Transcript Chapter 20: Environmental Changes in an Ecosystem

Chapter 20: Environmental
Changes in an Ecosystem
Foundations
Ms. Johnson
Objectives
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Plants and animals within a community are dependent on
each other and tend to develop a stable community in
balance with their environment.
Ecological succession is a natural process by which one
community is replaced by another community in an orderly,
predictable sequence.
Certain natural processes, such as volcanic eruptions, severe
weather changes, and forest fires, put stress on ecosystems
and may disrupt or destroy them.
Humans affect the environment by causing pollution, killing
animal populations, destroying forests, and so on. These
actions put stress on ecosystems and may disrupt or destroy
them.
Both natural and human processes that cause environmental
disturbances can endanger species populations and even
cause species extinction.
Vocabulary
Community
 Succession
 Global warming
 Biodiversity
 Extinction
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Changing
Ecosystems
Biological Balance in Nature
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An ecosystem consists of all factors, living and
nonliving, necessary to sustain a living community.
◦ Will remain stable if the factors stay constant
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A biological community can contain many types
of plants and animals living in association with one
another.
◦ Food sources, environmental conditions, balanced
populations
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Changes in the environments can cause stress on
the ecosystem and effect the community.
◦ Can be slow or sudden
Biological Balance
in Nature
What do you think community A might look like midway
in its change to becoming like community B?
Succession
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Succession is a natural process by which
one living community is replaced with a
new community.
Succession
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After a fire destroys a forest, the
soil becomes enriched with
minerals from the remains of
plants and animals that once lived
there.
Soon after mosses and small
lichens sprout attracting insects.
◦ Eventually they die out and get
replaced by larger plants (grasses,
shrubs, small trees)
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Larger animals start to move in
such as foxes and deer.
As the trees grow larger a forest
develops.
Each new community changes the
environment, making it more
suitable for the next community,
until one emerges that does not
get replaced because it is stable
(climax community).
Competition
Competition for food and
space is an important part
of the relationships among
living things in an
ecosystem.
 Example:
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◦ Moose and snowshoe hare
live in same area and both
eat birch tree.
◦ The moose has an advantage
because it is larger.
◦ In the winter, the hare is
more likely to die from
starvation because of
competition for limited food.
Environmental
Threats That Upset
the Ecosystem
Geologic Events
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Some geologic events can disrupt or
devastate and ecosystem and can it to
change.
◦ Volcanic eruptions, earthquakes, tsunamis, etc.
Geologic Events
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The 1980 eruption of
Mount St. Helens
destroyed 100,000 acres.
The eruption also
caused mud slides,
flooding, and a blanket of
volcanic ash.
Aquatic animals, large
animals, and birds
perished.
Smaller animals, like
rodents, survived due to
living underground.
After the eruption
organisms reappeared.
Climatic Changes
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Climate is the average
condition of the
atmosphere over a large
region for a period of
many years.
◦ Creates a wide variety of
ecosystems.
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18,000 years ago a large
portion of the North
was covered in ice and
organisms such as
mammoths and saber
tooth tigers lived near
the ice sheet.
◦ The warming climate
changed the ecosystem and
they went extinct.
Flooding
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A condition of excessive
water on land.
◦ Heavy rainfall and melting ice
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Can upset aquatic
ecosystems.
Droughts
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Caused by a lack of
precipitation for extended
periods of time.
◦ Causes many plants to die
removing a primary source of
food.
◦ Lack of water
Floods and Droughts
Storms
Thunderstorms, hurricanes,
tornadoes, and blizzards
 Thunderstorms
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◦ Can ignite fires
◦ Cause hail
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Hurricanes
◦ Storm surge along the coast
◦ Destroy beach ecosystems
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Tornadoes
◦ Disrupt life in a narrow strip
of land
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Blizzards
◦ Snow, cold, high winds, can
cause organisms to freeze to
death or starve
Forest Fires
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Forest fires destroy large
areas of timber each
year.
◦ Destroy trees, ecosystems,
and animals
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Can be started naturally
or by human.
They play an important
environmental role
because ecosystems are
renewed by the carbon
or nutrients, succession
takes place, and new
plants and animals are
introduced.
Human Interference
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Pollution
Pumping pollutants into the air
Leads to global warming
Burial and burning of garbage and toxic material
Release of sewage in rivers, lakes, oceans
Growth and land exploitation
As human population increases, we take up more
land and destroy ecosystems
Introduction of new species
When “foreign” animals are introduced they can
disrupt an ecosystem
Competition for food and space
Results of
Environmental
Change
Biodiversity
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Biodiversity: describes the
variety of life-forms that
exist.
◦ Example: there are 1,500
different fish species in the
great barrier reef and 350
coral species.
There are still millions of
species on earth that have
yet to be identified.
 Failure to preserve the
diversity of life on earth
could limit our ability to
solve future problems and
could limit our existence
on Earth.
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Biodiversity
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An endangered
species is a plant or
animal species that is
close to extinction.
◦ Ex. Polar bears, pandas,
tigers, blue whale,
rhinos, gorillas
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Most of the animals
that are endangered
are because of
humans.
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Reasons why:
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Loss of habitat
Introduced species
Overgrazing lands
Developed areas
Low gene pool
diversity
Predation
Vegetation changes
Competition
Deforestation
Extinction
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Extinction occurs when a species dies out.
◦ Usually happens when part of the living or
nonliving environment is removed.
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Can be caused naturally or by humans.
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Climate changes
Floods
Habitat invasions
Excessive hunting
Pollution of land, water, and air
Dinosaurs, woolly mammoths, dodo birds,
passenger pigeons
Homework
Pages 252-253
Pages 257-259
Pages 262-264