Water Chemistry and Water Chemistry and Primary ProductivityPrimary Productivity

Mrs. Daniels IB HL/ AP Mrs. Daniels IB HL/ AP BiologyBiology

Revised September 2008Revised September 2008

Atomic StructureAtomic Structure

• Proton (pProton (p++)):: A positively A positively charged particle found in the charged particle found in the central core of an atom (called the central core of an atom (called the nucleus)nucleus)

• Neutron (nNeutron (n00)):: A neutral particle A neutral particle found in the nucleus of an atomfound in the nucleus of an atom

• Electron (eElectron (e--)):: A tiny negatively A tiny negatively charged particle found outside of charged particle found outside of the atomic nucleusthe atomic nucleus

Atomic StructureAtomic Structure

• The mass of a proton and a neutron is The mass of a proton and a neutron is relatively equalrelatively equal

• However, the electron has a mass However, the electron has a mass equal to 1/1840 of a protonequal to 1/1840 of a proton

• Which subatomic particles do you Which subatomic particles do you think take up the most space in the think take up the most space in the atom?atom?

Organization of the AtomOrganization of the Atom

• The protons and neutrons are tightly The protons and neutrons are tightly packed in a central core called the packed in a central core called the nucleusnucleus

• If an atom were the size of a football If an atom were the size of a football stadium, the nucleus would be a stadium, the nucleus would be a tiny marble sitting in the center of ittiny marble sitting in the center of it

• The electrons are found in different The electrons are found in different layers (energy levels) of a “cloud” layers (energy levels) of a “cloud” around the nucleusaround the nucleus

Atomic # & Mass #Atomic # & Mass #

• Elements differ because of the Elements differ because of the number of protons they havenumber of protons they have

• The Atomic NumberThe Atomic Number is the number is the number of protonsof protons

• The number of electrons in an atom The number of electrons in an atom must equal the number of protons in must equal the number of protons in order for the atom to be neutralorder for the atom to be neutral

• The Mass NumberThe Mass Number is the whole is the whole number of protons plus neutrons in number of protons plus neutrons in an atoman atom

Atomic # & Mass #Atomic # & Mass #

O16

8

Mass Number

AtomicNumber

ChemicalSymbol

Mass # vs. Atomic MassMass # vs. Atomic Mass

Ne20.18

10

Atomic mass

AtomicNumber

ChemicalSymbol

IsotopesIsotopes

• Isotopes of an atom occur when the Isotopes of an atom occur when the number of neutrons changesnumber of neutrons changes

• Isotopes have the same chemical Isotopes have the same chemical properties as the original atom because properties as the original atom because the charged particles remain the samethe charged particles remain the same

• Later in the year, we’ll discuss Later in the year, we’ll discuss radioactive isotopes in more depth. radioactive isotopes in more depth. Their role in biology is very significant.Their role in biology is very significant.

Atomic MassAtomic Mass• A weighted average mass of the atoms A weighted average mass of the atoms

in a naturally occurring sample of an in a naturally occurring sample of an element is called the element is called the Atomic MassAtomic Mass

• This number represents the mass as This number represents the mass as well as the relative abundance of each well as the relative abundance of each isotopeisotope

• Since atoms are so small, grams are Since atoms are so small, grams are not typically used as units of massnot typically used as units of mass

• Instead, an Instead, an Atomic Mass UnitAtomic Mass Unit is used is used (mathematically defined as 1/12(mathematically defined as 1/12thth of of the mass of Carbon-12.)the mass of Carbon-12.)

Journal Entry #4 - part bJournal Entry #4 - part b• Calculate this student’s grade if the class Calculate this student’s grade if the class

is weighted as follows:is weighted as follows:

• Tests = 75%Tests = 75% Homework = 5%Homework = 5%

• Lab = 10%Lab = 10% Final exam = 10%Final exam = 10%

Test scores: 89, 84, 72, 90Test scores: 89, 84, 72, 90

Lab :Lab : 99, 100, 98, 99, 94, 97 99, 100, 98, 99, 94, 97

Homework : 92, 93, 96, 98, 105, 94Homework : 92, 93, 96, 98, 105, 94

Final exam : 90Final exam : 90

Journal Entry #4 – part bJournal Entry #4 – part b• Calculate this student’s grade if the class Calculate this student’s grade if the class

is weighted as follows:is weighted as follows:

• Tests = 75%Tests = 75% Homework = 5%Homework = 5%

• Lab = 10%Lab = 10% Final exam = 10%Final exam = 10%Test scores: 89, 84, 72, 90 = 335/4 = 83.75%Test scores: 89, 84, 72, 90 = 335/4 = 83.75%

Lab :Lab : 99, 100, 98, 99, 94, 97 = 587/6= 97.8% 99, 100, 98, 99, 94, 97 = 587/6= 97.8%

Homework : Homework : 92, 93, 96, 98, 105, 94 = 578/6= 92, 93, 96, 98, 105, 94 = 578/6= 96.3%96.3%

Final exam : 90%Final exam : 90%

83.75(.75) + 97.8(.10) + 96.3(.05) + 90(.10) =83.75(.75) + 97.8(.10) + 96.3(.05) + 90(.10) =

86.4% 86.4% BB

• Now if this teacher did NOT weight Now if this teacher did NOT weight grades, what would this student’s grade grades, what would this student’s grade be?be?

Test scores:Test scores: 89, 84, 72, 9089, 84, 72, 90Lab :Lab : 99, 100, 98, 99, 94, 9799, 100, 98, 99, 94, 97Homework :Homework : 92, 93, 96, 98, 105, 9492, 93, 96, 98, 105, 94Final exam :Final exam : 9090

1590/1700 = 93.5% 1590/1700 = 93.5% A… A…very very differentdifferent

Valence ElectronsValence Electrons

• The shell or energy level (n) The shell or energy level (n) containing the outermost electrons for containing the outermost electrons for an element is called the valence shellan element is called the valence shell

• The electrons in that shell are called The electrons in that shell are called valence electronsvalence electrons

• These electrons are the farthest from These electrons are the farthest from the atom’s nucleus and are therefore the atom’s nucleus and are therefore the easiest to removethe easiest to remove

• Because of this, these are the Because of this, these are the electrons involved in bonding.electrons involved in bonding.

BondingBonding• Covalent bond – electrons are “shared”Covalent bond – electrons are “shared”

– Polar – shared unequallyPolar – shared unequally– Non-polar – shared equallyNon-polar – shared equally

• Ionic – transfer of electrons causes change Ionic – transfer of electrons causes change in charge and electrostatic attraction in charge and electrostatic attraction between ionsbetween ions

• Hydrogen – weak attraction between Hydrogen – weak attraction between partially positive and partially negative partially positive and partially negative poles of H and other atoms (N,O, F) polar poles of H and other atoms (N,O, F) polar covalently bonded within different covalently bonded within different moleculesmolecules

Other discussion-worthy Other discussion-worthy topicstopics

• Bonding – we’re going to continue with Bonding – we’re going to continue with bonding when we discuss water in a few bonding when we discuss water in a few minutesminutes

• Intermolecular forces – types and where Intermolecular forces – types and where you would find examples of eachyou would find examples of each

• Reactions – single, double, combustion, Reactions – single, double, combustion, redox, combination (synthesis), and redox, combination (synthesis), and decomposition and where you would find decomposition and where you would find examples of each in biologyexamples of each in biology

Water contributes to the Water contributes to the fitness of the environmentfitness of the environment

• One theory of the origin of life that it evolved One theory of the origin of life that it evolved in waterin water

• Living cells are 70-95% HLiving cells are 70-95% H2200• Water covers about 3/4 of the earth’s surfaceWater covers about 3/4 of the earth’s surface• It exist in three distinct phases in nature: It exist in three distinct phases in nature:

solid, liquid, and gassolid, liquid, and gas• The extraordinary properties of water are The extraordinary properties of water are

emergent properties resulting from water’s emergent properties resulting from water’s structure and molecular interactionsstructure and molecular interactions

The polarity of water molecules results in The polarity of water molecules results in hydrogen bondinghydrogen bonding

• Water is a polar molecule; its polar Water is a polar molecule; its polar bonds and asymmetrical shape bonds and asymmetrical shape give water molecule opposite give water molecule opposite charges on opposite sidescharges on opposite sides

• Each water molecule can form Each water molecule can form hydrogen bonds to a max of four hydrogen bonds to a max of four neighborsneighbors

-+

+

-+

+-

++

- ++

-+ +

Unique Properties of WaterUnique Properties of Water

– The uniqueness of water arises from the The uniqueness of water arises from the emergent properties due to hydrogen emergent properties due to hydrogen bonding that orders the molecule into a bonding that orders the molecule into a higher level of organizationhigher level of organization

– Has cohesive behaviorHas cohesive behavior– Resist change in temperatureResist change in temperature– ~Has a high heat of vaporization and cools ~Has a high heat of vaporization and cools

surface as it evaporatessurface as it evaporates– Expands when it freezesExpands when it freezes– Is a versatile solventIs a versatile solvent– Ice floats (least dense as a solid)Ice floats (least dense as a solid)

Organisms depend upon the cohesion of water Organisms depend upon the cohesion of water moleculesmolecules

– Cohesion: Substance being held together by Cohesion: Substance being held together by H-bondsH-bonds

– Adhesion: water is attracted to and holds Adhesion: water is attracted to and holds onto the walls and overcomes gravity (this onto the walls and overcomes gravity (this is the idea behind capillary action)is the idea behind capillary action)

– Capillary action- movement of water up Capillary action- movement of water up vessels against gravity, (xylem tubes)vessels against gravity, (xylem tubes)

– Surface Tension: measure of how difficult it Surface Tension: measure of how difficult it is to stretch or break the surface of a liquidis to stretch or break the surface of a liquid•hydrogen bonding is 20 X weaker than nonpolar hydrogen bonding is 20 X weaker than nonpolar

covalent bonds - so they form, break, and covalent bonds - so they form, break, and reform constantly and dynamically giving water reform constantly and dynamically giving water more structure than most liquidsmore structure than most liquids

Water contributes to Earth’s habitability by Water contributes to Earth’s habitability by moderating temperaturesmoderating temperatures

– Heat Heat • Kinetic energyKinetic energy• Calorie (cal) 1 cal = 4.184 Joules (J)Calorie (cal) 1 cal = 4.184 Joules (J)• Joule (4.184 J = 1.00 calJoule (4.184 J = 1.00 cal

– TemperatureTemperature• Intensity of heat due to its average kinetic energyIntensity of heat due to its average kinetic energy• Celsius, Fahrenheit, Kelvin Celsius, Fahrenheit, Kelvin • Convert from Convert from 00F to F to 00C by (9/5) C by (9/5) 00C + 32C + 3200

• Convert from Convert from 00C to C to 00F by (5/9)F by (5/9) 0 0F - 32F - 3200

• Convert from 0C and Kelvin by using 273Convert from 0C and Kelvin by using 273

– Water’s high specific heat keeps temperature Water’s high specific heat keeps temperature fluctuations within a range suitable for lifefluctuations within a range suitable for life• Water’s high Specific Heat: 1 cal/g/ Water’s high Specific Heat: 1 cal/g/ oo C C

Evaporative coolingEvaporative cooling• Vaporization (evaporation)- phase change from liquid Vaporization (evaporation)- phase change from liquid

to a gasto a gas• Water has a relatively high heat of vaporization (540 Water has a relatively high heat of vaporization (540

cal/g), which means that it requires a large amount of cal/g), which means that it requires a large amount of energy for the liquid to break the hydrogen bonds and energy for the liquid to break the hydrogen bonds and leave the liquid stateleave the liquid state

• The molecules left behind on the surface thus have a The molecules left behind on the surface thus have a lower kinetic energy and have a lower temperaturelower kinetic energy and have a lower temperature

• Evaporative cooling stabilizes temperatures in aquatic Evaporative cooling stabilizes temperatures in aquatic ecosystem, helps organisms from overheating, and ecosystem, helps organisms from overheating, and helps solar heat by tropical seas dissipate helps solar heat by tropical seas dissipate

Oceans and lakes don’t freeze solid because Oceans and lakes don’t freeze solid because ice floatsice floats

– Water reaches its greatest density at 4 Water reaches its greatest density at 4 degrees Celsiusdegrees Celsius

– Water contracts as it cools to 4Water contracts as it cools to 400C, then as it C, then as it cools from 4cools from 400C to freezing, it expands and C to freezing, it expands and becomes less dense than liquid water…ice becomes less dense than liquid water…ice floats.floats.

– Expansion of water:Expansion of water:• Prevents deep bodies of water from freezing Prevents deep bodies of water from freezing

solid from the bottom upsolid from the bottom up• Ice forms on the top first because it is less Ice forms on the top first because it is less

dense. As water freezes, it releases heat to dense. As water freezes, it releases heat to the water below it and insulates.the water below it and insulates.

Hydrogen bonds create crystalline latticeHydrogen bonds create crystalline lattice

•As water cools, the molecules move slightly As water cools, the molecules move slightly closer to one another - as cooling continues, closer to one another - as cooling continues, the hydrogen bonds are not broken as often the hydrogen bonds are not broken as often as in warmer temps and as water reaches as in warmer temps and as water reaches the freezing point - a crystalline lattice forms the freezing point - a crystalline lattice forms as the molecules “lock” into a hydrogen as the molecules “lock” into a hydrogen bonded position. This bonding event bonded position. This bonding event organizes the molecules apart slightly more organizes the molecules apart slightly more than when they were still in the liquid phase.than when they were still in the liquid phase.

Water is the solvent of lifeWater is the solvent of life

– SolutionSolution- dissolved substances in liquids - dissolved substances in liquids – SoluteSolute- the substance that dissolves- the substance that dissolves– SolventSolvent- liquid capable of dissolving- liquid capable of dissolving– Aqueous solutionAqueous solution

• Molarity- mol/liter of waterMolarity- mol/liter of water– Mole: amu or molecular mass (g) x Avogadro's #Mole: amu or molecular mass (g) x Avogadro's #– Molecular weightMolecular weight

– Hydrophilic- water loving (attraction to HHydrophilic- water loving (attraction to H22O)O)

– Hydrophobic- water hating (repels HHydrophobic- water hating (repels H22O)O)

– Concentration: MolarityConcentration: Molarity

Organisms are sensitive to changes Organisms are sensitive to changes in pHin pH

– Hydrogen ion (H+)Hydrogen ion (H+)– Hydroxide ion (OH-)Hydroxide ion (OH-)– Hydronium ion (HHydronium ion (H33O+) HO+) H++ bonded to H bonded to H2200– Acid (high concentration of HAcid (high concentration of H++) pH < 7) pH < 7– Base (high concentration of OH-) pH > 7 Base (high concentration of OH-) pH > 7 – pH (scale ranging 0 to 14)pH (scale ranging 0 to 14)– pH HpH H++ 0H- = 1.0 x 10 0H- = 1.0 x 10-14-14 M M– pH = -log HpH = -log H++

– Only 1 out of 554,000,000 molecules actually Only 1 out of 554,000,000 molecules actually dissociatedissociate

– Buffers- minimize pH changeBuffers- minimize pH change

BuffersBuffers

• Substances that prevent sudden changes in pHSubstances that prevent sudden changes in pH• Help to minimize wide fluctuations in pH and Help to minimize wide fluctuations in pH and

therefore help organisms maintain the pH of therefore help organisms maintain the pH of body fluids within the narrow range necessary body fluids within the narrow range necessary for lifefor life

• HH22COCO3 3 <---------> HCO<---------> HCO33-- + H + H++

• In the presence of strong acid, it forms the In the presence of strong acid, it forms the conjugate base and weak acidconjugate base and weak acid

• In the presence of a strong base, it forms the In the presence of a strong base, it forms the conjugate acid and a weak baseconjugate acid and a weak base

Acid precipitation threatens the Acid precipitation threatens the fitness of the environmentfitness of the environment

– Acid Precipitation (more acidic than 5.6 pH)Acid Precipitation (more acidic than 5.6 pH)• Sulfur oxides & Nitrogen oxides react with Sulfur oxides & Nitrogen oxides react with

water in the air to form acidswater in the air to form acids• Major source of oxides is combustion of fossil Major source of oxides is combustion of fossil

fuels by industry and carsfuels by industry and cars

– Lowers soil pH which affects mineral Lowers soil pH which affects mineral solubility (throws things out of balance)solubility (throws things out of balance)

– Adverse affects on aquatic systems Adverse affects on aquatic systems because of lower pH of lakes and pondsbecause of lower pH of lakes and ponds

Aquatic OrganismsAquatic Organisms

• We will be discussing several different We will be discussing several different aquatic organisms this yearaquatic organisms this year

• Let’s turn our focus to protistsLet’s turn our focus to protists

• Characteristics:Characteristics:– Single-celled, aquatic, eukaryotic, some are Single-celled, aquatic, eukaryotic, some are

heterotrophic and some are autotrophicheterotrophic and some are autotrophic

• Photoautotrophs vs. chemoautotrophsPhotoautotrophs vs. chemoautotrophs

• Photoautotrophs vs. chemoheterotrophsPhotoautotrophs vs. chemoheterotrophs

• Organisms that produce organic Organisms that produce organic compounds such as glucose, starch, compounds such as glucose, starch, and even polyunsaturated fatty acids and even polyunsaturated fatty acids are called PRODUCERSare called PRODUCERS

• These are the autotrophsThese are the autotrophs

• Ultimately LIGHT is the energy source Ultimately LIGHT is the energy source for most food chainsfor most food chains

• What happens to the producers?What happens to the producers?

• They live, they produce, and they…They live, they produce, and they…

• Either get eaten by consumers or they Either get eaten by consumers or they die and their nutrients are recycled.die and their nutrients are recycled.

Energy flow through ecosystems

Energyfromsun

Firsttrophic level:

producers

Secondtrophic level:

primaryconsumers

Thirdtrophic level:

secondaryconsumers

Fourthtrophic level:

tertiaryconsumers

Decomposers(saprotrophs)

Producer100%

(of harvested energy…not

100% of solar energy hitting the

surface of the producer)

QuaternaryConsumer0.01%

TertiaryConsumer0.1%

SecondaryConsumer~1%

PrimaryConsumer~10%

A food web at the edge of an eastern deciduous forest

-Simple food “chains” are merely part of a more complex food web

-Is each organism only assigned to ONE trophic level?

Why or why not?

Pyramid of energy

Tertiary consumers (21)

Secondary consumers (383)

Primary consumers (3,368)Saprotrophs (5,060)

Producers (20,810)

Notice that there is roughly a 90% reduction in energy with each consecutive trophic level…WHY IS THIS

TRUE?

-not all parts are used as a food source-not everything is digestible

-heat loss-some organisms never have the privilege of being eaten

ProductivityProductivity

• Just like there is a difference between Just like there is a difference between your gross annual salary and your net, your gross annual salary and your net, there is a mandatory deduction that there is a mandatory deduction that must be made to the amount of energy must be made to the amount of energy trapped by producers as organic mattertrapped by producers as organic matter

• Gross production - energy lost during Gross production - energy lost during respiration = NET productivityrespiration = NET productivity

• SAPROTROPH – you’ve seen the word…SAPROTROPH – you’ve seen the word…what does it mean?what does it mean?

• Organisms that live on or in non-living Organisms that live on or in non-living organic matter (decomposers)organic matter (decomposers)

• Organisms that feed on non-living Organisms that feed on non-living organic matter, but don’t necessarily organic matter, but don’t necessarily live on or in it are called DETRITIVORESlive on or in it are called DETRITIVORES

• An organism can be a detritivore An organism can be a detritivore without being a saprotroph, but all without being a saprotroph, but all saprotrophs are detritivores.saprotrophs are detritivores.

Accumulation of BiomassAccumulation of Biomass

• When producers convert light energy When producers convert light energy into chemical energy stored in the into chemical energy stored in the bonds of organic molecules, they bonds of organic molecules, they increase in massincrease in mass

• The mass of all (dried) organic The mass of all (dried) organic matter is referred to as BIOMASSmatter is referred to as BIOMASS

Pyramids of biomass

Tropical forest in Panama

Primary consumers (4)Saprotrophs (10)

Secondary consumers (1)

Producers(40,000)

Traditional pyramids of biomass tend to follow traditional pyramids of energy