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.