Temperature and Performance of Organisms

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Temperature and Performance of Organisms
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Temperature Effects on Metabolic Reactions
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Temperature Effects on Metabolic Reactions
The increase in organism performance with
temperature is accounted for in part by metabolic
effectiveness. For each 10 deg C rise in temp,
the rate of biological enzymatic processes often
roughly doubles. This is because high temp
increases the speed of molecular movement and
speeds up chemical reactions.
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Temperature Effects on Metabolic Reactions
The decrease in organism performance at higher
temperatures is because excessively high temps
destroy the shapes of the enzymes, and compromise
their fit with the substrate and enzyme function.
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Temperature and enzyme activity
Rates of reaction often vary with adaptation of
the organisms to the local environment Rainbow
trout produce two forms of this enzyme. One
performs best at 2 deg C, the other at 17 deg
C. These two temps correspond with average winter
and summer temps.
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Degree-day concept
The effects of chemical reactions often
influences organism growth rates and rates of
development. For many organisms, there is a
linear relationship between temperature and rate
of growth or development. Degree-days number
of day-degrees above a temperature threshold.
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Degree-day concept
The effects of chemical reactions often
influences organism growth rates and rates of
development. For many organisms, there is a
linear relationship between temperature and rate
of growth or development. Degree-days number
of day-degrees above a temperature threshold.
Dev threshold 9.9 deg C Temp days to
dev day-degrees 15 24.22 24.22 x 5.1
123.5 25 8.18 8.18 x 15.1 123.5
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Despain 2006
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• Beginning about 1998 willows that had been
  surpressed by elk browsing for more than 50 years
  on Yellowstone National Parks northern winter
  range began to grow tall in some places.

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• Two unusual things happened
• to produce tall willows.
• Phenomenal growth
• Effectively defended against large
• herbivores
• Why?? Could it be induced by warmer temperatures?

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• Temperature has a definite affect on carbohydrate
  production
• Day length control means that growth occurs
  during early half of warm season leaving
  carbohydrates produced during last half available
  for storage, defensive chemical production and
  other processes.
• Longer periods of favorable conditions in the
  spring provide longer stems
• Longer periods of favorable conditions in the
  fall provide more defensive chemicals

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Conclusion Willow physiology indicates that the
increase in days with minimum temperature greater
than 0ºC could explain the recent change in
willow growth habit. But what about wolves and
50 reduction in elk herds?
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Summary These are examples of organisms having
maximum performance at a fairly narrow range of
env conditions. Given how the environment
varies over space and time, it is clear how no
one organism can monopolize all environments and
why there is such a diversity of life.
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Regulating Body Temperature
Vectors of Heat Exchange between Organisms and
Environment

• HS Hm Hcd Hcv Hr Hc
• HS Total heat stored in an organism
• Hm gained via metabolism
• Hcd gained / lost via conduction
• Hcv gained / lost via convection
• Hr gained / lost via electromag. radiation
• Hc lost via evaporation

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Body Temperature Regulation

• Poikilotherms
• Body temp varies directly with env. temps.
• Ectotherms
• Rely mainly on external energy sources.
• Endotherms
• Rely heavily on metabolic energy.
• Homeotherms endotherms that use metabolic
  energy to maintain a constant body temperature

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Temperature Regulation By Plants

• Desert Plants Must reduce heat storage.
• (HS) Hcd Hcv Hr
• To avoid heating, plants have (3) options
• Decrease heating via conduction (Hcd).
• (place foliage above ground)
• Increase convective cooling (Hcv).
• (leaves with high surface to volume)
• Reduce radiative heating (Hr).
• (Increase reflectivity via hairs)

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Temperature Regulation By Arctic and Alpine Plants

• Increase radiative heating (Hr).
• Dark pigments to absorb radiation, orient to
  maximize solar radiation uptake
• Decrease Convective Cooling (Hcv).
• Cushion growth from to be in lower windspeed and
  increase conduction from ground

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Temperature Regulation by Ectothermic Animals

• Liolaemus Lizards
• Thrive in cold environments.
• Burrows, Dark pigmentation, Sun Basking
• Grasshoppers
• Some species can adjust for radiative heating by
  varying intensity of pigmentation during
  development.

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Temperature regulation by Liolaemus multiformis

• - lives in the cold environment in the Andes
  mountains at over 4800m.
• - night temperatures can be 5 deg C.
• - at night the lizard stays in burrows to reduce
  cooling but its temp still falls (to 2.5 deg C).
• - morning behavior
• perching on plant material to reduce conduction.
• basking in sun to increase radiation, including
  orienting its back to the sun, and using dark
  skin pigmentation.
• crouching low to reduce convective heat loss.
• - as air temp rises to 1.5 deg C, body temp rises
  to 33 deg C.

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Temperature Regulation by Endothermic Animals

• Also use metabolic heat to regulate temperature
• Reduce heat loss by insulation (fur, feathers,
  fat)
• Increase heat loss via evaporative cooling
  (panting, sweating).
• Thermoneutral zone - the range of environmental
  temperatures over which the metabolic rate of a
  homeotherm does not change.

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Thermoneutral Zone
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Temperature/thermal neutral zone of mammals
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Life at Low Temperatures

• Chilling injury
• damaged by exposure to temperatures that are low
  but above freezing
• mechanisms is not well known, but may be
  associated with breakdown of membrane
  permeability and the leakage of specific ions.

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Life at Low Temperatures

• Freezing injury
• Water can supercool to temperatures to -40 deg C
  and body fluids in organisms seldom freeze until
  well below 0 deg C.
• But at temperatures below 40, trees are not able
  to persist, this explains the northern limit of
  forests.
• Between 0 and -40 damage comes from water outside
  of cells freezes, drawing water from the
  supercooled cells and causes cell death to
  osmotic forces similar to drought or salinity.

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Strategies to Cope with Cold

• Avoid freezing. Production of alcohols and
  proteins that allow supercooling.
• Tolerate freezing. Production of alcohols that
  do not inhibit extracellular water freezing, but
  seal cell membranes to avoid water loss.
• Acclimatization, where exposure to cold is
  gradual and allows the strategies to develop.
• Topor. This is a state of low metabolic rage and
  lowered body temperature.
• Hibernation. Extended state of reduced metabolism
  and inactivity .

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Strategies to Cope with Heat

• Evaporation leads to cooling.
• Some plants in hot environments maximize
  transpiration to facilitate cooling.
• Where water is short, this becomes impossible.
• Here plants may use spines, hairs, or waxes to
  reflect incoming radiation.