Biological Succession

What is succession The change that occurs as one kind of living organism replaces another organism in an environment. Why does it happen? Animals need to adapt to changes If they don’t competition with other species will result in the replacement Happens all the time, and environment as seldom stable and unchanging.

Types of Succession Primary Occurs where organisms did not live before Species must migrate into area Example: Lava field Just like the development of the wild west it starts with a pioneer. Secondary Occurs when an ecosystem is damaged. Changing environment will support only those species that were found in the area before. Example: forest fire

How does primary succession begin? With a pioneer species. A pioneer species are the first plants in an environment. Normally lichens or fungi. These pioneer species help in the development of soil. Very slow process in order to reach a climax community. A climax community is accomplished when the succession of species is complete.

How does secondary succession work? After there is damage to an already established ecosystem, some organisms need to adapt. Some organisms find it difficult to adjust while others are actually benefited by this change. Competitive advantage exists when one organism is more able to survive and reproduce in the new environment then another.

What's your niche? All organisms have a niche, which is a description of the role that an organism fulfills in the environment. Includes position in food web Where they live What time they eat What if the niche is lost due to damage? Competitive Exclusion principle.

Competitive Exclusion Principle Two or more species can not co-exist on a scare single resource relative to the demand for it. Example: Big Horn Sheep and Burros The burros are better grazers They can scale steep hill sides When food supplies are low the Burros have a competitive advantage.

Range of Tolerance The range of conditions in which an organism can adapt to. Survival depends on this!!! If an organism can survive in a wide range of conditions then its ability to survive increases. Largely determined by inherited ability to adjust to new conditions.

Forest fires Forest fires as well as other natural disasters start secondary succession. To return to climax community could take hundreds or thousands of years. Once that stable climax community is accomplished it will remain stable for long periods of time until disturbed again.

This chart represents a typical succession which is observed in New York State.   The annual grasses represent the pioneer or first organisms in this succession.   The beech-maple forest would represent a typical Northern New York climax community.   The climax community will last hundreds or thousands of years unless again disrupted.  A forest containing oak and/or hickory trees would be a more typical Southern New York climax community.

Characteristics Pioneer Species Climax community species Small body size. Many offspring per generation. Many generations per season. Low species diversity. Linear food chain. Climax community species Large body size Few offspring per generation. One generation per season. High species diversity. Complex food web.