Eco-Physiology - adaptation to diverse environments Flashcards
getting bodys internal conditions right?
broad strategies
-conforming
-regulating
-avoiding
water balance
temperature
biotic interactions?
other lifeforms also part of environment
-plants important part of habitat
-predators important challenges
-conspecifics
-parasites
fundamental physiological challenges?
getting what you need from environment
-O2 - aerobic respiration
-metabolic fuel (food)
getting body’s internal conditions right
broad strategies
water balance
temperature
three broad coping strategies:
-avoidance
-conforming
-regulating
most animals will blend these somewhat
avoidance?
getting away from an environmental problem in space or time
-nocturnal
-hibernation (diapause)
blocking out environmental difficulties (shells, e.g. mussels closing to not dry when tide goes??)
conformer?
undergo changes in state similar to changes in the environment
(many marine organisms osmoconformers in water balance)
plot internal conditions against external conditions
will be just about linear for perfect conformer
regulator?
perfect regulator would maintain same internla environment regardless of external environment
straight level line on graph of internal against external
hyper-regulation - keep internal conditions above external
hypo-regulaiton - keep below
e.g. endothermic animals - can regulate internal body temp to tight stable range
ectotherms are able to do this as well as endotherms but just not as tightly
in between strategising?
most organisms blend strategies of
regulating
conforming
avoiding
e.g. regulating internal environment to a certain point where it begins to conform
^this could give organisms limits to the points of external environments they can handle
water balance?
cells need certain stable water:ion balance
passive exchange - water moves from dilute to concentrated via osmosis, ions other way vis diffusion
aquatic environments - water and ions can move in or out of organisms:
-marine environments concentrated - risk of water leaving cells
-freshwater environments very dilute - risk of water flooding cells (also losing ions?)
terrestrial environments:
water can move out into air - desiccation main problem - especially in dry hot conditions
water balance - surface barrier:
(skin e.g.)
critical in controlling water balance
INVERTEBRATES;
-epithelial cells with unrestricted permeability
-BUT - virtually waterproof exoskeletons control water entry/escape
VERTEBRATES:
-Amphibian: soft, non keratinised skin
-fish - keratinised scales
-other vertebrates - impermeable dead keratinised cells
exchange surfaces?
gills, lungs etc that meet external environment
“internal” tissues meeting external environment
need to be managed using active processes which need a lot of energy investment
(e.g. to avoid losing too much water/ions to air/outer water from lungs/gills)
marine water balance strategies:
seawater concentrated but relatively stable
-most invertebrates, hagfish (agnatha), cartilaginous fish have tissue concs similar to external
>OSMOCONFORMERS
-bony fish (teleosts) are OSMOREGULATORS - tissues are more dilute than seawater and have to deal with passive loss of water
dealing with passive loss of water into concentrated seawater?
-kidney produces very little, concentrated urine
-ions actively pumped out across gills (as ions are coming in from sea - need to maintain tissue conc)
-drink seawater - ions actively absorbed out
-can drink 25% of body weight per day, and absorb 80% of ingested seawater
freshwater water balance strategies:
very dilute environment
osmoconforming not an option as tissues would not work that dilute
OSMOREGULATION is essential
-tissues more concentrated than envitonment so need to avoid passive influx of water
-freshwater teleosts do opposite of marine:
-DO NOT drink water
-kidney adapted to produce lots of dilute urine (to lose water - retain ions)
-ions actively reabdorbed across gills/other surfaces
stenohaline?
aquatic animals living ONLY in either marine or freshwater
euryhaline?
aquatic animals adapted to be able to spend time in marine and freshwater
need specific osmoregulation strategies to cope with hugely varying external concentrations
euryhaline examples?
salmon migrating back to freshwater birthplace from sea to breed
bullsharks - cope with dramatic concentration changes by varying internal urea concentration in body - high in amrine, low in freshwater
water balance avoidance?
common where conditions change too
-brackish environments experience repid concentration shifts
effectively from marine-terrestrial depending on tide
changes in predation (marine to terrestrial at diff times)
physical pressure from waves/tidal movement
so organisms do:
-Hiding (rock pools, crevices, burrows)
-internal water stores as buffer (crustaceans, molluscs)
-resistant covering (mucuc, calcareous shells) -seal themselves off from outer environment
terrestrial water balance strategies:
main issue: losing water to air and drying out (lose across internal exchange sites)
-avoidance (astonishing strategeis in some microorganisms)
-desert mammals evolving to get more water from food and metabolism and internally conserve it
microorganism water balance avoidance strategy?
tardigrades
respond to severe lack of water by going into different morphological/physiological arrangement where they can survive extreme conditions (similar to bacteria sporulation)
PLASTIC response to water limitation
environment temperature properties:
has biphasic relationship with physiological processes
increasing temp->
activity (of eg enzyme) increases - reaches and optimum and then begins to get worse and eventually denature
aquatic temperature properties?
water much more thermally stable than air
but also conducts heat much better than air
so regulating internal temperature is much more challenging
many aquatic animals thermoconform
-because - bery difficult to change internal temperature from outside because high conductivity water draws heat out well
also environment very thermally stable so there arent really varying temperature conditions to regulate away from
terrestrial temperature properties:
lots of latitudinal variation
seasonal variation outside of tropics
pronounced daily variation
(lots of variation in conditions so regulation and avoidance strategies more common)
linked to water balance:
-dehydration risk unless v high humidity
-availablr drinking water depends on climate
metabolic heat generation key to most themoragulation strategies
terrestrial temperature avoidance strategies
Migration:
birds moving from temperate environments when gets colder
also avoid other things
Torpor and Diapause:
animals shut down, reduce core body temp and metabolism
avoid harsh winter conditions (also some organisms avoid dry hot conditions - eg dry season diapause)
as winter approaches
have some small drops in metabolism to “test” lower rates
then drops a lot
then comes back in spring as gets warmer
hide in underground burrows - avoidance combined with extreme thermoregulation
ecto vs endotherms
both ecto and endotherms thermoregulate
just differ in methods
ECTOTHERMS mostly conform to temp but regulate to some degree
many endotherms use can conform to some degree and use similar strategies to ectotherms
both use both metabolic and environmental heat
endotherms evolved to generate 4-8x more metabolic heat at big cost
endotherm regulation strats:
-increased metabolic potential of muscle cells (e.g. mitochondria numbers)
-voluntary and involuntary (shivering) muscle action
-metabolic short cuts to generate heat (e.g. brown fat)
size and thermoregulation
size matters to thermoregulation
thermal inertia
-rate of cooling slower in larger animals
-thermoregulation is potentially a more serious issue for smaller animals
-gigantothermy - being very big makes thermoregulation pretty easy
thermoregulation reptile example:
monitor lizard
basks in morning to get body temp above ambient temp
then at night -
large size and spending night time in den buffers heat loss (high thermal inertia)
and keeps it relatively warm through evening/night
temperature usually manages to stay above external
thermoregulation mammal example
mountain goats
shared ectotherm strategies
body temp always rose in the morning
so mustve been basking in sun in morning to raise body temp
then also has a drop in metabolic rate in winter despite not hibernating (heart rate drop observed, metabolic depression to save fuel)
amplitude of daily body temp change is higher in winter than summer
