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Botkin & Keller Environmental Science 5e Chapter 5 The Biogeochemical Cycles Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e • Chemical reaction: –The process in which new chemicals are formed from elements and compounds through chemical change –Examples – H2O + CO2 H2CO3 6H2O + 6CO2 C6H12O6 + 6O2 How Chemicals Cycle • Biogeochemical Cycle – The complete path a chemical takes through the four major components – or reservoirs – of Earth’s systems 1. Atmosphere (Air) 2. Hydrosphere (Water) 3. Lithosphere (Rocks) 4. Biosphere (Living Things) Botkin & Keller Environmental Science 5e Cycles Generalized Botkin & Keller Environmental Science 5e The “Big Six” Chemicals • Macronutrients – Elements required in large amounts by all life – Include the “big six” elements that form the fundamental building blocks of life: carbon oxygen hydrogen phosphorus nitrogen sulfur Botkin & Keller Environmental Science 5e Micronutrients Elements required either in small amounts by all life or moderate amounts by some forms of life and not all by others Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Limiting factor –When chemical elements are not available at the right times, in the right amounts, and in the right concentrations relative to each other Botkin & Keller Environmental Science 5e • The Geologic Cycle: –The processes responsible for formation and change of Earth materials –Best described as a group of cycles: • Tectonic • Hydrologic • Rock • Biochemical Botkin & Keller Environmental Science 5e The Rock Cycle • The rock cycle: – Numerous processes that produce rocks and soils – Depends on other cycles: • tectonic cycle for energy • Hydrologic cycle for water – Rock is classified as • Igneous • Sedimentary • Metamorphic Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Botkin & Keller Environmental Science 5e Tectonic Cycle • Tectonic cycle: – Involves creation and destruction of the solid outer layer of Earth, the lithosphere • Plate tectonics: – The slow movement of these large segments of Earth’s outermost rock shell – Boundaries between plates are geologically active areas Botkin & Keller Environmental Science 5e Tectonic Cycle: Plate Boundaries • Divergent plate boundary: – Occurs at a spreading ocean ridge, where plates are moving away from one another – New lithosphere is produced (seafloor spreading) • Convergent plate boundary – Occurs when plates collide • Produces linear coastal mountain ranges or continental mountain ranges • Transform fault boundary – Occurs where one plate slides past another • San Andreas Fault in California Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers The Water Cycle • The Hydrologic Cycle: – The transfer of water from the oceans to the atmosphere to the land and back to the oceans. Includes: • Evaporation of water from the oceans • Precipitation on land • Evaporation from land • Runoff from streams, rivers, and subsurface groundwater Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e The Carbon Cycle • All living things are made of molecules that contain Carbon – Organic = living = contains carbon! • Organic Molecules, Organic Matter… • Carbon is “the element of life!” The Carbon Cycle • Carbon is the element that anchors all organic substances • The carbon cycle: – Carbon combines with and is chemically and biologically linked with the cycles of oxygen and hydrogen that form the major compounds of life Botkin & Keller Environmental Science 5e The Carbon Cycle The Carbon Cycle • Carbon is found in the atmosphere as CO2. • Plants take CO2 in from the air, and in the process of photosynthesis, make carbohydrate sugars that are stored in the plant • Animals eat the plants, and also store Carbon in their bodies • Animals also breathe out CO2 back to the atmosphere as part of respiration • When any living thing dies, decomposers return some Carbon to the air as CO2, but the rest of the Carbon gets put into the soil or water DEAD - The Carbon compounds in decaying organisms deep underground or underwater are eventually turned into coal, oil, or gas - called “Fossil Fuels” - This Carbon is re-released to the air as CO2 when people burn fossil fuels DEAD The Carbon Cycle CO2 in air Carbohydrates in plants Carbon in animals Burning Fossil Fuels Decomposers Break down decaying animals DEAD Carbon in soil Fossil Fuels Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers The Carbon-Silicate Cycle • The carbon-silicate cycle: – A complex biogeochemical cycle over time scales as long as one-half billion years. – Includes major geological processes, such as: • • • • Weathering Transport by ground and surface waters Erosion Deposition of crustal rocks – Believed to provide important negative feedback mechanisms that control the temperature of the atmosphere. Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Your Ocean on Acid.m4v Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e The Nitrogen Cycle • The nitrogen cycle: – Cycle responsible for moving important nitrogen components through the biosphere and other Earth systems – Extremely important because nitrogen is required by all living things • Nitrogen fixation: – The process of converting inorganic, molecular nitrogen in the atmosphere to ammonia or nitrate • Denitrification: – The process of releasing fixed nitrogen back to molecular nitrogen Botkin & Keller Environmental Science 5e The Nitrogen Cycle Nitrogen is needed by all living things to build proteins Nitrogen is found in its gas form in the air around us but Plants and animals can't use nitrogen in its gas form! NITROGEN FIXATION: process where Nitrogen gas is converted into a form plants can use This process is done by certain bacteria that live in the water, soil, or that grow on the roots of some legume (bean) plants Bacteria capture the nitrogen gas from the atmosphere and make it usable Plants then absorb the usable Nitrogen from the soil Animals eat the plants – and Nitrogen is passed along through the food chain • Nitrogen is returned to the soil when – Animals excrete wastes (pee or poop) – living things die and are broken down by decomposers • Nitrogen is returned to the air by denitrifying bacteria • DENITRIFICATION: bacteria in the soil re-convert nitrogen compounds into nitrogen gas Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers The Phosphorus Cycle • The phosphorus cycle: – Involves the movement of phosphorus throughout the biosphere and lithosphere – Important because phosphorus is an essential element for life and often is a limiting nutrient for plant growth. Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers