unit ii cell energy and communication
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Unit II Cell Energy and Communication. Learning Goal 3 Explain how organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis. - PowerPoint PPT PresentationTRANSCRIPT
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Unit IICell Energy and Communication
Learning Goal 3Explain how organisms use feedback mechanisms
to regulate growth and reproduction, and to maintain dynamic homeostasis.
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I. Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes
A. Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target set point.
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Operons in gene regulation
• http://www.youtube.com/watch?feature=player_detailpage&v=iPQZXMKZEfw
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Temperature regulation in animals
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Plant responses to water limitations
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B. Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change.
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Lactation in mammals
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Onset of labor in childbirth
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Ripening of fruit
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C. Alteration in the mechanisms of feedback often results in deleterious consequences.
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Diabetes mellitus in response to decreased insulin
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Dehydration in response to decreased antidiuretic hormone (ADH)
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Graves’ disease (hyperthyroidism)
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Blood clotting
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II. Organisms respond to changes in their external environments.
A. Organisms respond to changes in their environment through behavioral and
physiological mechanisms.
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Photoperiodism and phototropism in plants.
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Hibernation and migration in animals
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Taxis and kinesis in animals
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Chemotaxis in bacteria
• http://www.youtube.com/watch?feature=player_detailpage&v=1wW2CZz6nM4
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Sexual reproduction in fungi
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Nocturnal and diurnal activity: circadian rhythms
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Shivering and sweating in humans