HOMEOSTASIS & TEMPERATURE REGULATION

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:

1. DETECT the change

2. COUNTERACT the change

Variables which are kept constant

• Temperature

• pH

• Concentration of reactants

• Water & salt concentration

• Toxins

Two Stages of Homeostasis

• DETECTING CHANGE

• COUNTERACTING CHANGE

Role of the Nervous System

Indicate on this diagram where FEEDBACK takes place in the STIMULUS-RESPONSE pathway.

Thermoregulation in Humans

Annotate the diagram to show how temperature is regulated in humans

Feedback Mechanisms

• http://www.johnwiley.net.au/highered/interactions/media/Foundations/content/Foundations/homeo2c/bot.htm

• Try this click & drag activity to test your understanding of feedback loops

Temperatures life is found inLife 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 106 C ⁰

and can withstand

temperatures

up to 113 C ⁰

Terrestrial Thermophiles

Cataglyphis bicolor - A heat tolerant

insect in Sahara that can

maintain a core body

temperature of 56 C ⁰

Hypothermophilic Organisms

Algae, bacteria and lichen found at

environments from

-17 C to 20 C ⁰ ⁰

Arctic Fox can survive in

temperatures as cold as -70 C; ⁰

uses countercurrent

exchange to

assist this.

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:

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….

Eg.

Inner body functions of an organism which contribute to the response which allows for temperature regulation ….

Eg.

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

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.

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?

Hibernation

Example: An echidna enters state of TORPOR during winter months when the average ambient temperature remains about 5 C ⁰- 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 9 C⁰- Return briefly to a body temperature of 30 C for about 3 days before ⁰

returning to torpor.

Would this adaptation be described as behavioural or physiological?

What is the advantage in terms of thermoregulation for this adaptation?

Advantages of Endothermy

Advantages of Ectothermy