5.1.3

• ectotherm - an organism that relies on external sources of heat to main body temperature
• endotherm - an organism that uses heat from metabolic reactions to maintain body temperature
• Controlling body temperature

  • enzymes

  → structure of protein can be affected

  → some enzymes are very sensitive to temperature change; if the body temperature drops by 10 degrees, the rate of enzyme-controlled reactions falls by half

  • if temperature drops + reaction slows down, less heat is released - positive feedback

  → the body cools down but as it cools down, the organisms is less able to function normally; however if temperature rises by a little above optimum, the enzymes denature
• Endotherm or Ectotherm ?

  • endotherms control their body temperature within very strict limits by using a variety of mechanisms to control body temperature + largely independent of external temperature
  • ectotherms are not able to control their body temperature as effectively as endotherms as they rely on external sources of heat + body temperature fluctuates with external temperature

  → however using various behavioural mechanisms, some ectotherms are able to control their body temperature in all but most extreme conditions
• Ectotherms Advantages + Disadvantages

  • use less heat for respiration
  • can survive a long period without food
  • energy obtain from food can be used for growth

  
  

  • greater risk of predation
  • not capable of activity during the winter/ not having sufficient stores of energy to survive over the winter