1. Maintaining a stable body temperature
Thermoregulation
Maintaining a stable body temperature

2. Why do organisms need to maintain a stable body temperature??

3. Optimum Temperatures
Organisms must keep their body temperature between a specific range in order to survive.
Enzyme activity
Metabolic processes

4. Body Temperature in animals
There are two types of organisms that maintain their body temperature in very different ways
Ectothermic organisms
Endothermic organisms
What do these terms mean? Can you give some examples of each?

5. Ecto (outside); therm (heat)
Use external environment to maintain body temperature.
Produce little heat
Lose heat quickly
Use less energy
Become very inactive when it gets cold
Fish, Reptiles, Insects

6. Endo (inside); therm (heat)
Maintain relatively constant body temperature
Generate a lot of heat from within via internal heat production
Generally have insulating structure to reduce heat loss (e.g. feathers, fur, fat)
Also develop behavioural and physiological adaptations to prevent heat loss

7. Endo (inside); therm (heat)
Mammals and birds

8. Homeothermic: organisms that can maintain a stable body temperature (e
Homeothermic: organisms that can maintain a stable body temperature (e.g. mammals)
Poikilothermic: organisms whose body temperature varies considerably due to its surroundings (e.g. reptiles and insects)

9. Heat Transfer Heat is a question of balance Too HOT and animals must
find ways to lose heat
Too COLD and animals must
find ways to gain heat

10. Heat Transfer
To understand why animals do the things they do you must understand how heat can be transferred.
QUESTION
What are the ways in which heat can be transferred?? How can animals lose or gain heat??

11. Heat Transfer
Conduction: transfer of heat from a hotter object to a cooler object via contact.
Radiation: transfer of heat from a hotter object to cooler object via infra-red waves.

12. Heat Transfer
Convection: Transfer of heat by warm air, or water, rising and being replaced by cooler air or water.
Evaporation: The process of changing a liquid into a gas. The heat from the body can evaporate water and cause a cooling effect.

13. Heat Transfer
Heat transfer RAP!!!!

14. Heat Gain and Loss Gain Basic metabolic processes Shivering
Exercise or other muscular activity
Radiation and conduction to the body
Loss
Evaporation sweat
Panting
Convection
Radiation and conduction from the body

15. Heat Loss and Gain
VIDEO!!!!!

16. Systems Involved Thermoregulation occurs via nerves and hormones
It involves many sensory inputs and several effector responses that act together to maintain a stable temperature

17. Linking to other systems
Thermoregulation is strongly related to the Nervous system and the Endocrine system
Worksheet

18. Investigating Sweating
What you need to know:
How does sweating affect body temperature?
Why does sweating affect body temperature?
How can models help us investigate how the body works?
Question:
How does water evaporate?

19. For water to evaporate, it must absorb heat from its surroundings

20. Cotton wool Dry towelling cloth Set up the equipment as shown opposite
Fill the conical flask with hot water from the kettle
Record the temperature and start your stop clock
Record the temperature every minute for 10 minutes. Record your data in a suitable table
Time (mins)
Temperature (°C)
Dry Flask
Wet Flask
(START) 1
Repeat with a wet towelling cloth

21. To Do:
Plot a graph of your data
Which flask cooled faster?
How do you explain your results?
Was your experiment a fair test – if not, why not?
How could you make this experiment more of a fair test?

22. Systems Involved Brain – Hypothalamus
Lowering or raising the temperature of the hypothalamus initiates regulatory responses
Changes occur in heat production and heat exchange
Temperature cells act
as misalignment
detectors

23. Muscles of skin arteriole walls relax
Core body temperature >37°C
Thermoreceptors
Hypothalamus
nerves
Muscles of skin arteriole walls relax
Sweat glands increase secretion
Muscles
reduce activity
Skin arteries dilate
More blood to the skin.
More radiation & conduction of heat
More water covers the skin.
More evaporation
Less heat generated

24. Systems Involved
Hypothalamus responds to receptors and coordinates appropriate nerve and hormonal responses

25. Systems Involved
The hypothalamus can release hormones that initiate the release of further hormones.
For example as the temperature drops the pituitary gland will be stimulated and release a thyroid stimulating hormone
The thyroid gland in turn produces hormones which increase the metabolic rate therefore increasing heat production

26. Systems Involved

27. Systems Involved Skin – thermoreceptors act as disturbance detectors.
Detect change in external environment and triggers responses before it effects internal body temperature.
Responses include erector muscles of hairs contract and hairs stand up, blood vessels constrict.
These are the effectors for mediating change.

28. Skin

29. Negative feedback
Temperature regulation by the skin is part of a negative feedback system.
Output is fed back to receptors and becomes part of a new stimulus response cycle.

30. Muscles of skin arteriole walls relax
NEGATIVE FEEDBACK
Blood temperature
Muscles of skin arteriole walls relax
Core body temperature >37°C
Hypothalamus
Sweat glands increase secretion
nerves
Muscles
reduce activity
Thermoreceptors
Thermoreceptors
Body loses heat
Return to 37°C

31. Thermoregulation
VIDEO REVIEW

32. Summary Ectothermic Endothermic Homeothermic Poikilothermic
Heat transfer – Conduction, Convection, Radiation & Evaporation
Heat Gain and Loss
Endocrine and Nervous system involved

33. Review Questions
Page 256 of the text book.
- Questions

34. Adaptations and Thermoregulation
Apart from physiological adaptations, animals also develop behaviours and physical structures that help them regulate their body temperature.

35. Heat Loss and Gain
Must remember the ways in which heat can be transferred.
These processes work on a temperature gradient.
Can you explain what this means?

36. Heat Loss and Gain
Temperature gradient simply refers to the difference in temperature between two things.
For example the lizard and the rock.

37. Heat Loss and Gain

38. Heat Loss and Gain
The rock is warmer than the lizard so the heat moves, via conduction, from the rock to the lizard.
As the lizard heats up and the gradient decreases and eventually changes the heat moves from lizard to rock.

39. Structural & Behavioural
The transfer of heat needs to be controlled.
What examples of structural and behavioural adaptations can you think of?

40. Behavioural Responses
Penguins huddling
Burrowing underground
Seeking shade
Basking
Fanning from honeybees

41. Behavioural Responses
VIDEO

42. Counter current heat exchange

43. Counter current heat exchange
The arteries and veins in certain areas, like the foot of the penguin, run very close to each other.
The warmer blood in the arteries heats the cooler blood in the veins.

44. Structural Responses
Animals need to control exchange. This can also be achieved through:
Insulation: - Fur
- Feathers
- Fat

45. Structural Adaptations
Feathers and fur insulate by trapping a thick layer of warm air next to the skin.
The layer of air has a protective insulating affect keeping the animal warm.

46. Structural Adaptations
The layer of air trapped by the otters fur helps reduce the temperature gradient between the otter and its surroundings.
Therefore reducing heat loss and gain.

47. Structural Adaptations
Blubber is also used as insulation.
Thick layers of fat are very effective in insulating animals against extremely cold conditions.

48. Structural Adaptation
Shape and size also play an important role.
How do you think shape and size of an animals can help?

49. Structural Adaptations
A large surface area to volume ratio increases heat loss
A small surface area to volume ratio reduces heat loss.

50. Structural Adaptations

51. Structural Adaptations
So being larger and rounder in shape is beneficial in a cold climate.
For example whales and seals
Being smaller is better for individuals in hot climates.

52. Shutting Down Sometimes these adaptations are not enough.
The external temperature can reach such a point that the internal temperature of animals reaches a critical level

53. Shutting Down
The external temperature at which metabolic activity begins to rise is called the lower critical temperature
The increase in metabolic rate means the animal needs more energy.
This can often be too difficult to find.

54. Shutting Down
At this point animals will often go into hibernation to conserve energy.

55. Shutting Down
The upper critical temperature refers to the point at which cooling mechanisms fail.
The metabolic rate rises with the increase in the external temperature. This an be very dangerous.

56. Shutting Down

57. Summary
Explain how behavioural adaptations help regulate body temperature using specific examples.
Explain how structural adaptations help regulate body temperature using specific examples.
Explain how counter current heat exchange works

58. Adaptations Design your own animal (groups of 3)
Choose an environment (extreme HOT or extreme COLD)
Draw and label adaptations that help it survive
Include physiological, behavioural & structural (physical)
Present to the class!!!
Give it a name (be creative)
Think about possible adaptations for water balance.

59. BINGO
Thermoregulation, Osmosis, Radiation, Convection, Freshwater Fish, Poikilothermic, Insulation, Pituitary Gland, Ectotherm, Hypothalamus, Conduction, Counter Current heat exchange, Homeothermic, Marine Fish, Endotherm, Receptors, Evaporation, Loop of Henle, Thyroid Gland, Hibernation, Shivering, Dilation of Blood Vessels.