Community Stability

TSUNAMI

http://video.nationalgeographic.com/video/environment/environment-natural-disasters/tsunamis/tsunami-101/

What happens to an area after it is changed by an event…whether it is natural or man made?

Ecosystem Disturbance Disturbances in nature are common. They can

modify the make-up, structure, or function of an ecological community.

How communities react to those disturbances is a measure of stability….or lack of.

GUIDING QUESTION…

How do communities respond to disturbances?

What Happens? After a disturbance, some communities return

to normal or close to normal. Some disturbances or so large that they can

change a community permanently. Resources change and therefore, populations

must change as well. When this occurs, a community experiences a

somewhat predictable series of changes over time called, SUCCESSION.

Ecological Succession A change in the types of species in a

community and/or an ecosystem. It could take hundreds or thousands of years

for a change to occur. Change is constantly occurring.

Primary Succession When a disturbance is so severe that no vegetation or soil

remains…or where there was nothing existing before. A community is built from scratch after glaciers retreat,

lakes dry up, or lava or volcanic ash spread across the landscape.

Primary Succession It can occur on rocks, cliffs,

sand dunes. Moss and lichens are

examples of organisms that appear during primary succession.

Lichens are formed by a mutualistic relationship between algae and fungi. The algae provide food and energy through photosynthesis, while the fungi anchor the organisms to the rock and capture moisture. Moss

Lichen

Secondary Succession More common type of succession that occurs in a place where an

ecosystem already exists. Occurs in places where ecosystems have been disturbed by natural

disasters, humans, or animals. Secondary succession occurs more quickly than primary succession.

Succession in WaterPrimary aquatic succession occurs when an area fills with water for the first time.

Disturbances such as floods or excess nutrient runoff can lead to secondary aquatic succession.

Climax Communities A stable community that completes the

succession process. This does not mean that changes or

adjustments to condition stop…what it means that the community has gone through the steps of succession and will slowly adjust as time goes on.

That is…until a major event alters the landscape and forces the process of succession again.

REVIEW

1. What are the major differences between primary succession and secondary succession?

2. Why does secondary succession occur faster than primary succession?