CORE CASE STUDY: a Lake of Salt Water, Dust Storms, and Endangered Species

Chapter 2-Environmental Systems

CORE CASE STUDY: A Lake of Salt Water, Dust Storms, and Endangered Species

·  Mono Lake in California is a terminal lake, meaning the water that flows in does not flow back out.

·  The water that flows in is mineral rich, which become deposits as the water evaporates. The lake is actually saltier than the ocean.

·  The lake is home to unique species and is an important feeding ground for many species of migrating birds.

·  Los Angeles started diverting water from the lake in 1941 and almost destroyed the ecosystem. In 1994, conservation groups got more water going back into the lake and the ecosystem was almost completely restored by 2009.

I.  Earth is a Single Interconnected System

·  A change in any one factor can have other, often unexpected, consequences on the system.

II.  All Environmental Systems Consist of Matter

·  Matter is anything that has mass and takes up space, living or not. It comes in chemical forms, as an element or a compound.

·  The mass of an object is the measure of the amount of matter it contains.

A. Atoms and Molecules

·  An atom is the smallest unit of matter that exhibits the characteristics of an element.

·  An element is the distinctive building block that makes up every substance.

·  Chemists classify elements by their chemical behavior by arranging them in a periodic table of elements

·  An ion is an electrically charged atom or combinations of atoms.

·  A molecule is a combination of two or more atoms/ions of elements held together by chemical bonds.

·  Molecules that contain more than one element are called compounds.

·  Each atom has a nucleus containing protons and neutrons. Electron(s) orbit the nucleus of an atom.

·  A proton (p) is positively charged, a neutron (n) is uncharged, and the electron (e) is negatively charged.

·  Each atom has an equal number of positively charged protons in the nucleus and negatively charged electrons outside the nucleus, so the atom has no net electrical charge.

·  Each element has a specific atomic number that is equal to the number of protons in the nucleus. This is called the atomic number.

·  The mass number of an atom equals the total number of neutrons and protons in its nucleus.

·  Isotopes are various forms of an element that have the same atomic number, but different mass number.

B. Radioactivy

·  Radioactive decay is the spontaneous release of material from the nucleus.

·  Radioactive decay changes the radioactive element into a different element.

·  We measure radioactive decay by recording the average rate of decay of a quantity of a radioactive element.

·  Half-life is the time it takes for one-half of the original radioactive parent atoms to decay.

·  Measurement of radioactive decay can tell us how long a radioactive sample may be

dangerous. It can also be used to determine how old an object is through radioactive dating.

C. Chemical bonds

i. Covalent Bonds

·  Covalent bonds are formed by elements that share electrons.

·  Compounds made of uncharged atoms are called covalent compounds (CH4).

ii. Ionic Bonds

·  Ionic compounds are made up of oppositely charged ions, (Na+ and Cl-).

·  Ions are created through the transfer of electrons.

·  The attraction between two oppositely charged ions is called an ionic bond.

iii. Hydrogen Bonds

·  A hydrogen bond is a weak bond that forms when hydrogen atoms that are covalently bonded to one atom are attracted to another atom on another molecule.

·  In some cases, the strong attraction of the hydrogen electron to other atoms creates a charge imbalance within the covalently bonded molecule.

·  A polar molecule is a covalently bonded molecule in which one side is more positive and the other side is more negative, due to the unequal sharing of bonding electrons.

D. Properties of Water

·  Hydrogen bonding makes water molecules stick strongly to one another and other substances.

·  Surface tension results from the cohesion of water molecules at the surface of a body of water, creating a “skin” on the water’s surface.

·  Capillary action happens when adhesion of water molecules to a surface is stronger than cohesion between the molecules.

·  The hydrogen bonding between water molecules means it takes a great deal of energy to change the temperature.

·  Ice is less dense than water because its molecules realign into a crystal lattice structure, trapping air as its volume expands.

·  Due to being a polar molecule, water will dissolve many substances.

E. Acids, Bases, and pH

·  Elements known as metals tend to lose one or more electrons to become positively charged cations.

·  Elements known as nonmetals tend to gain more electrons to become negatively charged anions.

·  An acid is a substance that contributes hydrogen ions to a solution.

·  Hydrogen ions (H+) in a solution are a measure of how acidic a solution is.

·  A base is a substance that contributes hydroxide ions to a solution.

·  Hydroxide ions (OH-) in a solution are a measure of how basic a solution is.

·  The pH scale is a way to indicate the strength of acids and bases.

·  Neutral pH is 7, acid solutions are below 7, and basic solutions are above 7.

F. Chemical Reactions and the Conservation of Matter

·  A chemical reaction occurs when atoms separate from the molecules they are a part of or recombine with other molecules.

·  The Law of Conservation of Matter states that no atoms are created/destroyed during a physical or chemical change.

G. Biological Molecules and Cells

·  Inorganic compounds are compounds that either 1do not contain the element carbon or 2do contain carbon, but only carbon bound to elements other than hydrogen.

·  Ex. NH3, NaCl, H2O, CO2

·  Organic compounds are compounds that have carbon-carbon and carbon-hydrogen bonds.

·  Ex. C6H12O6, CH4

·  Carbohydrates are compounds composed of carbon, hydrogen, and oxygen.

·  Glucose is a simple sugar called a monosaccharide. Used for energy by plants and animals.

·  Complex carbohydrates contain two or more monomers of simple sugars linked together and are called polysaccharides. Used for storage (starch, glycogen) or to make structures such as cellulose.

·  Proteins are made up of long chains of nitrogen-containing organic molecules called amino acids.

·  Proteins are used for structural support, energy storage, internal transport, and immune defense and response.

·  Enzymes are proteins that help control the rates of chemical reactions.

·  Nucleic acids are long chains of nucleic acids that form DNA and RNA.

·  DNA (deoxyribosenucleic acid) is the genetic material organisms pass on to their offspring that contains the code for reproducing the components of the next generation.

·  RNA (ribonucleic acid) translates the code stored in the DNA and allows for the synthesis of proteins.

·  Genes are specific sequences of nucleotides in a DNA molecule.

·  Chromosomes are combinations of genes that make a single DNA molecule, plus some proteins.

·  Lipids are smaller biological molecules that do not mix with water.

·  Form a major part of the membranes that surround cells. Include fats, oils, waxes, and steroids.

H. Cells

·  A cell is a highly organized living entity that consists of the four types of macromolecules and other substances in a watery solution, surrounded by a membrane.

·  Unicellular organisms (bacteria, protists) contain all of the functional structures, called organelles, needed to keep the cell alive and allow it to reproduce.

III.  Energy is a Component of Environmental Systems

·  Energy is the capacity to do work and transfer heat; it moves matter.

·  Electromagnetic radiation is energy that travels as a wave, a result of changing electric and magnetic fields.

·  Emitted by the sun

·  Includes visible light, ultraviolet light, and infrared energy

·  Carried by photons, massless packets of energy that travel at the speed of light and can move even through the vacuum of space.

·  The amount of energy contained in a photon depends on its wavelength—the distance between two identical points on the wave.

A. Forms of Energy

·  The basic unit of energy in the metric system is the joule (J).

·  A joule is the amount of energy used when a 1-watt light bulb is turned on for 1 second.

i. Energy and Power

·  Power is the rate at which work is done.

o  Energy = power x time

o  Power = energy / time

·  The kilowatt (kW) is a unit of power.

·  The kilowatt-hour (kWh) is a unit of energy.

ii. Kinetic and Potential Energy

iii. Temperature

·  Potential energy is stored energy.

·  Potential energy can be changed into kinetic energy.

·  Kinetic energy is the energy of motion; it has mass and speed.

·  Wind, electricity, and heat are examples.

B. The First Law of Thermodynamics

·  Just as matter can neither be created nor destroyed, energy is neither created not destroyed.

·  You can’t get something from nothing; energy is converted from one form to another form.

·  Some energy stays within a system and some leaves the system.

C. The Second Law of Thermodynamics

·  When energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes.

·  In changing forms of energy, there is a loss in energy quality; heat is often produced and lost.

i. Energy Efficiency

·  Energy efficiency is the ratio of the amount of work that is done to the total amount of energy that is introduced into the system in the first place.

·  Changing forms of energy produces a small percentage of useful energy; much is lost in the process.

ii. Energy Quality

·  Energy quality is the ease with which an energy source can be used for work.

·  A high-quality energy source has a convenient, concentrated form so that it does not take too much energy to move it from one place to another.

·  Ex. Gasoline is a high-quality energy source, wood is a low-quality energy source

iii. Entropy

·  The second law of thermodynamics tells us that all systems more toward randomness rather than order.

·  Entropy is the name for this randomness, which is always increasing in a system, unless new energy from outside is added to create order.

·  Food is a high-quality, low-entropy energy source because it is easily converted to usable energy and ordered.

·  The waste heat your body produces has a high degree of entropy, because heat is the random movement of molecules that it imparts to the universe.

IV.  Energy Conversions Underlie All Ecological Processes

·  The amount of available energy determines which organisms can live in a natural system.

V.  Systems Analysis Shows How Matter and Energy Flow in the Environment

·  In an open system, exchanges of matter or energy occur across system boundaries.

·  In a closed system, matter and energy exchanges across system boundaries do not occur.

·  Earth is an open system with respect to energy but a closed system in regards to matter.

A.  Inputs and Outputs

·  Inputs are additions to a given system

·  Outputs are losses from the system

·  People who study systems often conduct a systems analysis, in which they determine inputs, outputs, and changes in the system under various conditions.

B.  Steady States

·  A system is in a steady state when inputs equal outputs, so the system is not changing over time.

C.  Feedbacks

·  Adjustments in input or output rates caused by changes to a system are called feedbacks.

·  The term feedback means the results of a process feed back into the system to change the rate of a process.

·  Negative feedback loops occur when a system responds to change by returning to its original state, or by decreasing the rate at which change is occurring.

·  Positive feedback loops amplifies change by increasing the rate at which change is occurring.

·  Systems often show time delays between input and response.

·  Problems can build slowly in systems until reaching a tipping point.

·  Synergy is when processes interact such that the combined effect is greater than the individual effects.

VI.  Natural Systems Change Across Space and Over Time

·  Small natural changes have had large effects on complex systems, but human activities have increased both the pace and intensity of these natural environmental changes.

WORKING TOWARD SUSTAINABILITY: Managing Environmental Systems in the Florida Everglades

·  Comprehensive Everglades Restoration Plan

o  Increase water flow to the Everglades to support aquatic and marsh organisms by restoring natural water flow and hydroperiods and through water conservation

o  Reduce pollutants coming in by improving waste treatment facilities, restricting use of agricultural chemicals, and building artificial marshes

o  Develop strategies for dealing with future problems through an adaptive management plan

5 / Chapter 2