Bio20B_Lecture3

Bio20B_Lecture3 - Bio 20B - April 10, 2007 First Lecture...

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Bio 20B - April 10, 2007 First Lecture Stuff First Then Digestion and Nutrition Homeostasis provides a constant environment in which chemical reactions (e.g. enzyme reactions) can occur (specifically for this lecture, temperature) o This does not mean that processes in the body are at equilibrium. Having chemical gradient differences is what drives work. Two main physiological States of Homeostasis: o Conformational Homeostasis: Thermo conformers Allow body to conform to environmental conditions Example: Antarctic Ice Fish allows body temperature to remain at - 1.9 ° C, which is the same as surrounding water o Regulatory Homeostasis: Thermo regulators Requires a physiological adjustment to adjust internal environment Adjusts to specific state or within limits for proper function Example 1: body temperature in mammals (37 ° C) Example 2: Osmotic balance (Next lecture) Regulating body temperature: a model of homeostasis o Endotherms: generate their own heat from within the body itself Ex: mammals, birds, some fish (tuna and marlin), and sharks o Ectotherms: gain heat from the environment, typically energy from the sun Ex: amphibians, lizards, most fish, invertebrates, dinosaurs? o Figure 41-15, Freeman Homeotherms: keep body temperature constant Heterotherm: allow body temperature to fluctuate o Endothermy vs. Ectothermy: Life History Implications Endotherm: High maintenance costs Less energy devoted to: growth and reproduction Live in cool environments (greater range in eco-types) Ectotherm: Low maintenance costs More energy devoted to: growth and reproduction
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Bio20B_Lecture3 - Bio 20B - April 10, 2007 First Lecture...

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