Regulation of Heat and Energy

1. Regulation of Heat and Energy • Bioenergetics… flow of energy through an animal • determines the behavior, growth, and reproduction of an organism. • Allocation of Energy • Energy obtained through hydrolysis of food is distributed according to the following needs • production of ATP 1st • biosynthesis for growth and repair second • storage in the form of starch and fat third • excess energy is released as thermal energy

2. Metabolic Rate • Amount of energy used per unit time is the organism's metabolic rate • measured in 2 ways • energy consumed compared to heat loss - measured with a calorimeter • O2 consumed compared to the CO2 produced • both require a closed system to measure • cannot simply use calories consumed (fat 9Cal/g, carb 4 Cal/g, & protein 4Cal/g) due to the fact that excess calories are used for storage • Metabolic rate determines bioenergetic strategy • birds and mammals have high metabolic needs which makes them endothermic • heat obtained from within • fish and reptiles have low metabolic needs which makes them ectothermic • heat obtained from an outside source

3. Metabolic Rate • Metabolic rate and size are inversely related (in mammals) • due to the need to regulate body temp and the larger surface area to volume relationship of smaller animals • Metabolic rate and activity are directly related • basal metabolic rate (BMR) is the resting/non-stressed metabolic rate of an endotherm • standard metabolic rate (SMR) is the resting /non-stressed metabolic rate of an ectotherm at a specific temperature • the max metabolic rate is inversely related to the duration of activity • due to the debt that must be paid for the contribution of anaerobic respiration • average daily metabolic rate is influenced by the time of day, sex, age, size, temperature (internal & external), food (quality and quantity), activity, O2 uptake, & hormone balance of an organism • most terrestrial animals have a average metabolic rate of 2 - 4 times their BMR/SMR • Humans average is ~1.5 x BMR (unusually low)

4. Energy Budget • compares the amount of energy needed by an organism to complete the tasks necessary for sustaining life and to reproduce • examples of categories are: • BMR • reproduction • temp regulation • growth • activity costs

5. Homeostasis • Regulation if the internal environment • managed through he interstitial fluid of an organism • pH, blood sugar, & temp are the key components • all must be maintained in a very narrow range regardless of the outside environment • strategies • regulators - maintain internal environment regardless of the outside environment • conformers - alter their internal environment with changes in the outside environment • most organisms do a combination of both

6. Mechanisms of homeostasis - 3 functional components • receptor - detects a change in the internal environment and sends a message to the control center • control center - processes the information and relays a message to the effector • effector - acts to change the condition • 2 basic mechanisms • negative feedback • positive response from the effector switches off the control center • most mechanisms are like this as they prevent small changes from having an exaggerated effect on the organism • positive feedback • positive response amplifies the action • example: cervical pressure and strength of contractions in child birth • under most circumstances the regulation on homeostasis in incompatible with a positive feedback loop