Download Ecology CH 6

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
•
Weeds
3. Grasses
•
Adds 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