1 / 41

Water Chemistry and Primary Productivity

Water Chemistry and Primary Productivity. Mrs. Daniels IB HL/ AP Biology Revised September 2008. Atomic Structure. Proton (p + ) : A positively charged particle found in the central core of an atom (called the nucleus)

marah-madden
Download Presentation

Water Chemistry and Primary Productivity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Water Chemistry and Primary Productivity Mrs. Daniels IB HL/ AP Biology Revised September 2008

  2. Atomic Structure • Proton (p+): A positively charged particle found in the central core of an atom (called the nucleus) • Neutron (n0): A neutral particle found in the nucleus of an atom • Electron (e-): A tiny negatively charged particle found outside of the atomic nucleus

  3. Atomic Structure • The mass of a proton and a neutron is relatively equal • However, the electron has a mass equal to 1/1840 of a proton • Which subatomic particles do you think take up the most space in the atom?

  4. Organization of the Atom • The protons and neutrons are tightly packed in a central core called the nucleus • If an atom were the size of a football stadium, the nucleus would be a tiny marble sitting in the center of it • The electrons are found in different layers (energy levels) of a “cloud” around the nucleus

  5. Atomic # & Mass # • Elements differ because of the number of protons they have • The Atomic Number is the number of protons • The number of electrons in an atom must equal the number of protons in order for the atom to be neutral • The Mass Number is the whole number of protons plus neutrons in an atom

  6. Atomic # & Mass # O 16 Mass Number Chemical Symbol 8 Atomic Number

  7. Mass # vs. Atomic Mass Ne 20.18 Atomic mass Chemical Symbol 10 Atomic Number

  8. Isotopes • Isotopes of an atom occur when the number of neutrons changes • Isotopes have the same chemical properties as the original atom because the charged particles remain the same • Later in the year, we’ll discuss radioactive isotopes in more depth. Their role in biology is very significant.

  9. Atomic Mass • A weighted average mass of the atoms in a naturally occurring sample of an element is called the Atomic Mass • This number represents the mass as well as the relative abundance of each isotope • Since atoms are so small, grams are not typically used as units of mass • Instead, an Atomic Mass Unit is used (mathematically defined as 1/12th of the mass of Carbon-12.)

  10. Journal Entry #4 - part b • Calculate this student’s grade if the class is weighted as follows: • Tests = 75% Homework = 5% • Lab = 10% Final exam = 10% Test scores: 89, 84, 72, 90 Lab : 99, 100, 98, 99, 94, 97 Homework : 92, 93, 96, 98, 105, 94 Final exam : 90

  11. Journal Entry #4 – part b • Calculate this student’s grade if the class is weighted as follows: • Tests = 75% Homework = 5% • Lab = 10% Final exam = 10% Test scores: 89, 84, 72, 90 = 335/4 = 83.75% Lab : 99, 100, 98, 99, 94, 97 = 587/6= 97.8% Homework : 92, 93, 96, 98, 105, 94 = 578/6= 96.3% Final exam : 90% 83.75(.75) + 97.8(.10) + 96.3(.05) + 90(.10) = 86.4% B

  12. Now if this teacher did NOT weight grades, what would this student’s grade be? Test scores: 89, 84, 72, 90 Lab : 99, 100, 98, 99, 94, 97 Homework : 92, 93, 96, 98, 105, 94 Final exam : 90 1590/1700 = 93.5% A…very different

  13. Valence Electrons • The shell or energy level (n) containing the outermost electrons for an element is called the valence shell • The electrons in that shell are called valence electrons • These electrons are the farthest from the atom’s nucleus and are therefore the easiest to remove • Because of this, these are the electrons involved in bonding.

  14. Bonding • Covalent bond – electrons are “shared” • Polar – shared unequally • Non-polar – shared equally • Ionic – transfer of electrons causes change in charge and electrostatic attraction between ions • Hydrogen – weak attraction between partially positive and partially negative poles of H and other atoms (N,O, F) polar covalently bonded within different molecules

  15. Other discussion-worthy topics • Bonding – we’re going to continue with bonding when we discuss water in a few minutes • Intermolecular forces – types and where you would find examples of each • Reactions – single, double, combustion, redox, combination (synthesis), and decomposition and where you would find examples of each in biology

  16. Water contributes to the fitness of the environment • One theory of the origin of life that it evolved in water • Living cells are 70-95% H20 • Water covers about 3/4 of the earth’s surface • It exist in three distinct phases in nature: solid, liquid, and gas • The extraordinary properties of water are emergent properties resulting from water’s structure and molecular interactions

  17. The polarity of water molecules results in hydrogen bonding • Water is a polar molecule; its polar bonds and asymmetrical shape give water molecule opposite charges on opposite sides • Each water molecule can form hydrogen bonds to a max of four neighbors + + + - - + + + - - + - + + +

  18. Unique Properties of Water • The uniqueness of water arises from the emergent properties due to hydrogen bonding that orders the molecule into a higher level of organization • Has cohesive behavior • Resist change in temperature • ~Has a high heat of vaporization and cools surface as it evaporates • Expands when it freezes • Is a versatile solvent • Ice floats (least dense as a solid)

  19. Organisms depend upon the cohesion of water molecules • Cohesion: Substance being held together by H-bonds • Adhesion: water is attracted to and holds onto the walls and overcomes gravity (this is the idea behind capillary action) • Capillary action- movement of water up vessels against gravity, (xylem tubes) • Surface Tension: measure of how difficult it is to stretch or break the surface of a liquid • hydrogen bonding is 20 X weaker than nonpolar covalent bonds - so they form, break, and reform constantly and dynamically giving water more structure than most liquids

  20. Water contributes to Earth’s habitability by moderating temperatures • Heat • Kinetic energy • Calorie (cal) 1 cal = 4.184 Joules (J) • Joule (4.184 J = 1.00 cal • Temperature • Intensity of heat due to its average kinetic energy • Celsius, Fahrenheit, Kelvin • Convert from 0F to 0C by (9/5) 0C + 320 • Convert from 0C to 0F by (5/9) 0F - 320 • Convert from 0C and Kelvin by using 273 • Water’s high specific heat keeps temperature fluctuations within a range suitable for life • Water’s high Specific Heat: 1 cal/g/ o C

  21. Evaporative cooling • Vaporization (evaporation)- phase change from liquid to a gas • Water has a relatively high heat of vaporization (540 cal/g), which means that it requires a large amount of energy for the liquid to break the hydrogen bonds and leave the liquid state • The molecules left behind on the surface thus have a lower kinetic energy and have a lower temperature • Evaporative cooling stabilizes temperatures in aquatic ecosystem, helps organisms from overheating, and helps solar heat by tropical seas dissipate

  22. Oceans and lakes don’t freeze solid because ice floats • Water reaches its greatest density at 4 degrees Celsius • Water contracts as it cools to 40C, then as it cools from 40C to freezing, it expands and becomes less dense than liquid water…ice floats. • Expansion of water: • Prevents deep bodies of water from freezing solid from the bottom up • Ice forms on the top first because it is less dense. As water freezes, it releases heat to the water below it and insulates.

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

  24. Water is the solvent of life • Solution- dissolved substances in liquids • Solute- the substance that dissolves • Solvent- liquid capable of dissolving • Aqueous solution • Molarity- mol/liter of water • Mole: amu or molecular mass (g) x Avogadro's # • Molecular weight • Hydrophilic- water loving (attraction to H2O) • Hydrophobic- water hating (repels H2O) • Concentration: Molarity

  25. Organisms are sensitive to changes in pH • Hydrogen ion (H+) • Hydroxide ion (OH-) • Hydronium ion (H3O+) H+ bonded to H20 • Acid (high concentration of H+) pH < 7 • Base (high concentration of OH-) pH > 7 • pH (scale ranging 0 to 14) • pH H+ 0H- = 1.0 x 10-14 M • pH = -log H+ • Only 1 out of 554,000,000 molecules actually dissociate • Buffers- minimize pH change

  26. Buffers • Substances that prevent sudden changes in pH • Help to minimize wide fluctuations in pH and therefore help organisms maintain the pH of body fluids within the narrow range necessary for life • H2CO3 <---------> HCO3- + H+ • In the presence of strong acid, it forms the conjugate base and weak acid • In the presence of a strong base, it forms the conjugate acid and a weak base

  27. Acid precipitation threatens the fitness of the environment • Acid Precipitation (more acidic than 5.6 pH) • Sulfur oxides & Nitrogen oxides react with water in the air to form acids • Major source of oxides is combustion of fossil fuels by industry and cars • Lowers soil pH which affects mineral solubility (throws things out of balance) • Adverse affects on aquatic systems because of lower pH of lakes and ponds

  28. Aquatic Organisms • We will be discussing several different aquatic organisms this year • Let’s turn our focus to protists • Characteristics: • Single-celled, aquatic, eukaryotic, some are heterotrophic and some are autotrophic • Photoautotrophs vs. chemoautotrophs • Photoautotrophs vs. chemoheterotrophs

  29. Organisms that produce organic compounds such as glucose, starch, and even polyunsaturated fatty acids are called PRODUCERS • These are the autotrophs • Ultimately LIGHT is the energy source for most food chains • What happens to the producers? • They live, they produce, and they… • Either get eaten by consumers or they die and their nutrients are recycled.

  30. Energy flow through ecosystems First trophic level: producers Second trophic level: primary consumers Third trophic level: secondary consumers Fourth trophic level: tertiary consumers Decomposers (saprotrophs) Energy from sun Producer 100% (of harvested energy…not 100% of solar energy hitting the surface of the producer) Primary Consumer ~10% Secondary Consumer ~1% Tertiary Consumer 0.1% Quaternary Consumer 0.01%

  31. 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?

  32. 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

  33. Productivity • Just like there is a difference between your gross annual salary and your net, there is a mandatory deduction that must be made to the amount of energy trapped by producers as organic matter • Gross production - energy lost during respiration = NET productivity

  34. SAPROTROPH – you’ve seen the word…what does it mean? • Organisms that live on or in non-living organic matter (decomposers) • Organisms that feed on non-living organic matter, but don’t necessarily live on or in it are called DETRITIVORES • An organism can be a detritivore without being a saprotroph, but all saprotrophs are detritivores.

  35. Accumulation of Biomass • When producers convert light energy into chemical energy stored in the bonds of organic molecules, they increase in mass • The mass of all (dried) organic matter is referred to as BIOMASS

  36. Pyramids of biomass Secondary consumers (1) Saprotrophs (10) Primary consumers (4) Producers(40,000) Tropical forest in Panama Traditional pyramids of biomass tend to follow traditional pyramids of energy

More Related