• Effects of Change Key Concepts

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    • Organisms may exist as members of a population; populations interact with other populations in a community; and communities together with the physical environment form ecosystems.

    • Changes that affect organisms over time may be daily, seasonal, or long-term.

    • Plants may respond to light by growing toward it or away from it, a behavior known as phototropism .

    • Animals may respond to cold conditions with a period of lowered metabolism, a behavior know as hibernation .

    • Organisms may respond to adverse conditions with a period of lowered or suspended metabolism, a behavior known as dormancy .

    • A variety o f environmental factors may cause the size of a population to increase or decrease. (This requires students to brainstorm examples of factors and predict the possible effects.)

    • Large-scale changes may affect entire communities and ecosystems.     • Such large-scale changes include the addition of excess nutrients to the system ( eutrophication ), which alters environmental balance; dramatic changes in climate ; and catastrophic events, such as fire, drought, flood, and earthquakes.