Environmental Systems
CHAPTER 2
A Lake of Salt Water, Dust Storms and Endangered Species • Mono Lake – CA
• Terminal lake – water flows into it, no flow out • High mineral/salt concentrations = no fish can survive
• Only 2 animal species: Mono brine shrimp and Mono Lake alkali fly (larvae stage only)
• 1913 – LA wants to redirect water from feeder streams of Mono Lake and nearby Owens Lake • Owens Lake redirected 1st via aqueduct – effects?
• 1941 –Mono Lake aqueducts begin diverting water • 1982 – depth of Mono Lake decreased by ½; increased salinity
levels • 1994 –LA agreed to reduce amount of water it was diverting to
help refill lake to 2/3 of historical depth • How?
• 2009 – almost at goal and ecosystem slowly recovering
Earth is a single interconnected system • Largest system that environmental science considers – Earth
• Many important current environmental issues exist at global scale
• Can look at many smaller systems though within a larger system
• Next slide
• Important to always define the given system
Fisheries of North Atlantic • Example of a
interconnecting systems
• Operate at multiple space and time scales
All environmental systems consist of matter • Matter- anything that occupies space and has mass.
• Mass- a measure of the amount of matter an object contains.
• Weight- the force that results from the action of gravity on mass.
**Mass and Weight are different!!**
Atoms and Molecules • Atom- the smallest particle that can contain the chemical properties
of an element.
• Made of protons, neutrons and electrons
• Element- a substance composed of atoms that cannot be broken down into smaller, simpler components.
• Can be solid, liquid or gas.
• Periodic Table- lists all the elements currently known.
• Molecules- particles containing more than one atom.
• Compounds- molecules that contain more than one element.
Atoms and Molecules • Atomic Number- the number of protons in the nucleus of a
particular element.
• Unique for each element
• Mass Number- the total number of protons and neutrons in an element.
• Protons and neutrons only
• Isotopes- atoms of the same element that have different numbers of neutrons, and therefore different atomic masses.
• Mass number takes into account the various isotopes that exist in nature
Radioactivity • Unstable isotopes are radioactive
• Radioactive decay- the spontaneous release of material from the nucleus of an unstable isotope. • Changes the radioactive element into a different element.
• i.e. Uranium-235 decays to form Thorium-231.
• Uranium is called the parent and thorium the daughter.
• May release lots of energy/heat
Radioactivity Half-life- the time it takes for one-half of the original radioactive
parent atoms to decay. • Some elements that undergo radioactive decay emit harmful radiation. • Can determine the length of time that a radioactive element may be
dangerous.
• Application – carbon dating
Chemical bonds • Covalent bonds- elements that form compounds by sharing
electrons.
• Ie. Methane and water
Chemical bonds Ionic bonds- elements that form
compounds by transferring electrons from one element to another. • One atom becomes electron deficient
(positively charged) and one atom becomes electron rich (negatively charged)
• Oppositely charged ions attracted
• Weaker than covalent bonding • Compounds can readily dissolve
(separate in water)
Chemical bonds • Hydrogen bonds- a weak
chemical bond that forms when hydrogen atoms that are covalently bonded to one atom are attracted to another atom on another molecule. • Water is known as a polar molecule,
one side is more positive and the other side is more negative.
• Other example: H-bonds between the nitrogenous bases in DNA
Properties of water • Surface tension- the result from the cohesion of water molecules
at the surface of a body of water.
• Cohesion – ability of water molecules to stick together
• Capillary action- when adhesion of water molecules to a surface is stronger than cohesion between the molecules.
• Adhesion – ability of water molecules to stick to other substances
Properties of water • Boiling and freezing- at Earth’s surface:
• Boils (l g) at 100 degrees C
• Freezes (l s) at 0 degrees C
• High heat capacity
• Water helps to regulate climates near large lakes/oceans
• Density of water is greatest at 4 degrees C
• Water as a solvent- many substances dissolve well in water because their polar molecules bond easily with other polar molecules.
• Why is this bad?
Properties of water Top: water at 0 degrees C – molecules further apart
Bottom: water at 4 degrees C
Acids, bases, and pH • Acid- a substance that contributes hydrogen ions to a solution.
• We’ll talk about nitric acid and sulfuric acids – acid rain
• Base- a substance that contributes hydroxide ions to a solution.
• Examples: sodium hydroxide and calcium hydroxide – neutralize acidic emissions from power plants
Acids, bases, and pH • pH- a way to indicate the strength of
acids and bases. • The pH scales ranges from 0 - 14.
• pH value of 7 is neutral • pH above 7 is basic • pH below 7 is acidic
• Scales is logarithmic • Water in Earth’s atmosphere – pH ~5.65
• Due to?
Chemical reactions and the conservation of matter • Chemical reaction- occurs when atoms separate from the molecules
they are a part of or recombine with other molecules.
• Law of conservation of matter- matter cannot be created or destroyed; it can only change form.
• Must have the same number and type of atom at end as what you started with
• Shows we cannot easily dispose of hazardous materials
Even though forest appears to be disappearing, matter is conserved in form of water vapor, carbon dioxide and solid particles
Biological molecules and cells • Inorganic compounds- compounds that do not contain carbon or do
contain carbon, but only carbon bound to elements other than hydrogen. • ex. NH3, NaCl, H2O, and CO2
• Organic compounds- compounds that have carbon-carbon and carbon-hydrogen bonds.
• ex. Glucose (C6H12O6) and methane (CH4)
• Are the basis of important biological macromolecules: carbohydrates, proteins, nucleic acids, lipids
Biological molecules and cells • Carbohydrates- compounds composed of carbon, hydrogen, and
oxygen atoms. • Used by plants and animals for quick energy
• Proteins- made up of long chains of nitrogen-containing organic molecules called amino acids. • Provides structural support, energy storage, internal transport, defense
against foreign substances • Nucleic Acids- organic compounds found in all living cells.
• DNA • RNA
• Lipids- smaller biological molecules that do not mix with water. • Ex. fats, waxes and steroids. • Major part of cell membrane (phospholipid bilayer)
Biological molecules and cells • Cells- the smallest structural and functional component of
organisms. • Single cell organisms - bacteria and some algae
• Multicellular organisms - bring shrimp and humans
Energy is a fundamental component of environmental systems • Energy- the ability to do work or transfer heat
• All living systems absorb energy from surrounds – use it to organize and reorganize molecules within their cells and to power movement
• Autotrophs
• Heterotrophs
• Sun’s energy – electromagnetic radiation
Forms of Energy • Basic unit of energy is joule (J) see conversions for others
• Joule – amount of energy used when a 1-watt light bulb is turned on for 1 second
• Power- the rate at which work is done. • energy = power x time
Forms of Energy • Potential energy – energy that is
stored. • Ie water behind a dam
• Kinetic energy – energy of motion. • Ie water released from dam
• Chemical energy – potential stored in chemical bonds. • Ie energy in food
• Temperature – the measure of the average kinetic energy of a substance.
First Law of Thermodynamics • Energy is neither created or destroyed.
• Will just change forms • You can’t get something from nothing.
Second Law of Thermodynamics • When energy is transformed, the quantity of energy remains the
same, but its ability to do work diminishes. • Some energy is lost as heat
Second Law of Thermodynamics • Energy Efficiency- the ratio of the amount of work that is done to
the total amount of energy that is introduced into the system.
Traditional fireplace has a low energy efficiency since so much heat can escape through chimney; Modern woodstove (uses less wood) is more
energy efficient.
Second Law of Thermodynamics Calculating Energy Efficiency • Multiple all the individual efficiencies:
Electricity Generation (from coal to your house) – an inefficient process
Second Law of Thermodynamics • Energy quality- the ease with which an energy source can be used
for work. • Includes obtaining and then conversion process • High energy quality ex: gasoline • Low energy quality ex: wood
• Entropy- all systems move toward randomness rather than toward order.
• This randomness is always increasing in a system, unless new energy from the outside of the system is added to create order.
Energy conversions underlie all ecological processes • Life requires order • This requires continuous energy input
(survival, growth, reproduction) • Form and amount of energy available
determines types of organisms can live in an environment
System analysis shows how matter and energy flow in the environment • Important to study systems to look at how matter and energy flow
in the environment • Open system- exchanges of matter or energy occur across system
boundaries. • Closed system- matter and energy exchanges across system
boundaries do not occur.
Inputs and Outputs • Inputs – additions to a given system • Outputs – losses from system • Systems analysis – process by which you determine the inputs,
outputs and changes in the system under various conditions • Check out the “Do the Math” section on page 44 of your textbook!
Steady states • Steady state- in a system, when input
equals output it is said to be in a steady state. • System not changing over time
• Most systems are in steady state • A natural system can respond to
changes in its inputs and outputs
Steady states • Feedback: adjustments to input/output rates cased by changes to a
system • Negative feedback loops- when a system responds to change by returning
to its original state, or at least by decreasing the rate at which the change is occurring.
• Positive feedback loops- when a system responds to change by increasing the rate at which the change is occurring.
Natural systems change across space and over time • What affects natural systems and what can grow/live there:
• Differences in environmental conditions (ie. temperature, soil composition, etc.) • Results in geographic variation among systems
• Passage of time • HUMANS!
• Response to changing conditions: migrations, extinctions, evolution of new species
Check out the Working Toward Sustainability: Managing Environmental Systems in the Florida Everglades