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Lecture 5

Biology 2601A/B Lecture Notes - Lecture 5: Acclimatization, Atp Synthase, Cytoplasm


Department
Biology
Course Code
BIOL 2601A/B
Professor
Jennifer Taylor
Lecture
5

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Lecture 5: Endothermic Homeotherms
PART 1: THE INCREDIBLE ENDOTHERM
Patterns of Tb in Animals
Endothermic
Heat from environment
Tb = Ta (body temperature = ambient temperature)
Ta can have profound effects on enzymes
Homeotherm
Highly stable core body temperature, regardless of changing ambient temperature
Example of the penguin from lecture 1: as it enters water, Tb is constant
- Unique adaption  birds and mammals defend against the ambient
environment and have a constant Tb
- Mammals use hair/fur to maintain Tb
Endothermic homeotherms
Heat is derived from internal metabolism
Tb is usually higher than Ta
Tb usually constant regardless of Ta
Ta has little direct effect on enzymes  homeostasis regardless of enzymes
Graph: red line is the basal metabolic rate (BMR)
- BMR: rate of amount of energy being consumed at rest
- The graph is taken after someone has fasted (no food in stomach)
- For homeotherms, we use BMR and for ectotherms, we use MR
- When BMR is constant, then you are in the TNZ
PART 2: GETTING COLD
Am bie nt tem pe rature
Metabolic Rate
Therm oneutral
Zon e (TNZ)

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Am bient tem perature
Metabolic Rate
Increased energy
consumption due to
heat generation
Changes to the TNZ graph when it’s cold:
If you are cold and find any insulation, you are outside of the TNZ?
BMR will go up because you have to spend more energy to maintain that constant
internal temperature
Blue circle: lower critical temperature
- It means you spend more energy
- If you expand that lower critical temperature, that means death (but not for
homeotherms)
Gray box says: increased energy consumption due to heat generation
Seasonal variation in insulation
Thicker Coat
Homeothermy allows you to expand your thermal niche
They have summer and winter coats
- Cats/dogs will have a thicker coat in winter
- Thick coat allows them to stay within the TNZ
This is an adaptation you see in larger mammals
Textbook Figure 10.40, pg. 264  the red is the summer fox and the blue if the
winter fox
Fluffing up
They become fluffy
Birds and mammals can erect their feather or fur
Their TNZ doesn’t get larger like in the graph above for thick fur
Disadvantage: it doesn’t help if the bird moves around
- Then the feathers have to be compressed, and they still have to rely on fat
build up and insulation
Arrector pili muscle
Our skin uses adaptation to protect body temperature
Our arterioles will constrict (close) or dilate (open)
Arterioles feed capillaries beds in skin when theyre open, and then this blood
flows to our outer skin
If skin is in contact with cold, then we lose heat to the outside temperature
Am bient tem perature
Metabolic Rate
Seasonal variation in insulation
Arrector pili m uscle
Arrector pili m uscle
I.e. FOX
Vasoconstriction
Vasodilation
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