Because change is inevitable Except from a vending
Because change is inevitable. Except, from a vending machine.
� SWBAT describe the process by which ecosystems change and adapt to external influences by identifying the two types of succession and the end result of each.
How do you define “equilibrium”? � e·qui·lib·ri·um (kw-lbr-m, kw-) n. pl. e·qui·lib·ri·ums or e·qui·lib·ri·a (-r-) 1. A condition in which all acting influences are canceled by others, resulting in a stable, balanced, or unchanging system. � 2. Mental or emotional balance; poise. � 3. Physics The state of a body or physical system at rest or in unaccelerated motion in which the resultant of all forces acting on it is zero and the sum of all torques about any axis is zero. � 4. Chemistry The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the reactants and products does not change with time. �
There is no ecosystem which is unchanging. � External influences (input) are forever changing and the resultant changes within the ecosystem (throughput) result in a change in the ecosystem that will restore some semblance of balance (output) � Which feedback loop would be analogous to this situation? � Most of the time, influences cause no measurable change, as the ecosystem is so complex it “absorbs” these and continues as before. � Sometimes the influences are cumulative, or the change is so drastic, that a new equilibrium will be achieved. � The brick analogy. �
� What external influences might we expect to put pressure on an ecosystem in balance? � Changes in: � Climate Drought Rainfall patterns Average temperatures � Topography Earthquakes Geologic uplifting Volcanic activity � Nutrient � We resources Species extinction Migration patterns Species competition (invasive) call these changes “disturbances”.
� After a disturbance has been visited on an ecosystem, a new equilibrium will be achieved. � These disturbances can range from cataclysmic (volcanic activity) to subtle (slight variations in gene pool due to evolution). � They can be natural (examples above) or humaninduced (species introduction). � The orderly process by which an ecosystem changes is called “succession”. � In what ways have you heard of “succession”? � What does it mean?
� Ecological succession can be broken into two varieties: �Primary – where no ecological community has previously existed. �Secondary – where a community is removed or destroyed and a new community is established
� Where no ecological community has previously existed. � Examples would include oceanic volcanic eruptions and rock exposed by a retreating glacier.
� Where a community is removed or destroyed and a new community is established. � You give me examples.
� Specialists are organisms with a narrow niche and do not readily tolerate changes to their food supply and/or environment. � Herbivores are often deemed specialists. � A good example of a specialist would be the koala bear (eats only eucalyptus leaves). � Generalists are organisms with a broad niche and are tolerant of changes to their food supply and/or environment. � Omnivores are often deemed generalists. � A good example of a generalist would be the raccoon (eats a variety of foods). � Are humans specialists or generalists?
� At the point where two adjacent habitats meet is defined as the “edge”. � Edges can be: �Inherent – formed by natural features �Induced – natural disasters or human activities �Narrow – abrupt change �Wide – “ecotone” �Convoluted – nonlinear �Perforated – other habitats interspersed � Core would be the interior of a habitat.
� Where would you expect to find specialists? In the core, or on the edge? � What about generalists? � Why?
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