Symbiosis Clip

Ecological SuccessionEcological 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 SuccessionPrimary SuccessionSuccession 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 SuccessionSecondary 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

Wildfire Wind

Logging

Secondary SuccessionSecondary Succession

Primary forest with shade intolerant

trees: Pines, Larch, Douglas fir.

Shade intolerant

trees create shaded forest

floor.

Conditions favor growth of shade tolerant species:

Grand fir, Hemlock, Red cedar.

Shade tolerant species cont.

to create conditions for shade tolerant

trees until a disturbance

occurs.

Climax CommunitiesClimax 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.

DesertCoral Reef

Forest