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3.1 How Changes Occur Naturally in Ecosystems . By the end of section 3.1 you should be able to understand the following: Over time, and many generations, organisms change along with the biotic and abiotic factors in their environments through the process of natural selection .

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3 1 how changes occur naturally in ecosystems
3.1 How Changes Occur Naturallyin Ecosystems

  • By the end of section 3.1 you should be able to understand the following:

  • Over time, and many generations, organisms change along with the biotic and abiotic factors in their environments through the process of natural selection.

  • In natural selection, the best-adapted members of a species survive, grow strong and reproduce more easily than the rest of that species.

  • In ecosystems, ecological succession (primary succession and secondary succession) also occurs, as changes tend to favour certain ecological conditions over others as an ecosystem matures.


3 1 how changes occur naturally in ecosystems1
3.1 How Changes Occur Naturally in Ecosystems

  • Natural selection

    • process where individuals with advantages are better able to reproduce and pass along their traits.


Example:

  • The Finches of the Galapagos Islands (off the coast of Ecuador)

  • There are 13 species of finches on the island…

http://science.discovery.com/videos/100-greatest-discoveries-shorts-natural-selection.html


  • All the species are descended from one finch species on the mainland.

    • Each species has uniquecharacteristics that allows them to thrive in their own niche,

    • and not compete with other finches for resources.

  • Adaptive radiation

    • a form of natural selection when many different species appear from one original species.


  • Natural changes to ecosystem
    Natural Changes to Ecosystem

    Life Without People


    1 steps of primary succession
    1) Steps of Primary Succession


    1 steps of primary succession1
    1) Steps of Primary Succession

    • Pioneer Speciesare the first organisms to survive and reproduce. e.g. Lichens and mosses



    2 secondary succession
    2. Secondary Succession:


    Disturbances that might cause secondary succession
    Disturbances that Might Cause Secondary Succession

    • Flooding

      • Leads to soil erosion,

      • spread of pollutants and harmful bacteria associated with sewage

      • Climate change and global warming may be increasing incidents

        of flooding.

      • A tsunami occurs when huge waves from large earthquakes, flood coastal areas.


    Disturbances that might cause secondary succession1
    Disturbances that Might Cause Secondary Succession

    - Most insects are helpful, but when normal conditions change, infestations can occur.

    - Example: Mountain Pine Beetle:

    Usually it is not a problem…it helps remove old trees, but….

    • Drought

    • Insect infestation


    In our forests there are …

    • a lot of old trees,

    • the climate is warming, and

    • the bugs are not dying in the winter.

      Pine beetle has

    • blue stain fungus in its mouthparts, which it transmits to the trees (symbiotic relationship).

    • Fungus slows down resin production on trees so the beetle can eat the tree more easily.


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