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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?
260
ENGAGE
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)
Materials
How do different ecosystems
compare?
Purpose
Earth’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.
• masking tape
• long piece of
white butcher
paper or chart
paper
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.
• reference
materials
Research the ecosystem your group has
selected. Find out about the ecosystem’s
location, climate, soil, plants, and animals.
• crayons and
colored markers
• index cards
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.
Step
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?
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)
261
EXPLORE
How do ecosystems compare?
▶ Essential Question
What are the characteristics
of different land and
aquatic ecosystems?
LS.26, LS.27
▶ Vocabulary
biome, p. 262
wetlands, p. 269
estuary, p. 269
▶ Reading Skill
Compare and Contrast
Different
Alike
Different
▶ Technology
e-Glossary, e-Review, and
animations online at
www.macmillanmh.com
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.
Louisiana Ecosystems
American alligators are
adapted to live in swamp
and wetland ecosystems.
262
EXPLAIN
Brown pelicans live mainly
near saltwater ecosytems,
such as bays and oceans.
Earth’s Major Land Ecosystems
ARCTIC OCEAN
ATLANTIC
OCEAN
30˚ N
PACIFIC
OCEAN
Equator
INDIAN
OCEAN
Ice
Tundra
30˚ S
Taiga
Deciduous forest
Tropical rain forest
Grassland
Desert
Read a Map
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.
Where are tropical rain forests
usually located?
Clue: Around what range of
latitudes is this type of major
land ecosystem most often
found?
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.
Quick Check
Compare and Contrast How are
ecosystems similar? How are they
different?
Critical Thinking In what kind of
ecosystem do you live? Explain.
263
EXPLAIN
What are tundras, taigas, and deserts?
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.
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.
Tundras
Taigas
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.
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.
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.
tundra
264
EXPLAIN
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.
taiga
desert
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.
SI.18
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.
Not all deserts are hot. Some deserts are
located in cold regions near the South Pole.
Quick Check
Compare and Contrast How are
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.
265
EXPLAIN
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.
grassland
266
EXPLAIN
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.”
deciduous forest
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.
tropical rain forest
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.
Quick Check
Compare and Contrast How are
tropical and temperate rain forests
similar? How are they different?
Critical Thinking What do
grassland biomes have in common
with deserts?
267
EXPLAIN
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.
268
EXPLAIN
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.
Wetlands as Water Filters
SI.15, SI.22
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?
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
Compare and Contrast How are
estuaries and wetlands similar? How
are they different?
Critical Thinking What role do
plankton play in lakes and ponds?
▲ This Tricolored Heron is adapted to
living in this Louisiana wetland.
269
EXPLAIN
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?
Zones of Ocean Life
neritic
zone
intertidal
zone
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.
270
EXPLAIN
Read a Diagram
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
oceanic
zone
Visual Summary
Ecosystems differ
according to their
animals, plants, soil,
ATL and climate.
OC
FIC
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?
Different
Major land ecosystems
include tundras, taigas,
deserts, grasslands, rain
forests, and deciduous
forests.
Alike
Different
Critical Thinking Explain why parts of
Water ecosystems
include ponds, lakes,
streams, rivers,
wetlands, estuaries, and
oceans.
Make a
Study Guide
Antarctica can be classified as desert.
Test Prep The major land ecosystem
dominated by trees that shed their
leaves in autumn is the
A tropical rain forest.
B grassland.
C deciduous forest.
D taiga.
Test Prep Which organisms are
nekton?
whales, turtles, sharks
sea stars, plankton, lobsters
crabs, tube worms, algae
rays, crabs, diatoms
Make a trifold
book. Complete
the statements
and add details
about major
land and water
ecosystems.
A
B
C
D
Essential Question What are the
characteristics of different land and
aquatic ecosystems?
Writing Link
Social Studies Link
Persuasive Writing
Compare Cultures
Prepare 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.
Plants 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
271
EVALUATE
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?
CO2 Concentration
(parts/million)
Spring
As 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.
272
EXTEND
Minimum
CO2
Maximum
CO2
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
Month
ELA.12 Demonstrate understanding of information in grade-appropriate texts using a
vvariety of strategies, including:
• identifying ... main ideas and supporting details for each (ELA-7-M1)
History of Science
spring
summer
winter
fall
These photos show
Howland Forest during
all four seasons.
Fall
Shorter 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.
Winter
Winter 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 It
Main 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.
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.
Connect to
-Journal Research and write about it online
at
www.macmillanmh.com
at www.macmillanmh.com
273
EXTEND
Bill Beatty/Visuals Unlimited