Metabolic rate and homeothermy

Question 1

why does body temperature matter

Answer 1

effects physiology processes
- increases membrane permeability
- changes enzyme reaction rate
- quicker energy extraction from food and energy available for use
- movement/speed varies

Question 2

what is the Q10

Answer 2

describes the rates of reaction and how they vary with every 10 degrees of temp

Question 3

why does speed/movement increase with temperature

Answer 3

• increased ATP availability by mitochondria
• increased muscle output

Question 4

what % of total metabolic cost of contraction results in mechanical work

Answer 4

25%= the rest lost as heat= why you heat up as you move

Question 5

how do we define body temperature

Answer 5

1) heat source= endo/ecto
2) the variability of the body temp= poil and homeotherm

Question 6

define ecto/endothermy

Answer 6

Ecto= reliant on external sources of heat to raise body temperature needed for activity

Endo= use of internal heat to maintain temperature such as metabolic heat

Question 7

define metabolic rate

Answer 7

the rate at which organisms take up, transform and expend chemical energy
= in metabolic oxidation of food, more than half of the energy in the bonds of the substrate is released as heat
= increasing/decreasing MR changes the production of metabolic heat

Question 8

define poikilothermy and homeothermy

Answer 8

P= body temperature varies with that of the enviro, most terrestrial ectotherms are also this

H= maintenance of stable internal body temp, usually associated with endothermy

Question 9

outline torpor

Answer 9

a state of physical/mental inactivity, some animals who are heterothermic
= they can drop temperatures to within 1 degree of ambient temp

deep torpor= oxidative metabolism and energy use are reduced to 1/20th normal rate as well as decreased respiration and heat beat

Question 10

outline how deep torpor can help the survival in chickadees

Answer 10

The species rley on fat stores accumulated in the day to sustain them through the night= not enough for survival during the winter

instead they undergo torpor as to maintain body temp of 40 degrees would need 0.92g of fat which is more than the actual bird

Question 11

what is meant by gigantothermy/megalothermy

Answer 11

some large ectotherms can maintain body temps similar to endotherm animals due to low surface area to volume rations

= they are able to generate heat but not lose it rapidly so can hang onto it- this allows them to live in colder areas e.g. leatherback turtles can live in colder areas than other turtle species

Question 12

outline how Ectotherms metabolic rate changes with temperature

Answer 12

Body temp increases as temperature increases

MR - increases as temp increases until reaching optimum temp, but cant go above or will experience heat stress

therefore many ectotherms live in high temp areas such as tropical belt

Question 13

outline how ectotherms control heat exchange with the environment

Answer 13

Gains and losses occur through
1) Radiation = transfer of heat through electromagnetic waves

2) convection = transfer of heat by the movement of air/liquid past a surface e.g. a breeze/blood moves heat from the body

3) conduction= transfer of heat between molecules of objects in contact with each other

4) Evaporation = loss of heat from a wet surface due to evaporation

Question 14

outline some thermoregulatory behaviours in ectotherms

Answer 14

1) body orientation to the sun = effect the level of radiation exposed
2) body contour= change SA such as expanding rib cage
3) movement = from cold to warmer area
4) huddle

Question 15

outline some physiological thermoregulation strategies in ectotherms

Answer 15

1) Skin colour = lizards heat 10-75% when darker, melanophores contain melanin which can be drawn away from the skin surface

2) Vasodilation to increase blood flow

Question 16

outline how thermoregulation enables lizards to exploit extraordinary habitats

Answer 16

Galapoagos iguanas heat up on land by basking and cool down in water
= by basking it allows them to dive for up to 1 hr and feed on marine algae in cold water

this is only viable due to heat available above water

Question 17

what is the limitations to thermoregulation in ectotherms

Answer 17

limit on where they can live and the seasons which are warm enough to get energy from enviro for foraging and reproduction

regulation can take a long time precluding other activates

Question 18

what are the adaptations for endothermy

Answer 18

• higher mitochondrial densities
• greater amounts of metabolically active tissue (kidney, heart, brown fat)
• thermal insulation = feathers, fur, fat, blubber
• reduction of body surface area: volume rations e.g. dorso-ventral flattening increases SA, long thin bodies are common in ecotherms

Question 19

outline how endotherm MR changes in endotherms

Answer 19

Range of temps where MR is the same (thermal neutral zone), above this in upper critical temps, MR increases to keep cool and in lower critical temps MR increases to keep warm

Question 20

define TNZ and upper critical temp

Answer 20

TNZ= range of ambient temps where thermoregulation can be accomplished by non-evaporative heat loss

UPT = point where non evaporative heat loss has been maximised, above this heat can be lost evaporative cooling e.g. sweating/panting

if this cant balance heat flow from environmemt body temp will rise = hyperthermia and death

Question 21

define lower critical temp and lower lethal temp

Answer 21

LCT= where an animal must increase metabolic heat production to maintain body temp

LLT= metabolic heat production is insufficient to balance heat loss, body temp falls reducing ability to generate further heat, usually resulting in death by hypthermia

Question 22

outline how taxa vary in their thermal neutral zone

Answer 22

Birds = 40 degrees
mammals = 37 degrees
marsupials = 36 degrees
egg laying monotremes = 30-31 degrees
differences are not understood

Question 23

why are most thermal neutral zones between 35-40 degrees

Answer 23

endotherm body temps ensure that animals are generally warmer than the environment as dumping heat is easier than being cooler and then over heating

Question 24

outline some thermoregulatory behaviours in endotherms to stay in TNZ

Answer 24

1) alter surface area
2) huddle
3) alter air trapped by feather or fur
4) move= avoid heat/cold

Question 25

outline some physiological strategies in endotherms to stay in TNZ

Answer 25

counter current heat exchange
extremities often have minimal muscle and dont need large blood flow

Question 26

outline the conseuquence for trophic structure and interaction depending on being and ecto/endotherm

Answer 26

MR of terrestrial ecto are only 10-14% of those of endo the same size so endo more likley to experience comp

ecto have advanatge in warm climates where food scarce as 30-40% of energy intake is available for growth/reproduction not keeping warm

birds/mammals over 10% of food intake is used for growth/repro