Download 3 Freshwater Ecosystems

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.
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The Earth’s Ecosystems
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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.
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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?
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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.
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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.
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Interactive Textbook Answer Key
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Life Science