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260ENGAGE

Lesson 4

Comparing Ecosystems

Great Egret at Lake Martin, Louisiana

When you visit a lake or wetland ecosystem, you see certain types of plants and animals. What if you visited a desert or grassland ecosystem? Would you see the same kinds of organisms? How does one ecosystem compare with another?

LS.26 Identify and describe ecosystems of local importance (LS-M-C3) LS.27 Compare common traits of organisms within major ecosystems (LS-M-C3)

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• masking tape

• long piece of white butcher paper or chart paper

• reference materials

• crayons and colored markers

• index cards

How do different ecosystems

compare?

PurposeEarth’s major land ecosystems include taigas, tundras, rain forests, deciduous forests, deserts, and grasslands. Do all ecosystems have the same kinds of plants and animals? Research the characteristics of one ecosystem, and draw a mural to represent it.

Procedure

Work in groups of four or five. Each group should select one ecosystem to study.

Tape the paper to the walls of the classroom.

Research the ecosystem your group has selected. Find out about the ecosystem’s location, climate, soil, plants, and animals.

Make a Model Draw a mural that represents your ecosystem. Show at least two plants and two animals that live in the ecosystem. Include a world map that shows the locations of the ecosystem.

Communicate List on index cards the information you collected, and attach the cards to your mural. Indicate where you obtained the information.

Draw Conclusions

Compare Compare your group’s mural to the other groups’ ecosystem murals. What similarities and differences do the plants and animals in the ecosystems seem to have?

Explore More

Compare various food chains in the ecosystems. What are the main producers in each? What are the main consumers?

Materials

Step

261EXPLORE

SI.3 Use a variety of sources to answer questions (SI- M-A1) SI.19 Communicate ideas in a variety of ways … (SI-M-A7)a


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262EXPLAIN

How do ecosystems compare?Take a look out your window. If you are in

Louisiana, you might see wetlands, Kisatchie National Forest, or the ocean. If you are in Arizona, you might see a desert. In Iowa the scene outside your window is likely to be a golden grassland. Each environment is an ecosystem. Recall that an ecosystem is all the living and nonliving things interacting in an environment.

A biome (BI•ohm) is one of Earth’s major land ecosystems, with its own characteristic animals, plants, soil, and climate. Climate is the average weather pattern for a region. How is a biome different from other habitats? You can think of a biome as a set of habitats or ecosystems all grouped together into a kind of “super-ecosystem.”

There are six major land ecosystems: taiga (TI•guh), tundra, desert, grassland, rain forest, and deciduous forest. A particular type of biome may be found in different parts of the world. For example, desert biomes exist in North America, South America, Europe, Africa, Asia, Australia, Antarctica, and the Arctic.

▶ Essential QuestionWhat are the characteristics of different land and aquatic ecosystems?

▶ Vocabularybiome, p. 262

wetlands, p. 269

estuary, p. 269

▶ Reading Skill Compare and Contrast

AlikeDifferent Different

▶ Technology e-Glossary, e-Review, and animations online at www.macmillanmh.com

LS.26, LS.27

Louisiana Ecosystems

American alligators are adapted to live in swamp and wetland ecosystems.

Brown pelicans live mainly near saltwater ecosytems, such as bays and oceans.


Ice

Tundra

Taiga

Deciduous forest

Tropical rain forest

Grassland

Desert

INDIANOCEAN

ATLANTICOCEAN

PACIFICOCEAN

ARCTIC OCEAN

Equator

30 ̊N

30 ̊S

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263EXPLAIN

Earth’s ecosystems are not just restricted to land. There are also water ecosystems. Most of Earth’s surface is covered by water. Water ecosystems may be freshwater, saltwater, or a mixture. Ponds, lakes, streams, rivers, wetlands, estuaries, and oceans are all water ecosystems found on Earth.

Areas closer to the equator receive more direct sunlight than areas closer to the poles. For this reason, ecosystems near the equator are rich with plants and animals, while fewer organisms live in Earth’s polar regions.

Climate affects living organisms. Most organisms are adapted to living in one particular region’s climate. That is why you would not find a penguin in the Gulf of Mexico or a bald cypress tree in the Arctic.

Some ecosystems, such as tropical rain forests, are warm and wet, while other ecosystems, such as tundras, are cold and dry. Ecosystems often have different types of soil. Desert soil is usually nutrient-poor, and grassland soil is nutrient-rich.

Where are tropical rain forests usually located?

Clue: Around what range of latitudes is this type of major land ecosystem most often found?

Quick Check

Compare and Contrast How are

ecosystems similar? How are they

different?

Critical Thinking In what kind of

ecosystem do you live? Explain.

Earth’s Major Land Ecosystems

Read a Map

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264EXPLAIN

What are tundras, taigas, and deserts?Only about 25 centimeters (10 inches) of precipitation fall in tundra ecosystems each year. Tundras cover about one-fifth of Earth’s land surface. In the Northern Hemisphere, tundras circle the land just south of the North Pole.

Taigas

Taigas are found south of the northern tundras. Taiga is a Russian word meaning “forest.” A taiga is a cool forest of cone-bearing evergreen trees.

Taigas in the Northern Hemisphere stretch across parts of Europe, Asia, and North America. Taiga winters are cold, and the short summers are warm, wet, and humid. Summer conditions encourage insects to reproduce. The huge insect population is a rich food source that attracts many migrating birds, such as the Siberian thrush. Life on the taiga is limited to the species that can survive the rugged winters. These include low-growing lichens and mosses; trees such as pine, spruce, and hemlock; and animals such as rodents, foxes, wolves, and ravens.

taigatundra

Biomes such as tundras, taigas, and deserts have harsh climates. They may have extremely hot or cold temperatures or very little precipitation. These conditions limit the types of plants and animals that can live there.

Tundras

Tundras are found in far northern regions. These ecosystems have very cold winters and short summers. A tundra is a cold, dry biome that includes a layer of permanently frozen soil called permafrost. Sometimes permafrost is only 1 meter (3.2 feet) below the surface. The permafrost layer prevents trees and large plants from developing deep roots. However, lichens, mosses, grasses, flowers, and low shrubs with shallow root systems can grow above the permafrost.

Tundras support fewer species than most other biomes, and some areas are covered with ice. However, some species thrive there, especially during the short summers when the top layer of permafrost melts and the ground is soggy.


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265EXPLAIN

Deserts

All deserts are dry—they receive less than 25 cm (10 in.) of precipitation per year. Deserts are found on every one of Earth’s continents.

Hot deserts have high temperatures, as their name suggests. The dry desert air contains little moisture to block the Sun’s warming rays. At night, the desert air can be cool because there is no cloud cover and the dry air loses heat easily after dark. When it rains, water often evaporates before reaching the ground. Occasionally short periods of heavy rain occur and cause flooding.

One example of a desert biome is the Sonoran Desert, which covers parts of Arizona, California, and Mexico. It has organisms that are adapted to live in dry conditions. Plants that conserve water, such as the agave or the saguaro cactus, can survive there. Many species of insects, spiders, reptiles, birds, and burrowing animals are also adapted to life in the desert. They often rest during the heat of the day and become active when the temperature falls at night.

The jerboa, a small rodent, is an animal that is well adapted to a desert biome such as the African Sahara. The jerboa rests during the day in a cool burrow and then comes out at night to search for food. This behavior protects the animal from the intense daytime heat. Additionally, the jerboa’s characteristic long leaps help it avoid predators.

Some deserts have cold seasons, but other deserts are cold year-round. A desert is defined by the amount of precipitation in the area, not by its location or temperature. Cold deserts are found in places such as Greenland, central Asia, and Antarctica. Like tundras and taigas, these deserts have long, cold winters and short summers.

desert

Quick Check


tundras and taigas similar? How are

they different?

Critical Thinking Explain why

deserts might seem to have fewer

animals during the day than other

biomes do.

Not all deserts are hot. Some deserts are located in cold regions near the South Pole.SI.18


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266EXPLAIN

grassland

What are grasslands and forests?Before the arrival of immigrant

settlers, much of North America was grassland or forest. Grasslands are biomes in which various species of grasses are the main form of plant life. In North America, grasslands are sometimes called prairies. In the late 1800s, thousands of settlers moved into the area of North America known as the Great Plains. They found large areas full of tall grasses. Before long, these tallgrass prairies were plowed under for farmland. Today, less than 1 percent of the original tallgrass prairies remain. Southwestern Louisiana has a small amount of coastal prairie that is similar to the midwestern prairies.

Rainfall in grasslands is irregular and usually not plentiful. Temperatures are cool in winter and warm in summer. Some of the world’s most fertile soil is found in grasslands. For this reason grasslands are often used for farming. The roots of grassland plants hold soil in place. If the plants are removed, the soil can be blown away by winds.

The plants and animals found in grasslands vary from place to place. In North America, herbivores such as bison, gophers, ground squirrels, and prairie dogs live in the grasslands. Carnivores there include coyotes, badgers, and black-footed ferrets. The grasslands of central Russia, known as steppes, have different animals, such as Siberian chipmunks and wild boars. The grasslands of Argentina, known as the pampas, are home to other kinds of animals, such as pampas deer.

Deciduous Forests

For only a few months each year, the deciduous (dih•SIH•juh•wus) forests in some parts of North America are bright with color. This is the time during which the leaves of the forests’ trees turn from green to the characteristic colors of autumn—red, orange, yellow, and brown—before falling to the ground. The term deciduous means “falling off.”


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267EXPLAIN

In deciduous forests, many trees lose their leaves during winter. With fewer leaves, less transpiration occurs, enabling trees to conserve water. This is important when rainfall is scarce and the ground is frozen. Deciduous trees include ash, oak, beech, hickory, and maple trees. Louisiana’s Kisatchie National Forest has many deciduous hardwood trees in its bottomlands.

Deciduous forests are found in eastern North America, northeastern Asia, and western and central Europe. In these forests mosses, mushrooms, and ferns grow on the forest floor.

Rain Forests

Tropical rain forests are located close to the equator. The climate there is hot and humid. Tropical rain forests have abundant rainfall, often more than 2 m (6.5 ft) per year. This type of climate supports an enormous variety of species. Tropical rain forests are home to more species than are found in all other land biomes combined.

Temperate rain forests are found in some Pacific Northwest areas, such as Oregon. Temperate means “mild.” Temperate rain forests have lower temperatures than tropical rain forests. However, they have plentiful rainfall. Temperate rain forests are also home to many different species.

Although the species found in the two rain forest environments differ, some have similar roles. For example, the squirrel monkey lives in large troops in the tropical rain forests of South America. The talapoin, another monkey, lives in large troops in the tropical rain forests of central Africa. Both monkeys eat rain-forest fruits, seeds, insects, and eggs.

deciduous forest

Quick Check


tropical and temperate rain forests

similar? How are they different?

Critical Thinking What do

grassland biomes have in common

with deserts?

tropical rain forest


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268EXPLAIN

What freshwater

ecosystems are found

in Louisiana?Freshwater ecosystems exist within

and around bodies of water that contain little salt. These bodies of water include ponds, lakes, streams, rivers, and wetlands.

Ponds and Lakes

In most ponds and lakes, such as Lake Pontchartrain, the water does not appear to move. A layer of green algae might cover the water’s surface. Plants there may include cattails, reeds, and water lilies. Insects that glide over the water’s surface often become food for fish swimming below. Turtles, crayfish, and frogs may live there as well. Birds, snakes, and raccoons look for prey along the shore. At first it may seem as if the entire freshwater ecosystem can be easily observed at the surface.

However, it would take much closer observation to see the plankton (PLANG•tuhn) upon which insects and small fish feed. Plankton are tiny organisms that live in water. Some plankton species make their own food through photosynthesis, and others must ingest food. Plantlike plankton and algae form the base of the food chain in water ecosystems.

Streams and Rivers

Streams and rivers, such as the Tchefuncte River in southeastern Louisiana, have moving water. Organisms there have adaptations to keep from being swept away. Reeds have roots that anchor them to the bottom. Fish, such as blue catfish, have streamlined bodies to help them swim in the currents. Other animals have hooks and claws that help them cling to rocks and other objects.

Cypress trees in Lake Fausse Pointe State Park in Louisiana live and grow in this freshwater ecosystem.


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269EXPLAIN

Wetlands

Wetlands are areas in which water is near the surface of the soil much of the time. Coastal Louisiana has many wetland habitats. In fact, about 40 percent of the wetlands in the continental United States are in Louisiana! Wetlands include marshes, swamps, and bogs. These environments are rich in plant life, so they provide a home for many living things. They also are important breeding grounds for birds and other animals. Wetlands serve as natural water filters and sponges. They can help remove various pollutants released by nature, by industry, or by agriculture. Wetlands also provide flood protection and erosion control for the surrounding areas.

Estuaries

Estuaries (ES•chuh•wayr•eez) are water ecosystems that are located where rivers flow into oceans. The water in estuaries contains less salt than ocean water, but it is saltier than water in rivers. The plants and animals that live in estuaries have adaptations that help them survive the variations in salt content, or salinity.

Estuaries are important natural resources. Most of the fish species caught in the United States each year spend part of their lives in estuaries.

Quick Check


estuaries and wetlands similar? How

are they different?

Critical Thinking What role do

plankton play in lakes and ponds?

Wetlands as Water Filters

Make a Model Place two small, potted plants in two clear containers. Each plant and pot represents a wetland.

Slowly pour clean water into one of the pots. Observe the liquid that comes out of the bottom of the pot.

Experiment Stir some colored, powdered drink mix into a cup of water. This represents polluted water. Slowly pour the mixture into the second pot. Note the color of the water that drains from the pot.

Draw Conclusions Based on your observations, what can you conclude about the role of wetlands?

SI.15, SI.22

▲ This Tricolored Heron is adapted to living in this Louisiana wetland.


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270EXPLAIN

What lives in the ocean?The ocean covers more than

70 percent of Earth’s surface. Ocean water plays an important role in the water cycle and contains nutrients that support a variety of life-forms. Ocean food chains begin with plankton, which live near the surface of the water. Nekton (NEK•tun) are animals that swim through the water. Benthos (BEN•thahs) are organisms that live on or near the ocean floor.

The ocean is divided into regions, and each region affects living things in different ways. Factors include tides, temperature, salinity, water pressure, and the amount of sunlight penetrating the water. Near the surface, sunlight warms the water and provides energy for different photosynthetic species.

Almost no sunlight reaches depths greater than 200 m (656 ft). Depths beyond this point are increasingly dark and cold, and photosynthesis does not occur there. Most deep-ocean organisms feed on each other and on materials that sink down from the ocean’s surface. Other deep-ocean organisms, such as certain kinds of bacteria, feed on hot chemicals that flow from hydrothermal vents, which are deep cracks in the ocean floor.

Quick Check

Compare and Contrast How do

ocean ecosystems compare to and

contrast with land biomes?

Critical Thinking How does depth

affect ocean water’s temperature?

Which ocean zone would not have algae growing on the ocean floor?

Clue: What do algae need to make food?

Watch ocean life

at www.macmillanmh.com

Plankton, such as diatoms, copepods, and dinoflagellates, live near the ocean’s surface. Plankton make up the base of the ocean food chain.

Nekton, such as squid, fish, and dolphins, swim through the water.

Benthos, such as crabs, sponges, and corals, are bottom-dwelling animals.

neritic zone

intertidal zone

oceanic zone

Zones of Ocean Life

Read a Diagram


ATLOC

FIC

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271EVALUATE

Writing Link

Ecosystems differ according to their animals, plants, soil, and climate.

Major land ecosystems include tundras, taigas, deserts, grasslands, rain forests, and deciduous forests.

Water ecosystems include ponds, lakes, streams, rivers, wetlands, estuaries, and oceans.

Make a Study GuideMake a trifold book. Complete the statements and add details about major land and water ecosystems.

Think, Talk, and Write Vocabulary A major land ecosystem with a particular climate and certain types of organisms is a(n) .

Compare and Contrast How are freshwater and ocean ecosystems similar? How are they different?

AlikeDifferent Different

Critical Thinking Explain why parts of Antarctica can be classified as desert.

Test Prep The major land ecosystem dominated by trees that shed their leaves in autumn is theA tropical rain forest.B grassland.C deciduous forest.D taiga.

Test Prep Which organisms are nekton?A whales, turtles, sharksB sea stars, plankton, lobstersC crabs, tube worms, algaeD rays, crabs, diatoms

Essential Question What are the characteristics of different land and aquatic ecosystems?

Visual Summary

Persuasive WritingPrepare a travel brochure encouraging

people to visit one of the ecosystems

you have studied. Include important

facts, such as the location, climate, soil,

plants, and animals.

Compare CulturesPlants and animals adapt to their

ecosystems. People do too. Research the

food, shelter, and clothing of people in

two different ecosystems. Write a report

comparing the cultures of the two groups.

-Review Summaries and quizzes online at www.macmillanmh.com

Social Studies Link


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272EXTEND

Did you know that forests breathe? Scientists can measure the gases in the forest air to gather

data about the photosynthesis and respiration of trees, animals, and other organisms that live there.

Take a look at the carbon dioxide data that scientists measured in the air from Howland Forest, a deciduous forest in Maine. Howland Forest has cold, snowy winters and hot, humid summers. How do these changes in seasons affect the amount of carbon dioxide in the air?

SpringAs the days become longer and warmer,

activity in the forest increases. This increased activity results in higher levels of respiration, so the amount of carbon dioxide measured in the air starts to rise. The trees sprout new leaves and begin to photosynthesize.

Summer Summer days are the longest and warmest of

the year. Because the forest is so active, a lot of photosynthesis and respiration occurs. During the day, the amount of carbon dioxide is low. That’s because the trees are taking in carbon dioxide and transforming it into food to store in their roots. During the night, the amount of carbon dioxide is high. All organisms in the forest, including the trees, are respiring and releasing carbon dioxide. These two processes together result in the different day and night carbon dioxide levels you see in the chart.

CO2 Concentration (parts/million)

MonthMinimum

CO2

Maximum CO

2

Jan. 378 388

Feb. 377 385

March 377 384

April 376 388

May 371 393

June 362 413

July 356 427

Aug. 355 424

Sept. 362 418

Oct. 358 386

Nov. 366 379

Dec. 368 377

ELA.12 Demonstrate understanding of information in grade-appropriate texts using a variety of strategies, including:

• identifying ... main ideas and supporting details for each (ELA-7-M1) v

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273EXTEND

These photos show Howland Forest during all four seasons.

History of Science

FallShorter days mean fewer hours of sunlight. Trees begin to

lose their leaves, and the forest becomes less active. The forest is photosynthesizing and respiring less. Day and night carbon dioxide levels are similar.

WinterWinter days are the shortest and coldest of the

year. The forest is much less active. Most of the trees have lost their leaves, and there is no photosynthesis. Day and night carbon dioxide levels are very similar as all the life-forms continue to respire.

Write About ItMain Idea and Details

1. Tell how the levels of carbon dioxide change in Howland Forest throughout the year.

2. Research other biomes and explain how they change during the year.

-Journal Research and write about it online


Main Idea and Details

▶ Look for the central point of a selection to find the main idea.

▶ Details are important parts of the selection that support the main idea.

spring summer

winter fall

Connect to


Bill Beatty/Visuals Unlimited

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