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35.5 Disturbances are common in communities

35.5 Disturbances are common in communities. Objectives. Describe how disturbances can have positive and negative effects. Compare primary and secondary succession. Explain how human activities can affect species diversity. Vocabulary. e cological succession p rimary succession

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35.5 Disturbances are common in communities

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  1. 35.5Disturbances are common in communities

  2. Objectives • Describe how disturbances can have positive and negative effects. • Compare primary and secondary succession. • Explain how human activities can affect species diversity.

  3. Vocabulary • ecological succession • primary succession • secondary succession • introduced species

  4. Disturbances to Communities • continually changing • fires, floods, droughts, etc. • not always negative • sometimes human-caused

  5. Ecological Succession • The series of predictable changes that occurs in a community over time is called succession. • To remember: Think of succession as it relates to monarchies (governments based on kings and queens).

  6. Primary Succession • primary succession: the series of changes that occur in an area where no ecosystem previously existed • Examples: new island, area of rock uncovered after ice melts

  7. Pioneer Species • pioneer species: the first species to populate an area • To remember: The Wright brothers were pioneers of aviation.

  8. Pioneer Species • These are often lichen and mosses carried by wind and water. • little needed to survive • They break rock as they grow. • In death, they provide nutrients to develop soil.

  9. So what happens next? • Plant seeds land in this soil. • Over time, soil grows richer. • Eventually the community becomes stable unless disrupted. • Stability can take centuries!

  10. Secondary Succession • secondary succession: the series of changes that occur after a disturbance in an existing ecosystem • causes: fires, hurricanes, tornadoes, farming, logging, mining • faster than primary succession

  11. Human Activities and Species Diversity • humans have greatest impact on communities • 60% of Earth’s land used by humans • negative effects on diversity

  12. Clearing the Land • forests cut down • plains used for farming • diverse forest or grassland used to grow single crop

  13. Introduced Species • organisms that humans move from native location to a new area • intentional and accidental • can disrupt ecosystem for native organisms

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