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Changes in Ecosystems: Ecological Succession

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Presentation on theme: "Changes in Ecosystems: Ecological Succession"— Presentation transcript:

1 Changes in Ecosystems: Ecological Succession

2 Succession Definition:
Natural, gradual changes in the types of species that live in an area; can be primary or secondary The gradual replacement of one plant community by another through natural processes over time

3 What is Succession? Succession is the series of predictable changes that occur in a community over time. A community is all the different organisms that live together. A community in an ecosystem is in equilibrium, or a state of balance, when the numbers and species of organisms in it do not change suddenly. 3

4 What causes succession?
Fires Floods Volcanoes Hurricanes 4

5 Types of Succession!! After a disaster, succession helps an ecosystem recover. There are two Main types of ecological succession: Primary succession Secondary succession 5

6 Primary Succession Begins in a place without any soil
Sides of volcanoes glaciers melting away Starts with the arrival of living things such as lichens and moss that do not need soil to survive Called PIONEER SPECIES

7 Primary Succession Primary Succession - series of changes that occur in an area where no ecosystem previously existed. Example: An area might be a new island formed by the eruption of an undersea volcano Example 2: An area of rock uncovered by a melting sheet of ice. The first species to populate the area are called Pioneer Species. Lichens and mosses – carried by the wind or water 7

8 Primary succession - occurs on an area of newly exposed rock, sand, or lava or any area that has not been occupied previously by a living (biotic) community Glaciers scrape the Earth as it moves. Some land may have been buried under ice for thousands of years. Rocks are carried along by the ice. As the glacier melts, the rocks are left behind. After about a year, lichens begin to grow on the rock surface. Lichens slowly break the rock down. Primary succession areas have no soil.

9 Volcanoes create new land on which primary succession occurs.
Changes by Fire Volcanoes create new land on which primary succession occurs. 9

10 Primary Succession Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil


12 Primary Succession Simple plants like grasses, mosses and ferns can grow in the new soil

13 Primary Succession The simple plants die, adding more organic material
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

14 Primary Succession These plants die, and they add more nutrients to the soil Shrubs and trees can survive now


16 Primary Succession Insects, small birds, and mammals have begun to move in What was once bare rock now supports a variety of life

17 Primary Succession Climax Community - is a community of organisms in equilibrium, which does not change drastically unless the ecosystem is disturbed.(The final step in the process) 17

18 Secondary Succession Begins in a place that already has soil and was once the home of living organisms Occurs faster and has different pioneer species than primary succession Example: after forest fires, flooding etc.

19 Secondary Succession Secondary Succession- the series of changes that occur after a disturbance in an EXISTING ecosystem. Unlike primary succession, secondary succession occurs in a place where an ecosystem has previously existed. Secondary succession restores the ecosystem to a state in which equilibrium can be maintained. occurs somewhat more rapidly than primary succession. 19

20 Forest fires create the opportunity for secondary succession.
Changes by Fire Forest fires create the opportunity for secondary succession. 20




24 Secondary succession - takes place where a community has been removed, e.g., in a plowed field or a clear-cut forest or fire. Pioneer Community The pioneer community is made up of grasses. Insects, small mammals and reptiles make their home here. If the soil has been disturbed, weeds are the first plants to grow. They secure the soil. Shrubs and bushes begin to grow. Other mammals, such as rabbits and birds, join the developing community. A climax community of trees can support a wide variety of larger mammals such as foxes and badgers. Climax Community Weeds appear first, followed by grasses. The next to appear are shrubs, then a pine forest. The mature hardwood oak and hickory trees form the climax community. This is the last stage of succession. These are plants that can reproduce successfully beneath their own shade and can maintain the community indefinitely if conditions don’t change.

25 Climax Community A stable group of plants and animals that is the end result of the succession process Does not always mean big trees Grasses in prairies Cacti in deserts

26 Wrap Up! Vocabulary: Community Equilibrium Succession
Succession occurs when a disaster occurs and disturbs the equilibrium of a community. There are two types of succession: Primary Succession occurs where no previous ecosystem exists and establishes equilibrium. Secondary Succession occurs after a disturbance and restores equilibrium in an already existing ecosystem. Vocabulary: Community Equilibrium Succession Primary Succession Pioneer Species Secondary Succession 26

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