Symbiosis Clip
Ecological Succession:
Series of predictable changes in a community over time.
• Ecosystems are constantly changing because
environmental conditions change. Some species die
out and others move in.
– Change may be caused by a disturbance (natural or
human caused)
• Flood, land slide, volcano, fire, insects, disease, etc.
– Or conditions in one stage of succession may benefit
another set of species.
• Shade, change in moisture or nutrients, soil, etc.
Primary Succession
Succession that occurs where no soil exists.
Pioneer species are the first species to colonize and area
• Lichens (break down rock into soil)
Melting Glacier
Secondary Succession
*Still some remaining plant matter and soil
• When a disturbance affects an existing ecosystem (wind
storm, flood, fire, insects)
• Then the community tends to interact to restore the
ecosystem and works faster than primary succession
Logging
Wildfire
Wind
Secondary Succession
Primary forest with
shade intolerant
trees: Pines,
Larch, Douglas fir.
Conditions favor Shade tolerant
species cont.
growth of shade
Shade
to create
tolerant species:
intolerant
Grand fir, Hemlock, conditions for
trees create
shade tolerant
Red cedar.
shaded forest
trees until a
floor.
disturbance
occurs.
Climax Communities
Ecological community in the final stage of succession, in which the
species composition remains relatively stable (and resembles the
original community) until a disturbance such as fire occurs.
Desert
Coral Reef
Forest