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Environmental Systems CHAPTER 2
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Page 1: CHAPTER 2missclarkswebsite.weebly.com/uploads/5/0/3/8/5038779/ppt_chapte… · CHAPTER 2 . A Lake of Salt Water, Dust Storms and Endangered Species • Mono Lake ... Half-life- the

Environmental Systems

CHAPTER 2

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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

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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

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Fisheries of North Atlantic • Example of a

interconnecting systems

• Operate at multiple space and time scales

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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!!**

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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.

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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

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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

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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

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Chemical bonds • Covalent bonds- elements that form compounds by sharing

electrons.

• Ie. Methane and water

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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)

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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

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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

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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?

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Properties of water Top: water at 0 degrees C – molecules further apart

Bottom: water at 4 degrees C

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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

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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?

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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

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Even though forest appears to be disappearing, matter is conserved in form of water vapor, carbon dioxide and solid particles

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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

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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)

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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

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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

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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

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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.

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First Law of Thermodynamics • Energy is neither created or destroyed.

• Will just change forms • You can’t get something from nothing.

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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

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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.

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Second Law of Thermodynamics Calculating Energy Efficiency • Multiple all the individual efficiencies:

Electricity Generation (from coal to your house) – an inefficient process

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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.

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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

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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.

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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!

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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

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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.

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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

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Check out the Working Toward Sustainability: Managing Environmental Systems in the Florida Everglades


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