2 What IS a “biogeochemical cycle”? BIO = “life”GEO = “earth”CHEMICAL = “elements – C, O, N, P, Sa cycling of nutrients (water, carbon, oxygen, nitrogen, phosphorus, sulphur) from the abiotic components of the ecosystem (water, air, soil, rock) through the biotic components (plants, animals, fungi, bacteria)
3 Objectives:Identify and describe the flow of nutrients in each biogeochemical cycle.Explain the impact that humans have on the biogeochemical cycles.
4 Objectives:Identify and describe the flow of nutrients in each biogeochemical cycle.Explain the impact that humans have on the biogeochemical cycles.
5 What Sustains Life on Earth? Solar energy, the cycling of matter, and gravity sustain the earth’s life.Figure 3-7
6 Two Secrets of Survival: Energy Flows and Matter Cycles An ecosystem survives by a combination of energy flow (from Sun to Earth) and matter cycling.Remember: the Earth is a CLOSED systemFigure 3-14
7 MATTER CYCLING IN ECOSYSTEMS Nutrient Cycles: Global RecyclingGlobal Cycles recycle nutrients through the earth’s air, land, water, and living organisms.Nutrients are the elements and compounds that organisms need to live, grow, and reproduce.Biogeochemical cycles move these substances through air, water, soil, rock and living organisms.
8 Water’s Unique Properties There are strong forces of attraction between molecules of water. (due to H bonds)Water exists as a liquid over a wide temperature range.Liquid water changes temperature slowly.It takes a large amount of energy for water to evaporate.Liquid water can dissolve a variety of compounds. (due to polar nature of water)Water expands when it freezes.
9 THE HYDROLOGIC (WATER) CYCLE CondensationRain cloudsTranspirationEvaporationPrecipitation to landTranspiration from plantsPrecipitationPrecipitationEvaporation from landEvaporation from oceanSurface runoff (rapid)RunoffPrecipitation to oceanInfiltration and PercolationSurface runoff (rapid)Figure 3.26Natural capital: simplified model of the hydrologic cycle.Groundwater movement (slow)Ocean storageFig. 3-26, p. 72
10 Effects of Human Activities on Water Cycle We alter the water cycle by:Withdrawing large amounts of freshwater.Clearing vegetation and eroding soils.Polluting surface and underground water.Contributing to climate change.
13 Effects of Human Activities on Carbon Cycle We alter the carbon cycle by adding excess CO2 to the atmosphere through:Burning fossil fuels.Clearing vegetation faster than it is replaced photosynthesis = CO2Figure 3-28
16 Effects of Human Activities on the Nitrogen Cycle We alter the nitrogen cycle by:Adding nitrous oxide to the atmosphere from vehicles and factories which contributes to acid rain.Contaminating ground water from nitrate ions in inorganic fertilizers.Releasing nitrogen into the troposphere through deforestation (less N assimilated by trees).
17 Effects of Human Activities on the Nitrogen Cycle Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.Figure 3-30
19 Effects of Human Activities on the Phosphorous Cycle We remove large amounts of phosphate from the earth to make fertilizer.We reduce phosphorous in tropical soils by clearing forests.We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers – excess phosphorus causes algal blooms
21 Acidic fog and precipitation THE SULPHUR CYCLEWaterSulfurtrioxideSulfuric acidAcidic fog and precipitationAmmoniaAmmoniumsulfateOxygenSulfur dioxideHydrogen sulfidePlantsDimethyl sulfideVolcanoIndustriesAnimalsOceanFigure 3.32Natural capital: simplified model of the sulfur cycle. The movement of sulfur compounds in living organisms is shown in green, blue in aquatic systems, and orange in the atmosphere. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the sulfur cycle?Sulfate saltsMetallicsulfidedepositsDecaying matterSulfurHydrogen sulfideFig. 3-32, p. 78
22 Effects of Human Activities on the Sulfur Cycle We add sulfur dioxide to the atmosphere by:Burning coal and oilRefining sulfur containing petroleumConvert sulfur-containing metallic ores into free metals such as copper, lead, and zinc releasing sulfur dioxide into the environment
23 Assignment: Put the 6 cycles together on one poster! Draw the hydrologic, carbon, oxygen, nitrogen, phosporus and sulphur cycles onto one piece of poster paper.Include the required terminologyFollow the criteria on the rubric providedAssessment will be done by performance (explanation of the cycles by the group)
24 The Gaia Hypothesis: Is the Earth Alive? Some have proposed that the earth’s various forms of life control or at least influence its chemical cycles and other earth-sustaining processes.The strong Gaia hypothesis: life controls the earth’s life-sustaining processes.The weak Gaia hypothesis: life influences the earth’s life-sustaining processes.