Eco-Physiology - adaptation to diverse environments

Question 1

getting bodys internal conditions right?

Answer 1

broad strategies
-conforming
-regulating
-avoiding

water balance

temperature

Question 2

biotic interactions?

Answer 2

other lifeforms also part of environment
-plants important part of habitat
-predators important challenges
-conspecifics
-parasites

Question 3

fundamental physiological challenges?

Answer 3

getting what you need from environment
-O2 - aerobic respiration
-metabolic fuel (food)

getting body’s internal conditions right
broad strategies
water balance
temperature

Question 4

three broad coping strategies:

Answer 4

-avoidance
-conforming
-regulating

most animals will blend these somewhat

Question 5

avoidance?

Answer 5

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??)

Question 6

conformer?

Answer 6

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

Question 7

regulator?

Answer 7

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

Question 8

in between strategising?

Answer 8

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

Question 9

water balance?

Answer 9

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

Question 10

water balance - surface barrier:

Answer 10

(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

Question 11

exchange surfaces?

Answer 11

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)

Question 12

marine water balance strategies:

Answer 12

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

Question 13

dealing with passive loss of water into concentrated seawater?

Answer 13

-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

Question 14

freshwater water balance strategies:

Answer 14

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

Question 15

stenohaline?

Answer 15

aquatic animals living ONLY in either marine or freshwater

Question 16

euryhaline?

Answer 16

aquatic animals adapted to be able to spend time in marine and freshwater

need specific osmoregulation strategies to cope with hugely varying external concentrations

Question 17

euryhaline examples?

Answer 17

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

Question 18

water balance avoidance?

Answer 18

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

Question 19

terrestrial water balance strategies:

Answer 19

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

Question 20

microorganism water balance avoidance strategy?

Answer 20

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

Question 21

environment temperature properties:

Answer 21

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

Question 22

aquatic temperature properties?

Answer 22

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

Question 23

terrestrial temperature properties:

Answer 23

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

Question 24

terrestrial temperature avoidance strategies

Answer 24

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

Question 25

ecto vs endotherms

Answer 25

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

Question 26

endotherm regulation strats:

Answer 26

-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)

Question 27

size and thermoregulation

Answer 27

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

Question 28

thermoregulation reptile example:

Answer 28

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

Question 29

thermoregulation mammal example

Answer 29

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