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HOMEOSTASIS & TEMPERATURE REGULATION. Importance of Constant I nternal 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
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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
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 Pyrolobusfumariigrows best at 106⁰C and can withstand temperatures up to 113⁰C Terrestrial Thermophiles Cataglyphisbicolor - 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.
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 ectothermsare:
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 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?
