Transcript Biological Succession

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 beechmaple 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
• 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.