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.

 VENUS EARTH MARS

SURFACE PRESSURE

100,000 mb 1,000 mb 6 mb

  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%

 

                      

               

                      

                                        

The Biosphere

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

Figure 19.1 (1)How the atmosphere

formedIt 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 withHydrogen to form water vapor.

Figure 19.1 (2)How the atmosphere

formedA 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.

Figure 19.1 (3)How the atmosphere

formedWith 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?

Figure 19.2Stanly 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

How the atmosphere formed

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 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

The Biosphere

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.

Figure 19.6Acid Rain• 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, including the brook trout in some Appalachian streams and creeks.

Not all fish, shellfish, or the insects that they eat can tolerate the same amount of acid; for example, frogs can tolerate water that is more acidic (i.e., has a lower pH) than trout.

Surface Waters and Aquatic Animals

Figure 19.8Ozone depletion•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.

Figure 19.8Ozone depletion•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.

Figure 19.8Ozone depletion•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.

Figure 19.8Ozone depletion•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.

Figure 19.9CO2 and Global Warming•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.

Figure 19.9CO2 and Global Warming•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.

Figure 19.9CO2 and Global Warming•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.

Figure 19.9CO2 and Global Warming•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?