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Transcript
Changes in Ecosystems: Ecological Succession Ecological Succession Copyright Pearson Prentice Hall What is Ecological Succession? • The gradual and predictable process of change in the species structure of an ecological community over time. • The process begins with pioneer species and develops through increasing complexity until a climax community is developed. There are 2 types! • Primary Succession • Secondary Succession Primary Succession • Begins in a place without any soil: » Sides of volcanoes » Landslides » Flooding » Glaciers receding • First, lichens that do not need soil to survive grow on rocks • Next, mosses grow to hold newly made soil • These 1st species to populate an area are called PIONEER SPECIES Pioneer Species Lichens break down rock to form soil. Low, growing moss plants trap moisture and prevent soil erosion 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 Primary Succession • Simple plants like mosses and ferns can grow in the new soil Primary Succession • The simple plants die, adding more organic material (nutrients to the soil) • The soil layer thickens, and grasses, wildflowers, and other plants begin to take over Primary Succession • These plants die, and they add more nutrients to the soil • Shrubs and trees can survive now Primary Succession • Insects, small birds, and mammals have begun to move into the area • What was once bare rock, now supports a variety of life Ecological Succession In this example, a volcanic eruption has destroyed the previous ecosystem. Copyright Pearson Prentice Hall Ecological Succession The first organisms to appear are lichens. Copyright Pearson Prentice Hall Ecological Succession Mosses soon appear, and grasses take root in the thin layer of soil. Copyright Pearson Prentice Hall Ecological Succession Eventually, tree seedlings and shrubs sprout among the plant community. Copyright Pearson Prentice Hall Mix-Up Secondary Succession Not always is an ecosystem totally wiped out. Sometimes just local areas are affected. Once a disturbance (a fire, storm, etc.) is over, community interactions tend to restore the ecosystem to its original condition through secondary succession. Copyright Pearson Prentice Hall 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, in an abandoned yard, etc. 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 Primary vs. Secondary Online Demonstration Succession Game