Transcript Chapter 4 Temperature Relations

Chapter 4 Temperature
Relations
 1. Macroclimate & Microclimate
Macroclimate: is what weather stations
report and what we represented with climate
diagrams in Chapter 2.
Microclimate: is climatic variation on a scale
of a few kilometers, meters, or even
centimeters, usually measured over short
periods of time.
2. Factors affecting microclimate
temperature
 Altitude: as discussed in chapter (Fig.2c1)
 Aspect:
Northern aspect: where temperature is
higher at Southern Hemisphere.
Southern aspect: where temperature is
higher at Northern Hemisphere.
 Vegetation: vegetation can greatly
modify temperature (Fig.4.3)
 Color of the Ground (Fig.4.5)
 Presence of Boulders（大石块） &
Burrows (Fig.4.6)
3. temperature & performance of
organisms
 Temperature & Performance at the
Molecular Level
Too low temperature decreases the
flexibility of enzymes, so decreases their
functions.
Too high temperature destroys the shape
of enzymes, so decreases their functions.
 Example: Fig.4.8 energies activity at
different temps .
Two forms of acetycholinesterase (an
enzyme) of fish:
one form works in winter, the optional
temp. is 2 ℃,
the other form works in summer, the
optional temp. is 17 ℃.
 Temperature & Photosynthesis
Photosynthesis increases with
temperature and reaches it maximum rate
at an optional temperature, and then
decreases with temp.. Different species
has different temp. range (Fig.4.9).
Acclimation(驯化): Short-term
physiological adjustment of animal/plant
response to temp (Fig.4.10).
Case Histories: regulating body
temperature
 Balancing Heat Gain Against Heat Loss
Hs=Hm + Hcd + Hcv + Hr + He
Hs: Total heat stored in the body;
Hm: Heat gained from metabolism
(Hm of plant is very small, of
ectothermic
animal is small, and of endothermic
animal is very important.) ;
Hcd: Heat gained or lost through
conduction;
Hcv: Heat lost or gained by convection;
Hr: Heat gained or lost through
electromagnetic radiation;
He: Heat lost through evaporation
(Fig.4.13).
Temp. Regulation by Plants
 Desert plants
 Morphological adaptations:
1). Reduce Hr (electromagnetic
radiation)by orienting their leaves
parallel to sunlight;
2). Have high rate of convective (对流)
cooling with open growth form and
small leaves to increase exposure of
plant surfaces to wind;
3). Highly reflective leaves/dense
and white hairs ect. reduce heat
gain by radiation (Hr);
4). Low conductive heat gain from
ground (Hcd) by placing their foliage
far enough above the ground.
 Arctic & Alpine Plants
1). Increase radiative heat gain with dark
pigments; by orienting their leaves and
flowers.
2). Increase radiative heat gain and
reduce heat loss by cushion growth
form which can decrease exposure of
plant surface to wind, so can reduce
convective heat loss to wind, and get
heat from warm substrate through
conduction, Hcd Fig.4.15
 Tropical Alpine Plants
Great variation of temp. during the day.
1). Rosette (莲座状) growth form: which retains
dead leaves to insulate the stem and protect it
form freezing.
2). Thick pubescence (短柔毛) covering leaves
which can create a dead air space above the
leaf surface to reduce heat losses, and reduce
radiation during hot day.
3). Retaining large volume of water to store heat
to protect from freezing during night.
Temp. Regulation by Ectothermic
Animals
 Example of a Liolaemus Lizards, a
Lizard in cold high Andes Mountains of
South America at altitude over 4,800 m.
1). Pressing flat against the substrate to
reduce heat loss by convection (Hcv).
2). Perching on a bed of plant of material
to reduce heat loss to ground by
conduction (Hcd).
3). Exposing the darkly pigmented back to
the sun to increase heat gain by radiation
(Hr). Fig.4.17
Other example: Grasshoppers (P96).
Temp. Regulation by Endothermic
Animals
 Environmental Temp. & Metabolic Rates
Thermal neutral zone: the range of
environmental temp. over which the
metabolic rate of a homeothermic animal
（恒温动物）does not change.
The breadth of the thermal neutral zone
varies a great deal among endothermic
species. Tropical species have a smaller
breadth and arctic species, a much wider
one. Fig.4.21.
 Adaptation
--At low temp.:
shivering releasing hormones to
increasing metabolic rate.
--At high temp.:
sweating, pant (气喘) salivating (大量
分泌唾液) & licking (伸出舌头).
Aquatic Birds & Mammals
 Temp. characteristics of water
(1) has a capacity to absorb heat energy
without changing temp. is about 3,000
times that of air;
(2) conductive and convective heat losses
to water are much more rapid than to air,
over 20 times faster in still water and up
to 100 times faster in moving water.
 Temp. adaptation of aquatic birds &
mammals:
1). Air breathing instead of grill breathing;
2). Thick layer of fat or fur to protect heat
loss;
3). Countercurrent heat exchange,
selectively heat certain muscle groups and
perhaps increase their swimming
performance over a larger range of
temperatures, as shown in Fig.4.23.
Temp. Regulation by Thermogenic
Plants
 An example of eastern skunk cabbage, Fig.4.26,
Fig.4.27
Plant of Symplocarpus foetidus can emerge from
the frozen landscape.
Starch is translocated from the taproot to the
spadix;
High metabolic rate of spadix generates sufficient
heat to melt snow;
Snow is melted by radiation and conduction
Surviving extreme temperature
 Inactivity Fig.4.28.
 Reducing Metabolic Rate:
Torpor(蜤伏): a state of low metabolic
rate
and lowered body temperature.
During torpor , a hummingbird’s body
temperature is 12 to 17 ℃,quite a
reduction from 39 ℃.
Hibernation: Reducing metabolic rate for
several months in winter.
During hibernation , the body temp. of
arctic ground squirrels (松鼠) may drop
to 2 ℃.
Estivation: Reducing metabolic rate for
several months in summer.
During estivation, the metabolic rate of
long-neck turtles may fall to 28% of their
normal metabolic rate.