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G3-Impacts of Humans on Ecosystems

Page history last edited by Eunji 10 years ago

 

G3:  Impacts of Humans on Ecosystems     

Obj.

Assessment Statement

Notes

Student  Links 

G.3.1

(2)

Calculate the Simpson diversity index for two local communities.

 

D= [N(N-10]/[∑n(n-1)]

 

Where D – diversity index; N = total number of organisms of all species found and n = number of individuals of a particular species.

Teachers are strongly advised to make students collect actual data.  This is an opportunity to use the graphic display calculator and spreadsheets.

   

G.3.2

(3)

Analyze the biodiversity of the two local communities using the Simpson index.

GP – R = NP

   

G.3.3 (3)

Discuss reasons for the conservation of biodiversity using rainforests as an example

Reason should include ethical, ecological, economic and aesthetic arguments. 

 

Aim 8:  There are environmental issues affecting the whole planet and also ethical issues involved in conservation that could be raised here.

   

G.3.4 (1)

List three examples of the introduction of alien species that have had significant impacts on ecosystems.

Choose one example of biological control, and one example each of accidental and deliberate release of invasive species.

   

G.3.5 (3)

Discuss the impacts of alien species on ecosystems

Limit the discussion to inter-specific competition, predation, species extinction and biological control of pest species, with named examples of each.

   

G.3.6 (2)

Outline one example of biological control of invasive species.

Aim 8:  Invasive alien species are such a widespreak prolem that it will almost certainly be possible to find a good local example.  Such species are a real threat to the biodiversity of the planet, with many species facing extinction as a result.  The uniqueness and cultural diversity of human populations are also being affected.

   

G.3.7 (1)

Define biomagnification

Biomagnification is a process in which chemical substances become more concentrated at each trophic level

   

G.3.8 (3)

Explain the cause and consequences of biomagnifications, using a named example

Examples can include biomagnifications of mercury in fish, and organophosphorus pesticides, DDT or TBT (tributyl tin) in ecosystems.

   

G.3.9 (2)

Outline the effects of ultraviolet (UV) radiation on living tissues and biological productivity

 

   

G.3.10 (2)

Outline the effect of chlorofluorocarbons (CFC) on the ozone layer

Details of the chemical reaction are not required.

   

G.3.11 (1)

State that ozone in the stratosphere absorbs UV radiation

There is a limit to UV absorption in the stratosphere.  There is no need to mention UV-A, UV-B and UV-C.

   

 

 

 

G.3.1 Calculate the Simpson diversity index for two local communities (2)

 

The formula to calculate the Simpson diversity index:

             D= (N(N-1))/(sum of n(n-1)) or D= [N(N-10]/[∑n(n-1)]

  

Where

D= Diversity

N= total number of organisms in the ecosystem

N= number of individuals of each species

 

 

This table records the plant species on the foredune of the Indiana Dunes.

Plant Species

Number of individuals, n

N(n-1)

Marram grass

50

50(49) = 2450

Milkweed

10

10(9) = 90

Poison ivy

10

10(9) = 90

Sand cress

4

4(3) = 12

Rose

1

1(0) = 0

Sand cherry

3

3(2) = 6

totals

N=78

2648

 

 

This table records the plant species on the mature dune of the Indiana Dunes

Plant Species

Number of individuals, n

N(n-1)

Oak tree

3

3(2) = 6

Hickory tree

1

1(0) = 0

Maple tree

1

1(0) = 0

Beech tree

1

1(0) = 0

Fern

5

5(4) = 20

Moss

3

3(2) = 6

Columbine

3

3(2) = 6

Trillium

3

3(2) = 6

Virginia creeper

4

4(3) = 12

Solomon seal

3

3(2) = 6

totals

N=27

62

 

Using the formula above, the calculation for the foredune is:

                           D = (78(77))/2648

                           D = 2.27

The calculation for mature dune is:

                           D = (27(26))/62

                           D = 11.3

 

 

 

G.3.2 Analyze the biodiversity of the two local communities using the Simpson index. (3)

 

Biological diversity can be described in two separate ways: Evenness and richness.

- The number of different organisms in a particular area is richness.

- Evenness is how the quantity of each different organism compares with the other.

- Richness only takes into account the kinds of species present in the ecosystem while evenness take abundance into account.

 

A measure that takes into account both richness and evenness is the Simpson diversity index.

 

To see how this works, consider the community of plants the foredune at the Indiana Dunes and the community of plants on the mature dune.

 

The formula to calculate the Simpson diversity index:

             D= (N(N-1))/(sum of n(n-1)) or D= [N(N-10]/[∑n(n-1)]

 

Where

D= Diversity

N= total number of organisms in the ecosystem

N= number of individuals of each species

 

 lake shore dune succession

 

The above picture shows the beach and foredune area. Plants such as marram grass (Ammophila spp.) and cottonwood trees (Populus spp.) help to stabilize dunes and facilitate primary succession.  (http://www.iecology.net/pano_dunes.html)

 

This table records the plant species on the foredune of the Indiana Dunes.

Plant Species

Number of individuals, n

N(n-1)

Marram grass

50

50(49) = 2450

Milkweed

10

10(9) = 90

Poison ivy

10

10(9) = 90

Sand cress

4

4(3) = 12

Rose

1

1(0) = 0

Sand cherry

3

3(2) = 6

totals

N=78

2648

 

 

Indiana dunes

 

The above picture shows the beach and the mature dune area of the Indiana Dunes. (http://www.nd.edu/~adinega/WAL/WAL.recreation.html)

 

This table records the plant species on the mature dune of the Indiana Dunes

Plant Species

Number of individuals, n

N(n-1)

Oak tree

3

3(2) = 6

Hickory tree

1

1(0) = 0

Maple tree

1

1(0) = 0

Beech tree

1

1(0) = 0

Fern

5

5(4) = 20

Moss

3

3(2) = 6

Columbine

3

3(2) = 6

Trillium

3

3(2) = 6

Virginia creeper

4

4(3) = 12

Solomon seal

3

3(2) = 6

totals

N=27

62

 

Using the formula above, the calculation for the foredune is:

                           D = (78(77))/2648

                           D = 2.27

The calculation for mature dune is:

                           D = (27(26))/62

                           D = 11.3

The total number of plants of mature dune is 27 while the total number of plants of foredune is 78. Although mature dune has less total number of plants than the foredune, it is more diverse according to the Simpson diversity index, which shows that the mature dune has a diversity index of 11.3, while the foredune has a diversity index of only 2.27.

Sampling and calculation of the Simpson index periodically can assess the health of an ecosystem.   

 

 

G.3.3 Discuss reasons for the conservation of biodiversity using rainforests as an example. (3)

 

 

These photographs show the destruction of tropical rain forests (http://rainforests.mongabay.com/0804.htm)

 

Economic Reasons

The attempt to create farms on rainforest soils has met with dismal results. Most of the nutrients of rainforests are locked up in the tissues of the plants. The soil left behind after logging is devoid of nutrients.

Moreover, plant sources of medicines and chemicals are lost forever if species are extinct. As long as the rainforest exists, there is the possibility that local crop plants and farm animals could be improved with alleles from wild populations. In addition, ecotourism could improve the local economy.

 

Ecological reasons

An organism key to an ecosystem’s health may be destroyed. Ecosystems have evolved over millions of years. Species are linked together in ecosystems like pieces of a puzzle. We have no idea how many, or which, species we can lose before the puzzle falls apart. Loss of one species could affect other species because many organisms in the ecosystem are interdependent.

Diversity protects an ecosystem against invaders. If alien species are introduced, they will be competing with the existing species in the ecosystem. The more diverse the ecosystem is, the better able it is to withstand pressure from alien species. At the moment, the rainforests are still diverse, but for how long? In the next section, we look at the devastation that happens when alien species move into an ecosystem that is not diverse.

Fewer plants in the biosphere means in the biosphere mean more carbon dioxide in the atmosphere. Excess carbon dioxide caused by burning of fossil fuel is one of the main causes of global warming. Destruction of the rainforest removes a huge number of plants from the biosphere. More plants, not fewer, are needed to remove excess carbon dioxide from the atmosphere.

Disruption of the ecosystem can lead to soil erosion and flooding.

 

Ethical reasons

The local populations is most affected by rainforest destruction. The ethical solution to saving the rainforest is to include the local population in creative ways to conserve it. Many organizations are helping communities make a living from the rainforest while at the same time preserving it.

Do we have a right to destroy an ecosystem, which may be enjoyed in the future generations? We actually have an ethical responsibility to conserve the rainforest so that future generations have access to its beauty and wealth of organisms.

Do we have the right to decide which organisms survive? Human impact on ecosystems is often due to lack of educations and awareness of the problem so that this important resource does not slip away.

 

Aesthetic reasons.

Human well-being is linked to the ability to visit natural areas in our biosphere which have been preserved. The rainforest is one of these areas. Ecotourism is a booming industry, which is helping save parts of the rainforest.

Many artists and writers have been inspired by the beauty of natural ecosystems. Just visit an art museum and you will see the many scenes painted by artists motivated by the natural landscape. The rainforest has inspired thousands of painter and poets.

 

 

G.3.4 List three examples of the introduction of alien species that have had significant impacts on ecosystems. (1)

 

              Introduction of alien species into an ecosystem disrupts communities. Alien species are often able to out-compete native species. This eventually reduces biodiversity. Many native species can be forced out of an ecosystem by one invader.

 

     1. Biological control: In Australia there was a serious problem of the dramatically rapid growth rate of cactus. Therefore a moth, Cactoblastic cactorum, was introduced to Australia to destroy the cactus. Now, a balance exists between the two populations.

 

     2. Accidental release of invasive species: Zebra mussels

Zebra Mussels (Dreissena polymorpha) are tiny black and white striped bivalve mollusks that were accidentally introduced into the US by a European cargo ship which contained zebra mussels in its ballast water.  Now the Zebra mussels have spread all over the Great Lakes causing many economic problems. The Zebra Mussels clog any pipe, which transports surface waters, thus affecting utility plants, factories and water-treatment plants.

 

     3. Deliberate release of invasive species:

Kudzu is a Japanese vine that were purposely planted in the southern US by the Civilian Conservation Corp to solve the problem of soil erosion. 

 

 

G.3.5 Discuss the impacts of alien species on ecosystems. (3)

 

 Alien introductions can lead to interspecific competition, predation, and extinction of native species. All cause a reduction in diversity.

 

Interspecific competition

Species that invades an ecosystem can out-compete the native species.

Ex) The red squirrel lives in the UK; its habitat is forest and woodland. In the 19th century, the grey squirrel was introduced from North America. By the 20th century, the grey squirrel had taken over much of the habitat of the red squirrel. The red squirrel is now only found in areas, which have never been invaded by the grey squirrel. When an animal is lost from an ecosystem many other organisms are affected. Losing these interactions is usually disruptive to biodiversity.

So far, no damage to the ecosystem has been documented by the exclusion of the red squirrel. It is difficult to do controlled studies on a forest ecosystem. However, we must assume that no damage has occurred unless there is data to show the harm.

 

File:Grey squirrel.jpg

Grey Squirrel (http://commons.wikimedia.org/wiki/File:Grey_squirrel.jpg

 

 

Red Squirrel

Red Squirrel (http://www.firstmistake.org/article_red_squirrel_survey.html)

 

Predation

A species that invades an ecosystem can eat another species.

ex) After the opening of the St. Lawrensen Seaway, which connected the Great Lakes to the Atlantic Ocean, ocean fish were free to travel to these freshwater areas. One that made the journey was the sea lamprey. Adult sea lampreys looks like eels but have a round mouth with several rows of rasping teeth. Lake trout were the favorite prey of the lamprey. As that population dropped, the lamprey turned to whitefish. Soon the whitefish population was decimated.

An unexpected benefit of the lamprey was that it facilitated the introduction of salmon to replace the whitefish and lake trout in the Lake Michigan ecosystem. Biologists realized that the population of small fish, especially alewives that had also come from the ocean, was growing out of control. They introduced salmon as a predator to eat the small fish. In addition to eating the small fish, it has become a much sought-after game fish, bringing many tourist dollars to the area.

 

(http://blogs.nationalgeographic.com/blogs/news/chiefeditor/2009/01/lampreys-lured-into-sex-traps.html)

 

(http://blogs.nationalgeographic.com/blogs/news/chiefeditor/2009/01/lampreys-lured-into-sex-traps.html)

 

A Sea Lamprey (Petromyzon marinus) affixed to a host (http://nelson.beckman.illinois.edu/courses/neuroethol/models/lamprey_swimming/lamprey_swim.html)

Species Extinction

Species that invades an ecosystem can out-compete the native species and cause its extinction.

The Nile perch in Lake Victoria provides a good example of species extinction. The African countries Kenya, Tanzania and Uganda share Lake Victoria. In the 1950s, the fish population in the lake had declined because of overfishing. The Nile perch was introduced to increase the fish population. Originally, 80% of the fish in Lake Vicotria were cichlids. But by 1970, the cichlid population had dropped to 1% of the total fish population. Of 400 species of cichlids in Lake Victoria, 200 species are now extinct.

However, the introduction of the Nile perch is seen as a benefit to commercial fishermen who sell them.

 

Nile Perch (http://www.vietfish.com/En/view.php?id=9&&page_number=23)

 

Cichlids (http://www.versaquatics.com/cichlids.htm)

Summary Chart

Impact of alien species on ecosystem

Inter-specific Competition

In UK existed Red Squirrels, however, as the grey squirrels from N. America were introduced, the number of Re Squirrels decreased dramatically due to competition.

Predation

As Sea Lampreys were introduced into the Great Lakes, the Sea Lamprey preyed the lake trout. However, as the population of lake trout’s dropped, the Sea Lamprey preyed for the whitefish and so on.

Species Extinction

As the fish population in lake Vicotria had declined due to overfishing, the Nile Perch was introduced into the lake. However, the cichlids population, which covered 80% of the fish population declined to 1% and eventually became extinct.

Biological control of pest species

Kudzu was introduced to US to solve the problem of Soil erosion. Although the Kudzu did solve the soil erosion problem in Southeastern states, it brought repercussions such as the decrease in diversity of plants in the area as the kudzu rapidly invaded other plants niche.

 

 

G.3.6 Outline one example of biological control of invasive species (2).

 

Biological control is the idea of using a natural predator to control an unwanted or invasive species. However, there is always a risk when introducing a new organism into an ecosystem. Unexpected consequences may occur even though rigorous testing has been done. Scientists look at risk – benefit analysis and make decisions based on that analysis.

 

Example of Biological control of invasive species:

Purple loosestrife (Lythrum salicaria) is an aggressive plant which has invaded the US and Canada. They are extremely fast in their reproduction rate and it also displaces native wetland plants and can become the dominant in this ecosystem. Therefore this plant is a serious threat to the biodiversity of the ecosystem.

So several states decided to release two beetles as biological control agents. Both beetles feed on the leaves of purple loosestrife and thus stablelizing the number of pruple loosestrife in the ecosystem.

 

 

G.3.7 Define biomagnifications (2).

 

Biomagnifications is a process in which chemical substances become more concentrated at each trophic level (ie. Moving up the food chain)

Biomagnification is basically stating that as trophic level goes up, the amount consumed increases. Therefore, although only 10% of the energy is passed on to the next trophic level when consumed, the amount of chemical taken in by the secondary consumer is magnified even more because they consume vast amounts of the primary consumers.

 

bio-magnification in the food chain - DDD applied to Clear Lake

http://www.btoxicfree.com/healthy%20eating.htm

 

 

G.3.8 Explain the cause and consequences of biomagnifications, using a named example. (3)

 

Causes of biomagnification

Some toxic chemicals were deliberately put in the environment to kill insect pests. One of these pesticides was DDT (dichlorodiphenyltrichloroethane, is a well known synthetic pesticide), which was used to control mosquitoes and other insect pests. At the time, it was not known that DDT didn’t break down and would persist for decades in the environment. DDT was commonly sprayed on plants and eventually entered water supplies. There it was absorbed by microscopic organisms. The organisms were eaten by small fish and the small fish eaten by birds the magnification of DDT was even greater.

  

(http://rockandecology.blogspot.com/2008/12/d-d-t-on-my-brain-by-malvina-reynolds.html)

 

Consequence of Biomagnification

The first sign of the problem was a decline in the number of predator birds. Studies showed that the eggs of these birds were easily cracked. In fact, the weight of the mother sitting on the eggs cracked them. It was finally discovered that DDT was building up in the tissue of the birds and interfering with the calcium needed for the shell to be hard. DDT was banned in the US in 1971. The bird population has begun to recover following the ban.

  

 

 

G.3.9 Outline the effects of ultra violate (UV) radiation on living tissues and biological productivity (2).

  •   Non-lethal skin cancer: Basal and squamous cell carcinoma are common factors of skin cancer which are not lethal. Scientists have been collecting data on these forms of skin cancer and have found that a decrease of 1% of stratospheric ozone layer increases these cancers by 2%
  •   Lethal skin cancer: Malignant melanoma is a form of skin cancer which is lethal in 15—20% of cases. Early detection is the key factor in recovery from this type of skin cancer
  •  Mutation of DNA: UV radiation causes changes in the structure of DNA.
  •  Sunburn: Reddening of the skin due to UV radiation is caused by enlargement of small blood vessels. Some cells of the epidermis die and peel off.
  • Cataracts: a cataract is clouding of the lens of the eye leading to loss of vision. Long-term exposure to UV rays is a risk factor for cataracts
  • Reduced Biological productivity: UV radiation can damage and kill plant cells. This affects the ability of the plant to photosynthesize. UV radiation can also damage the DNA of cells involved in growth.

 

G.3.10 (2) Outline the effect of chlorofluorocarbons (CFC) on the ozone layer 

             The CFC is one of the factors that cause the thinning of the ozone layer. Also calculations show that one CFC molecule can move up to the stratosphere in 15 years and remains there destroying ozone molecules for a century.

 

G.3.11 (1) State that ozone in the stratosphere absorbs UV radiation

             In the Stratosphere, chlorofluorocarbons (CFCs) break down to release chloride ions. Then:            

             -Chloride ions react with ozone molecules (03) to produce cio AND OXYGEN 

             -The CIO joins with an oxygen atom to form more oxygen gas and release a chloride ion. 

                                 

 

Visit the following pages for more knowledge about G.3

 

p.27 Competition and Niche Size

p.69-70 Inter specific Competition

p.71 Intraspecific competition

 

 

 

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