Talk Eight:The Biosphere

Chapter 16

Biology Today (BIOL 109)

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 19.2Stanly 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

Origin of Life

• Small Organic Molecules.– Primitive gases may have reacted with

one another and produced small organic compounds such as nucleotides and amino acids.

• Macromolecules.– RNA-first hypothesis.– Protein-first hypothesis.

RNA-first Hypothesis

• Only RNA is needed to progress towards the first cells

• RNA is both a substrate and an enzyme (ribozymes)– First cell had RNA genes (mRNA) – make proteins

• Some of these newly formed proteins were enzymes•Reverse transcriptase (found in retrovirus)

• Can make DNA from RNA• DNA self replication can then occur

Protein-first hypothesis• Amino acids join together under dry heat

– Such as along shallow puddles on a rocky shore.

– Heat from sun formed proteinoids (enzymes)

• These then could form DNA from nucleotides present in the ocean.

• This DNA can code for specific protein synthesis– Thus the cell could acquire of its enzymes,

even the ones which replicates DNA

Origin of Life

• Protocell.– A protocell, which could carry on

metabolism but not reproduce, may have formed when lipids and microspheres formed a lipid-protein membrane.

• A True Cell.– A true cell can reproduce.

• Modern cells replicate before cell division occurs.

Figure 6.2Biological Evolution• First true cells were

prokaryotic.– Eukaryotic cells evolved

later, followed by the other kingdoms.

Biological evolution is a change in life forms that has taken place in the past and will take place in the future.

Adaptation is a characteristic that makes an organism able to survive and reproduce in an environment.

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?

Think of the time line!

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

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

•When ultraviolet light waves (UV) strike CFC (CFCl3) molecules in the upper atmosphere, a carbon-chlorine bond breaks, producing a chlorine (Cl) atom.

•The chlorine atom then reacts with an ozone (O3) molecule breaking it apart and so destroying the ozone.

Provided for use by the National Oceanic and Atmospheric Administration (NOAA)

Figure 19.8Ozone depletion

•This forms an ordinary oxygen molecule(O2) and a chlorine monoxide (ClO) molecule. •Then a free oxygen atom breaks up the chlorine monoxide. The chlorine is free to repeat the process of destroying more ozone molecules.

•A single CFC molecule can destroy 100,000 ozone molecules. Provided for use by the National Oceanic

and Atmospheric Administration (NOAA)

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

•2011 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

Fracking• According to the U.S.

Energy Information Administration:– In 2000, the USA had

342,000 natural gas wells.

– By 2010, more than 510,000 were in place — a 49% jump!

• Twenty states have shale gas wells– they tap rock layers that

harbor the gas in shale formations  Taken from USA Today

29th May 2012

Fracking• Drill down to gas layer

– Pump in sand/water/chemicals

• Mixture cracks shale rock and fills in with sand– Allows gas to move

up well hole

• Gas collected.

• Water recover for reuse or sent to treatment plant.

Fracking

Used with permission from Fracfocus.com

• The most commonly used in the USA:-

• Methanol• Cellulose• Boric acid• zirconium, chromium, antim

ony, and titanium salts– The first three are known

carcinogens!

• Blowout – gas can explode out the wellhead, injuring people and spewing pollutants.

• Gas leak – Methane could travel into the water table.

• Air pollution – When methane is released without being burned, it acts as a potent

greenhouse gas, trapping 20 times as much heat as carbon dioxide.

• Wastewater overflow – If stored in open pits that emit noxious fumes and can overflow with rain.

• Other leaks  – spills or illicit dumping.

• Home explosions – If methane does get into the water table — because of cracked cement, local

geology or the effects of old wells — it can build up in homes and lead to explosions.

Potential hazards due to Fracking

Then why Frack in the first place?

• Good• According to the  National

Petroleum Council:– Without it, we would lose

45 percent of domestic natural gas production and 17 percent of our oil production within 5 years

• Development of shale resources supported 600,000 jobs in 2010

• Natural Gas prices will continue to drop

• Bad/Ugly• Ground water

contamination

• CO2 in shale released

• Radioactive isotopes released from shale– Mostly Radium & Radon

gas

• Silicon dioxide released from shale– Natural compound, but

too much – stunted plant growth and lung cancer

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 end!

Any Questions?