Metabolism

• Chain of chemical reactions that takes place in the body to convert food into energy

• Assimilated energy: nutrient that contributes to living tissue, biosynthesis (assembling new cells/tissues and lipid stores) maintenance (respiration, circulation, digestion, nervous coordination, tissue repair)  + activity (external work)  + (F(feces) + U(urine) 

• Influences on metabolism: body size, temperature, activity level, digestive strategy, resource availability, and reproductive status (metabolism increases) . 

  • Body size: smaller animals = higher mass-specific metabolic rate (MR), 1 gram of shrew consumes oxygen at 100 times the rate of 1 gram of elephant, whole body MR - the amount of energy expended by an animal over the period, difference? Small animals lose heat faster and have to work harder to keep their temperature up. The physiology of animals directly correlates with respiration rate, heart rate, and more. 

  • Temperature: Basal metabolic rate (BMR) - resting metabolic rate of endothermic species (thermoneutral zone TNZ - range of ambient temperature where normal metabolic rate provides enough heat to maintain steady body temperature), Standard metabolic rate - resting metabolic rate of exothermic species, which varies by temperature. 

Endothermy (high metabolic rate, maintains stable body temperature through adjustment of metabolic heat production, body temperature stays within a narrow range), ectothermy (relatively low metabolic rate, body temperature mainly relies on external factors and behavior). What physiological difference accounts for the difference in metabolic rate? - high surface area to volume ratio of lungs in endotherms, complex heart of endotherms, large metabolically active organs of endotherms. Advantages of ectothermy: small body size (requires less to maintain), plasticity of shape (specialized body form (worm) allows for the exploitation of microhabitats, ability to exploit resources (low food requirement for basic maintenance, the amount of food required by small insectivorous bird for 1 day is enough for a similar sized ACTIVE reptiles for approximately 5 days) 

• Activity level: Hibernation (long-term, seasonal reduction in metabolic rate), torpor (short-term reduction in metabolic rate, usually daily, 5 to 75% reduction), Estivation (short-term reduction in metabolic rate due to heat) 

• Digestive strategy: specific dynamic action (makes internal temperature increase to aid in digestion), metabolic rate increases after a meal (induced by digestion, ectotherms have variable increase 4x, mammals increases MR about 30%), starvation leads to drop in metabolic rate (can be adaptive) 

• Reproductive status: The metabolic needs of the mother increase throughout pregnancy for fetal growth, fetal metabolic requirements and mammary tissue growth. In mammals milk production after birth maintains higher MR 

  • How does metabolism enter the conservation conversation?

- Stress and disease physiology 

- Conservation 

- Ecotoxicology 

- Evolutionary Biology 

Measure Metabolism - (Indirect Measure) Fuel + O2 ->CO2 + H2O + ATP (direct Measures)  + Heat

Direct calorimetry = 1 Calorie = heat required to raise 1 g of water 1 C

Locomotion Energetics

• Difference between locomotion in air and water 

  • Support provided by the medium 

  • The resistance provided by the medium 

  • Energetic cost and body size 

    • Cost decreases as body size increases