SuccessionEquilibrium in

Ecosystems

Changes by FireVolcanoes create new land on which primary succession occurs

Changes by FireForest fires create the opportunity for secondary succession.

??Questions??

• What did the events do to the Earth?• How did the events do this?• What part of the Earth was affected?• What differences were there between the two

events other than one was caused by a volcano and the other by a fire?

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.

What causes succession?

• Fires

• Floods

• Volcanoes

• Hurricanes

Types of Succession!!

• After a disaster, succession helps an ecosystem recover. There are two Main types of ecological succession:

– Primary succession

– Secondary succession

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

Primary succession - occurs on an area of newly exposedrock, 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.

After the lichens create cracks in the rocks, mosses begin to grow in the cracks. The moss further breaks down the rock helping to form soil.Both lichens and mosses are pioneer species.

Pioneer species create soil in primary succession.

Soil is a thin layer that covers the land. Soil goes down into the ground a short way. Soil is more than rock particles. It includes all the living things and the materials they make or change.

Herbs and shrubs follow the lichens and mosses. Then pine trees and aspens are next. The Climax community are the birches and spruces.

Primary SuccessionPrimary succession may lead to a community of organisms in equilibrium, which does not change drastically unless the ecosystem is disturbed.

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.

Secondary succession - takes place where a community hasbeen removed, e.g., in a plowed field or a clear-cut forest

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 firstplants 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.

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.

Pioneer Community

Climax Community

Secondary SuccessionSecondary Succession occurs when a disturbance occurs in an already existing ecosystem. A forest fire burns an ecosystem, then it goes through to secondary succession to restore the ecosystem.

Wrap Up!• 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

SCHOOLYARD SUCCESSIONThink about how our school campus looks today. Imagine that the school

will be closed down permanently at the end of the day. The building will be bulldozed down and all the grass scraped off during removal of

debris. Most of the soil remains. Create a timeline of the succession of the area. Assume that the area will remain undisturbed by humans.

• In your groups, create a timeline to describe the series of changes that restore equilibrium to an ecosystem.

• Begin with year “0” and labeL it “LAND DISTURBANCE”. Write a one or two sentence description of what the area looks like.

• Imagine you can revisit the area and document the changes. Record the year and write a one or two sentence description of what the area looks like each time you visit. BE SURE TO IDENTIFY THE TYPE OF PLANTS THAT ARE GROWING.

• The revisiting points are 1 YEAR, 15 YEARS, 85 YEARS.• Label the timeline with the type of succession that is occurring and the campus name. i.e.

THE ______________ SUCCESSION OF _____________ SCHOOL CAMPUS.