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Human Causes of Extinction

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When Do Ecosystems Go Wrong?
Teacher Contributed

When Species Become Bad

Source: Video Journalism Movement (www.vjmovement.com) in The Netherlands
License: CC BY-NC 3.0

becoming an invasive species

All species are important and necessary for the survival of the ecosystem but sometimes when some species are introduced to a foreign environment, then it will be a different story.

 Invasive Species
can harm both the natural resources in an ecosystem as well as threaten human use of these resources.

How Can An Organism Become Invasive?

1.  Introduction to a new area:

  • via the ballast water of oceangoing ships
  • intentional and accidental releases of aquaculture species
  • aquarium specimens
  • bait
  • hurricanes, typhoons, tsunamis
  • and other means:
    • Globalization:  Global trade has become the single largest factor in the worldwide spread of invasive species by means of ships, planes, and railroads (Bright 1999).
    • Climate Change:  Invasive species are also closely connected with climate change. Biological changes caused by heightened levels of carbon dioxide and variations in temperature and precipitation patterns will have major impacts on the distribution and population levels of species, in addition to the composition and relationships between species in ecosystems (Chornesky and Randall 2003).

2.    Eats the Natural Food Source of the Native and Endemic Species.

3.      Overpopulates the ecosystem disrupting the food web in the process.

What Are The Roles Of The Invasive Species?

  1. Invasive species are capable of causing extinctions of native plants and animals
  2. reducing biodiversity
  3. competing with native organisms for limited resources
  4. and altering habitats  

What Are The Effects of These Invasive Species?

Environmental Impacts

  1. The introduction of invasive species can result in the extinction of local species and irreparable changes to the habitat and biodiversity of invaded ecosystems (Chornesky and Randall 2003).
  2. These species lead to the killing or crowding out of native species through predation, parasitism, disease, and competition (Chornesky and Randall 2003).
  3. They also alter ecological processes such as the water, nutrient, and energy cycles, thus completely changing how ecosystems function (Union of Concerned Scientists 2007).
  4. Invasive and native species can mate to form hybrid species, which can potentially displace the native species, leading to a loss of stability among the native population and eventual extinction (Cleeland and Mooney 2001).

Economic Impacts

  1. The economic impact of invasive species is derived from direct and indirect costs.
    • Direct costs are those related to controlling the spread of invasive species, such as the use of pesticides applied in an attempt to contain the spread of pests.
    • Indirect costs relate to billions of dollars are spent annually as a result of invasive species (Invasive Species Specialist Group 2007).

Health Impacts

  1. Invasive species spread disease that can be devastating to human health (National Environmental Coalition on Invasive Species 2004).
  2. Increased transportation and accessibility have allowed for new interaction between diseases and human hosts.
  3. Many non-native species can act as reservoirs for disease, including insects, rodents, and birds, which carry diseases such as yellow fever and malaria.
  4. Invasive species include food security and water depletion, which are significant concerns in developing countries (Global Invasive Species Program 2007).

What Can Be Done To Combat Invasive Species?

Extension Investigation

Read an article about the Taal Lake in the Philippines and create a Mindomo app , make a concept map using two major topics: native and endemic species against the invasive species. Include the description and photo for each organism.

Sources:    http://en.wikipedia.org/wiki/Taal_Lake , http://www.agnet.org/htmlarea_file/activities/20110826121346/paper-729213301.pdf,

Rubrics:   20 pts Understanding






Organization (x3)

Presents all key words and concepts

In a  well-organized manner to give added meaning.

Presents most of the key words and concepts in a thoughtfully organized manner.

Presents some of the key words and concepts in a somewhat organized manner.

Presents most of the key words and concepts in a choppy and confusing manner.

Content, Concepts and Terminology (2)

Shows an overall understanding of the topic’s concepts and principles using appropriate terminology with no evident misconceptions and errors.

Shows a basic understanding of the topic’s concepts and principles with some mistakes in terminology with few evident misconceptions.

Shows a lack of understanding of many concepts and principles with some evident misconceptions.

Shows no understanding of the topic’s concepts and principles with many evident misconceptions.


Connections and Knowledge of the Relationships Among Concepts

All words are accurately connected indicating superior organization and understanding of the relationship among the concepts conveying precise meaning and overall clarity.

Most words are accurately connected  with few incorrect representation of the relationship between concepts conveying an overall meaning and promotes clarity.


Some words are accurately connected. with incorrect representation of the relationships between concepts conveying some meaning and somewhat promotes clarity.

Most words are inaccurately connected with incorrect representation of the relationships between concepts conveying little meaning and does not promote clarity.

Resources Cited

Image Attributions

  1. [1]^ Source: Video Journalism Movement (www.vjmovement.com) in The Netherlands; License: CC BY-NC 3.0


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