Metabolic Rate & Allometric Scaling Flashcards
Ingested chemical energy
energy contained in chemical bonds of food animals ingest
Fecal chemical energy
Energy contained in chemical bonds of undigested compounds
Absorbed chemical energy:
Energy contained in chemical bonds of materials that are absorbed from intestine to blood stream
Heat
All living animals generate heat
Biosynthesis
making of proteins and lipids (use of absorbed chemical energy)
Maintenance
circulation and tissue repair (use of absorbed chemical energy)
Internal work
Movement of inner body stuff
External work
Movement of limbs
Metabolic rate
Rate at which an animal converts absorbed chemical energy to heat. Heat production per unit time
Direct calorimetry/ Direct calorimeter
o Measuring the rate at which an animal produces heat
o 1 calorie/sec = 4.186 joules/sec = 1 watt
Indirect calorimetry
Measuring metabolism through physiological and chemical associations
Respirometry
Because of the consistent relationship between O2, CO2, and heat produced, you can calculate metabolic rate by simply measuring O2 consumption of CO2 production
Mass Balance
Chemical Energy Input = Chemical energy output. Way to measure indirect calorimetry
Respiratory exchange ratio
o Moles of CO2 Produced * time-1/Moles of O2 Consumed * time-1
Specific dynamic action
Following consumption of a meal, metabolic rate briefly increases over basal levels
Basal metabolic rate
o Homeotherms within thermoneutral zone
o Fasting
o Resting (lying down, but awake)
Standard metabolic rate
o Polikilotherms at any specific body temp (SMR at Tb=25 c)
o Fasting
o Resting
Metabolic scaling
Study of the relationship between metabolic rate and body mass
Weight – specific metabolic rate
M/W = aW(b-1) Metabolic rate/unit body mass
Allometric equation
Log(M)=Log(aWb) makes equation linear. Advantageous for expression the allometric relationship in the linear form
Rubner’s surface law
o BMR is proportionate to a mammal’s surface area
o Reasoning
• Mammals maintain 37C Tb, tend to lose heat to environment
• Rate of heat loss proportionate to surface area of mammal
• Smaller mammals have more surface area per unit weight, and therefore faster hear loss
• Head loss must be replace metabolically to maintain Tb
Fractal geometry
o Internal transport of O2 and nutrients via circulatory system necessary for metabolism to occur.
o Branching nature of this system imposes constraints on delivery as you scale up and down
o Because of these constraints, smaller animals more efficient at delivering resources throughout the body hence higher mass-specific metabolic rates.
o Fractal theory predicts a metabolic rate scaling exponent of b=0.75
