your personal food web. LS2-29 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Evaluate 10.Think of other organisms that might compete with you for your food. List at least 4 other organisms that might eat some of the same foods as you. Add these organisms to your food web. For example, coyotes try to eat young cows (calves). 11.Make a simple energy transfer diagram in your science notebook. The diagram should summarize one pathway of energy transfers from the Sun to you. Make sure to show where thermal energy leaves the pathway. 12.Exchange your food web and your energy transfer diagram with a partner. Follow Steps 12a–d as you review your partner’s work. a. Provide at least 2 pieces of feedback to your partner on separate sticky notes. Stick the notes on your partner’s work near the location where it best applies. You may want to add additional organisms to your partner’s food web. You might also think about the following questions: • Are the arrows on the food web pointing in the correct direction? • Are the organisms in the correct row? For example, are all the plants included in the producers’ row? • Is thermal energy included in the energy transfer diagram? b. Return your partner’s food web. c. Examine the feedback you received from your partner. Carefully consider each suggestion. evise your design based on helpful feedback. Make any revisions d. R in a different color. 13.Corn can be used for food or to make fuel. Predict how 2 of the other organisms in the food web could be affected if a lot of corn were used for fuel instead of food. Write your prediction in your science notebook. At least one of the other two organisms should not eat corn directly. Recall how changes in grass influenced sheep and wolf populations in the simulations. 14. In the Engage activity, you answered the question “Which do you think are more important to human survival: plants or animals? Why do you think that?” Revise your answer to this question after examining your lunch food web. Use what you know about energy at different feeding levels. LS2-30 Life Science Unit · Living Energy Chapter 2 · Ecosystems and Energy Spanish Vocabulary Spanish Vocabulary analogy: analogía arthropods: artrópodos biosphere: biósfera carnivores: carnívoros community: comunidad consumers: consumidores decomposers: descomponedores ecosystem: ecosistema energy pyramid: pirámide de energía food chain: cadena alimenticia food web: red alimenticia fungi: hongos herbivores: herbívoros mass: masa model: demostrar (verb)/ modelo (noun) producers: productores species: especie LS2-31