Animals - Energy Requirements and Thermoregulation

Animals - Energy

• require energy for growth, repair, activity, and reproduction

Bioenergetics

the overall flow and transformation of energy in an animal

Metabolic Rate

the amount of energy an animal uses during a given time interval

• measured in joules or kilojoules

Determining Metabolic Rate

• direct calorimetry

  • directly determined by the amount of heat generated by metabolism

• indirect calorimetry

  • indirectly determined by the amount of oxygen consumed or carbon dioxide produced

Basal Metabolic Rate (BMR)

base line metabolic rate required to survive

Metabolic Rate and Body Size

• larger animals have higher metabolic rate than smaller animals

• smaller animals have higher metabolic rates per gram of tissue than larger animals

Thermoregulation

• most biochemical and physiological reactions are temperature dependent

• every species has an optimal temperature range

  • modifications in physiology or behaviour to maintain temperature within that range

Endotherms

generate heat through metabolic processes

Ectotherms

do not generate heat

• obtain their heat from external sources

• behavioral changes allow them to control their temperature

Homeotherms

maintain stable body temperature

Poikilotherms

allow body temperature to fluctuate with the environment

Endotherm and Homeotherm - Examples

mammals and birds

Poikilotherm and Ectotherm - Examples

amphibians, reptiles, fish and invertebrates

Polar Fish

ectotherms but kind of like homeotherms because they live in a stable temperature environment

Large Flying Insects

generally ectotherms but can produce some heat to allow them to fly

4 Physical Processes for Heat Exchange

• Radiation

• Evaporation

• Conduction

• Convention

Radiation

heat coming from the sun

Evaporation

Heat is lost through evaporation of water

Convention

wind going by the animal takes heat away

Conduction

heat transfer between two objects in contact

Evaporative Cooling

water loss from panting, rolling in the mud or sweating takes heat away

Vasodilation

open blood vessels to allow heat to escape

Vasoconstriction

less heat loss, heat stays trapped inside to keep warm

Gular Sack in Birds

give off heat when expanded

Urohidrosis

some long legged birds pee on themselves to disapate heat

Insulation

structures to trap heat close to the surface of the body

• skin, hair, blubber, fur, feathers

Countercurrent Blood Flow

blood enters the legs through a blood vessel and heat is lost as it gets close to the feet

• blood goes back up in a vein right next door

• as the artery loses heat it goes into the vein instead of being lost so that the blood going into the heart stays warm

Negative Feedback - Body Temperature

increased body temperature

• thermostat in hypothalamus activates cooling mechanisms

  • vasodilation

  • sweating

• body temperature drops back down to normal

decreased body temperature

• thermostat in hypothalamus activates warming mechanisms

  • shivering

  • vasoconstriction

Behavioural Thermoregulation

• sitting in the sun or on a rock increases temperature

• burrowing underground to avoid the sun and decrease temperature

Regional Endothermy

fast swimmers need to generate some heat in order to swim

Hibernation

animals lower their metabolic rate and oxygen consumption so that they can survive without eating for long periods