Transcript Chapter 3

Index cards…
But first..
 Monday
schedule.
• 11.00 to 12.30?
• 12.30 to 2.00 ?
• 2.00 to 3.00?
 Received…
 Books
to get here Friday (except…)
 Do
them
 Do them on time
 UN
says: 1.3 million people have already
been affected by the drought in Syria
 Check out the news story…
 Check
out ‘man in the cube’ on Kalam el
Nass tomorrow
 Hormones
in U.S. Beef Linked to Increased
Cancer Risk
“- Beef produced in the United States is heavily
contaminated with natural or synthetic sex hormones,
which are associated with an increased risk of
reproductive and childhood cancers, warns Dr. Samuel
S. Epstein, Chairman of the Cancer Prevention
Coalition.”
 What
are the interactions?
 Will
not go over pages 40 to 47
• Since it is covered in biology introductory
courses
• most life processes occur within the temperature
range of liquid water, 0o-100oC
• few living things survive temperatures in excess of
45oC
• freezing is generally harmful to cells and tissues
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Most life processes are dependent on water in its
liquid state (0-100oC).
Typical upper limit for plants and animals is 45oC
(some cyanobacteria survive to 75oC and some
archaebacteria survive to 110oC).
Good: high temp -> organisms develop quicker
The bad: High temperatures:
• denature proteins
• accelerate chemical processes
• affect properties of lipids (including
membranes)
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 Temperature
has consistent effects on a
range of processes important to ecology
and evolution (Univ of New Mexico ecologists)
• Rates of metabolism
• Rates of development of individuals
• Productivity of ecosystems
• Rates of genetic mutation
• Rates of evolutionary change
• Rates of species formation
 Temperatures
rarely exceed 50 degrees C
(except….)
 Temperatures below freezing point of
water are common
• On land
• In small ponds which may become solid during
winter
 So: adaptation
is necessary
•
•
Freezing disrupts life processes and ice
crystals can damage delicate cell structures.
Adaptations among organisms vary:
• maintain internal temperature well above freezing
• activate mechanisms that resist freezing
• glycerol or glycoproteins lower freezing point
effectively (the “antifreeze” solution)
• glycoproteins can also impede the development of
ice crystals, permitting “supercooling”
• activate mechanisms that tolerate freezing
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 Pure
water: freezes at 0 degrees C
 Seawater: freezes at -1.9 degrees C
• Contains about 3.5% dissolved salts
Another physical solution to freezing
 is the process of lowering the temperature of a
liquid or gas below its freezing point w/o it
becoming a solid
 Liquids can cool below the freezing point w/o ice
crystals development

• Ice generally forms around some object (a seed)
• In a seed’s absence, pure water may cool more than 20C
below its freezing point w/o freezing
• Recorded to -8C in reptiles and to -18 in invertebrates
• Glycoproteins in the blood impede ice formation by
coating developing crystals

“About a dozen species of amphibians and reptiles are known to
be “freeze tolerant,” able to tolerate tissue freezing under
naturalistic thermal and temporal conditions. Generally, ice
formation is restricted to extracellular spaces, as intracellular
freezing is not tolerated. Some species survive freezing at
temperatures as low as -6°C and endure freezing episodes
lasting more than a month. Fully-frozen animals, in which up to 6570% of the body fluid has become ice, appear lifeless: muscle
contraction, heartbeat, and breathing have ceased. There is no
flow of blood to the frozen tissues, which become depleted of
oxygen and energy. Nevertheless, frozen specimens arouse after
thawing and can resume normal physiological and behavioral
functions within a day or two. Natural freeze tolerance is promoted
by special physiological adaptations, including an accumulation of
certain cryoprotective compounds, a redistribution of bulk water
within the body, and an innate tolerance of cells to hypoxia and
dehydration.”
Link is on the ecology page on the website
 …under
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
a restricted range of temperatures (but
of course!)
Optimum: narrow range of environmental conditions to
which organism x is best suited
Temperature! One such example.
Put a tropical fish in cold water and it becomes
sluggish and soon dies; put an Antarctic fish in
temperatures warmer than -5C, and it won’t tolerate it
but
Many fish species from cold environments swim as
actively as fish from the tropics
 Different
temperatures result in different
enzyme formation (in quantity or in
qualitative difference of the enzyme
itself)
 Rainbow trout:
• Low temp in its native habitat during the winter
• Higher temp in the summer
 Many
organisms accommodate to
predictable environmental changes
through their ability to “tailor” various
attributes to prevailing conditions:
• rainbow trout are capable of producing two forms
of the enzyme, acetylcholine esterase:
 winter form has highest substrate affinity between 0
and 10oC
 summer form has highest substrate affinity between
15 and 20oC
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The heat, water, food and salt budgets of
animals (including us) are coupled by diet,
evaporative water loss and excretion
Although few animals
sweat the way that we
do, all lose heat by
evaporation from their
respiratory surfaces
 When water is
scarce…stay out of the
sun
 Why then do several
species of seabirds
nest in full sun on bare
sand, while wedgetailed shearwater
builds it nests undersand?


Sooty terns can tolerate a
hot nesting environment
 Theories?
• Predators?
•
Diets and feeding regimes
• Sooty Terns feed on fish and squid – close to the nesting
sites; male and female cooperation in incubation duty
• Shearwaters, similar diet, but feed hundreds of
km from their nesting sites
•
So:
• Sooty terns have stomach full of water-laden
food  water for evaporative heat loss
(remember: fish provide supply of free water)
• Shearwaters  plenty of fat for fast but little
water (fat has less water than fresh fish)
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 (moan. groan. sigh.)
 Use scientific literature (what is that?)
 Read 1 article (no older than 2005) on
issue of: impact of climate change.
 Summarize the article.
the
• Grammar. Reference. Logic. Etc. no cut and paste.
 Email me the summary.
 Present the material during
 Due: November 4.
 No late papers accepted.
 Why?
class (5-7 min)
 An
organism’s ability to maintain
constant internal conditions in the face of
a varying environment is called
homeostasis:
• homeostatic systems consist of sensors,
effectors, and a condition maintained constant
• all homeostatic systems employ negative
feedback -- when the system deviates from set
point, various responses are activated to return
system to set point
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42
 Principal
classes of regulation:
• homeotherms (warm-blooded animals) -
maintain relatively constant internal
temperatures
• poikilotherms (cold-blooded animals) - tend to
conform to external temperatures
 some poikilotherms can regulate internal
temperatures behaviorally, and are thus considered
ectotherms, while homeotherms are endotherms
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 As
the difference between internal and
external conditions increases, the cost of
maintaining constant internal conditions
increases dramatically:
• in homeotherms, the metabolic rate required to
maintain temperature is directly proportional to
the difference between ambient and internal
temperatures
44
 Homeotherms
are limited in the extent to
which they can maintain conditions
different from those in their
surroundings:
• beyond some level of difference between
ambient and internal, organism’s capacity to
return internal conditions to norm is exceeded
• available energy may also be limiting, because
regulation requires substantial energy output
45
 Some
animals (and plants!) may only be
homeothermic at certain times or in
certain tissues…
 pythons maintain high temperatures when incubating
eggs
 large fish may warm muscles or brain
 some moths and bees undergo pre-flight warm-up
 hummingbirds may reduce body temperature at night
(torpor)
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47
 Oxidative
metabolism releases energy.
 Low O2 may thus limit metabolic activity:
• animals have arrived at various means of
delivering O2 to tissues:
 tiny aquatic organisms (<2 mm) may rely on diffusive
transport of O2
 insects use tracheae to deliver O2
 other animals have blood circulatory systems that
employ proteins (e.g., hemoglobin) to bind oxygen
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 Opposing
fluxes of fluids can lead to
efficient transfer of heat and substances:
• countercurrent circulation offsets tendency
for equilibration (and stagnation)
• some examples:
 in gills of fish, fluxes of blood and water are opposed,
ensuring large O2 gradient and thus rapid flux of O2
into blood across entire gill structure
 similar arrangement of air and blood flow in the
lungs of birds supports high rate of O2 delivery
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 Countercurrent
fluxes can also assist in
conservation of heat; here are two examples:
• birds of cold regions conserve heat through
countercurrent circulation of blood in legs
 warm arterial blood moves toward feet
 cooler venous blood returns to body core
 heat from arterial blood transferred to venous blood returns
to core instead of being lost to environment
• kangaroo rats use countercurrent process to reduce
loss of moisture in exhaled air
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