CHAPTER 170 LESSON 4
Weather and Its Impacts Effects of Weather on the Land
Key Concepts What do you think? Read the two statements below and decide whether you agree or disagree with them. Place an A in the Before column if you agree with the statement or a D if you disagree. After you’ve read this lesson, reread the statements to see if you have changed your mind. Before
Statement
After
7. All Earth’s climates are part of one ecoregion.
• What is an ecoregion? • How does weather affect ecoregions? • What is a watershed? • How does human activity affect a watershed?
8. Human activity can change a watershed.
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Ecoregions
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An ecoregion is a large area of land that has a distinct group of plants, animals, and other species. The species in an ecoregion have adaptations for the weather, elevation, soil, and amount of water available for that region. One example of an ecoregion is the Great Plains, located in central North America. The Great Plains usually receives little rain. Grasses can grow there because they can survive periods with little moisture. Another ecoregion is the Arctic tundra of Canada. This ecoregion is frigid and has a thin layer of soil. Only adapted plant species can survive there.
Create a Quiz about the effects of weather on the land. Exchange quizzes with a partner. After taking the quizzes, discuss your answers. Reread the information about the topics you don’t understand.
Key Concept Check
1. Define What is an ecoregion?
In many areas, human activities have disturbed ecoregions. For example, in Texas’s Pineywoods ecoregion, only about 3 percent of the forests remain. Most of the original forests were cut down for timber and to build towns and cities.
Weather, Climate, and Ecoregions Some areas of Earth are hot and dry. Other areas are cool and rainy. Some places are cold all year. Although short-term variations in the wind, rain, and temperature in an area can occur, each area has a typical overall weather pattern. The long-term weather conditions in an area make up its climate. Climates determine the distribution of ecoregions on Earth. Different species of plants, animals, and other organisms thrive in different climates. Reading Essentials
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Weather and Its Impacts
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Weather and Ecoregions Central Texas and the Panhandle Prairie grasses grow in many of this area’s ecoregions. Large thunderstorms and tornadoes are common in the panhandle, an area where drought is common. On the South Texas Plains, grasses and other plants have adaptations to a dry climate.
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West Texas Ecoregions The desert of West Texas receives very little rain, less than 30 cm each year. The nearby Edwards Plateau receives slightly more rain, enough for trees adapted to a dry climate to survive.
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East Texas Ecoregions Rain is more common in East Texas than in other parts of the state. There are several ecoregions in this environment, including Pineywoods forests and the tall grasses of the Blackland Prairie. In the Pineywoods ecoregion of Texas, temperatures are mild and enough rain falls for forests to grow.
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Ecoregions of Texas 1 2 3 4 5 6 7 8 9
Post Oak Savannah Blackland Prairies Cross Timbers and Prairies South Texas Plains Edwards Plateau Rolling Plains High Plains West of the Pecos (”Trans-pecos”)
Visual Check
2. Identify Where in Texas is rain most common?
Key Concept Check
3. Explain How do weather and climate affect ecoregions?
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Coastal Ecoregions The Gulf Coastal Plain ecoregion includes narrow islands made of sand, marshes, dunes, and rivers draining into the gulf. Hurricanes and tropical storms occasionally impact this ecoregion.
Have you noticed that some areas of Texas are different from other areas? That’s because different parts of the state have different weather patterns. That means the state has many different ecoregions. The figure above shows some of the varied ecoregions in Texas and their characteristics.
Surface Water and Groundwater The amount of water available to an area is an important feature of an ecoregion. How much precipitation falls and where the precipitation drains are factors that determine which organisms can live in an area. Precipitation that soaks into the cracks and pores beneath Earth’s surface is groundwater. Surface water is the water that fills lakes and rivers. Humans rely on groundwater and surface water to irrigate crops, to provide drinking water, for recreation, and for other uses.
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Weather and Its Impacts
Reading Essentials
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East Texas Pineywoods Gulf Coast Prairies and Marshes
Watersheds Water that falls on land flows in streams and rivers and drains into a larger body of water. A watershed is an area of the land where all runoff drains to the same body of water. High points, such as mountains, form boundaries between different watersheds. The amount and the availability of water in a watershed affect all organisms in the watershed.
How Watersheds Can Change Watersheds change naturally over time. Over millions of years, the shape of the land changes. This can change the direction water flows. In a shorter time, floods can carry nutrients and sediments to new parts of a watershed.
Key Concept Check
4. Relate What is a watershed?
Human Impacts Humans also can change watersheds. For example, people build dams that change the flow of rivers. Lakes called reservoirs form behind the dams. People use the water in reservoirs to irrigate farms and to provide water for towns and cities. Changing the flow of rivers can change the watershed—and the organisms that live there.
Changing the Flow of Rivers Dams on a river prevent water from flowing through the watershed. That means areas downstream do not have as much water as they once did. This can change ecoregions.
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Irrigation In order to water crops, some farmers irrigate land with groundwater pumped from wells. Others irrigate crops with surface water from reservoirs, streams, or lakes.
Make a two-tab matchbook to organize your notes about the impact of humans on climate and water. … Ecoregions … Watersheds
Human Impact on…
Water Pollution Pollution can affect rivers and lakes. Pollution can harm organisms. Pollutants can come from factories. Water flowing through farms or towns can pick up pesticides or oil and carry it into lakes and rivers.
Key Concept Check
5. Describe How can humans change watersheds?
Erosion and Deposition Moving water can pick up and move rocks, sand, and other particles. The process of moving weathered material, or sediment, from one location to another is called erosion. Erosion can change ecoregions. It can change the landscape, change a river’s course, or sweep beaches into the ocean. As water slows, the eroded material, or sediment, is laid down and settles in a process called deposition. The cycle of erosion and deposition can move fertile soil to new areas. It also can move pollutants or cover up areas where plants and animals once lived. Erosion and deposition are natural processes, but the way humans use land can affect the impact of these processes. For example, when trees, grasses, and other plants are cleared from the land, erosion increases. Reading Essentials
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Reading Check
6. Express How can erosion and deposition affect ecoregions?
Weather and Its Impacts
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Mini Glossary climate: the long-term weather conditions in an area
groundwater: precipitation that soaks into the cracks and pores beneath Earth’s surface
deposition: the process that occurs as water slows and eroded
surface water: water that fills lakes and rivers
material, or sediment, is laid down and settles
ecoregion: a large area of land that has a distinct group of
watershed: an area of the land where all runoff drains to the
plants, animals, and other species
same body of water
erosion: the process of moving weathered material, or sediment, from one location to another
1. Review the terms and their definitions in the Mini Glossary. Write a sentence that describes how erosion can change the landscape.
2. Use the following graphic organizer to list ways people can impact watersheds.
Human Impacts
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3. Explain how surface water is related to watersheds.
What do you think Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind?
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Connect ED
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END OF LESSON
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