5.1.3-4(Thermoregulation in endotherms and ectotherms)

Define what is meant by ectotherm and endotherm

• An ectotherm is an organism that relies on external sources of heat to maintain body temperature

• An endotherm is an organism that is able to control its body temperature by using heat from metabolic reactions to maintain body temperature

Describe features of an endotherm

• Can be very active in cold environments

• Vulnerable to bacteria and virus attack as internal environment is stable and ideal for growth

• Has developed a stronger immune system to deal with pathogens

• Can maintain internal body temperature around a set point

• A lot of energy from food is used to maintain internal body temperature

Describe features of an ectotherm

• Converts lots of food into biomass

• Body temperature depends on external environment

• More active in warmer environments

• Rarely found in consistently cold environments

• Low activity in cold temperature

• Less suspectable to fluctuating internal body temperatures

Name the 2 ways which body temperature can be regaulated

• Behavioural

• Physiological

Describe how ectotherms regulate their temperature

• Ectotherms rely on their environment to maintain their body temperature and so rely on behavioural methods to maintain temperature

• The behaviours they do affect how much heat they exchange with their environment

Describe some behavioural methods that ectotherms do to if they are cold

• Move into a sunny area

• Lie on a warm surface

• Expose a large surface area to the sun

Describe some behavioural methods that ectotherms do to if they are warm

• Move out of the sun

• Move underground

• Reduce surface area exposed to the sun

Describe the advantages and disadvantages of being an ectotherm

• Advantages:

  • Less of their food is used in respiration

  • More of the energy and nutrients gained from food can be converted to growth

  • They need to find less food

  • They can survive for long periods without food

  • Less suspectable to disease

• Disadvantages:

  • Less active in cooler temperatures

  • Risk of predators when cold

State what detects changes in temperature internally and externally

• Internally:

  • Thermoreceptors in the hypothalamus detect blood temperature

• Externally:

  • Thermoreceptors in the skin called peripheral thermoreceptors detect external temperature

• Both together to send information to the thermoregulatory centre in the hypothalamus for processing

Describe the process of generating a response to the temperature changes

• Thermoreceptors in the hypothalamus and peripheral thermoreceptors detect change in temperature

• They a send a signal via the CNS, as nerve impulses to the thermoregulatory centre in the hypothalamus

• The hypothalamus then coordinates a response and sends signals to the effector cells to then generate a response and decrease the temperature

Describe and explain the physiological mechanisms used by endotherms to maintain body temperature if it increases

• Vasodilation occurs and more blood is directed to the skin surface so more heat is radiated off

• Hairs lie flat to reduce insulation and allow convection currents

• Decreased release of thyroxine from the thyroid glad leads to Reduction in exergonic reactions(increase metabolic reactions) in the liver so less heat is produced

• Sweating occurs which leads to heat from the blood to evaporate with it, which cools the body

Describe and explain the physiological mechanisms used by endotherms to maintain body temperature if it decreases

• Vasoconstriction occurs which leads to less blood directed to the skin and so less heat radiated off

• No sweating occurs

• Hairs become erect to allow for insulation by trapping air and for convection currents to keep warm air in ski

• Release of thyroxine from the thyroid glad causes Increased exergonic reactions in the liver which leads to more energy being produced

• Shivering generates heat due to rapid contraction and relaxation of skeletal muscles

Describe some behavioural mechanisms used by endotherms to regulate body temperature if its too high

• Hide away from sun in shade

• Remain inactive and spread limps out to enable greater heat loss

• Wet the skin to use evaporation to help cool down the body

Describe behavioural mechanisms used by endotherms to regulate body temperature if its too low

• Expose body to the sun

• Move more and stay active to generate heat in muscles or in extreme conditions, roll into a ball shape to reduce surface area and heat loss

• Remain dry