Midterm 2

6, 7, part of 8

How do mammals deal with cold?

1. acclimate (thereby adjusting MRC (metabolic response curve)
2. evolutionary changes in basal metabolic rate (BMR)
3. modify body configuration
4. employ insulation
5. employ heterothermy

How do animals use acclimation to deal with the cold?

* metabolic acclimation - produce more heat
* non-shivering thermogenesis (e.g. increased heat production)
* cellular level
* mitochondria - gen heat
* physiologic acclimation - loose less heat
* insulation (blubber, fur)
* reduce conductance

what is the TNZ?

thermoneutral zone

what is UCT?

upper critical temperature

what is LCT?

lower critical temperature

What rules are associated with modifying body configuration to deal with the cold?

bergmann’s rule

inverse bergmann’s rule

allen’s rule

what is bergmann’s rule?

body size tends to increase in colder regions

body size varies _____ with ambient temperature

inversely

in comparison to smaller animals, larger animals die of heat stress at (higher/lower) temperatures

lower

fecal width _____ with body size

correlates

What is inverse bergmann’s rule?

* reflects lower food availability
* scarcity of food, especially in winter, is major factor selecting for small body sixe in shrews in northern areas, as smaller indivs should require less food

what is allen’s rule?

body extremities tend to decrease in colder regions

What body feature is associated with employing insulation to deal with the cold?

blubber

* insulation by blubber can be by-passed when needed (fur cannot)

What are some behavioural adaptations that are associated with employing insulation to deal with the cold?

* beavers build lodges
* squirrels make big nests
* complex chambers for mole rats

Increasing evidence suggests that while homeothermy is a derived (_____) trait, it appears (more/less) universal than believed.

apomorphic

less

Numerous scholars are now suggesting that synapsid vertebrates may have evolved “controlled _____” from a fully ectothermic ancestor.

heterothermy

Some mammals evolved _____, while others frequently retained _____.

homeothermy; heterothermy

What are 2 ways mammals employ heterothermy to deal with the cold?

regional hypothermy

whole-body facultative (adaptive) hypothermy

What kind of mammals employ regional hypothermy? How does it work?

* dolphins, lots of marine mammals maintain cooler temperatures in their fins by warming up the veins by passing warmer veins by cooler veins
* whales also keep their tongue v cool since it touches cool water often

What kind of mammals employ regional hypothermy? How does it work?

* dolphins in their flippers, whales in their tongue
* arteries carry warm blood out to fins which cool as they get to the tips
* veins carry cold blood back past the arteries, which warms the reentering blood through the process of counter current heat exchange

What kind of mammals employ whole-body facultative (adaptive) hypothermy? How does it work and why is it done?

* done by lots of animals
* mammals reduce metabolic rate and therefore reduce body temperature
* this serves to reduce energetic needs and conserve water

What is torpor and what mammals do it?

torpor - short bouts of facultative hypothermy

not sleep, looks like they are dead

done by: lots of rodents, small mammals

What is hibernation?

hibernation - prolonged periods of deep facultative hypothermy

What are possible inductors of hibernation?

temperature

photoperiod

food and/or water availability

Before hibernation, there may be a preparatory phase that includes . . .

* increasing body fat (often eat voraciouly = hyperphagia)
* storing vitamins
* shrinking the size of many organs

What are five things that happen during deep hibernation?

* EKG (kinda like heart rate) drops as low as 10% normal
* Tb drops to ca 1 deg C of Ta (not bears) - (approach poikilothermy (albeit controlled, but not in bears)
* may be intermittent periods of arousal
* gonads may be functional during hibernation (some mammals mate during this period of hibernation)
* late winter: heart and brain arouse first

What happens in hibernation if the temperature drops too low?

1. built-in alarm → arousal
2. increase metabolic rate to compensate
3. die

Arousal is often the most _____ _____ part of _____ or _____.

energetically expensive; torpor; hibernation

Arousal is likely caused by _____ _____. For example, the lack of _____ or _____ _____.

internal rhythms; light; thermal “cues”

Arousal involves often _____ _____ and/or the _____ of muscles

violent shivering; contractions

To aid in arousal, many species use _____ _____ in addition to _____ _____ and _____.

brown fat; white fat; muscles

Brown fat has higher _____ content, which metabolizes more rapidly than _____ _____. This produces more _____.

cytochrome; white fat; heat

Where is brown fat often located?

around the shoulder blades

During hibernation, yellow-bellied marmot’s heart rate declines from \~___ bpm to \~___ bpm. O2 consumption is ___% of normal rates. They breath once every ___ minutes. Temperature declines from ___ deg C to ___ - ___ deg C.

100 bpm; 15 bpm

10%

6 minutes

39 deg C; 2-8 deg C

What is notable about hibernation in arctic ground squirrels?

theyre body temperature drops below 0 deg C in some areas of their body, but there is no tissue freezing and no evidence of antifreeze molecules.

they supercool to a metastable state of below freezing temps that persist in the absence of a nucleator which would readily instigate crystalization.

What strategies do nothern temperate bats use for hibernation?

* they use brown fat, which is kept between shoulders on back
* they selectively choose cave microsites w not too much wind movement
* they often group tog - this is referred to as behavioural thermoregulation
* bats are known to copulate during hibernation

What is unusual about hibernation in bears?

* temp only drops about 5-10 deg C below normal temp of 38 deg C; therefore they are not operationally poikilothermic

Why are bears not operationally poikilothermic?

body size

* cost of warming a small mammal is much less than the cost o f warming a very large animal
* bears also loose heat less at a lower rate because of their body mass

How do mammals deal with cold?

1. behavioural thermoregulation
2. physiological thermoregulation

What makes a fossorial mammal’s environment challenging?

* high CO2
* low O2
* low air movement
* digging is v expensive

How big can naked mole rat colonies be?

50 or more

What are the different castes in naked mole rat colonies?

* frequent workers
* infrequent workers
* non-workers
* single breeding female

Describe the frequent workers caste in naked mole rat colonies.

* 25-30 g
* burrow cooperatively
* forage
* build communal nest

Describe the infrequent workers caste in naked mole rat colonies.

* ca 35 g
* work ca 1/2 rate of frequent workers

Describe the non-workers caste in naked mole rat colonies.

* ca 46 g
* rarely work
* care for young - is this not fucking work? wth?

Describe the single breeding female caste in naked mole rat colonies.

* 80 g
* 1-4 litter/year; up to 24/litter

What are environmental constraints for naked mole rat colonies?

* short moist season
* extremely hard soils
* dispersed food sources (large tubers - to 50 kg)

Explain the Aridity Food-Distribution Hypothesis for the Evolution of Eusociality.

\

eusociality

kin selection, helping behaviour, and caste structure → reproductive skew

overlapping generations

increased philopatry

long tunnels expensive to build

high dispersal costs

right chain start

food items widely dispersed

hot environment predators

sociality

individual poikilothermy

high thermal conductance

high capillary density (lungs, muscles)

carbonate and bicarbonate secretion in urine

low bmr, naked, small

high CO2, low O2, high temps, high humidity

left chain start

subterranean habit

What are three characteristics of eusociality?

* reproductive division of labor
* social overlap of generations
* cooperative care of young

What are 4 strategies for physiological thermoregulation?

1. avoid the heat - aestivate
2. evolutionary change in BMR
3. get rid of heat
4. tolerate the heat

What is aestivation? What is it equal to? Who does it?

* avoiding the heat
* equivalent to torpor
* monotremes (echidna), marsupials (smaller species), bats (common), rodents

How do mojave ground squirrels aestivate?

* active above ground spring/early summer
* initiate aestivation July/August
* intermittent arousal; emerge March/June (varies by elevation)

Explain how some species use evolutionary change in BMR to reduce heat production as a part of physiological thermoregulation.

studies found that species that exist in different enviros have different BMRs in different enviros that have developed genetically

What are 2 methods mammals use to get rid of heat?

panting and sweating

What is the process of panting?

unidirectional airflow - inhale via nose, exhale via mouth

Panting uses _____ and creates _____, which means that mammals need to pant at a _____ _____.

energy; heat; resonant frequency

What are 2 risks associated with panting?

hyperventilation and alkalosis

How are the risks associated with panting avoided?

by breathing shallow, but rapidly

What happens when a mammal exhales too much CO2 while panting?

* the blood supply of carbonic acid is drawn down
* blood buffer (carbonate and bicarbonate) levels are reduces
* this leads to alkalinity and poor O2 transport

What is the chemical formula for how alkalosis happens?

CO2 + H2O

Panting is _____. Therefore, it uses _____ and generates _____, but allows for _____ heat loss.

\
Sweating, on the other hand, is _____. The mammal has no _____ rate of heat loss. The rate depends on _____ _____.

active; energy; heat; controlled

\
passive; controlled; air movement

What are some cons of sweating (as compared to panting)?

loses more H2O

loses metabolites and salts

What are the benefits of panting (as compared with sweating)?

lower loss of metabolites and salts

Panting is _____ in many carnivora and some other groups such as bovidae.

conspicuous (i think tldr; common)

Sweating is done by . . .

. . . most mammals.

What method to stay cool is associated with tolerating the heat?

facultative adaptive whole body hyperthermy

How does the antelope ground squirrel employ facultative adaptive whole body hyperthermy?

it will emerge from its burrow to feed until it gets too hot; after its body temp has increased considerably, it goes back into its burrow to rest for a little while before coming back out again

How do camels employ facultative adaptive whole body hyperthermy?

they allow their temp to drop below 35 deg C at night and above 40 - 41 deg C in the day

How do gemsboks (oryx gazella) use counter-current heat exchange to regulate their body temperature in extreme heat?

* counter current heat exchange happens in the sinus cavernosus
* arterial warm blood (ab 43 deg C) comes from the heart (body)
* heat is exchanged in cavernous sinus between warm arterial blood and cool venous blood from nasal passages
* evaporation occurs in nasal passages which gives it a cool temp
* cooled arterial blood finally reaches its destination, the brain
* cool arterial blood (ab 40 deg C) is in brain

What are 3 sources of water loss?

feces - ca 5%

urine - ca 25%

evaapotation - ca 70%

What are 3 sources of water gain?

drinking

free water in food

oxidative water in carbohydrates

What can be said about the loss of water in feces amongst different species?

moisture in feces varies widely amongst species

How much urine is produced by a human in a day?

1 liter/day

What are the steps involved in the filtration of water out of urine?

1. ultrafiltration
2. \

1. active transport of ions (ion pump)
2. passive reabsorption
3. tubular reabsorption

What is the first step of filtering water out of urine and how does it work?

1. ultrafiltration
* how liquid is forced out of somewhere
* happens in bowman’s capsul
* in the glomerulus (tubes)
* these 2 parts make up the renal or bowman’s corpuscle

What is step 2a of filtering water out of urine and how does it work?

2. \

1. active transport of ions (ion pump)
* liquid travels down descending loop, then up descending loop, ions out, osmosis, active transport out via ions pumps, passively picked up in passive reabsorption (2b.)
* occurs in ascending loop

What is step 2b of filtering water out of urine and how does it work?

2. \
b. passive reabsorption
* ions passively picked up in passive reabsorption
* gradual accumulation deep in kidneys
* at this point, liquid is dilute
* point is to create concentrated urine
* happens in the descending loop and loop of Henle
* henle loop job is to create high concentration urine by collecting
* produces high concentration urine

What is the third step of filtering water out of urine and how does it work?

3. tubular reabsorption
* this is how concentrated urine is created and concentrated
* happens in collecting duct

try and understand this

¯\\_(ツ)_/¯

If liquid exiting the nephron is dilute, how do we produce concentrated urine?

The walls of the collecting duct in the kidneys easily allow _____ out, but not _____ things.

water; other

Kidney stuff: The more _____ there are, the less room for actual _____.

solutes; water

Kidney stuff: Longer loops of _____ creates (more/less) concentrated urine.

Henle; more

Mammals in _____ enviros have longer loops of Henle to make even (more/less) watery urine.

dryer; less

Humans have relatively (long/short) loops of Henle.

short

What hormone regulates the permeability of water through duct in the loop of Henle?

diuretic hormones

specifically antidiuretic hormone (ADH)