1. HOMEOSTASIS & TEMPERATURE REGULATION

2. Importance of Constant Internal Environment
HOMEOSTASIS is defined as:
the maintenance by an organism of a constant internal state, regardless of external environmental change
This is essential so that an organism’s systems can function efficiently
TWO STEPS are essential in achieving homeostasis:
DETECT the change
COUNTERACT the change

3. Variables which are kept constant
Temperature pH
Concentration of reactants
Water & salt concentration
Toxins

4. Two Stages of Homeostasis
DETECTING CHANGE
COUNTERACTING CHANGE

5. Role of the Nervous System
Indicate on this diagram where FEEDBACK takes place in the STIMULUS-RESPONSE pathway.

6. Thermoregulation in Humans
Annotate the diagram to show how temperature is regulated in humans

7. Feedback Mechanisms
Try this click & drag activity to test your understanding of feedback loops

8. Temperatures life is found in Life in general can be found across a BROAD range of temperatures on Earth, while individual species can only withstand narrow limits
Hyperthermophilic Microbes Pyrolobus fumarii grows best at 106⁰C and can withstand temperatures up to 113⁰C Terrestrial Thermophiles Cataglyphis bicolor - A heat tolerant insect in Sahara that can maintain a core body temperature of 56⁰C
Hypothermophilic Organisms Algae, bacteria and lichen found at environments from -17⁰C to 20⁰C Arctic Fox can survive in temperatures as cold as -70⁰C; uses countercurrent exchange to assist this.

9. Endotherms & Ectotherms
ENDOTHERMS endo- meaning ‘within’ So, an animal which …. Classes of vertebrates which are endotherms are:
ECTOTHERMS ecto- meaning ‘outside’ So, an animal which…. Classes of vertebrates which are ectotherms are:

10. Adaptations for temperature regulation
BEHAVIOIURAL
STRUCTURAL
PHYSIOLOGICAL
Organism will alter its body position in order to increase or decrease its exposure to the ambient temperature….
Eg.
Physical characteristics of an organism which assist with temperature regulation- how the animal is built….
Inner body functions of an organism which contribute to the response which allows for temperature regulation ….

11. Australian Examples- endotherms
RED KANGAROO
fur
shivering
sun basking
seek shelter from the sun
lick their forelimbs
rely heavily on panting
tail pulled into the shade of the body

12. Australian Examples- ectotherms
BLUE TONGUE LIZARD
During the early morning locates itself in small depressions in the open or on tree trunks
basking in the sun with its body as perpendicular as possible to the sun's rays
Throughout the day seeks cooler shadier
microhabitats.
Inactive in burrows on cold
days.

13. Consider….
What temperature is the blood of a lizard, such as the Blue-tongue when it is active?
What happens to a lizard’s blood temperature when the environment cools down?
Does an active lizard have warm or cold blood?
WHY IS IT MISLEADING TO REFER TO ECTOTHERMS AS COLD BLOODED?

14. Hibernation
Example: An echidna enters state of TORPOR during winter months when the average ambient temperature remains about 5⁰C
Torpor is a state of inactivity, when an animal is ‘sluggish’
Echidnas enter a state of torpor every 22 days or so.
Body temperature goes down to 9⁰C
Return briefly to a body temperature of 30⁰C for about 3 days before returning to torpor.
Would this adaptation be described as behavioural or physiological?
What is the advantage in terms of thermoregulation for this adaptation?

15. Advantages of Endothermy

16. Advantages of Ectothermy