Ectotherms

• what is an ectotherm


  animals that depend on external sources of body heat

  • like invertebrates, fish, amphibians, and reptiles
• many ectotherms living in water do not need to thermoregulate

  • high heat capacity of water ensures that the temperature of the environment does not change much
• behavioural responses to increase temperature


  • basking in the sun
  • orienting bodies so max surface area is in the sun
  • extend body parts to increase exposure to the sun
  • conduction by pressing body against the ground
  • due to exothermic metabolic reactions
• behavioural responses to decrease temperature


  • the warming processes are often reversed
  • seek shade to shelter from the sun
  • hide in cracks in rocks, or digging burrows
  • press bodies against cool, shady earth or stones, or move into water or mud
  • orientate so that bodies are minimally exposed to the sun
  • minimise movements to reduce metabolic heat generated
• physiological responses to warming


  • dark colours absorb more radiation than light colours
  • heart rate alters to change metabolic rate, or affect the warming or cooling across body surfaces
  • require less food than endotherms, as less energy required to regulate temperatures, able to survive in difficult habitats