3.2: Equilibrium and Change
pg. 80
Key Concepts:
2. Ecosystems are at equilibrium but can change overtime.
Equilibrium: describes the state of an ecosystem with relatively constant conditions over
a period of time.
Succession: the gradual and usually predictable changes in the composition of
community and the abiotic conditions following a disturbance.
- Most ecosystems are in a state of equilibrium, a dynamic balance.
- Biotic and abiotic features are relatively constant over time.
- Abiotic conditions, energy flow and nutrient cycling are stable, equilibrium is created.
- Ecosystem populations will be healthy and sustainable.
Ecological Succession
Primary Succession: succession on newly exposed ground, such as; following a volcanic
eruption.
Secondary Succession: succession in a partially disturbed ecosystem, such as; following
a forest fire.
- Ecological succession can be either primary or secondary in form. Succession is
initiated after a disturbance in the ecosystem has occurred, such as; geological, fire, or
even human activity.
- Succession leads to gradual changes, plants, animals, fungi and micro-organism
reestablished in the area disturbed.
- Succession pattern usually follows: small hardy plants (grasses) colonize the open
landscape, creating a fertile soil. Shrubs and small trees follow, and then large trees. As
nutrients, and shelter are being established animals start to migrate back to the area, small
to large.
- Others areas of succession, bogs being covered by vegetation, and sandy shores are
converted (sand Dune Succession)
Figure 3: During forest succession, the plant community changes from low-growing,
non-woody pants to shrubs and then trees.
Benefits of Succession
- Succession allows ecosystems to maintain their long term sustainability.
- Ecosystems can recover from natural and human caused disturbances.
- Succession requires a long period of time to occur.
Evidence of Learning: Students can …
- describe the biotic and abiotic characteristics of equilibrium.
- describe the process of ecological succession.
- distinguish between primary and secondary.
- describe the benefits of succession.
Check Your Learning
Questions 1 – 9, page 82
Summary:
- The key biotic and abiotic features of large ecosystems remain relatively constant
overtime. They are in a state of equilibrium.
- Succession is the gradual changes in the biotic and abiotic features of an ecosystem
following a disturbance.
- Succession allows an ecosystem to recover following a natural or human-caused
disturbance.