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G-3 Impacts of humans on ecosystems

Page history last edited by Eunji 10 years, 2 months ago

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.

 

http://www.forestryimages.org/browse/detail.cfm?imgnum=5015058

 

 

2. Accidental release of invasive species:

     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.

 

http://texasliberal.wordpress.com/2008/04/12/if-only-we-could-communicate-with-zebra-mussels/

 

 

3. Deliberate release of invasive species:

     

 

Kudzu, a Japanese vine species invasive in the southeast United States, growing in Atlanta, Georgia(http://en.wikipedia.org/wiki/File:Kudzu_on_trees_in_Atlanta,_Georgia.jpg)

G.3.7 (1) Define biomagnifications

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.

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

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.

http://kcm.kr/dic_view.php?nid=39974&key=&kword=&page=

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

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.

 

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

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.

http://www.macalester.edu/environmentalstudies/threerivers/studentprojects/LakesStreamsRiversFall09/InvasiveSpeciesWeb/PurpleLoosestrife.html

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

  • 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.

 

 

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