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Natural Changes in Ecosystems: Understanding Ecological Succession and Natural Selection

Explore how organisms evolve and ecosystems change naturally over time through natural selection and ecological succession. Discover how environmental factors influence the survival and reproduction of species in ecosystems. Learn about primary and secondary succession, plus examples like the Galapagos finches and adaptive radiation. Understand the impact of disturbances like flooding, climate change, and insect infestations on ecosystem dynamics. Watch how pioneer species pave the way for new growth and biodiversity.

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Natural Changes in Ecosystems: Understanding Ecological Succession and Natural Selection

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  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. Natural Changes to Ecosystem Life Without People

  6. 1) Steps of Primary Succession

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

  8. p. 112,113

  9. 2. Secondary Succession:

  10. 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.

  11. 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

  12. 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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