Lecture 7 - Environmental Adaptations Flashcards
what must plants and animals deal with in the boreal?
snow
wind
drought
lack of nutrients in soil
what happens to plant tissues when water freezes?
water expands in the cells and destroys living tissues
sharp ice crystals can damage and kill cells
in what 2 ways does frozen water injure cells?
- rupturing cell membranes
2. altering permeability of membranes
what 2 methods do boreal plants escape frost damage?
- extra-cellular freezing
2. supercooling
briefly describe extracellular freezing
antifreeze accumulates inside cell walls allowing cells to prevent freezing.
plants encourage ice formation in between cells and prevent them in cells
briefly describe supercooling
lowing temp of liquid or gas below its potential freezing point w/o becoming a solid
how do cold temps affect animals?
food scarcity
metabolism is disrupted
freezing
what are 3 broad methods of staying able 0C
migration
stay warm
dormancy
what are 2 broad methods of dropping below 0C
Freeze avoidance
Freeze tolerance
how does the choice of habitat reflect the difference strategies of coping with extreme temperatures?
above snow = accept cold temperatures and manage being cold
@ freezing zone = freeze tolerance (frogs)
below frost line = freeze avoidance
where is the best play to go for aquatic animals?
deeper bc fresh water is most dense at 4C so it sinks (warmer at bottom)
why do fish dive deep in salt water?
avoid ice
what subnivean snow zone do arctic animals inhabit?
ex?
pukak
lemmings
what adaptation do greenland collared lemmings have to avoid freezing?
grow long wide claws in winter for digging snow since there are larger crystals in the pukak layer
acclimation vs adaptation
acclimation: readily and reversible modification caused by exposure to the environment (not inherited)
adaptation: accumulation of genteel changes to increase survival/reproduction. not readily reversible
define homeotherm?
maintain a constant body temperature
define endotherm
generates own body heat using own energy to maintain temperature
define poikilotherm
ex?
animals with a variable body temp
moths/butterflies
example of a poikilothermic endotherm
hibernating animals
define ectotherm
generally do not produce enough heat to maintain a constant body temp. Rely on external sources of heat.
MAY have constant Tb depending on behaviour and environment
example of a homeothermic ectotherm
several antarctic fish
how do bee hives stay warm in winter?
bumblebees shiver to produce heat via muscle contraction. communal effort used to heat the colony and keep the queen warm
list the general ways to reduce heat loss
get big (bergman's rule) get round (allen's rule) adjust MBR prevent heat loss (insulate, lower conductive HL, restrict evaporative HL)
bergmann’s rule
animals of larger size found in colder envr (poles)
decrease SA:V
why doesn’t bergmann’s rule always hold true with arctic animals?
large body size means more food is required
advantages of being large outweigh the disadvantages
allen’s rule
roundness is most effective for SA:M
example of allen’s rule
arctic foxes ears, muzzle, legs, tail
~allows them to conserve heat
what can heat loss through conduction be prevented?
increase insulation
increase fur/feather thickness
how is caribou hair adapted to cold environments?
hair is hollow and filled with air pockets since it’s such a good insulator
also increase density and thickness of fur
what environmental variables decrease insulation through fur?
example of how this is mitigated
water
-pb fur sheds water efficiently
wind
- muskoxen w/ very long fur that isn’t affected by high winds
Glogers Rule
pigmentation declines towards to poles since black objects absorb AND radiate more heat
briefly, why are arctic animals white?
- reduce heat gain from sun during activity to cool down and prevent overheating
- lack of melanin increases room for air cavities (insulator)
- reflect light onto black skin of the animal (doesn’t reflect but scatters!)
how do animals cope with limited food availability in winter?
use fat deposits
2 methods of lowering conductive heat loss
insulate extremities
allow peripheral tissues to cool
example of insulating extremities
underside of paw with fur in caribou, polar bears and arctic fox
benefits of knobbly feet?
reduce contact (conductive heat loss) between feet and ground
how does foot size related to latitude?
increases with latitude
-> better at walking through snow
why are huskies feet maintained so cold?
what is responsible for this?
decreases gradient tf less heat loss
cutaneous vascular plexus
how to reduce convective heat loss? (evaporative less)
reindeer - conchae
- increase SA
- divide air flow
- thick mucosal layer
explain the process of inhaling and exhaling over conchae
inhale = air pass over warm mucosa, saturated with water. Mucosa cooled and warm air to lungs
exhale = air passing over cool mucosa is warm and wet from lungs. water condenses and mucosa warmed. animal exhales cool “dry” air
4 options to dealing with temp when living in cold climate
- migration
- habitat selection
- adjust lifecycle
- adjust body temp
what coping strategies are used that include a reduced metabolism?
hibernation
diapause
freezing
anoxia
what are the 2 supercooling chemical categories and what habitats are each used in?
antifreeze proteins = subnivean habitats
cryoprotectants = exposed habitats
what do antifreeze proteins do? where are they found?
decrease the freezing point
in plasma
what does glycerol (cryoprotectant) do? where is it produced from?
reduce the nucleation potential of seed crystals
produced from fat
what is it called when ice crystals form?
seeding
what does freezing cause in the body?
freezing of intracellular fluids
change structure of proteins and inhibit function of enzymes
cause sells to shrink
examples of freeze tolerate species
frogs painted turtles garter snakes some lizards many insects
freeze tolerance is most commonly seen in what animals?
those that cannot avoid coming in contact with ice
how can wood frogs freeze without dying?
ice forms extracellularly but their growth it prevented.
Ice nucleating proteins initiate, antifreeze proteins prevent growth. high level of polyols intracellularly to prevent ice
define hypothermia
core temperature drops below that required for normal metabolism and body functions
define torpor
entry of animal into hypothermia with behavioural inactivity
define hibernation
sustained state of torpor, entry to and exit from which is governed by internal signals together with exclusively seasonal external cues
examples of animals that hibernate
richardson’s ground squirrel
arctic ground squirrel
little brown bat
what are the precursors to hibernation?
seasonal phenomenon
gain up to 40% body mass
need polyundsaturated fats
find hibernaculum
what indicates timing of hibernation?
circannual and environmental cues
during hibernation, what slows down?
DNA/RNA synthesis protein synthesis fuel metabolism ion pumping ATM turn over decrease to <5% normal
what mechanism is used for arousal in hibernation?
BAT
function of BAT vs WF
heat production via non shivering thermogenesis
insulation, energy and storage
