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Name CHAPTER 20 Class Date The Earth’s Ecosystems SECTION 3 Freshwater Ecosystems National Science Education Standards BEFORE YOU READ After you read this section, you should be able to answer these questions: LS 1a, 3d, 4a, 4b, 4c, 4d • What organisms live in stream and river ecosystems? • What are the three zones in a pond or lake? • What are two kinds of wetlands? What Are Stream and River Ecosystems? One important abiotic factor that affects freshwater ecosystems is how quickly the water is moving. In rivers and streams, the water is moving faster than in other freshwater ecosystems. The water in streams may come from melted ice or snow. It may also come from a spring. A spring is a place where water from under the ground flows to the surface. Each stream of water that joins a larger stream is called a tributary. As more tributaries join a stream, it becomes stronger and wider. A very strong, wide stream is called a river. STUDY TIP Answer Questions Before reading this section, write the three Before You Read questions on a piece of paper. As you read, write down the answers to the questions. Springs or melting snow and ice Tributary River Ocean TAKE A LOOK 1. Describe What happens to the size of a stream when a tributary flows into it? Stream and river ecosystems are full of life. Plants live along the edges of streams and rivers. Fish live in the open waters. Clams and snails live in the mud at the bottom. Organisms that live in fast-moving water have to keep themselves from being washed away. Some producers, such as algae and moss, are attached to rocks. Consumers, such as tadpoles, use suction to hold themselves to rocks. Other consumers, such as crayfish, hide under rocks. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 331 The Earth’s Ecosystems Name SECTION 3 Class Date Freshwater Ecosystems continued What Are Pond and Lake Ecosystems? The water in ponds and lakes is not moving very much compared with rivers and streams. As a result, they have different types of ecosystems. Like marine ecosystems, pond and lake ecosystems are affected by water depth, sunlight, and temperature. LIFE NEAR THE SHORE READING CHECK 2. Identify Which consumers of the littoral zone are herbivores? READING CHECK The area of water near the edge of a pond or lake is called the littoral zone. Sunlight reaches the bottom, which allows producers such as algae to grow in this zone. Plants, such as cattails and rushes, grow here too, farther from shore. Many consumers, such as tadpoles and some insects, eat the algae and plants. Some consumers, such as snails and insects, make their homes in plants. Consumers that live in the mud include clams and worms. Other consumers, such as fishes, also live in this zone. LIFE AWAY FROM THE SHORE The area of a lake or pond away from the littoral zone near the surface is called the open-water zone. This zone is as deep as sunlight can reach. Producers such as phytoplankton grow well here. This zone is home to bass, lake trout, and other consumers. Beneath the open-water zone is the deep-water zone, where no sunlight reaches. Photosynthetic organisms cannot live in this zone. Scavengers, such as catfish and crabs, live here and feed on dead organisms that sink from above. Decomposers, such as fungi and bacteria, also help to break down dead organisms. 3. Explain Why can’t producers live in the deep-water zone? TAKE A LOOK 0LANTSANDOTHER?????????????? GROWINTHELITTORALZONEANDTHE OPENWATERZONE4HESEZONESGET PLENTYOF????????????????????? ?????????????AND???????????? LIVEINTHEDEEPWATERZONEANDEAT DEADORGANISIMSTHATFALLFROMTHE WATERABOVE 4. Identify Fill in the blank spaces in the figure with the correct words. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 332 The Earth’s Ecosystems Name SECTION 3 Class Date Freshwater Ecosystems continued What Is a Wetland? A wetland is an area of land that is sometimes under water or whose soil contains a lot of water. Wetlands help control floods. During heavy rains, wetlands soak up large amounts of water. This water sinks into the ground and helps refill underground water supplies. Wetlands contain many different plants and animals. There are two main types of wetlands: marshes and swamps. A marsh is a treeless wetland. Marshes form along the shores of lakes, ponds, rivers, and streams. READING CHECK 5. Define What is a wetland? A swamp is a wetland in which trees and vines grow. Swamps form in low-lying areas and near slow-moving rivers. TAKE A LOOK Grasses and other small plants are the main producers in marsh ecosystems. Consumers such as Trees and vines are turtles, frogs, and birds important producers live in marshes. in swamp ecosystems. Birds, fishes, and snakes are consumers that live in swamps. 6. Compare What is a quick way to tell the difference between a marsh and a swamp? How Can an Ecosystem Change? Did you know that a pond or lake can disappear? The water flowing into the lake carries sediment. The sediment, along with dead leaves and other materials, sinks to the bottom of the lake. Bacteria decompose the material at the bottom of the lake. The decay process uses up some of the oxygen in the water. As the amount of oxygen in the water goes down, fewer fish and other organisms can live in it. Over time, the pond or lake is filled with sediment. New kinds of plants grow in the new soil. Shallow places fill in first, so plants grow closer and closer to the center of the pond or lake. What is left of the pond or lake becomes a wetland. As the soils dry out and the oxygen levels increase, forest plants can grow. In this way, a pond or lake can become a forest. Critical Thinking 7. Apply Concepts Why is the amount of oxygen in pond water an abiotic factor? Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 333 The Earth’s Ecosystems Name Class Section 3 Review Date NSES LS 1a, 3d, 4a, 4b, 4c, 4d SECTION VOCABULARY deep-water zone the zone of a lake or pond below the open-water zone, where no light reaches littoral zone the shallow zone of a lake or pond where light reaches the bottom and nurtures plants marsh a treeless wetland ecosystem where plants such as grasses grow open-water zone the zone of a pond or lake that extends from the littoral zone and that is only as deep as light can reach swamp a wetland ecosystem in which shrubs and trees grow wetland an area of land that is periodically under water or whose soil contains a great deal of moisture 1. Compare Why are the kinds of producers in the littoral zone of a lake different from the producers in the open-water zone? 2. Compare How are the producers in a swamp different from those in a marsh? 3. Identify Give two examples of consumers in wetlands. 4. Describe What abiotic factors do organisms living in rivers and streams have to adapt to? 5. Describe Fill in the blank spaces in the flow chart below to show how a pond can become a forest. Sediment and dead plant material sinks to the bottom of the pond. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook 334 The Earth’s Ecosystems Life Science Answer Key continued 10. There would be little precipitation, climates abundant sunlight, and changing water levels. 5. From left to right: The pond slowly fills with sediment. Plants grow in the new soil, closer and closer to the center of the pond. Eventually, the pond is completely filled with new soil. Forest plants begin to grow. would be different, and there would be less food for humans. 11. They attach themselves to rocks and other hard objects. 12. Most of a coral reef is the nonliving remains of dead corals. It also contains living corals and many other organisms. Chapter 21 Environmental Problems and Solutions Review 1. The water in estuaries contains a changing 2. 3. 4. 5. amount of salt because fresh water is mixing with water from the ocean. The main producers in most marine ecosystems are microscopic, single-celled phytoplankton. Other producers are algae, such as kelp. phytoplankton krill fishes seals Most producers use sunlight to carry out photosynthesis. Since sunlight does not penetrate below 200 m, these producers cannot live at such depths. The neritic zone has relatively shallow water, a lot of light, and fairly warm temperatures. These conditions make the neritic zone habitable by many different organisms. SECTION 1 ENVIRONMENTAL PROBLEMS 1. No, some pollution is caused by natural events. 2. medical wastes, lead paint 3. Type of Examples or Harmful effects SECTION 3 FRESHWATER ECOSYSTEMS 1. 2. 3. 4. It gets wider. tadpoles and some insects There is no sunlight. Plants and other producers grow in the littoral zone and the open-water zone. These zones get plenty of sunlight. Scavengers and decomposers live in the deep-water zone and eat dead organisms that fall from the water above. 5. an area with a lot of water in the soil or that is sometimes underwater 6. A swamp has trees growing in it, and a marsh does not. 7. It is abiotic because it is not alive. pollution sources Chemicals CFCs, PCBs, fertilizer destroy ozone layer, cause cancer, pollute soil and water Nuclear wastes nuclear power plants can cause cancer or radiation poisoning Noise airplanes, loud music affects your ability to think clearly, harms your hearing Greenhouse gases carbon dioxide cause global temperatures to rise 4. Old refrigerators still release CFCs. 5. No, greenhouse gases keep Earth warm enough for life to exist. However, too many greenhouse gases can cause global temperatures to rise. 6. Renewable resources Nonrenewable resources sun oil wind coal trees natural gas 7. They may compete with native species for resources. They may also kill the native species. 8. Some resources may be depleted. One day there may not be enough resources for everyone. 9. when all the trees in a forest are cut down 10. Nonpoint-source—it has many sources. Review 1. The littoral zone is shallow, allowing for rooted plants such as cattails. The openwater zone is too deep for rooted plants, so the main producers are phytoplankton. 2. Swamp producers are mostly trees and vines. Marsh producers are mostly grasses and reeds. 3. fishes, turtles 4. Some abiotic factors are fast-moving water, Review 1. Overpopulation can lead to depletion of nonrenewable resources or to overuse of renewable resources, both of which can create pollution and can lead to habitat destruction and a loss of biodiversity. Copyright © by Holt, Rinehart and Winston. All rights reserved. Interactive Textbook Answer Key 23 Life Science