4.3 -- BIO

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Chapter 4
Lesson 3
Succession

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4.3 -- BIO

  1. 1. Lesson Overview 4.3 Succession
  2. 2. Primary and Secondary Succession <ul><ul><li>Ecological succession  a series of predictable changes that occur in a community over time. </li></ul></ul><ul><ul><li>Ecosystems change over time, after disturbances , as some species die out and new species move in. </li></ul></ul>
  3. 3. Primary Succession <ul><ul><li>Succession that begins in an area with no remnants of an older community is called primary succession. </li></ul></ul><ul><ul><li>Some disturbances that are followed by primary succession: </li></ul></ul><ul><ul><li>Volcanic explosions  create new land or sterilize existing areas. </li></ul></ul><ul><ul><li>Retreating glaciers  leaving only exposed bare rock behind them. </li></ul></ul>Retreating glaciers Volcanic explosions
  4. 4. Primary Succession <ul><ul><li>Ex., in Glacier Bay, Alaska, a retreating glacier exposed barren rock. </li></ul></ul><ul><ul><li>Over the course of more than 100 years, a series of changes has led to the hemlock and spruce forest currently found in the area. </li></ul></ul><ul><ul><li>Changes in this community will continue for centuries. </li></ul></ul>
  5. 5. Primary Succession <ul><ul><li>The first species to colonize barren areas are called pioneer species. </li></ul></ul><ul><ul><li>One ecological pioneer that grows on bare rock is lichen—a mutualistic symbiosis between a fungus and an alga. </li></ul></ul>
  6. 6. Secondary Succession <ul><ul><li>Secondary succession where existing communities are not completely destroyed by disturbances. </li></ul></ul><ul><ul><li>Secondary succession proceeds faster than primary succession, because the soil survives the disturbance. </li></ul></ul>
  7. 7. Secondary Succession <ul><ul><li>Secondary succession often follows </li></ul></ul><ul><ul><li>a wildfire (fires can stimulate seeds to grow) </li></ul></ul><ul><ul><li>hurricane, or other natural disturbance. </li></ul></ul><ul><ul><li>human activities like logging and farming. </li></ul></ul>
  8. 8. Why Succession Occurs <ul><ul><li>Every organism changes the environment it lives in. </li></ul></ul><ul><ul><li>When one species alters its environment, other species find it easier to compete for resources and survive. </li></ul></ul><ul><ul><li>Ex. as lichens add organic matter and form soil, mosses and other plants can colonize and grow, other species move in and change the environment further. </li></ul></ul>

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