Section 38.4 (Exam 3) Flashcards
Body Temperature Depends on the Balance between Heat In and Heat Out of the Body
What are the two classifications of animals based on constancy of body temperature?
Homeotherms and Poikilotherms
What are homeotherms?
animals that maintain a constant body temperature
What are poikilotherms?
animals with fluctuating body temperatures
What are the three classifications of animals based on the source of heat that determines their body temperature?
Endotherms
Ectotherms
Heterotherms
What are endotherms?
can vary metabolic heat production
(mammals and birds)
What are ectotherms?
body temperature depends on external sources of heat
(non avian reptiles, fishes, amphibians, invertebrates)
What are heterotherms?
can behave either as an endotherm or an ectotherm
(animals that undergo hibernation or daily torpor)
What are the two major differences between ectotherms and endotherms?
Resting metabolic rate
Response to changes in environmental temperatures
How does the resting metabolic rate of endotherms differ from ectotherms?
Endotherms have a higher resting metabolic rate
(they have to expend energy to gain or lose heat)
How does body temperature of endotherms and ectotherms vary with environmental temperature?
Endotherm body temperature remains constant within the survivable range
Ectotherm body temperature fluctuates directly with the environment
How does metabolic rate of endotherms and ectotherms vary with environmental temperature?
Endotherm metabolic rate decreases with increasing temperature because they have less need to generate heat
Ectotherm metabolic rate correlates directly with environmental temperature because higher temperature increases the rate of reaction
How can ectotherms regulate body temperature?
behavioral mechanisms
What are some behavioral mechanisms that animals can use to regulate temperature?
- Burrowing or basking in the sun
- Seeking shade
- Climb vegetation
- Changing body orientation
What is a behavioral mechanism humans use to regulate body temperature?
wear clothes
How can surface temperature of an organism be controlled?
By altering blood flow to the skin
How does increased blood flow to the skin affect body temperature?
Increases heat loss and lowers body temperature, but increases surface temperature
How does constriction of blood vessels to the skin affect body temperature?
Conserves heat and body temperature, but decreases surface temperature
How do Galapagos marine iguanas regulate body temperature?
Maintain body heat while swimming, and warm up quickly while basking by changing the heart rate (and the blood flow to the skin) to match the environmental temperature
What is the function of fur on mammals?
insulation that retains body heat
What if animals with fur are active and generate too much heat?
They lose excess heat by using special blood vessels that carry heat to hairless skin surfaces
How is heat loss tightly controlled in the hairless skin surfaces of furry mammals?
Opening and closing of the special blood vessels
How do fish produce heat?
metabolically
How do fish lose heat?
as blood travels over the gills
How does blood travel in “cold” fish?
cool, oxygenated blood travels from the gills to the aorta and is distributed to organs and muscles
How does blood travel in “hot” fish?
most of the cool, oxygenated blood to the body moves through large peripheral arteries rather than through a central aorta
Why does moving cool, oxygenated blood through the large peripheral arteries conserve more heat than moving blood through the aorta?
The large peripheral arteries are connected to countercurrent heat exchangers near swimming muscles that warm up the blood
What is the function of the countercurrent heat exchanger?
helps keep the heat within the muscle by returning heat back to the muscles before the blood returns to the gills and loses less heat
