BGYA02 - Lec2 (text+lec combined notes)

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Biological Sciences
Mary Olaveson

401 Why Must Animals Regulate their Internal EnvironmentsAll animals need nutrients and oxygen and must eliminate carbon dioxide and other waste products of metabolism Singlecelled organisms meet all these needs by direct exchanges with the external environmentAn internal environment makes complex multicellular animals possibleoCells of multicellular animals exist within an internal environment from which they get their nutrients from and dump their waste products into Under suitable circumstances cells are protected from changes or harsh conditions in the external environment How is the internal environment kept constantCells became specialized for maintaining specific aspects of the internal environment which enabled these specializations Some cells evolved to be the interface between the internal and external environments and to provide the necessary transport functions to get nutrients in move wastes out and maintain appropriate ion concentrations in the internal environment Other cells became specialized to provide internal functions eg energy storage movement The evolution of physiological systems made it possible for multicellular animals to become larger thicker and more complex and more adaptable to external environmentsThe maintenance of stable conditions within a narrow range in internal environment is called homeostasis If a physiological system fails to function homeostasis is compromised and as a result cells are damaged and can die To avoid this physiological systems must be controlled and regulated in response to changes in both the external and internal environmentsHomeostasis requires physiological regulationoActivities of all physiological systems are controlled by actions of the nervous and endocrine systems However to regulate the internal environment information is required LOOK at figure 402oSome components of physiological systems are called effectors because they effect changes in the internal environment They are controlled systems because their activities are controlled by from regulatory systems which obtain processes and integrate information then issue commands to controlled systems One of its
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