Changes in the ecosystem

Changes occur all the time in an ecosystem. Trees die and new trees take their place. Young animals are born as the older ones die.

As long as there are not major disturbances the ecosystem will remain essentially the same.

The natural stability of an ecosystem keeps it from undergoing major changes is called homeostasis.

It’s important to understand the changes in an ecosystem so that we can understand how the ecosystem will react to the changes that human activity tends to bring about.

 

Pioneer species: the first species to appear during the process of succession, usually mosses, lichens, grasses & weeds.

Climax community: the stable mature community

Succession is the process of community development over time.

 

A mature community will still change but its overall appearance will remain the same.

change in species over time that has not been inhabited by organisms. starts from bare rock.

Lichens are the most important element in the initial community called the pioneer community.

Lichens are important early pioneer species. Lichen is a species of alga and fungi that live together in a symbiotic relationship.

Lichens secrete an acid that breaks down the rock to begin soil formation.

If the process of succession occurs without any disturbances, the species will form the climax community. This is the last stage of succession

Each biome has its own climax community. The climax community for PA is the oak-hickory forest as well as the beech, hemlock & maple forest of Northern PA forest.

change in species composition and ecosystem overtime already within a pre-existing community.

Some animals can survive all stages of secondary succession. Most animals appear only in certain stages and disappear with others.

 

1. Abandoned farms2. Burned or cut forests3. Heavily polluted streams4. Areas affected by flood waters.

Fires can be set by lightning, storms or human activity. Burned areas undergo secondary succession.

Some communities are immune to fire. For example, the lodgepole pine tree needs temperatures of above several hundreds degrees to germinate their seeds.

Serotinous is an ecological adaptation exhibited by some seed plants, in which seed release occurs in response to an environmental trigger, rather than spontaneously at seed maturation. Best trigger is fire.

A disturbance can change an ecosystem both physically & biologically.

Disturbances can be natural or due to human actions.

Repeated disturbances will prevent an area from returning to its climax community.

1. Volcanic eruptions2. Tornadoes3. Hurricanes4. Floods/Drought5. Natural Wildfires

Now…read the chart with a partner.

1. Man started fire2. Land development3. Mining4. Farming5. Over hunting

Invasive species is a nonnative organism that spread widely in a community.

Invasive species are one type of community disturbance and a major problem in many parts of the world.

Invasive species become a problem when there are no limiting factors such as predators, parasites, or competitors.

Zebra mussels

Kudzo…

Invasive species in Washington State