Index cards

1
Chapter 3

• Index cards
• But first..

2
Make up session

• Monday schedule.
• 11.00 to 12.30?
• 12.30 to 2.00 ?
• 2.00 to 3.00?

3
Book requests

• Received
• Books to get here Friday (except)

4
Online quizzes

• Do them
• Do them on time

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News of the week

• 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

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News of the day

• 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?

8
Chapter 3

• Will not go over pages 40 to 47
• Since it is covered in biology introductory
  courses

9
Temperature limits the occurrence of life.

• 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

10
Tolerance of Heat

• 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 -gt organisms develop quicker
• The bad High temperatures
• denature proteins
• accelerate chemical processes
• affect properties of lipids (including membranes)

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Oxygen consumption increases as a function of
temperature
12
Metabolic theory of ecology

• 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

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What about freezing temperatures?
14
Freezing temperatures

• 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

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Tolerance of Freezing

• 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

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Glycoproteins act as a biological antifreeze in
the antarctic codthe fishs blood and tissues
dont freeze due to the accumulation of high
concentrations of glycoproteins, which lower its
freezing point to below the min temp of seawater
(-1.8C) and prevent ice crystal formation
18
supercooling

• 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 seeds 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

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Interesting?

• 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 -6C and endure freezing episodes lasting more
  than a month. Fully-frozen animals, in which up
  to 65-70 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.

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• Link is on the ecology page on the website

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Each organism functions best

• under 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 wont
  tolerate it
• but
• Many fish species from cold environments swim as
  actively as fish from the tropics

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Enzymes and temperatures and swimming

• 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

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Compensation is possible.

• 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 thermal environment includes numerous avenues
for heat gain and heat loss
26
Pathways of heat exchange
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Thermal image of Canada geese on a cold day
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What you eat

• The heat, water, food and salt budgets of animals
  (including us) are coupled by diet, evaporative
  water loss and excretion

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Keeping cool

• Although few animals sweat the way that we do,
  all lose heat by evaporation from their
  respiratory surfaces
• When water is scarcestay out of the sun
• Why then do several species of seabirds nest in
  full sun on bare sand, while wedge-tailed
  shearwater builds it nests under-sand?

• Sooty terns can tolerate a hot nesting environment

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Why?

• Theories?
• Predators?

32
Hatching success of wedge-tailed shearwaters is
highly dependent on the thermal environment
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Why?

• 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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The greenhouse effect
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Carbon dioxide concentrations in the atmosphere
measured at Hawaii
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39
Homework assignment 1

• (moan. groan. sigh.)
• Use scientific literature (what is that?)
• Read 1 article (no older than 2005) on the issue
  of impact of climate change.
• Summarize the article.
• Grammar. Reference. Logic. Etc. no cut and paste.
• Email me the summary.
• Present the material during class (5-7 min)
• Due November 4.
• No late papers accepted.
• Why?

40
Homeothermy increases metabolic rate and
efficiency
41
Organisms maintain a constant internal
environment.

• An organisms 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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Negative feedback system
43
Temperature Regulation an Example of Homeostasis

• 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

44
Homeostasis is costly.

• 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

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Limits to Homeothermy

• 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, organisms capacity to return
  internal conditions to norm is exceeded
• available energy may also be limiting, because
  regulation requires substantial energy output

46
Partial Homeostasis

• 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)

47
Hummingbirds maintain a constant low body temp
when in torpor
48
Countercurrent heat exchange
49
Delivering Oxygen to Tissues

• 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 (lt2 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

50
Countercurrent Circulation

• 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

51
Conservation and Countercurrents

• 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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A fishs gill is designed to promote
countercurrent circulation of blood and water
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Skin temperatures of the leg and foot of a gull
standing on ice show that heat is retained in the
body