Temperature Influences and Thermal Balance

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Temperature Influences and Thermal Balance

• Chapters, 7, 8
• Smith Smith

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Key Section Concepts

• Temperature is a key environmental variable that
  regulates productivity and limits ranges
  distributions of plants and animals.
• Organisms maintain thermal balance with their
  environment via radiation, convection,
  conduction, and evaporation.
• Body temps of most organisms vary with the
  environment, but birds mammals remain fairly
  constant.

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Key Section Concepts

• Ectothermic organisms depend upon the heat of the
  environment to maintain their body temps
  endothermic ones maintain their heat through
  metabolic heat.
• Organisms have evolved means of adapting to the
  stresses of heat and cold.
• Optimum temperatures for life processes influence
  the distribution of organisms.

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Temperatures vary greatly during the course of
a yearanimals plants must adapt to these
ranges to survive.
30 20 10 0
Avg. Daytime High Temperatures.
Feb. Apr. Jun. Aug. Oct. Dec. Feb.
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For example

• In WV the mean annual temp. is 12 C, but may
  range from 37 to 44 C.
• Also, surface temperatures may vary by 30 C from
  sunny to shaded areas at a time!
• In tidal flats, temps rise to 38 C in sun when
  exposed, but drop to 10 C when covered with water
  at high tide.

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Despite temp extremes and organisms ability to
cope with it, there are limits

• 52 C is the upper limits for animals or
  protozoans to live.
• Vascular plants survive from 60 to 60 C.
• Arctic algae complete life cycles Ps at _at_ 0 C.
• Non-Ps bacteria can inhabit hot springs at T gt 90
  C.

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To maintain temperature, organisms must balance
energy gained and lost..
Sources of Energy?
Source of Heat Transfer?
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SOURCES OF ENERGY

• RADIATION (e.g. sunlight) is a major source of
  heat transfer (_at_ 1.4 cal/cm2/minute at noon on a
  clear summer day).
• SKYLIGHT or DIFFUSE RADIATION _at_ 0.2 cal/cm2/min).
• REFLECTED LIGHT (0.1 0.3 cal/cm2/min)
• HEAT from METABOLSIM in metabolic oxidation, 1
  mole of glucose gives off 686 kcal of energy,
  only 40 kcal is trapped as ATP, the rest is lost
  as heat.

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SOURCES OF HEAT TRANSFER

• CONDUCTION direct exchange of heat between 1
  substance and another. Depends upon S.A.
  exposed Temp-differences between the two
  surfaces thickness of insulation (fur
  conductivity).

• COVECTION tranfer of heat by circulating of
  fluid (liquid or gas). e.g. circulating around
  an animals body and dissipating heat.

• EVAPORATION cools an organism by changing
  liquid to a vaporous state water absorbs a
  substantial amount of heat.

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TEMPERATURE METABOLSIM

• Temperature affects metabolism (and Ps) of
  organisms by affecting the speeds of chemical
  reactions and the effectiveness of enzymes.

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Temperature affects Plant photosynthesis and
respiration.
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Organisms Can Be Divided Into 2 Groups

• Those whose body temperature varies with the
  environment (protists to plants, to amphibians,
  fish, and reptiles).
• Those whose body temperatures are regulated by
  physiological means (ie, metabolism e.g. mammals
  and birds).

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We Have Terms for these two different thermal
groups

• Homeotherms self-regulate body temps thru
  metabolism.
• Poikilotherms body temps related to
  environmental temperatures.

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Regardless of the Source of Thermal regulation,
the heat balance of an organism can be described
by the balanced heat equation (Schmidt-Nielsen
1997) Htot Hc Hcd Hr He Hm Where
Htot is the rate of metabolic heat production
and the other terms are the rate of heat
gain/loss thru convection (Hc) conduction (Hcd)
radiation (Hr) evaporation (He) and the rate of
heat storage in the body thru metabolic processes
(Hm).
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The way temperature affects metabolism of
poikilotherms is described by Hoffs reactive
rate/temperature rule
For every 10 C rise in Temp.the rate of Oxygen
Consumption (metabolism) doubles. This
factorial increase in Metabolism for every 10 C
is called temperature coefficient or Q10 Q10
RT / R (T-10) Here, RT is the rate at any
given body temperature, and T-10 is the rate at T
10 C.
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The way temperature affects metabolism of
poikilotherms is described by Hoffs reactive
rate/temperature rule

• For most fish, the body temperature water
  temperature, so the Q10 is simplified.
• Overall, for many species, the Q10 relationships
  approach 2.0 in other words, for every 10 C
  increase in temperature, the metabolic rate
  doubles.
• However, within a species the Q10 may vary over
  different ranges of temperatures (not a linear
  response).

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We know from our lab exercises that temperature
influences the metabolism of fish.
What would the Q10 relationship be for BT and GF
from 10 20 C?
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What would the Q10 relationship be for BT and GF
from 10 20 C?
For Brook Trout T10 0.150 and T20
0.290 SO, Q10 0.290/0.150 or 1.93
For Goldfish T10 0.060 and T20 0.240 SO,
Q10 0.240/0.060 or 4.00
Thus, brook trout Q10 is close to 2.0, but
goldfish is much higher!
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Acclimation affects thermal limits.

• E.g. if acclimated to 22 C, brook trout may be
  able to tolerate immersion in 26 C water for a
  time (usually 23 C is lethal).
• BUT, if acclimated to 18 C, Brook trout exposed
  to 26 C will immediately lose balance and die.
• Fish can usually handle drops in temp better than
  increases Brown bullheads shocked from 25 C to
  4 C lay on bottom, eyes dilate and fish are
  motionless.
• Plants respond similarly to thermal acclimation.

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Plant Responses to Temperature

• Plants moderate their temps by losing part of the
  energy they absorb thru re-radiation, convection,
  and transpiration.
• Plants are not always the same as ambient
• sunny sides of trees are warmer than shady side.
• Winter perennials are warmer than the air.
• desert plants are cooler or warmer than
  ambient.

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Plant Responses to Temperature

• HEAT STRESS
• Leaves can become too warm for Ps, then
  Respiration gt Ps.
• When exposed to a rapid temp rise, shock proteins
  replace protein synthesis to aid in short-term
  survival.
• Most plants die at 44 50 C.

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Plant Responses to Temperature

• COLD STRESS
• Plants from warm and temperate areas have little
  tolerance for cold temps.
• Even plants from our latitudes with freezing, can
  suffer cold shock and freeze damage if temps drop
  too quickly or drastically.
• Roots, bulbs and rhizomes are most sensitive to
  freezing, but these are usually protected
  underground.

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Temperature influences Ps rates
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Animals and more about Temperature.

• Terms relating to how body temperature is
  determined.
• Endothermy maintaining of body temperature thru
  metabolic processes.
• Ectothermy body temperature is dependent upon
  radiation, re-radiation, etc., things other than
  metabolism.

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Animals and more about Temperature.

• Poikilotherms allocate more energy to biomass
  than to metabolism.
• Advantages can tolerate large periods of
  temperature extremes and drought or food
  shortages (e.g. crocodiles, annual feeding).
• Disadvantages. Active periods are restricted to
  spring, summer, early fall when temperatures
  are warm enough.

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Animals and more about Temperature.

• Poikilotherms allocate more energy to biomass
  than to metabolism.
• Most reptiles are sit-and-wait as opposed to
  chase predators due to build ups of lactic acid
  from aerobic metabolism (lactic acid must be
  reduced thru aerobic respirations which are
  limited by body temps).
• Also, terrestrial poikilotherms are less able to
  be active during cool mornings and evenings.that
  is when risk of poisonous snake bites are
  greatest cause snakes are less able to run away.

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Some other Thermal Terms

• Heliothermism animals that bask in the sun to
  raise body temperatures above ambient (e.g frogs
  go gt 10 C above ambient by basking).
• Heterothermism animals whose sometimes do, and
  sometimes do not regulate body temperatures.
• Homothermism animals whose body temperature is
  regulated by their metabolic processes.

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Some other Thermal Terms

• Critical thermal maximum (CTM) temperature at
  which an animals ability to move is so impaired
  as to keep it from moving out of a zone of
  thermal conditions that will cause death if not
  removed from it.
• Used a lot in federal regulations, e.g. for
  effluent discharges.
• Proportional Control ability of organisms
  (e.g. lizards) to flatten out and orient
  themselves to right angles with the sun to gain
  maximum warming from the suns rays.

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Proportional Control ability of organisms
(e.g. lizards) to flatten out and orient
themselves to right angles with the sun to gain
maximum warming from the suns rays.
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HOMEOTHERMS

• Birds and mammals are endothermic.
• They maintain their thermal optimum by oxidizing
  glucose and other energy rich molecules.
• They regulate the gradient between body air
  temperatures by seasonal changes in insulation
  (type thickness of fur, feather, fat), by
  evaporative cooling, increasing or decreasing
  metabolic heat production, altering activity
  (less active in hot weather, etc.)

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HOMEOTHERMS

• Can remain active at any temperature, but at high
  energy costs.

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HOMEOTHERMS

• Homeothermy has placed a size constraint upon
  ita close relationship exists between body size
  and basal resting metabolism rate.
• In general, weight-specific metabolism is
  proportional to body mass raised to the 0.75
  power.
• Just as we saw for Goldfish (a poikilotherm) in
  lab, the specific metabolic rate decreases as
  size decreases.

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In HOMEOTHERMS this size-relationship is very
clear.
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The question then arises, Why do larger
endotherms have lower specific metabolism rates?
ANSWER It is related to the relationship
between size and surface area.small objects have
a greater surface area (SA), thus more metabolic
activity is needed to maintain temperatures. Note
about 5 g is about as small a size as an
endotherm can be, smaller cannot maintain
metabolic heat balance (hence parental care in
birds, mammals). (A pygmy shrew is _at_ 2.0 g).
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because of conflicting metabolic demands
between maintenance of body temps and growth,
most young birds mammals are born in an
altrical state depending upon parents for heat
so that most of their energy goes into growth of
the young. Most mammal arms and legs, and
legs of birds, tails of beavers, have
countercurrent heat exchangers for arteries and
veins so that returning venous blood is heated by
arterial blood and returns to the body core only
slightly cooler than it left. Countercurrent
heat exchangers are what allow birds mammals to
swim or live in freezing waters, while being
endothermic.
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OTHER MEANS OF DEALING WITH HEAT AND COLD

• Countercurrent heat exchangers (e.g. mammal
  limbs, bird legs, beaver tails).
• Rete (heat exchanger) used to cool brain of
  African antelopes (Oryx) during high daytime
  temperatures.
• Countercurrent circulation (allows pads of artic
  fox to cool to _at_ 0 C)

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It is more difficult to deal with heat than cold
What are some means of dealing with the heat, for
Homeotherms?

• evaporative cooling
• Thermal windows, such as large ears in desert
  mammals.
• Seeking shade or underground burrows.
• Becoming nocturnal.
• Changing thickness of insulating layers.

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Heterotherms

• Among the poikilotherms and homeotherms exist
  species that sometimes do not regulate their body
  temps and sometimes do regulate it these are
  called heterotherms.
• Examples Insects, Tunas, Hummingbirds, Many
  small mammals, bears.
• Tuna use countercurrent heat exchangers to
  increase muscle temps above ambient water temps
  for better performance. In warmer waters they do
  not do this.

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Heterotherms Other Examples.

• Hummingbirds may have periods of the day with
  very low metabolism inactivity to reduce
  metabolic costs (Torpor).
• Bears as in the videowill become
  inactive/sleep for 6 months, living off of
  reserves of fat. Heartbeats drop from 40-50/min.
  to 8-10/min, with metabolism lt 50 of normal.
• Ground hogs true hibernation, with drastically
  reduced body temps (lt 10 C), heartbeat and
  respirations drastically reduced.

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TEMPERATURES AND DISTRIBUTIONS

• TEMPERATURES play a key role in the distributions
  of organisms
• LMB can live in temps from 0 32 C, but require
  temps of 20-25 C for spawning.
• Vampire bats are limited to a January minimum
  temps of 10 C due to their inability to
  thermoregulate at temps lt 10 C.
• Plants too are limited by tempseither not
  surviving, or being unable to reproduce outside
  their range.

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An important QUESTION. How will animals and
plants respond to Global Climatic Warming?????
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TEMPERATURE AND OTHER FACTORS.

• Temperature and sex of egg-born offspring.
• Temperature and rates of growth.
• Temperature egg hatching rates (implications
  for survival).
• Temperature and finding a mate (fronts, eels, and
  the Sargasso Sea)
• Temperature behavioral thermoregulation.