Content Benchmark L.8.C.3
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
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
Figure 1. Abiotic and Biotic Factors oin an Ecosystem.
(From
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
For more information on biotic and abiotic factors, seeMS 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
Invasive species are also a threat to biodiversity and impose enormous costs to agriculture, forestry and fisheries. Theintroduction of the alien species may be accidental or intentional. The introduction of non-native animals, plants or microbescan 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
The Southern Nevada Water Authority has additional information on the quagga mussel available at
To learn more about the zebra mussel and how they spread, go to
More information on invasive species in Nevada is available at
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 non-climate related factors.” (From
To find out more about climate change, go to
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
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
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
- 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
- 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
- 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
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.
- 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
2.Biodiversity in the Dzangha-SanghaRain Forest
“In this interactive activity from the AmericanMuseum 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
Teachers domain requires free registration.
- 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 RossIsland 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
Teachers domain requires free registration.
- AcidLake 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
Teachers domain requires free registration.
- 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
- 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
- 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