UNI101Y1 Chapter Notes - Chapter 3: Poikilotherm, Homeothermy, Homeostasis
Document Summary
Exchanges of nrg and materials b/w an orgnm and envmt occurs across body surfaces. Larger orgnm have less sa compared w/ their tissues than smaller orgnms. S increases as square of l, v increases as cube of length. Surface-to-volume ratio decreases in proportion to length. Larger orgnms lose heat less rapidly; this tthheerrmmaall iinneerrttiiaa (tendency to remain at same temp. ) is advantageous in cold envmts. But can"t rid excess heat rapidly (risk of overheating) Easier to maintain a constant internal envmt. Hhoommeeoossttaassiiss is an organism"s ability to maintain constant internal conditions in the face of a varying envmt. All homeostatic systems exhibit nneeggaattiivvee ffeeeeddbbaacckk (when the system deviates from its desired state, or set point, internal response mechanisms act to restore that state) Hhoommeeootthheerrmmyy is the maintenance of a constant body temp. (homeothermic) in the face of a fluctuating envmtal temp. (displayed by most mammals and birds) Ppooiikkiillootthheerrmmiicc organisms conform to the external temp. (ex. frogs, grasshoppers)