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Communities in Transition. Ecological Succession – The replacement of one community by another until a climax community is reached May take hundreds or.

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Presentation on theme: "Communities in Transition. Ecological Succession – The replacement of one community by another until a climax community is reached May take hundreds or."— Presentation transcript:

1 Communities in Transition

2 Ecological Succession – The replacement of one community by another until a climax community is reached May take hundreds or thousands of years Each new community makes it harder for the old communities to survive.

3 New environmental conditions allow one group of species in a community to replace other groups. All communities change their structure and composition in response to changing environmental conditions. During succession: Pioneer species arrive first.

4 (Examples only – Write what will help you) A forest hundreds of years old may have been a shallow lake thousands of years ago. A dead tree falls and allow sunlight to reach the forest floor. Sunlight allows seeds to germinate. Wildflowers and shrubs grow. Moss, shrubs, and small trees cover the concrete of an old city building.

5 Pioneer Species – The first organisms to colonize any newly available area and begin the process of ecological succession. The pioneer organism will alter the environment so that a bigger and better organism can move in. Climax Community – A final and stable community.

6 A climax community can only be disrupted by a catastrophe. After the catastrophe it will then rebuild itself back up again.

7 Primary Succession – Succession that occurs on a surface where an ecosystem did not previously exist Secondary Succession – Succession that occurs on a surface where an ecosystem had previously existed.

8 Starting from Scratch

9 Fig. 7-11, p. 156 Exposed rocks Lichens and mosses Small herbs and shrubs Heath mat Jack pine, black spruce, and aspen Balsam fir, paper birch, and white spruce forest community Time

10 DEFINITION: Succession that occurs on a surface where an ecosystem did not previously exist Examples: Bare rock, newly cooled lava, abandoned highway or parking lot Takes a long time because there is no fertile soil to provide the nutrients needed to establish a plant community. Begins when pioneer species arrive and attach themselves to bare rock. Examples of pioneer species: Lichens and mosses

11 Fig. 7-11, p. 156 Exposed rocks Lichens and mosses Small herbs and shrubs Heath mat Jack pine, black spruce, and aspen Balsam fir, paper birch, and white spruce forest community Time

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22 Starting Over With Some Help

23 Succession that occurs on a surface where an ecosystem had previously existed. Examples: Abandoned farmland, burned/cut forests, heavily polluted streams, and land that has been flooded New vegetation can usually germinate within a few weeks from seeds in the soil and those brought in from nearby plants by wind or by birds and other animals.

24 Secondary succession occurs in ecosystems that have been disturbed or disrupted by humans, animals, or natural processes.

25 Fig. 7-12, p. 157 Time Annual weeds Perennial weeds and grasses Shrubs and pine seedlings Young pine forest with developing understory of oak and hickory trees Mature oak-hickory forest

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27 Secondary Succession: Post-fire

28 Secondary Succession: Old Field

29 Secondary Succession: Post-Volcano


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