Download Lesson 4 - Changes in Ecosystems - Hitchcock

Unit 2 Lesson 4 Changes in Ecosystems
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Unit 2 Lesson 4 Changes in Ecosystems
Nothing Stays the Same
How quickly do ecosystems change?
• Some changes happen slowly. With enough slow,
constant change, a pond can develop into a
meadow.
• Eutrophication is the process by which organic
matter and nutrients slowly build up in a body of
water.
• The growth and decay of organisms in the pond
can fill it with organic material, which becomes
soil. Meadow plants then grow in the soil.
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Unit 2 Lesson 4 Changes in Ecosystems
How quickly do ecosystems change?
• Ecosystems can also change suddenly due to
catastrophic natural events.
• The strong winds of a hurricane, a forest fire
started by lightning, or a volcanic eruption can
lead to massive destruction of an ecosystem.
• However, recovery brings new changes to an
ecosystem.
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Unit 2 Lesson 4 Changes in Ecosystems
Ruin and Recovery
• In 1980, the volcanic eruption of Mount St. Helens
in Washington state killed people, plants, and
animals, and damaged much forestland.
• The eruption changed the ecosystem dramatically.
Trees fell, forests burned, ice and snow melted,
and flowing mud removed more trees.
• Some species were protected by snow patches
and ice, others were sheltered in burrows. As
more sunlight reached the ground, seeds sprouted
and the recovery began.
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Unit 2 Lesson 4 Changes in Ecosystems
Nothing Stays the Same
What are the two types of ecological
succession?
• The slow development or replacement of an
ecological community by another ecological
community over time is called succession.
• A community may start growing in an area that
has no soil. This process is called primary
succession.
• The first organisms to live in an uninhabited area
are called pioneer species. They grow on rock
and help form soil in which plants can grow.
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Unit 2 Lesson 4 Changes in Ecosystems
What are the two types of ecological
succession?
• Identify each step of primary succession.
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Unit 2 Lesson 4 Changes in Ecosystems
What are the two types of ecological
succession?
• Succession also happens to areas that have been
disturbed but that still have soil.
• An existing ecosystem may be damaged by a
natural disaster, or farmland may be cleared but
left unmanaged.
• If soil is left intact, the original community may
regrow through a series of stages called
secondary succession.
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Unit 2 Lesson 4 Changes in Ecosystems
What are the two types of ecological
succession?
• What are the features of each stage of secondary
succession shown here?
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Unit 2 Lesson 4 Changes in Ecosystems
It’s a Balancing Act
What are two signs of a mature
ecosystem?
• In the development of an ecosystem, a
community of producers forms first, followed by
decomposers and consumers.
• As a community matures, it may become
dominated by well-adapted climax species.
• An ecosystem dominated by climax species is
stable until it is disturbed.
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Unit 2 Lesson 4 Changes in Ecosystems
What are two signs of a mature
ecosystem?
• As succession moves along, richer soil, nutrients,
and other resources become available. This allows
more species to become established.
• By the time climax species are established, the
resources in the area support many different kinds
of organisms.
• The number and variety of species that are
present in an area is called biodiversity.
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