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Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate

BIOL 4120: Principles of Ecology Lecture 2: Adaptation to Physical Environment: Water and Nutrients. Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate.edu. Topics (Chapter 2): 2.1 Global water cycling 2.2 Water has many properties favorable to life

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Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate

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  1. BIOL 4120: Principles of Ecology Lecture 2: Adaptation to Physical Environment: Water and Nutrients Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate.edu

  2. Topics (Chapter 2): 2.1 Global water cycling 2.2 Water has many properties favorable to life 2.3 Many inorganic nutrients are dissolved in water 2.4 Plants obtain water and nutrients from soil 2.5 Maintain salt and water balance by plants and animals

  3. 2.1 Global Hydrologic (water) cycle between Earth and atmosphere • Water is essential for life (75-95% weight of living cell) • Over 75% of the Earth’s surface is covered by water • Oceans contain 97%. • Polar ice caps and glaciers contain 2%. • Freshwater in lakes, streams, and ground water make up less than 1%. (Saltwater and fresh water)

  4. Water Cycles between Earth and the Atmosphere • The water (or hydrologic) cycle is the process by which water travels in a sequence from the air to Earth and returns to the atmosphere • Solar radiation is the driving force behind the water cycle because it provides energy for the evaporation of water

  5. The Hydrologic Cycle • Precipitation (PPT) • Interception • Infiltration • Groundwater recharge • Runoff • Evaporation (E) • Transpiration (T) Distribution of water is not static (processes)

  6. Global water budget Land Pools (10^3 km3): Glaciers: 29,000 Groundwater:4,000 Lake: 229 Soil: 67 Fluxes (km3/yr): PPT: 111,000 ET: 71,000 River flow:40,000 Ocean Pools: (10^3 km3) Ocean:1.37*10^6 Fluxes: (km3/yr) PPT:385,000 ET: 425,000

  7. 2.2 Properties of water that favorable to life Basic Structure 1. Covalent bonding of 2H + O atoms 2. Polar-covalent bond 3. Inter-molecule attraction 4. H-bonds among water moleculars

  8. Physical and chemical properties • Thermal properties of water: High specific heat capacity 1.Specific Heat: 1.0 (also called Heat Capacity) • calories required to raise 1 g H2O 1oC high • (e.g. from 10 to 11oC) (Stable T in lakes and organisms) 2. Latent heat: energy released or absorbed in the transformation of water from one state to another. 1 calorie to raise 1oC; 536 calories to change 100oC water to vapor; 86 calories ice to 1oC water • 3. Peculiar density-temperature relationship Density increases as T decreases (when T> 4oC), then decrease to 0oC, freezing (ice), float.

  9. Cohesion Due to the hydrogen bonding, water molecules tend to stick firmly to each other, resisting external forces that would break the bonds (drop of water, transpiration). • Surface tension • Strong attraction within the water body and weaker attraction in the surface caused that molecules at the surface are drawn downward.

  10. High viscosity Viscosity: measures the force necessary to separate the molecules and allow passage of an object through liquid. • Frictional resistance is 100 times greater than air. • Water is 860 times denser than air. • Organisms in water have similar density to water, the neutral buoyancy helps against the force of gravity, thus require less investment in structure material such as skeletons • Organisms in deep water need to adapt to the high pressure (20 to 1000 atm).

  11. 2.3 Many inorganic nutrients are dissolved in water Solution: a homogeneous liquid with 2 or more substances mixed. Solvent: dissolving agent Solute: substance that is dissolved Aqueous solution: water as solvent Ions: Compounds of electrically charged atoms Cations: positive Anions: negative Practical salinity units (PSU, o/oo): grams of salt per kilogram of water. Ocean: 35 unit, Fresh water: 0.065-0.30 unit)

  12. Hydrogen ions in ecological systems Hydrogen ions are very active: 1) affect enzyme activities, and thus influence life processes; 2) dissolve minerals from rocks and soils. Acidity: the abundance of hydrogen ions (H+) in solution. Alkalinity: abundance of hydroxyl ions (OH-) in solution Acidity in water is related to carbon dioxide (CO2).

  13. Forms of carbon in water • Carbon-bicarbonate equilibrium • Carbon dioxide: CO2 • Carbonic acid: H2CO3 • Bicarbonate: HCO3- • Carbonate: CO32- CO2 + H2O H2CO3HCO3- + H+CO32- + 2H+

  14. Measurement: pH =-log([H+]) (value between 1-14) • Pure water: 7 Acidic: <7 Alkaline: >7 • Ocean water tends to be slightly alkaline with a pH range of 7.5-8.4

  15. 2.4 Plants obtain water and nutrients from soil • Plants and animals need water and nutrients to growth and reproduce.

  16. Plants acquire the inorganic nutrients as ions dissolved in water N: ammonium (NH4+), nitrate (NO3-) P: phosphate ions (PO43-) K: K+ Na: Na + Ca: Ca2+ The availability in soil is determined by their chemical forms in soil, temperature, acidity, and presence of other ions.

  17. 2.4.1 Ion exchange capacity is important to soil fertility Soil soluble nutrients are charged particles, ions. Cations: positively charged (Ca2+, Mg2+, NH4+) Anions: negatively charged (NO3–, PO34–) Ions are attached to soil particles, so they do not leach out of the soil. Ion exchange capacity: total number of charged sites on soil particles in a standard volume of soil.

  18. Soils have an excess of negative charged sites • Cationic exchange dominant (colloids) • Cation exchange capacity (CEC): total # of negatively charged sites, located on the leading edges of clay particles and Soil Organic Matter. • Concentration and affinity • Al3+ > H+ > Ca2+ > Mg2+ > K+ = NH4+ > Na+

  19. Process of cation exchange in soils In soils with high Mg++ or Ca++, K+ is lacking, why?

  20. 2.4.2 Soil properties and water-holding capacity • Texture • Variation in size and shape of soil particles • Gravel (NOT) • >2mm • Sand • 0.05mm to 2mm • Silt • 0.002mm to 0.05mm • Clay • <0.002mm Soil texture is percentage of sand, silt and clay. (Texture chart)

  21. Sand: 58% Clay: 14% Silt: 28%

  22. Water holding capacity is an essential feature of soils • Soil can become saturated if all pores filled • All water is hold by soil particulars, at field capacity (FC) • Capillary water is usually present • Extractable by plants • Wilting point (WP) • Plant no long extract water Available water capacity (AWC) • All affected by soil texture • Sand • Lower capacity • Clays • Higher capacity

  23. Water content at different soils

  24. 2.4.3 Water moves from soil to plant to atmosphere

  25. Water potential • Water moving between soil and plants flows down a water potential gradient. • Water potential ( ) is the capacity of water to do work, potential energy of water relative to pure water. • Pure Water = 0. • in nature generally negative. • solute measures the reduction in due to dissolved substances.

  26. Water potential of compartment of soil-plant-atmosphere • w = p + o + m • Hydrostatic pressure or physical pressure (cell wall). • Osmotic potential: tendency to attract water molecule from areas of low concentrations to high. This is the major component of total leaf and root water potentials. • Matric potential: tendency to adhere to surfaces, such as container walls. Clay soils have high matric potentials.

  27. Water moves from soil to plant to atmosphere

  28. The cohesion-tension theory explains the movement of water from the roots to a leaf of a plant. 1. Through Xylem 2. No metabolic energy required 3. Depends on physical-chemical properties of water, driven by water potential. Stick to each other and adhere to cell wall.

  29. BIOL 4120: Principles of Ecology Lecture 2: Adaptation to Physical Environment: Water and Nutrients Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate.edu

  30. Recap: Water properties Many inorganic nutrients are dissolved in water Nutrients, pH Plants obtain water and nutrients from soil Soil and nutrient (CEC) Soil properties and water (water holding capacity) Water movement from roots to plants to air

  31. 2.5 Maintenance of salt and water balance • To maintain proper amount of water and dissolved substances in their bodies, organisms must balance losses with intake. • When organisms take in water with solute concentration differs from that of their bodies, they must either acquire more solutes to make up the deficit or get rid of excess solutes: • Uptake of water with solutes • Evaporation from surface of terrestrial organisms into atmosphere • Solutes left behind, high salt concentration • Solutes determine osmotic potential of body fluids, the mechanisms that organisms use to maintain a proper salt balance are referred to as osmoregulation.

  32. 2.5.1 Management of salt balance by plants Transpiration – water uptake – dissolved salts along water will get into roots When salts concentrations in soil water are high, plants pump excess salts back into soil by active transport across their root surface, function as plant’s “kidneys”. One example: Mangroves on coastal mudflats Salt glands on the leaf surface

  33. 2.5.2 Water and salt balance in terrestrial animals • Terrestrial • Input • Drinking • Eating • Produced by metabolism (respiration) • Output – Need to control in extreme environments • Urine • Concentrated to avoid water loss (Kidneys). Human: 4 times high than in blood; Kangaroo rat: 14 times • Feces • Evaporation • No sweat glands in some mammals; • “salt glands” in birds and reptiles • Breathing

  34. What happens to ungulates in a hot dry climate like Africa? No pants, no sweating to save water, store heat in body (T up to 46oC at daytime, release heat at night 36oC) Countcurrent heat exchange to lower head T Eat at nighttime, more water in plants Respiration to produce water Oryx

  35. 2.5.3 Water and salt balance in aquatic animals • Freshwater (hyper-osmotic, high salt in body) • Prevent excess uptake of water • Remove excess water • Large amounts of very dilute urine • Retain salt in special cells (gills, kidneys) • Saltwater (hypo-osmotic, low salt in body) • If salt concentration is higher than in body, dehydrate • Drinking a lot to gain water • Some sharks: retain urea in the bloodstream (balance body surface water loss) • Ion pumps, gill (fish) • Kidneys (eliminate salts, marine mammals) • Salt secreting glands in birds

  36. The End

  37. Proportions of the formsof CO2 in Relation to pH Free Bicarbonate Carbonate pH CO2 HCO3– CO3= 4 0.996 0.004 1.26 x 10-9 5 0.962 0.038 1.20 x 10-7 6 0.725 0.275 0.91 x 10-5 7 0.208 0.792 2.60 x 10-4 8 0.025 0.972 3.20 x 10-3 9 0.003 0.966 0.031 10 0.000 0.757 0.243

  38. Recap: Water properties Many inorganic nutrients are dissolved in water Nutrients, pH Plants obtain water and nutrients from soil Soil and nutrient (CEC) Soil properties and water (water holding capacity) Water movement from roots to plants to air

  39. Recap: Physical environment: water and nutrient Water properties Inorganic nutrients need to be dissolved in water, Nutrients uptake from soil Ion exchange capacity is a measure of soil fertility Soil texture and water holding capacity Water movement from soil to plant to atmosphere

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