What mechanisms do warm-blooded animals have for generating heat that

cold-blooded animals do not?

By Stella AngeliBackground taken from: http://userwww.sfsu.edu/~infoarts/cdmain/Tele/competency/elephant.jpg, http://farm4.static.flickr.com/3001/2631251051_5d36b95788.jpg?v=0

Warm-blooded and cold-blooded animals

• Warm-blooded animals keep their body temperature at a constant level in environmental changes by homeostatic mechanisms

o Mammals o Birds

• Cold-blooded animals have their body temperature regulated by interaction with the environmento Reptileso Insectso Arachnidso Amphibianso Fish

Pictures taken from:http://coolcosmos.ipac.caltech.edu/image_galleries/ir_zoo/coldwarm.html, http://news.softpedia.com/images/news2/Cold-Blooded-Animals-Have-Larger-Offspring-in-Colder-Climate-2.jpg

Mechanisms for generating heat in warm-blooded animals

• Larger number of mitochondria per cell– Able to generate heat by increasing the rate at which they burn fats

and sugar – Greater quantity of food in order to replace the fat and sugar

reserves

Picture taken from:http://www.disaboom.com/photos/storage/1000.29381.44443.MitochondriaSMALL2.jpgBackground taken from:http://www.jigcardgallery.com/JigCard/icaPuzStore/Mammals2Part1.jpg

Mechanisms for generating heat cont.• Blood vessels in lower legs-heat exchangers (e.g. birds)

-Veins are close to arteries, extract heat from them- Causes friction that produces heat

Heat is spread in the body and escapes through the skin

Picture taken from:http://openlearn.open.ac.uk/file.php/2314/S204_1_010i.jpg

Mechanisms for generating heat cont.

• Vasoconstriction-Blood vessels close to the skin surface

become constricted-Smaller surface area for heat to be lost

Minimal heat loss occours

• Shivering-Muscle contraction around vital organs-Cell respiration

Heat is produced by using energy

Pictures taken from: http://www.biosbcc.net/doohan/sample/images/CO%20and%20MAP/VasTone.jpg,http://www.illustrationsof.com/images/clipart/xsmall2/2414_shivering_polar_bear_trying_to_warm_up_beside_a_campfire.jpg

Mechanisms for generating heat cont.• Insulation

-Adipose tissue(marine mammals): forms a thick layer of blubber

Thermal insulation

-Feathers and fur( birds, mammals): trap a layer of air next to the skin

Heat flow is reduced between the animal’s skin and the outside

Each feather has an individual muscle that allows it to be lifted away from the body

regulation of heat loss by changing the thickness of the air layer trapped among the feathers

Fur contains hair close to the skin underneath thicker and larger surface hairs longer hairs – better insulation

Pictures are taken from: http://marinebio.org/upload/_04/Hydrurga_leptonyx8.jpg,http://www.cartage.org.lb/en/themes/Sciences/Zoology/Biologicaldiverstity/AnimalsIII/featherstruct.gif

Cold-Blooded animals• Mechanisms for generating heat

-Snakes and Lizards sunning themselves on rocks.

-Fish changing depths in the water column to find a suitable temperature.

-Desert animals burrowing beneath the sand during the day.

-Insects warm their flight muscles by vibrating them in place.

Pictures taken from: http://curiousanimals.net/wp-content/uploads/2007/06/632604567-b5ba885b80-m-small.jpg, http://www.vegsoc.org/fish/images/single-fish.jpg

Summary

• Warm-blooded animals generate heat by:

Having larger number of mitochondria per cell Blood vessels in lower legs Vasoconstriction Shivering Insulation (adipose tissue, feathers and fur)

• Cold-blooded animals have different mechanisms for generating heat (sunning on rocks, burrow under the sand, muscle vibration etc.)

References Articles• Anissimov M., Wise GEEK , What is the Difference Between Warm-Blooded

and Cold-Blooded Animals?, 2003-2009• Watanabe M., Bioscience, Generating Heat: New Twists in the Evolution of

Endothermy,2005.55(6):470-475 WebPages• http://en.wikipedia.org/wiki/Warm-blooded• http://en.wikipedia.org/wiki/Cold-blooded• http://openlearn.open.ac.uk/• http://en.wikipedia.org/wiki/Shivering• http://www.compulink.co.uk/~argus/Dreambio/homeostasis/ectotherms

%20and%20endotherms.htm• http://coolcosmos.ipac.caltech.edu/image_galleries/ir_zoo/coldwarm.html