Content Benchmark L.8.C.3
Students will evaluate how changes in environments can be beneficial or harmful. E/S
Earth’s ecosystems are diverse and range in terms of their complexity. Although ecosystems are
never static, some changes cause more effects than others. When a change occurs in an
environment, there is usually a ripple effect. According to the EPA, “An ecosystem is an
interdependent, functioning system of plants, animals and microorganisms. An ecosystem can be
as large as the Mojave Desert, or as small as a local pond. Without the support of the other
organisms within their own ecosystem, life forms would not survive, much less thrive. Such
support requires that predators and prey, fire and water, food and shelter, clean air and open
space remain in balance with each other and with the environment around them.” (From
http://www.epa.gov/climatechange/effects/eco.html).
All ecosystems are vulnerable to natural changes or those caused by the direct influence of
human activity. Pressures such as habitat fragmentation and loss, the introduction of non-native
species, climate change, fire, and resource management have impacted ecosystems. The effects
may be beneficial, harmful, and/or neutral to parts of the ecosystem. Changes may cause a
population of species within an area to increase or decrease. Entire populations may become
extinct or new invasive species may be introduced. Due to the complex interactions of biotic and
abiotic factors within an ecosystem, evaluating the change in an ecosystem can be challenging.
Abiotic and Biotic Factors
Everything in an ecosystem can be classified as abiotic or biotic. The abiotic factors of an
ecosystem include all non-living components such as water, sunlight, oxygen, temperature, soil,
and climate. Social factors are also included in abiotic components of an ecosystem. This might
include things such as how humans use the land and water resources.
To learn more about abiotic factors go to
http://www.botany.uwc.ac.za/sci_ed/grade10/ecology/abiotic/abiot.htm
Figure 1. Abiotic and Biotic Factors oin an Ecosystem.
(From www.edquest.ca/content/view/32/)
Biotic factors include all living or once living things. It also includes the products of these living
things such as wastes and remains. Each biotic factor has a role within an ecosystem and would
have an effect on any change that may occur. Organisms not only interact with each other but
they also interact with the abiotic factors in the environment. The atmosphere, soil, and sun are
the abiotic factors in the diagram below.
Figure 2. Interactions of Biotic and Abiotic Factors within an Ecosystem.
(From www.physicalgeography.net/fundamentals/9j.html)
For more information on biotic and abiotic factors, see MS TIPS Benchmark L.8.C.4
Changes in Ecosystems
Many types of changes can occur in an ecosystem. The changes can be the result of human
impact or natural causes/ processes. Humans have impacted practically every ecosystem on
Earth. Humans have over-fished the oceans, polluted water sources, caused deforestation,
eradicated entire species, or introduced new invasive species. Most human activities cause
changes to the ecosystem in one way or another. Natural forces are also factors that cause
ecosystems to change. They can be large scale natural changes such as fire or they can be slow
changes such as erosion.
Biodiversity describes the variation of organisms found in an ecosystem. Biodiversity is the
foundation to a healthy ecosystem and may be impacted by pressures that cause environmental
change such as habitat loss, the introduction of invasive species, climate change, fire and
resource management. Figure 3 models the impact of three rates of infrastructure development
on the environment and its biodiversity. The development of roads, pipelines, and powerlines
causes natural habitats to become fragmented into islands and negatively impacts the natural
flora and fauna of the area.
Figure 3. Human Impact on Biodiversity. (From
http://maps.grida.no/go/graphic/changes_in_biodiversity_and_ecosystems_based_on_human_impact_1990_2050)
Invasive species are also a threat to biodiversity and impose enormous costs to agriculture,
forestry and fisheries. The introduction of the alien species may be accidental or intentional. The
introduction of non-native animals, plants or microbes can result in serious problems. For
example, if the non-native species does not have natural predators in their new environment, then
they may potentially rapidly reproduce, out-compete the native species in the area and alter
natural habitats. The spread of invasive species is a serious problem and may cause extensive
damage to ecosystems. One example of an invasive species is the zebra mussel. Primarily due
to recreational boating, this species has made its way across the United States. This invasive
species has caused millions of dollars of damage to municipal and private facilities relying on
freshwater. In Nevada, the quagga mussel (closely related to the zebra mussel) is an invasive
species that is causing problems in the freshwater reservoirs by clogging water intake pipes. The
quagga mussel, which is a filter feeder, can filter a liter of water a day and decrease the food
supply for the aquatic wildlife. They also reproduce at an incredible rate.
Figure 4. Distribution of Zebra and Quagga Mussels Across the United States.
(From http://nas.er.usgs.gov/taxgroup/mollusks/zebramussel/maps/current_zm_quag_map.jpg)
The Southern Nevada Water Authority has additional information on the quagga mussel
available at http://www.snwa.com/html/env_quagga_mussel.html.
To learn more about the zebra mussel and how they spread, go to
http://seagrant.wisc.edu/zebramussels/.
More information on invasive species in Nevada is available at
http://www.biodiversitypartners.org/invasive/factsheets/NV.pdf.
Climate change is another factor that impacts ecosystems. However, this controversial issue
debates whether the changes are a result of human activity or a natural change. Regardless of the
cause, the climate is changing. The effects of climate change are already evident in some
ecosystems. According to the EPA, “As the climate continues to warm, major changes may
occur in ecosystem structure and function, species’ ecological interactions, and species’
geographic ranges, with predominantly negative consequences for biodiversity. In addition,
climate changes such as increased floods and droughts are predicted to increase the risk of
extinction for some plant and animal species, many of which are already at-risk due to other nonclimate related factors.” (From http://www.epa.gov/climatechange/fq/effects.html#1)
To find out more about climate change, go to http://epa.gov/climatechange/kids/.
Fire is another important natural occurrence that causes drastic changes to ecosystems. While
many mistakenly believe that fire only causes danger, this is far from the truth. Fire helps
maintain such ecosystems as grasslands from turning into forests or scrublands. Fire also helps to
promote new growth in forest by clearing debris from the forest floor and allowing the
germination of seeds. In fact, some trees like the redwoods and giant sequoias need their seeds
“heat treated” by fire to germinate.
Teachers can find more about the importance of fire to various ecosystems within the United
States at http://www.nifc.gov/preved/comm_guide/wildfire/fire_6.html
As humans acquire the resources necessary for life, the environment is impacted. The
construction of dams for freshwater reservoirs and hydroelectric power plants has dramatically
affected freshwater habitats. For example, the reproduction of migrating fish is hindered or they
may be damaged by floodgates or turbines. Dams also restrict sediment from flowing down
stream. However, dams benefit by providing flood control, drinking water supply, clean
electricity generation, and fishing. In March 2008, the Department of the Interior and the United
States Geological Survey conducted a large scale experiment by increasing the flow of the river
to study the effects on aquatic wildlife and to restore the beaches of the Colorado River in the
Grand Canyon. Millions of cubic feet of water were released from the Glen Canyon Dam in 60
hours. Over time, scientists plan to document the effects of the higher flows of the river on the
rainbow trout, the endangered humpback chub, as well as non-native fishes.
For more information on the dam release and the Grand Canyon, go to
http://www.doi.gov/news/08_News_Releases/080305.html
There are trade-offs associated with resource management and protecting the environment.
Overall, the impact that humans have on the environment is negative. However, humans have
taken action to improve the ecosystems that were damaged or destroyed by human activities.
Examples of humans changing the environment to make a positive impact are natural/wildlife
preserves and national parks. These are areas of land that are protected, managed, and conserved
for the benefit of the environment. Many cities participate in recycling programs which limit the
amount of trash that enters the landfills and decreases the demand for non-renewable resources.
New fuels and improved engines reduce pollutants into the atmosphere. The mining industry,
which is a major source of income in Nevada, also has developed environmentally responsible
techniques to extract and process their resources. Environmental laws also require the mining
industry to reclaim the land that they use.
Content Benchmark L.8.C.3
Students will evaluate how changes in environments can be beneficial or harmful. E/S
Common misconceptions associated with this benchmark
1. Students incorrectly believe that humans cannot have a positive effect on an
environment.
There is ample news coverage on how humans are ruining the environment. Students do not
think about the positive effects that humans may have on the environment. Overall, the
impact that humans have on the environment is negative. However, humans have taken
action to improve the ecosystems that were damaged or destroyed by human activities. For
example, humans have designated protected areas such as wildlife refuges and national parks.
For more information on positive impacts humans have made go to
http://www.regentsprep.org/Regents/biology/units/humanimpact/improvements.cfm
2. Students incorrectly believe that when humans are having a negative effect on the
environment it could not be positive for the humans.
Students tend to feel empathy towards the ecosystem more than the needs of humans. There
is a cost benefit analysis that must be done to decide if the overall effect of the change was
beneficial or harmful. One change that has many negative impacts on the environment but is
beneficial in many ways to humans is a dam.
For more information on the negative environmental impacts and positive societal impacts of
dams go to http://www.dsi.gov.tr/english/congress2007/chapter_2/60.pdf.
3. Students have the misconception that fire does irreparable and permanent damage to
an ecosystem.
Fire is an important abiotic factor in many environments. Periodic fires in the grasslands will
prevent the establishment of trees which could grow in many grassland ecosystems such as
the North America prairie if not for these fires. In many coniferous forests, fires prepare
seedbeds by removing debris and may help to remove seed coats (scarification) and allow for
the germination of seeds. Some trees such as the ponderosa pine even show greater growth in
years after fires.
To find out more about the positive and negative effects of wildfire go to
http://www.googobits.com/articles/p2-547-are-you-wildfire-aware.html.
Content Benchmark L.8.C.3.
Students will evaluate how changes in environments can be beneficial or harmful E/S
Sample Test Questions
Questions and answers to be provided on a separate document
Content Benchmark L.8.C.3.
Students will evaluate how changes in environments can be beneficial or harmful E/S
Answers to Sample Test Questions
Questions and answers to be provided on a separate document
Content Benchmark L.8.C.3
Students will evaluate how changes in environments can be beneficial or harmful. E/S
Intervention Strategies and Resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. NASA Biotic vs. Abiotic Lesson Plan
In this lesson students observe and study different items to classify them as biotic or abiotic.
Then, they create a Venn diagram (or double bubble map). Students discuss why things were
placed in each category. The lesson ends with the students answering the question “What
tests could scientists who brought back an object from space do to determine if the object
was biotic or abiotic?”
To access this lesson go to http://media.nasaexplores.com/lessons/01-068/9-12_1.pdf
2. Biodiversity in the Dzangha-Sangha Rain Forest
“In this interactive activity from the American Museum of Natural History, explore
representations of three habitats within Africa's Dzanga-Sangha rainforest. Follow clues that
reveal how its resident animals, plants, and people depend on one another. The challenge
requires users to play "connect the dots" to identify feeding relationships, and highlights
animal behaviors and natural resources within the ecosystem.” Students have to predict
relationships between factors in the environment.
To access this activity go to
http://www.teachersdomain.org/resources/lsps07/sci/life/oate/biodiversity/index.html
Teachers domain requires free registration.
3. Penguin Response to Climate Change – 5 minutes 40 seconds
“This video segment adapted from Lloyd Fales and Sweetspot Pictures, Inc. examines how
the changing Antarctic climate affects the Adélie penguins that live there. Learn about the
penguin colonies on Ross Island and see how changes due to global warming affect the
success of these colonies. For example, ecologist Grant Ballard points out a snowfield where
thousands of penguins were buried alive during a single powerful storm. While storms can
also help break up the ice to increase access to open waters, other rapid climate change
events, such as the massive iceberg that broke off the Ross Ice Shelf in 2000, block access
between penguin feeding and breeding grounds and cause populations to decline.”
To access this video go to
http://www.teachersdomain.org/resources/ipy07/sci/ess/watcyc/penguinscience/index.html
Teachers domain requires free registration.
4. Acid Lake Interactive Activity
This interactive activity adapted from EcoKids introduces acid rain, how it affects aquatic
ecosystems, the difference between acid rain and normal rain, and how certain species as
well as entire ecosystems, react to emissions from industrial and other manmade sources that
contribute to acid rain.
To access this activity go to
http://www.teachersdomain.org/resources/lsps07/sci/life/oate/acidlake/index.html
Teachers domain requires free registration.
5. Reading on Human Impacts on Ecosystems
This is a sample chapter from McGraw-Hill which provides information on human impacts
on ecosystems. It also asks comprehension questions and has a lab activity that challenges
students to come up with a solution to help protect a wetland that a developer wants to build
a road through. While the information is focused for the Alberta, Canada area it does provide
information in a middle school friendly way.
To access this reading go to
http://www.mcgrawhill.ca/school/schoolGraphics/sf07_samplechapter_topic2.pdf
6. Natural Change in an Ecosystem Game
This game helps students learn about the natural changes that can occur in an ecosystem and
the effects these changes may have. All of the supplies are ready to print out including
worksheets and cards required. All of the information is also available in Spanish.
To access this activity go to
http://www.nmnaturalhistory.org/smnhc/Ecosystems%20Explorations%20Curriculum/6.%20
Natural%20Change.pdf
7. The University of Illinois Extension: Natural Resources, the Environment and
Ecosystem
This site includes the following activities titled:
Wildlife: Just One Piece of the Picture
In this lesson students study one animal’s requirements for living. They then study human
activity around their community and how it affects habitats of wildlife. Lastly, they make a
list of things that could be done in their community to improve protection of wildlife habitats.
Students are also challenged to find a way to get involved to help protect these habitats.
Integrated Pest Management
In this activity students analyze a graph of weeds in a soybean field and determine the effects
if the weeds are not controlled. They then decide whether it is beneficial to spray an
herbicide that helps control the weeds.
To access these activities go to
http://www.urbanext.uiuc.edu/ecosystems/teacherguide1.html