Protecting the Biosphere by ert554898

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									Protecting the Biosphere

       (Chapter 19)
                    The Biosphere
• Human populations have important impacts on ecosystems, both
  locally and globally.

• An ecosystem refers to the collection of biotic and abiotic components
  and processes that comprise, and govern the behavior of some defined
  subset of the biosphere. Elements of an ecosystem may include flora,
  fauna, lower life forms, water and soil.

• Introduction of new elements, whether abiotic or biotic, into an
  ecosystem tend to have a disruptive effect. In some cases, this can
  lead to ecological collapse or "trophic cascading" and the death of
  many species belonging to the ecosystem in question.
                 The Biosphere
• The biosphere is the outermost part of the planet's shell —
  including air, land, surface rocks and water — within which
  life occurs, and which biotic processes in turn alter or
  transform.

• The atmosphere supports all its ecosystems as most forms of
  life require oxygen.

• Atmosphere maintains Earths surface temp.
   – Cooler if we had a much denser atmosphere
   – Much warmer that no atmosphere at all.
      The Biosphere
            VENUS         EARTH       MARS

 SURFACE
           100,000 mb     1,000 mb    6 mb
PRESSURE
                        COMPOSITION
     CO2     >98%          0.03%       96%
      N2      1%            78%       2.5%
      Ar      1%            1%        1.5%
      O2     0.0%           21%       2.5%
     H2O     0.0%          0.1%       0-0.1%
      How the atmosphere formed
• The variations in concentration from the Earth to Mars and Venus
  result from the different processes that influenced the development of
  each atmosphere.

• While Venus is too warm and Mars is too cold for liquid water the
  Earth is at just such a distance from the Sun that water was able to
  form in all three phases, gaseous, liquid and solid.

• Through condensation the water vapor in our atmosphere was
  removed over time to form the oceans. Additionally, because carbon
  dioxide is slightly soluble in water it too was removed slowly from the
  atmosphere leaving the relatively scarce but unreactive nitrogen to
  build up to the 78% is holds today.
   How the atmosphere formed

• The Primitive Earth.
  – Theorized early primitive atmosphere consisted mostly
    of:
     • water vapor, nitrogen, and carbon dioxide, with small
       amounts of hydrogen and carbon monoxide.
     • Little, if any, free oxygen
• At first the earth was very hot
     • Water existed as a gas
   How the atmosphere formed
                      Figure 19.1 (1)
It is thought that the original
atmosphere was mostly H2.

Most Carbon was combined with
Hydrogen into Methane (CH3).

Most Nitrogen was combined with
Hydrogen into Ammonia (NH4).

Most Oxygen was combined with
Hydrogen to form water vapor.
   How the atmosphere formed
                    Figure 19.1 (2)
A heterotroph is an organism
that requires organic substrates
to get its carbon for growth and
development.

These simple bacteria gave off
CO2.
        So atmospheric CO2
levels increased.
   How the atmosphere formed
                    Figure 19.1 (3)
With the development of
photosynthetic organisms, the
CO2 was used to make sugars
with the by product of oxygen!

Over billions of years the O2
level increased as CO2 was
being used.

But wait!
       Where did the organic
material come from?
   How the atmosphere formed
                         Figure 19.2
Stanly Miller’s Experiment -1952.

Amino acids, simple sugars, and
most of the building blocks for
DNA and RNA were produced.

An energy source is required for
the formation of these molecules.

These expts, repeated thousands
of times have produced so many
biologically important products
that the conclusion is not in doubt
       All molecules important to life
where made in the primitive atmosphere
   Structure of the atmosphere
• In large measure, the atmosphere
  has evolved in response to and
  controlled by life processes.

• It continues to change as a
  consequence of human
  activities.


• Controls the climate and
  ultimately determines the quality
  of life on Earth
   Structure of the atmosphere
• The ground heats up due to the
  absorption of visible light from the
  Sun.

• The warm ground, in turn, heats the
  atmosphere via the processes of
  conduction, convection (turbulence)
  and infrared radiation


• The reason for the strange-
  looking temperature profile?
         Regions of high temperature are
   heated by different portions of the
   solar radiative output.
  Structure of the atmosphere
• The Troposphere –
   – where all weather takes place; it is the
     region of rising and falling packets of
     air.
   – The air pressure at the top of the
     troposphere is only 10% of that at sea
     level (0.1 atmospheres)


• The Stratosphere –
   – The thin ozone layer in the upper
     stratosphere has a high concentration
     of ozone, a particularly reactive form
     of oxygen.
   – This layer is primarily responsible for
     absorbing the ultraviolet radiation from
     the Sun.
  Structure of the atmosphere
• The Mesophere & Thermosphere–
   – Many atoms are ionized (have gained or
     lost electrons so they have a net
     electrical charge).

   – The Thermosphere is very thin, but it is
     where aurora take place
   – Is responsible for absorbing the most
     energetic photons from the Sun,
   – Reflecting radio waves, thereby making
     long-distance radio communication
     possible

   – Thermosphere is heated by the
     absorption of extreme ultraviolet (EUV)
     light
                   The Biosphere
• The atmosphere sustains life
  and is sustained by life.

• The Gaia hypothesis
   – The entire planet is a living
     breathing organism and will
     protect itself – homeostasis
     of the whole planet!!!
• The biosphere works in
  “cycles”
• Nitrogen
• Carbon
• Water
                 The Biosphere
• Water cycle
• The resulting water vapor
  mixes with the atmosphere

• At high altitudes where the
  air is cold enough it
  condenses to form rain and
  snow

• Falls back to Earth.
                The Biosphere
• Water cycle
• Water evaporates from
  bodies of fresh water and
  the oceans

• Much water is lost from the
  leaves of plants via
  transpiration.

• Also from respiration of
  almost all living species
So, what’S up with the bioSphere?
• POLLUTION!!!!!!!!!!!!!!!

• This is any substance that is present in the wrong
  quantities or concentration, in the wrong place, at
  the wrong time.

• Toxic dumps and oil spills are the main two forms
  of pollutants that damage the biosphere.
                          Acid Rain
                          Figure 19.6
• Occurs when sulphur dioxide and
nitrogen oxides are emitted into the
atmosphere, undergo chemical
transformations and are absorbed by
water droplets in clouds.

• The droplets then fall to earth as
rain, snow, mist, dry dust, hail, or
sleet.

• This can increase the acidity of the
soil, and affect the chemical balance
of lakes and streams
                         Acid Rain
• Wet deposition
• Occurs when any form of precipitation
  (rain, snow, etc) removes acids from
  the atmosphere and delivers it to the
  Earth's surface.

• This can result from the deposition of
  acids produced in the raindrops or by
  the precipitation removing the acids
  either in clouds or below clouds.

• Wet removal of both gases and aerosol
  are both of importance for wet
  deposition.
                        Acid Rain
• Dry deposition
• Acid deposition also occurs via dry
  deposition in the absence of
  precipitation.

• This can be responsible for as much as
  20 to 60% of total acid deposition.

• This occurs when particles and gases
  stick to the ground, plants or other
  surfaces
                        Acid Rain
• Dry deposition
• Acid deposition also occurs via dry
  deposition in the absence of
  precipitation.

• This can be responsible for as much as
  20 to 60% of total acid deposition.

• This occurs when particles and gases
  stick to the ground, plants or other
  surfaces
   Surface Waters and Aquatic Animals
• Both the lower pH and higher
  aluminium concentrations in
  surface water that occur as a
  result of acid rain can cause
  damage to fish and other aquatic
  animals.

• At pHs lower than 5 most fish
  eggs will not hatch and lower
  pHs can kill adult fish.
   – As lakes become more acidic
     biodiversity is reduced.

• Acid rain has eliminated insect
  life and some fish species,        Not all fish, shellfish, or the insects that they eat
  including the brook trout in       can tolerate the same amount of acid; for
  some Appalachian streams and       example, frogs can tolerate water that is more
  creeks.                            acidic (i.e., has a lower pH) than trout.
Surface Waters and Aquatic
         Animals
               Ozone depletion
                  Figure 19.8
•Used to describe two distinct but
related observations:
•A slow, steady decline of about 3
percent per decade in the total
amount of ozone in Earth's
stratosphere during the past twenty
years

•A much larger, but seasonal,
decrease in stratospheric ozone over
Earth's polar regions during the
same period. The latter phenomenon
is commonly referred to as the
ozone hole.
               Ozone depletion
                  Figure 19.8
•Ozone (O3) is a triatomic molecule,
consisting of three oxygen atoms.

•The highest levels of ozone in the
atmosphere are in the stratosphere, in a
region also known as the ozone layer
between about 10 km and 50 km above
the surface.

•Here it filters out the shorter
wavelengths (less than 320 nm) of
ultraviolet light (270 to 400 nm) from
the Sun that would be harmful to most
forms of life in large doses.
               Ozone depletion
                  Figure 19.8
•These same wavelengths are also
responsible for the production of
vitamin D, which is essential for human
health.

• Since 1955, the ozone levels have
steady declined each year.

•Main reason for this depletion:
   •Chlorofluorocarbons (CFCs)
   •Used as nontoxic refrigerants
   •Expellant in aerosols

•In 1987, 43 nations met to cut back on
the use of these compounds.
                  Ozone depletion
                     Figure 19.8
•Effects on Humans:
          UVB (the higher energy UV radiation
absorbed by ozone) is generally accepted to be a
contributory factor to skin cancer.
          In addition, increased surface UV
leads to increased tropospheric ozone, which is
a health risk to humans.

Effects on Crops:
          An increase of UV radiation would
also affect crop. A number of economically
important species of plants, such as rice, depend
on cyanobacteria residing on their roots for the
retention of nitrogen. Cyanobacteria are very
sensitive to UV light and they would be affected
by its increase.
               Global Warming
        CO2 andFigure 19.9
•The greenhouse effect:
   • The process in which the absorption
     of infrared radiation by an atmosphere
     warms a planet.
     •Without these greenhouse gases, the
     Earth's surface would be up to 30° C
     cooler.

•CO2 is used in photosynthesis to
make carbohydrates.
          CO2 levels rise at night and fall during
the day naturally.
          Due to the photosynthetic activity of
     plants


•CO2 is released during respiration
or when organic compounds are
burned.
            Global Warming
     CO2 andFigure 19.9
•An increase of CO2 decreases the
amount of heat which can escape
through the atmosphere.

•Thus the temperature of the Earth
increases.

•This has many effects.
   •Warmer Ocean layers.
   •Atmospheric shifts.
   •Warmer surface temperatures
       •2005 was hottest year on
       record.
             Global Warming
      CO2 andFigure 19.9
•First detected in 1896

•Causes droughts in semi-arid
grassland areas.

•Increase in number and severity of
forest fires.

•Partial melting of the polar ice caps.

•Will lead to increase in sea level.

•Pathogens that exist in warm
climates will become more
widespread.
             Global Warming
      CO2 andFigure 19.9
•As climates shift, many existing
species of plants and animals will
become extinct.
   •Biodiversity would suffer a decline of
   uncertain scope.

•Following the start of the industrial
revolution CO2 content has increased
25%.

•Global temperatures and CO2 levels
rise and fall together
                  Bioremediation
• Some types of pollution can be reduced, and habitats restored, with
  the help of living organisms.

• Use microorganisms, fungi, green plants or their enzymes to return the
  environment altered by contaminants to its original condition.

• may be employed to attack specific soil contaminants, such as
  degradation of chlorinated hydrocarbons by bacteria.

• An example of a more general approach is the cleanup of oil spills by
  the addition of nitrate and/or sulfate fertilizers to facilitate the
  decomposition of crude oil by indigenous or exogenous bacteria..
                Bioremediation
• Remember the Chernobyl
  Nuclear Disaster?

• Use of genetic engineering to create
  organisms specifically designed for
  bioremediation has great potential.


• The bacterium Deinococcus
  radiodurans (the most radioresistant
  organism known) has been modified
  to consume and digest toluene and
  ionic mercury from highly radioactive
  nuclear waste.
                    Bioremediation
• Septic tanks and leach beds
  removes waste from water and buts
  the water back into the ground.

• Larger scale sewage systems are
  actually very complex ecosystems
   – Have wastewater lagoons
   – Water sits here for 30 days
• Algae grow in the lagoon,
  photosynthesize and give off O2.

• Allows aerobic bacteria to grow
  and digest organic matter and kill
  fecal bacteria.
                        Summary
• Photosynthesis, and the production of O2, used to balance
  out the release of CO2 from respiration.

• However, with the destruction of over half the worlds
  Rainforests, CO2 levels are much higher
   – Also due to the growth of industry and modern transport systems


• The Earth is our mother. What befalls the Earth befalls
  all the children of the Earth…………Mankind did not
  weave the web of life, we are merely a strand in it.
  Whatever we do to the web, we do to ourselves.
 The end!
Any Questions?

								
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