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3.1 How Changes Occur Naturally in Ecosystems

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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.
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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

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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 succession1
1) Steps of Primary Succession
  • Pioneer Speciesare the first organisms to survive and reproduce. e.g. Lichens and mosses
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
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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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