Lecture 27- Animal Adaptations III Flashcards
What problems do the brids and mammals face when they remain active throughout the winter?
- Must maintain narrow range of body temperatures needed to be maintain or you get denaturing of enzymes
- Maintain body temperature much higher than air temperature
- Must produce enough metabolic heat to offset to cold air
What is conduction?
Loss of heat through physically touching something (heat transferred to the ground)
What is convection?
Loss of heat to a water or a gas
What is radiation?
Heat that is always given off by some sort of heat source
What is Evaporation?
Transfer of liquid to a gas (occurs through respiration)
What are the four ways that contribute to energy loss?
- Conduction
- Convection
- Radiation
- Evaporation
How is heat loss from a small homeotherm?
- Losing heat from the core body
- Cant store heat in the body
- Conduction
- Convection
- Radiation
- Evaporation
What are some assumptions of heat loss?
- Latent heat exchange is small in most homeotherms
- Total heat loss from outer surface = heat conducted from the core of the animal to the outside surface
- Heat cannot be stored on the surface of animals
Describe total heat loss
- Total heat loss is a function of the conductivity of the general thermal conductivity and the surface area exposure, so how much of the animal is being exposed to heat loss to occur on
- Relationship between temperature gradient and distance between the core and the outside air
- How much distance does the thermal energy need to travel from the core
How to maintain a constant metabolic rate?
- Decreasing thermal conductivity
- Decreasing surface area exposed
- Increasing thickness of insulating layer
- Modifying microclimate
- Nightly state of torpor
- Solitary mammals can group together
How do you increase the thickness of insulating layer?
- Increasing distance to core
- Add fat
- Erection of hairs
- Fluffing of feathers (trapping air)
- Thicker hair
How do you modify the mciroclimate?
- Build nest of insulating materials or go underground where there’s less wind
- Reduces the different between body temperature and air temperature
Whats an example of mammals grouping together?
Beaver lodges can be 35C warmer than outside air temperature, muskrats live in the beaver lodges, they bring in food and share the food, its a symbiotic interaction
How to Taiga Wolves survive the winter?
- Nests of 5-10 taiga wolves
- Never completely vacated so foraging animals return to warm nests
- Animals also huddle in the nest
- Nests about 15-20cm underground
What is a subnivean environment?
Habitat under the snow where small mammals will live in winter
What are the impacts of snow on small and larger mammals?
- Larger = must adapt behaviour, feeding habits (harder to find food)
- Smaller = can exploit snow to reduce thermal loss
What are some benefits to snow?
- Snow is a good insulator
- Fluffy snow has a lot of air trapped in it and contains a warm microclimate in it
- Barrier from dry, cold and windy air
- Under snow = humid, warm and stable
- Can form a crust on top of the snow that provides better protection from the cold
What type of animals use subnivan environments?
Small mammals and invertebrates
(birds can burrow in the top layer of the snow
At some point animals must ______
Must increase metabolic rate to balance heat loss (switch from physical to physiological changes)
What is the LCT?
- Lower critical temperature
- Temperatur at which a change in physical to physiological adjustments is necessary
What takes over when you go below the LCT?
Physiological thermoregulation takes over (get change in metabolic rate)
What is the thermal neutral zone?
The area in which you can still make physical adjustments
LCT varies based on?
Varies based on species and body size (larger body size has more leeway in reaching LCT)
What is non-shivering thermogenesis?
Heat production from burning brown fat
Secretion of ____ due to cold stimulates heat production in brown fat cells
Noradrenaline
Why brown fat?
More mitochondria = higher rate of O2 consumption and heat produced and highly vascularized
When is there an increase in brown fat and what causes it?
Accumulation occurs in early fall because of the decreasign day length and low temperatures (photoperiod and temperature)
Difference between white and brown fat?
- Brown fat much more granular and small
- Highly vascularized
- Heat dirrectly into the blood
- More mitochondria
The placement of brown fat is placed strategically to warm what up first?
To heat up the core first
What part of the brain gets triggered by temperature drops to release noradrenaline?
Hypothalamus
What happens to adipocytes for winter?
- Animals increase lipid storage
- Formation of additional adipocytes
- Enlarging adipocytes
Arctic animals have more _____
Adipocytes
What are some natural obese animals?
- Polar bear
- Arctic fox
- Caribou
- Muskoxen
What is shivering thermogenesis?
Rapid muscle activity that generates heat, this is critical last effort
What are some problems with appendages?
- Must be kept supplied with oxygen
- Must be kept warm by circulating blood through them
- Must avoid excess heat loss
How to animals in the north avoid issues with appendages?
- Shorter limbs
- Utilize countercurrent heat exchange
How does countercurrent heat exchange work?
Heat from arteries is transferred to veins
Who uses nasal microcirculation and what is it?
- Caribou
- High density of capillaries in nose that absorbs heat before exhalation and it heats the incoming air
What are some trade-offs between activity and avoidance?
- Freeze tolerance or avoidance
- Modified activity, changes in BMR
- Increased insulation, brown fat
- Countercurrent heat exchange
