Succession

SuccessionSuccession is the gradual change in a community over time.

Primary succession occurs when organisms colonize a lifeless habitat.

During succession the organisms within an ecosystem change its abiotic conditions.

Secondary succession occurs when organisms recolonize

a devastated ecosystem.

This allows better adapted organisms to colonize the area, replacing its current inhabitants.

A series of predictable changes that occur in a community over time due to events in the environment. The changes may happen suddenly or very slowly.

The series of changes that occur in an area where no ecosystem previously existed.

Eventually, primary succession will lead to equilibrium.

Primary Succession – the series of changes that occur in an area where no ecosystem previously existed.

An area of rock uncovered by a melting ice sheet

A new island formed by the eruption of an undersea volcano

Human made ponds

The first species to populate an area are the pioneer species.

They break up rock and begin soil formation

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

Lichen pictures

A combination of fungus and algae

Mosses -break down rock and add more soil

Grasses and small plants – protect the soil and add more nutrients

•The simple plants die, adding more organic material

•The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

•These plants die, and they add

more nutrients to the soil

•Shrubs and trees can survive now

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•Insects, small birds, and mammals have begun to move in

•What was once bare rock now supports a variety of life

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Larger plants with deep roots continue to break up rock and make more soil.A diverse forest ecosystem takes hundreds of years

1. Ground is solid rock2. Rock begins to weather, pioneer

species begin3. Weeds and grasses grow in soil -

making thicker, richer soil4. Eventually trees and shrubs sprout

- community of organisms develops5. Ecosystem reaches equilibrium

Reaching a stable community can take centuries.

Equilibrium

The series of changes that occur after a disturbance in an existing ecosystem.

It can occur more rapidly than primary succession.

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

Secondary Succession

Human disturbances:A pasture abandoned by a farmerLogging, or mining

Natural disturbances:

Fires, hurricanes, and tornadoes

Secondary Succession –

The series of changes that occur after a disturbance in an existing ecosystem.

1. Varies depending on the type of disturbance

2. A disturbed area returns to its previous condition, eventually reaches equilibrium

3. Soil and seeds are already present4. Organisms move in5. There is a quick recovery of the

ecosystem

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

• Equilibrium restored• State of balance • No sudden changes in

community

Secondary succession usually requires less time to form a climax community, since soil is already in place.

Equilibrium

Succession Review

Primary SecondaryWhat happens to the ecosystem

Length of Time

Example

Creates a new ecosystem

Restores a previous

ecosystem

May take a long time to reach equilibrium

A shorter time to reach

equilibriumNew land created

by volcanic eruption

An area destroyed by

fire

How do primary and secondary succession help maintain equilibrium in an ecosystem?

Answer:By fostering stability, over time, in the number

and species of organisms in a community.

What is a pioneer species?

Answer:The first species to populate an area.

Identify two natural disturbances and two human disturbances that can result in secondary succession.

Answer:Natural Disturbances: fire, hurricanes, volcanoes, tornadoes. Human Disturbances: farming, logging, mining.

Grass poking through the cracks in the sidewalk is an example of succession. Is this primary or secondary succession?

Answer:Secondary Succession; before the sidewalk was built, an ecosystem existed there.

Primary Succession occurs where no previous ecosystem exists and establishes equilibrium.

Secondary succession occurs after a disturbance restores equilibrium.