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EcoregionsAn 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.

In many areas, human activities have disturbed ecoregions. For example, in Texass 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 EcoregionsSome 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.

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 youve read this lesson, reread the statements to see if you have changed your mind.

Before Statement After

7. All Earths climates are part of one ecoregion.

8. Human activity can change a watershed.

Key Concepts What is an ecoregion? How does weather affect

ecoregions? What is a watershed? How does human activity

affect a watershed?

3TUDY#OACH

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 dont understand.

Key Concept Check1. Define What is an ecoregion?

Weather and Its Impacts

Effects of Weather on the Land

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Have you noticed that some areas of Texas are different from other areas? Thats 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 GroundwaterThe 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 Earths 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.

Key Concept Check3. Explain How do weather and climate affect ecoregions?

Visual Check2. Identify Where in Texas is rain most common?

Weather and Ecoregions

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6East Texas PineywoodsGulf Coast Prairies and MarshesPost Oak SavannahBlackland PrairiesCross Timbers and PrairiesSouth Texas PlainsEdwards PlateauRolling PlainsHigh PlainsWest of the Pecos (Trans-pecos)

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Ecoregions of Texas

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.

West Texas EcoregionsThe 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.

Central Texas and the PanhandlePrairie grasses grow in many of this areas 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.

East Texas EcoregionsRain is more common in East Texas than in other parts of the state. There are several ecoregions in this environment, including Pineywoodsforests 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.

20 Weather and Its Impacts Reading Essentials

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Key Concept Check5. Describe How can humans change watersheds?

WatershedsWater 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 ChangeWatersheds 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.

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 watershedand 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.

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.

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.

Erosion and DepositionMoving 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 rivers 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.

Key Concept Check4. Relate What is a watershed?

Reading Check6. Express How can erosion and deposition affect ecoregions?

Make a two-tab matchbook to organize your notes about the impact of humans on climate and water.

Ecoregions Watersheds

Human Impact on

Reading Essentials Weather and Its Impacts 21

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Mini Glossary

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?

What do you think

END OF LESSON

Log on to ConnectED.mcgraw-hill.com and access your textbook to find this lessons resources.

ConnectED

climate: the long-term weather conditions in an area

depositi on: the process that occurs as water slows and eroded material, or sediment, is laid down and settles

ecoregion: a large area of land that has a distinct group of plants, animals, and other species

erosion: the process of moving weathered material, or sediment, from one location to another

groundwater: precipitation that soaks into the cracks and pores beneath Earths surface

surface water: water that fills lakes and rivers

watershed: an area of the land where all runoff drains to the same body of water

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.

3. Explain how surface water is related to watersheds.

Human Impacts

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