Chapter 4 Biogeochemical Cycles

Objectives:  Identify and describe the flow of nutrients in each biogeochemical cycle.  Explain the impact that humans have on the biogeochemical cycles.

Chapter Overview Questions  What happens to energy in an ecosystem?  What happens to matter in an ecosystem?

What Sustains Life on Earth?  Solar energy, the cycling of matter, and gravity sustain the earth’s life. Figure 3-7

Two Secrets of Survival: Energy Flow and Matter Recycle  An ecosystem survives by a combination of energy flow and matter recycling. Figure 3-14

MATTER CYCLING IN ECOSYSTEMS  Nutrient Cycles: Global Recycling Global Cycles recycle nutrients through the earth’s air, land, water, and living organisms. Global 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. 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. Biogeochemical cycles move these substances through air, water, soil, rock and living organisms.

Objectives:  Identify and describe the flow of nutrients in each biogeochemical cycle.  Explain the impact that humans have on the biogeochemical cycles.

Water’ Unique Properties  There are strong forces of attraction between molecules of water.  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.  Water expands when it freezes.

Fig. 3-26, p. 72 Precipitation Transpiration Condensation Evaporation Ocean storage Transpiration from plants Precipitation to land Groundwater movement (slow) Evaporation from land Evaporation from ocean Precipitation to ocean Infiltration and Percolation Rain clouds Runoff Surface runoff (rapid)

Effects of Human Activities on Water Cycle  We alter the water cycle by: Withdrawing large amounts of freshwater. Withdrawing large amounts of freshwater. Clearing vegetation and eroding soils. Clearing vegetation and eroding soils. Polluting surface and underground water. Polluting surface and underground water. Contributing to climate change. Contributing to climate change.

Objectives:  Identify and describe the flow of nutrients in each biogeochemical cycle.  Explain the impact that humans have on the biogeochemical cycles.

What Sustains Life on Earth?  Solar energy, the cycling of matter, and gravity sustain the earth’s life. Figure 3-7

Fig. 3-27, pp

Effects of Human Activities on Carbon Cycle  We alter the carbon cycle by adding excess CO 2 to the atmosphere through: Burning fossil fuels. Burning fossil fuels. Clearing vegetation faster than it is replaced. Clearing vegetation faster than it is replaced. Figure 3-28

Objectives:  Identify and describe the flow of nutrients in each biogeochemical cycle.  Explain the impact that humans have on the biogeochemical cycles.

What Sustains Life on Earth? Solar energy, the cycling of matter, and gravity sustain the earth’s life. Figure 3-7

Effects of Human Activities on the Nitrogen Cycle  We alter the nitrogen cycle by: Adding gases that contribute to acid rain. Adding gases that contribute to acid rain. Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. Contaminating ground water from nitrate ions in inorganic fertilizers. Contaminating ground water from nitrate ions in inorganic fertilizers. Releasing nitrogen into the troposphere through deforestation. Releasing nitrogen into the troposphere through deforestation.

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

Objectives:  Identify and describe the flow of nutrients in each biogeochemical cycle.  Explain the impact that humans have on the biogeochemical cycles.

What Sustains Life on Earth? Solar energy, the cycling of matter, and gravity sustain the earth’s life. Figure 3-7

Fig. 3-31, p. 77 Dissolved in Ocean Water Marine Sediments Rocks uplifting over geologic time settling out weathering sedimentation Land Food Webs Dissolved in Soil Water, Lakes, Rivers death, decomposition uptake by autotrophs agriculture leaching, runoff uptake by autotrophs excretion death, decomposition miningFertilizer weathering Guano Marine Food Webs

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.

Objectives:  Identify and describe the flow of nutrients in each biogeochemical cycle.  Explain the impact that humans have on the biogeochemical cycles.

What Sustains Life on Earth?  Solar energy, the cycling of matter, and gravity sustain the earth’s life. Figure 3-7

Fig. 3-32, p. 78 Hydrogen sulfide Sulfur Sulfate salts Decaying matter Animals Plants Ocean Industries Volcano Hydrogen sulfide Oxygen Dimethyl sulfide Ammonium sulfate Ammonia Acidic fog and precipitation Sulfuric acid Water Sulfur trioxide Sulfur dioxide Metallic sulfide deposits

Effects of Human Activities on the Sulfur Cycle  We add sulfur dioxide to the atmosphere by: Burning coal and oil Burning coal and oil Refining sulfur containing petroleum. Refining sulfur containing petroleum. Convert sulfur-containing metallic ores into free metals such as copper, lead, and zinc releasing sulfur dioxide into the environment. Convert sulfur-containing metallic ores into free metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.

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 strong Gaia hypothesis: life controls the earth’s life-sustaining processes. The weak Gaia hypothesis: life influences the earth’s life-sustaining processes. The weak Gaia hypothesis: life influences the earth’s life-sustaining processes.

What do you think?  Does life on earth control earth’s life- sustaining processes or does life merely influence these life-sustaining process? FRQ Format. FRQ Format.

Objectives:  Identify and describe the flow of nutrients in each biogeochemical cycle.  Explain the impact that humans have on the biogeochemical cycles.