Module 8 Summarised Notes

Resource Description

IQ1: How is an organism’s internal environment maintained in response to a changing
external environment?

1.1 construct and interpret negative feedback loops that show homeostasis, including temperature and glucose

HOMEOSTASIS

• Homeostasis is the maintenance of a stable internal environment despite changes in the external environment.
•  Stimulus (change) – receptors (detect change and convert into nerve impulse) – control centre (brain/spinal cord) – messenger (communicates message from CNS to effector) – effector (receives message and causes response) – response (change in body).
•  Malfunctions in homeostatic mechanisms can lead to disease.
  o e.g. hyperglycaemia or hypoglycaemia – diabetes
  o e.g. hypothermia or hyperthermia –  heat stroke, pneumonia, etc.

1.2 investigate mechanisms used by organisms to maintain their internal environment, including:

− behavioural, structural and physiological adaptations in endotherms that assist homeostasis

ANIMAL ADAPTATIONS FOR HOMEOSTASIS

• Heat is exchanged with the environment through conduction, convection, radiation and evaporative cooling.
• Endotherms produce their own body heat through metabolism e.g. mammals and birds
• Ectotherms use the external environment to obtain heat energy e.g. fish, reptiles, invertebrates
•  Structural adaptations relate to the size and shape of an organism and its body parts.
  o e.g. kangaroos have a network of veins under thin forelimb skin
  o e.g. body proportions suited to climate
• Physiological adaptations relate to how an organism’s body works.
  o e.g. temperature regulation – vasoconstriction, vasodilation, sweating
  o e.g. hormonal control of water levels (see: kidneys)
• Behavioural adaptations relate to an organism’s behaviours.
  o e.g. snakes seeking sun or shade
  o e.g. kangaroos licking forelimbs to promote evaporative cooling
  o e.g. penguins huddling for warmth