Biogeochemical Cycles

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

Two Secrets of Survival: Energy Flow and Matter Recycling 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 called biogeochemical cycles, are cycling of nutrients from the abiotic reservoirs to biotic reservoirs. Nutrients are the elements and compounds that organisms need to live, grow, and reproduce. Biogeochemical cycles move all nutrients through air, water, soil, rock and living organisms over millions of years.

MATTER CYCLING IN ECOSYSTEMS Nutrient Cycles: Global Recycling Abiotic – nonliving cycles like rock cycle, water cycle and other chemical cycles. Biotic – living organism involved cycles like carbon and nitrogen cycle. All cycles enable a specific chemical element or nutrient to be taken and reused through various forms.

What Sustains Life on Earth? Figure 2

Closer look at cycles WATER CYCLE

Water’s 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 including rock. Water expands when it freezes.

Condensation Transpiration Evaporation Precipitation Precipitation Rain clouds Transpiration Evaporation Precipitation to land Transpiration from plants Precipitation Precipitation Evaporation from land Evaporation from ocean Surface runoff (rapid) Runoff Precipitation to ocean Infiltration and Percolation Surface runoff (rapid) Figure 3.26 Natural capital: simplified model of the hydrologic cycle. Groundwater movement (slow) Ocean storage Fig. 3-26, p. 72

Effects of Human Activities on Water Cycle We alter the water cycle by: Withdrawing large amounts of freshwater from the ground causing salt water to contaminate reservoir. Withdrawing large amounts from rivers and streams changes flow of nutrients Clearing vegetation causes eroding soils that clogs streams. Polluting surface and underground water. All of this contributes to climate change.

Carbon Cycles: One of the most complex cycles on Earth.

Carbon Cycles: Carbon just like all other nutrients cycles from one reservoir to another through many years. Eg: Carbon enters plants as CO2 which is incorporated into organic molecules by a process called photosynthesis When organisms respire, a portion of this carbon is returned to the atmosphere as CO2.

Carbon Reservoir pools: Where Carbon is stored Organic molecules – in living and dead organisms. Carbon Dioxide (CO2) in atmosphere. Organic matter in soil. Fossil fuels and sedimentary rock like limestone. CO2 in ocean/water bodies. Calcium carbonate in the shells of marine organisms.

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. Just Breathing Figure 3-28

The Nitrogen Cycle Nitrogen is the second largest nutrient cycle on the planet, second only to carbon.

Effects of Human Activities on the Nitrogen Cycle We alter the nitrogen cycle by: Adding gases to atmosphere that contribute to acid rain. 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. Releasing nitrogen into the troposphere through deforestation.

Effects of Human Activities on the Nitrogen Cycle Human activities such as production and use of fertilizers now “fix” (put into environment) more nitrogen than all natural sources combined. Figure 3-30

Phosphorous Cycle Phosphorous Cycle has been greatly affected by human activity in the last 100 years.

mining Fertilizer excretion Guano agriculture weathering uptake by autotrophs uptake by autotrophs leaching, runoff Marine Food Webs Dissolved in Ocean Water Dissolved in Soil Water, Lakes, Rivers Land Food Webs death, decomposition death, decomposition Figure 3.31 Natural capital: simplified model of the phosphorus cycle. Phosphorus reservoirs are shown as boxes; processes that change one form of phosphorus to another are shown in unboxed print. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the phosphorus cycle? (From Cecie Starr and Ralph Taggart, Biology: The Unity and Diversity of Life, 9th ed., Belmont, Calif.: Wadsworth © 2001) weathering sedimentation settling out uplifting over geologic time Marine Sediments Rocks Fig. 3-31, p. 77

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: STOP 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

Acidic fog and precipitation Water Sulfur trioxide Sulfuric acid Acidic fog and precipitation Ammonia Ammonium sulfate Oxygen Sulfur dioxide Hydrogen sulfide Plants Dimethyl sulfide Volcano Industries Animals Ocean Figure 3.32 Natural 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 salts Metallic sulfide deposits Decaying matter Sulfur Hydrogen sulfide Fig. 3-32, p. 78

Effects of Human Activities on the Sulfur Cycle We add sulfur dioxide to the atmosphere by: Burning coal and oil Refining sulfur containing petroleum. 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 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.

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