Chapter 20
Section 2 Marine Ecosystems
Life in the Ocean
• Abiotic Factors Marine ecosystems are shaped
by abiotic factors including water temperature,
water depth, and the amount of sunlight that
passes into the water.
• Plankton Trillions of plankton live in the ocean.
Plankton are tiny organisms that float near the
surface of the water.
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Chapter 20
Section 2 Marine Ecosystems
Temperature
• Depth and Temperature The temperature of
ocean water decreases as the depth of the water
increases.
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Chapter 20
Section 2 Marine Ecosystems
Depth and Sunlight
• The Intertidal Zone The intertidal zone is the
place where the ocean meets the land.
• The Neritic Zone As you move farther away from
shore, into the neritic zone, the water becomes
deeper.
• The Oceanic Zone In the oceanic zone, the sea
floor drops sharply
• The Benthic Zone The benthic zone is the ocean
floor. The deepest part does not get any sunlight.
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Chapter 20
Section 2 Marine Ecosystems
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Chapter 20
Section 2 Marine Ecosystems
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Chapter 20
Section 2 Marine Ecosystems
A Closer Look
• Intertidal Areas Intertidal areas are found near
the shore. These areas include mudflats, sandy
beaches, and rocky shores.
• Coral Reefs Coral reefs are found in warm,
shallow areas of the neritic zone. Reefs provide
homes for many marine animals and plants.
• Estuaries An area where fresh water from rivers
spills into the ocean is called an estuary. Plants
and animals living in estuaries must be able to
survive in a changing concentration of salt.
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Chapter 20
Section 2 Marine Ecosystems
A Closer Look, continued
• The Sargasso Sea An ecosystem called the
Sargasso Sea is found in the middle of the
Atlantic Ocean. The ecosystem contains floating
rafts of algae.
• Polar Ice The Arctic Ocean and the ocean around
Antarctica have icy waters, which are rich in
nutrients. Many fishes, birds, and mammals live in
this ecosystem.
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Chapter 20
Section 3 Freshwater Ecosystems
Stream and River Ecosystems
• Water in Streams and Rivers The water in
brooks, streams, and rivers may flow from melting
ice or snow. Or the water may come from a
spring.
• Tributaries Each stream of water that joins a
larger stream is called a tributary.
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Chapter 20
Section 3 Freshwater Ecosystems
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Chapter 20
Section 3 Freshwater Ecosystems
Pond and Lake Ecosystems
• Life near Shore The are of water closest to the
edge of a lake or pond is called the littoral zone.
The plants in the littoral zone are homes to small
animals.
• Life Away from Shore The area of a lake or pond
that extends from the littoral zone across the top
of the water called the open-water zone. Beneath
the open-water zone is the deep-water zone,
where no sunlight reaches.
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Chapter 20
Section 3 Freshwater Ecosystems
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Chapter 20
Section 3 Freshwater Ecosystems
Wetland Ecosystems
• Marshes A treeless wetland ecosystem where
plants, such as grasses, grow is called a marsh.
Muskrats, turtles, frogs, and birds live in marshes.
• Swamps A wetland ecosystem in which trees and
vines grow is called a swamp. Water lilies and
other plants grow in standing water. Many fishes,
snakes, and birds also live in swamps.
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Chapter 20
Section 3 Freshwater Ecosystems
From a Lake to a Forest
• Build Up of Sediments Water entering a
standing body of water usually carries nutrients
and sediments. These materials build up on the
bottom of the lake or pond.
• Formation of a Wetland Over time, the pond or
lake is filled with sediments. Plants grow in the
new soil and the pond or lake starts becoming a
wetland. The wetland then may develop into a
forest.
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