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Chapter 5 Ecosystems and the Physical Environment. Overview of Chapter 5. Biogeochemical Cycles Solar Radiation The Atmosphere The Global Ocean Weather and Climate Internal Planetary Processes. Biogeochemical Cycles.
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Overview of Chapter 5 • Biogeochemical Cycles • Solar Radiation • The Atmosphere • The Global Ocean • Weather and Climate • Internal Planetary Processes
Biogeochemical Cycles • Matter moves between ecosystems, biotic & abiotic environments, and organisms • Unlike energy • Biogeochemical cycling involves • Biological, geologic and chemical interactions • Five major cycles: • Carbon, Nitrogen, Phosphorus, Sulfur and Water (hydrologic)
Carbon Cycle • The global movement of carbon between organisms and the abiotic environment is known as the carbon cycle • 1. Carbon is present in the atmosphere as carbon dioxide(CO2), the ocean as carbonate and bicarbonate (CO32-, HCO3-) and sedimentary rock as calcium carbonate (CaCO3) • 2. Proteins, carbohydrates, and other molecules essential to life contain carbon • Carbon makes up approximately 0.04% of the atmosphere as a gas
Carbon Cycle • ii. Carbon primarily cycles through both biotic and abiotic environments via photosynthesis, cellular respiration and combustion (CO2) • 1. Photosynthesis incorporates carbon from the abiotic environment (CO2) into the biological compounds of producers (sugars) 6CO2 + 12H20 + energy C6H12O6 + 6O2 + 6H2O • 2. Producers, consumers and decomposers use sugars as fuel and return CO2 to the atmosphere in a process called cellular respiration C6H12O6 + 6O2 + 6H2O 6CO2 + 12H2O + Energy
Carbon Cycle… • 3. Carbon present in wood and fossil fuels (coal, oil, natural gas) is returned to the atmosphere by the process of combustion (burning) • The carbon-silicate cycle (which occurs on a geological timescale involving millions of years) returns CO2 to the atmosphere through volcanic eruptions and both chemical and physical weathering processes
Nitrogen Cycle i. The global circulation of nitrogen between organisms and the abiotic environment is know as the nitrogen cycle 1. Atmospheric nitrogen (N2) is so stable that it must first be broken apart in a series of steps before it can combine with other elements to form biological molecules 2. Nitrogen is an essential part of proteins and nucleic acids (DNA) 3. The atmosphere is 78% nitrogen gas (N2)
Nitrogen Cycle ii. Five steps of the nitrogen cycle 1. Nitrogen fixation • Conversion of gaseous nitrogen (N2) to ammonia (NH3) Formula: N2 + 3H2 2NH3 (Ammonia), which dissolves to form NH4+ (Ammonium)
Nitrogen Cycle • Nitrogen-fixing bacteria (including cyanobacteria) fixes nitrogen in soil and aquatic environments (anaerobic process) • Combustion, volcanic action, lightning discharges, and industrial processes also fix nitrogen • Nitrogen-fixing bacteria contain a special enzyme called Nitrogenase that is used to split atmospheric nitrogen. • Legumes such as alfalfa and beans are planted to reduce nitrogen loss in soil, since they contain helpful Rhizobium nitrogen-fixing bacteria which live inside special nodules on their roots!
Nitrogen Cycle 2. Nitrification a. Conversion of ammonia (NH3) or ammonium (NH4+) to nitrate (NO3-) b. Soil bacteria perform nitrification in a two-step process (NH3 or NH4+ is converted to nitrite (NO2-) then to NO3-) • Nitrifying bacteria is used in this process Formula: NH3 + NH4+ NO2- (nitrite) + NO3- (nitrate)
Nitrogen Cycle 3. Assimilation a. Plant roots absorb NO3-, NO3 or NO4+ and assimilate the nitrogen of these molecules into plant proteins and nucleic acids b. Animals assimilate nitrogen by consuming plant tissues (conversion of amino acids to proteins) • This step does not involve bacteria Formula: NH3 + NH4+ + NO3- DNA, Proteins, Amino Acids
Nitrogen Cycle 4. Ammonification – when plants or animals die, or when animals emit wastes, the nitrogen in the organic matter re-enters the soil, where it is broken down by decomposers. This decomposition produces ammonia! a. Conversion of biological nitrogen compounds into NH3 (ammonia) and NH4+ (ammonium) b. NH3 is released into the abiotic environment through the decomposition of nitrogen-containing waste products such as urea and uric acid (birds), as well as the nitrogen compounds that occur in dead organisms c. Ammonifying bacteria is used in this process
Nitrogen Cycle 5. Denitrification a. Reduction of NO3- to N2 b. Anaerobic denitrifying bacteria reverse the action of nitrogen-fixing and nitrifying bacteria
Phosphorous Cycle i. Phosphorus cycles from land to sediments in the ocean and back to land • Phosphorus erodes from rock as inorganic phosphates and plants absorb it from the soil • Animals obtain phosphorus from their diets, and decomposers release inorganic phosphate into the environment ii. Once in cells, phosphates are incorporated into biological molecules such as nucleic acids and ATP (adenosine triphosphate) iii. This cycle has no biologically important gaseous compounds, so it is essentially NOT found in the atmosphere!
Phosphorous Cycle… • iv. Phosphorous exists in the hydrosphere primarily due to absorption and assimilation of phosphorous by algae & plants in the oceans, which are then eaten by larger plankton, moves phosphorous up the food chain into fish, birds, humans, etc. • Decomposers then release the inorganic phosphates back into the seawater.
Sulfur Cycle • i. Most sulfur is underground in sedimentary rocks and minerals or dissolved in the ocean • ii. Sulfur gases enter the atmosphere from natural sources in both ocean and land • 1. Sea spray, forest fires and dust storms deliver sulfates (SO42-) into the air • 2. Volcanoes release both hydrogen sulfide (H2S) and sulfur oxides (SOx)
Sulfur Cycle • iii. A tiny fraction of global sulfur is present in living organisms • 1. Sulfur is an essential component of proteins • 2. Plant roots absorb SO42- and assimilate it by incorporating the sulfur into plant proteins • Animals assimilate sulfur when they consume plant proteins and covert them to animal proteins • iv. Bacteria drive the sulfur cycle
Hydrologic Cycle • The hydrologic cycle is the global circulation of water for the environment to living organisms and back to the environment • It provides a renewable supply of purified water for terrestrial organisms • the hydrologic cycle results in a balance between water in the ocean, on the land, and in the atmosphere • Water moves from the atmosphere to the land and ocean in the form of precipitation • Water enters the atmosphere by evaporation and transpiration • The volume of water entering the atmosphere each year is about 389,500 km3
Hydrologic Cycle… • Water is returned to the oceans quickly by runoff of surface water, or more slowly by the processes of infiltration and groundwater flow.
Solar Radiation • 70% of incoming solar radiation is absorbed by atmosphere and earth • Remainder is reflected • Albedo • The reflectance of solar energy off earth’s surface • Dark colors = low albedo • Forests and ocean • Light colors = high albedo • Ice caps • Sun provides energy for life, powers biogeochemical cycles, and determines climate
Incoming Solar Radiation (Insolation) • On a typical day, 49% the Incoming Solar Radiation reaches Earth’s surface and is absorbed by the ground. • After Visible Light is absorbed, the Earth heats up and re-radiates the energy as Infraredradiation, which is also called Terrestrialradiation.
Temperature Changes with Latitude • Solar energy does not hit earth uniformly • Due to earth’s spherical shape and tilt Equator (a) High concentration Little Reflection High Temperature Closer to Poles (c) Low concentration Higher Reflection Low Temperature From (a) to (c) In diagram below
Temperature Changes with Season • Seasons determined by earth’s tilt (23.5°) • Causes each hemisphere to tilt toward the sun for half the year • Northern Hemisphere tilts towards the sun from March 21- September 22 (warm season)
Temperature Changes with Season • On June 21st, the northern hemisphere experiences the longest day of the year (sun is out the longest), and the sun is at it’s highest altitude in the sky (highest angle of insolation); This day is called the summer solstice! • Earth is actually further from the Sun in July than January…so the ANGLE of insolation is the main cause of warmer temps. In summer!
Temperature Changes with Season • Places on earth receiving a lower angle of insolation will be colder, while locations receiving a higher sun angle will be hotter!
The Atmosphere • Invisible layer of gases that envelopes earth • Content • 21% Oxygen • 78% Nitrogen • 1% Argon, Carbon dioxide, Neon and Helium • Density decreases with distance from Earth’s surface! • Pressure decreases with distance from Earth’s surface! • Our atmosphere shields earth from high energy radiation
Atmospheric Layers • Troposphere (0-10km) • Where weather occurs • Temperature decreases with altitude • Highest airplanes fly near the top of the troposphere • This layer is warming up due to the trapping of greenhouse gases (carbon dioxide mainly)
Atmospheric Layers • Stratosphere (10-45km) • Temperature increases with altitude- very stable • Ozone layer absorbs UV radiation, which is why temperature rises here! • Mesosphere (45-80km) • Temperature decreases with altitude
Atmospheric Layers • Thermosphere (80-500km) • Gases in thin air absorb x-rays and short-wave UV radiation = very hot • Source of aurora • Exosphere (500km and up) • Outermost layer • Atmosphere continues to thin until converges with interplanetary space
Atmospheric Circulation • Near Equator • Warm air rises, cools and splits to flow towards the poles • ~30°N&S sinks back to surface • Air moves along surface back towards equator • This occurs at higher latitudes as well • Moves heat from equator to the poles
Surface Winds • Large winds due in part to differences in pressure caused by global circulation of air • Left side of diagram • Winds blow from high to low pressure • Right side of diagram High Low High Low High Low High
