3.4 Cycles of Matter Lesson Objectives Describe how matter cycles among the living and nonliving parts of an ecosystem. Describe how water cycles through the biosphere. Explain why nutrients are important in living systems. Describe how the availability of nutrients affects the productivity of ecosystems. Lesson Summary Recycling in the Biosphere Matter, unlike energy, is recycled within and between ecosystems. Elements pass from one organism to another and from one part of the biosphere to another through biogeochemical cycles, which are closed loops powered by the flow of energy. The Water Cycle Water moves between the ocean, the atmosphere, and land. Evaporation is the process in which water changes from a liquid to a gas. Transpiration is the process in which water evaporates from the leaves of plants. Nutrient Cycles The chemical substances that an organism needs to survive are called nutrients. Like water, nutrients pass through organisms and the environment. Carbon Cycle: Carbon is a key ingredient of all organic compounds. Processes involved in the carbon cycle include photosynthesis and human activities such as burning. Nitrogen Cycle: Nitrogen is needed by all organisms to build proteins. Processes involved in the nitrogen cycle include nitrogen fixation and denitrification. In nitrogen fixation, certain bacteria convert nitrogen gas into ammonia. In denitrification, other soil bacteria convert nitrogen compounds called nitrates back into nitrogen gas. Phosphorus Cycle: Phosphorus is needed for molecules such as DNA and RNA. Most of the phosphorus in the biosphere is stored in rocks and ocean sediments. Stored phosphorus is gradually released into water and soil, where it is used by organisms. Nutrient Limitation A nutrient that, in short supply, can limit the productivity of an ecosystem is called a limiting nutrient. Recycling in the Biosphere For Questions 1 3, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. carbon 1. The four elements that make up over 95 percent of the body in most organisms are oxygen, sulfur, nitrogen, and hydrogen. True 2. Matter moves through an ecosystem in cycles. lightning 3. Chemical and physical processes include the formation of clouds and precipitation, burning food, and the flow of running water. 39
4. The illustration draws an analogy between the way energy drives matter to cycle in an ecosystem and the way water causes a waterwheel to turn. Give an example of another analogy that could be used to show the relationship between energy and the cycles of matter. Possible analogies include wind causing Cycles of Matter Energy a windmill to turn or a foot pushing a bicycle pedal around and around. 5. Explain why Earth is considered a closed system. Earth is a closed system because matter does not enter and matter does not escape. The materials used by organisms cannot be lost; they are recycled. 6. How might building a new highway affect the cycles of matter? When a new highway is being built, trees and other plants are cleared. The removal of plants limits the food, energy, and habitats available to other organisms, like animals. The removal of plants and animals stops nutrients from being recycled. The Water Cycle 7. What role do plants play in the water cycle? Plants absorb groundwater through their roots. That water re-enters the atmosphere in the form of water vapor when it evaporates from the leaves of plants during transpiration. This transpired water then continues the cycle. 8. Draw a diagram explaining the water cycle. Label the processes involved as biological or physical/chemical. Drawings should include the following: Physical/Chemical processes: Water evaporates from bodies of water and then condenes into clouds in the atmosphere. Water falls to the surface as precipitation. Surface runoff goes to rivers and oceans. Water seeps into the ground and becomes groundwater. Biological Processes: Ground water is absorbed by plant roots. Plant leaves release water vapor into the atmosphere through transpiration. 40
Nutrient Cycles 9. Complete the chart about the carbon cycle. Processes That Cause Carbon to Move into the Atmosphere Processes That Cause Carbon to Move out of the Atmosphere Process Description Process Description Respiration the release of CO 2 by an organism after breaking down carbohydrates into usable energy Photosynthesis the use of sunlight and CO 2 to produce carbohydrates Volcanic Activity the release of CO 2 and other gases into the atmosphere through vents in Earth s crust SAMPLE ANSWER: Dissolving SAMPLE ANSWER: CO 2 dissolves in rainwater and oceans. For Questions 10 12, write the letter of the correct answer on the line at the left. B 10. The carbon in coal, oil, and natural gas came from A. the combustion of fossil fuels. B. the remains of dead organisms. C. carbon-fixing bacteria in swamp soil. D. carbon dioxide dissolved in ocean water. A 11. How does most of the carbon in an organism s body return to the environment after the organism dies? A. Decomposers break the body down into simpler compounds. B. Heat from the sun causes the carbon in the body to evaporate. C. Geological processes cause the body to turn into a fossil fuel. D. Rainwater dissolves the carbon in the body and carries it to the ocean. A 12. Human processes mainly contribute to the A. release of carbon dioxide into the atmosphere. B. decrease of the total amount of carbon found on Earth. C. depletion of carbon dioxide reserves in the atmosphere. D. increase in the amount of carbon contained in rock materials. 41
Write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true. True 13. Nitrogen, in the form of ammonia, nitrate, and nitrite, is found in the soil. ammonia 14. Nitrogen fixation is the process in which certain bacteria convert nitrogen gas into nitrates. True 15. Denitrification is the process by which some soil bacteria convert nitrates into nitrogen gas. proteins 16. All organisms require nitrogen to make amino acids, which in turn are used to build carbohydrates. True 17. Phosphate is released as rocks and sediments wear down. True 18. Plants absorb phosphate from the soil or from water. Nitrogen 19. Phosphorus is the most abundant gas in the atmosphere. Carbon dioxide 20. Organic phosphate is taken up by producers during photosynthesis and released by cellular respiration. True 21. Phosphorus forms part of the important life-sustaining molecules such as DNA and RNA. soil 22. Plants absorb phosphorus from the atmosphere or water. 23. List and describe the biological steps in the nitrogen cycle. Bacteria convert nitrogen gas into ammonia during nitrogen fixation. Other soil bacteria convert ammonia into nitrates and nitrites. Primary producers use nitrates and nitrites to make proteins and nucleic acids. Consumers eat producers and reuse nitrogen to make compounds. Decomposers release nitrogen from waste and dead organisms. Bacteria convert nitrates into nitrogen gas during denitrification. 24. What is atmospheric nitrogen fixation, and how does it affect organisms? Atmospheric nitrogen fixation is the process in which lightning converts nitrogen gas in the atmosphere into usable compounds. It makes nitrogen available to organisms. 25. How do humans add nitrogen to the biosphere? Humans add nitrogen to the biosphere by using fertilizers that contain nitrogen. 26. Which parts of the phosphorus cycle are geological processes? Geological activity turns marine sediments into rock and washes the phosphates from the rock into the ocean. 42
Nutrient Limitation Use the diagram of the interlocking nutrients to answer Question 27. 27. The visual analogy compares interlocking gears to the major nutrients potassium, phosphorus, and nitrogen. What other gears would be affected if these gears stopped working together? Plants and other organisms can also be added to this analogy. Without potassium, phosphorus and nitrogen, plants would not be able to live and Micronutrients Potassium Phosphorus Nitrogen thrive. Plants produce oxygen and carbohydrates. Without these gears, animals and most living things would not survive. 28. If a nutrient were in short supply in an ecosystem, how might it affect an organism? SAMPLE ANSWER: It would limit an organism s growth. 29. When is a substance a limiting nutrient? A substance is a limiting nutrient when it is scarce or cycles very slowly and limits an ecosystem. 30. Compare and contrast the flow of energy through an environment with the flow of matter through that same environment. Matter moves through an environment differently than the way in which energy moves. Energy is captured by producers and then passed in a linear progression from one trophic level to the next. At each level, much of the energy escapes the ecosystem as heat. Unlike this one-way flow of energy, matter is recycled within and between ecosystems. Elements pass from one organism to another and among parts of the nonliving environment through closed loops called biogeochemical cycles. 43
Chapter Vocabulary Review Match the term with its definition. Term D B C A H F E G 1. nutrient 2. chemosynthesis 3. consumer 4. ecosystem 5. photosynthesis 6. ecology 7. primary producer 8. biosphere For Questions 9 12, complete the analogies. SAMPLE ANSWERS 9. omnivore : human :: carnivore : Definition A. all the organisms in one area and their physical environment B. a process in which producers use chemical energy to make carbohydrates C. an organism that feeds on other organisms D. a chemical substance that an organism needs to survive E. an organism that uses chemical or light energy to produce its own food supply F. the study of the biosphere G. the portion of Earth and its atmosphere that contains organisms H. a process in which producers use light energy to make carbohydrates lion 10. detritivore : earthworm :: herbivore : 11. autotroph : heterotroph :: phytoplankton : cow zooplankton 12. biotic factor : elephant :: abiotic factor : precipitation 13. What is the difference between a food chain and a food web? A food chain is a series of steps in which organisms transfer energy by eating and being eaten. A food web is a network of several interacting food chains. Complete each statement by writing the correct word or words. 14. There are several hundred squirrels living in an oak forest. The squirrels make up a(n) population. 15. Fungi and some kinds of bacteria are decomposers that obtain nutrients by chemically breaking down organic matter. 16. Ecologists measure biomass in grams of organic matter per unit area. 17. In a process known as denitrification, some types of soil bacteria obtain energy by converting nitrates into nitrogen gas. Chapter 3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 44
CHANGES IN THE BAY Rhode Island s Narragansett Bay is not the only ecosystem that suffers from changes in abiotic factors such as temperature. This is happening within many biomes and ecosystems around the world. Learning Rising Temperatures in a Lake The northwest coniferous forest is a small biome along the coast of the northwestern United States. It experiences seasonal variations in temperature and precipitation. Close to Seattle, Washington, is Lake Washington, which is a freshwater ecosystem in peril from decades of sewage dumping and rising water temperatures. The following is a brief summary of an environmental report on Lake Washington. ENVIRONMENTAL REPORT: Lake Washington Status PREPARED BY: Environmental Sub-Committee SUMMARY: While it has been more than 40 years since sewage has been dumped into Lake Washington, problems still exist in this freshwater ecosystem. The lake s overall temperature has increased by 0.5 C in the past 40 years. Its upper layer, which is 9 meters deep, has experienced a temperature increase of 1.25 C. These rising temperatures are negatively affecting the ecosystem s food chain. Zooplankton numbers are declining. These microscopic organisms eat algae, which are at the base of the food chain. Zooplankton are also prey for salmon. Higher temperatures are generating more frequent algal blooms, which are starting to create eutrophic conditions in the lake. Eutrophication is a condition in which a body of water is very high in nutrients, but low in oxygen. Salmon populations are also declining due to these conditions. Spring turnover in the lake, a process by which warmer surface water sinks and mixes with deep, cold water, is occurring a month later than in the past. The result is that some fish that prefer colder water are migrating into deeper waters, where they encounter more predatory species than they would in shallow water. Studies indicate that global warming is the major contributor to the rising temperatures. Continued on next page Chapter 3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 45
Themes Science and Global Awareness, Science and Civic Literacy 1. What abiotic factor is changing the ecosystem of Lake Washington, and how has this factor changed over time? Temperature is the abiotic factor that is changing the ecosystem. Both the top layer temperature and the overall temperature of the lake are increasing. 2. Explain how this change has affected the mixing of warm and cold water in the lake. How does this in turn affect fish? The warmer temperatures have delayed the yearly springtime mixing of warm and cold water in the lake. Consequently, some fish that prefer colder water migrate to deeper water layers that are cooler but that hold larger populations of predatory fish species. 3. This report suggests that global warming is a primary contributor to the increased temperature in the lake. What does this suggest about other lake ecosystems in the northwest coniferous forest? Other lakes in the northwest coniferous forest may also have increased water temperatures. Their fish, algae, and zooplankton populations may also be in danger. Seasonal turnover may also be later, as it is in Lake Washington. 4. Briefly describe a food chain in Lake Washington. Algae are at the bottom of the food chain and are eaten by zooplankton. Salmon eat the zooplankton. 5. If the zooplankton population is decreasing in Lake Washington, what do you think is happening to the salmon population? Explain your answer. The salmon are not able to find as much food, and their numbers are decreasing. Lake Presentation The skills used in this activity include critical thinking and systems thinking; problem identification, formulation, and solution; communication; information literacy; and leadership and responsibility. Working with a small group, research information about Lake Washington s past issues with sewage disposal and current trends in increasing water temperature. Or, conduct research about a body of water in your community or state. You may find it helpful to start your research at the Web sites of federal and state environmental agencies. Visiting your local public library and inquiring at government offices can offer valuable information, too. Find evidence about the relationship between global warming and these rising temperatures. Prepare a presentation describing the information that you find. In your presentation, provide at least one example and show the effects of changing conditions on this ecosystem. Present your findings to the class in an oral report, using figures, tables, and illustrations. Evaluate students presentations by their inclusion of descriptions and past and current data about the body of water, including charts, graphs, and/or diagrams. Evaluation should also depend on the reliability of the sources students use. Chapter 3 Workbook A Copyright by Pearson Education, Inc., or its affiliates. All Rights Reserved. 46