Ecology CH 6 Section 2 Ecological Succession

Introduction  Organisms interact with their environment  This interaction may cause change in the environment  Other forces may also cause change  This change may cause a niche to disappear  Change tends to happen in a predictable and orderly fashion

Primary Succession  The progression of species replacement in a previously life-less environment  New volcanic island  New soil formed by the weathering of rocks  New soil exposed by a glacier  Happens almost immediately

Order of Primary Succession 1.Soil formation by weathering and work of lichens 2.Pioneer species WeedsWeeds 3.Grasses Adds to soil depth and fertilityAdds to soil depth and fertility 4.Shrubs 5.Pine trees and other shallow roots 6.Hardwood Trees

Secondary Succession  Often Occurs after a human disturbance or minor environmental event  Fire, drought, disease, storm, etc.  Opens up a niche that is quickly occupied  Order of replacement similar to primary  Would end in a climax community as well  Many ecosystems never get there due to disturbances

Aquatic Succession  A new lake formed after a glacier is similar to new soil  Organisms will inhabit the new area  Aquatic plants are first and as they die they add nutrients to the water and create sediment  Over time the lake fills with sediment and becomes a marsh, then a meadow, and land succession takes over and ends in a forest

Island Succession  New land forms by volcanic eruptions  Living things quickly move in and find a niche  Animals must be mobile to reach the isolated islands (limits species)  Often leads to evolution to fit into the many possible niches  Galapagos Island birds and tortoises

6.3 Ecosystem Balance  Complex interactions in an ecosystem  Try to maintain equilibrium  A change triggers a counter to maintain balance  Very complex, but some scientists are trying to figure it out  Chaos Theory (Butterfly Effect) used to study ecosystems