BIO-GEO-CHEMICAL CYCLES Nutrient cycling in an ecosystem Biogeochemical Cycles (Matter moving through the environment) • All living organisms need certain elements/compounds for life processes – Ex: your cells need C,H,O,P,N & S in order to live and reproduce (make more cell) • Cycles in nature keep these elements “moving” from organisms to organism (and sometimes into the atmosphere) Biogeochemical Cycles (Matter moving through the environment) • The flow of a nutrient from the environment to living organisms and back to the environment • Main reservoir for the nutrient is in the environment or the abiotic reservoir. • Transfer rates to and from abiotic reservoirs are usually lower than the rates of exchange between and among organisms or biotic reservoirs. • Matter is recycled through an ecosystem – not one a way flow as with energy. Three Main Abiotic Reservoirs • Hydrologic cycle – Water, (hydrogen and oxygen) • Atmospheric cycles – Nitrogen, carbon, oxygen • Sedimentary cycles – Phosphorus and sulfur WATER CYCLE Water Cycle - Earth’s water supply is constantly recycled throughout the biosphere: Evaporation – water vapor leaves the oceans and joins the atmosphere. Transpiration – water vapor evaporates off of plant leaves. Condensation – water vapor in the atmosphere forms clouds. Precipitation – water vapor in the atmosphere falls to the ground (rain.) Carbon Cycle • Carbon moves through the atmosphere and food webs on its way to and from the ocean, sediments, and rocks. • Atmospheric carbon is mainly carbon dioxide • Carbon dioxide is added to atmosphere – Aerobic respiration, volcanic action, burning fossil fuels, decomposition of organic materials • Removed by photosynthesis Carbon Cycle Diagram Carbon in Atmosphere Decomposers break down dead things, releasing carbon to atmosphere and soil Fossil fuels are burned; carbon is returned to atmosphere Carbon slowly released from these substances returns to atmosphere Plants use carbon to make food Plants and animals die Bodies not decomposed — after many years, become part of oil or coal deposits Animals eat plants and take in carbon Carbon Cycle Diffusion Atmosphere Bicarbonate, volcanic action carbonate TERRESTRIAL Marine food ROCKS webs Marineweathering Sediments Terrestrial Rocks photosynthesis Land Food Webs Soil Water Peat, Fossil Fuels Human Impact • Fossil fuels release carbon stores very slowly • Burning anything releases more carbon into atmosphere — especially fossil fuels • Increased carbon dioxide in atmosphere increases global warming • Fewer plants mean less CO2 removed from atmosphere The Carbon Cycle Plants Nitrogen Cycle What is Nitrogen? • Nitrogen is the most abundant element in the Earth’s atmosphere. • Nitrogen cannot be absorbed directly by plants and animals until it is converted into compounds they can use. This process is called the Nitrogen Cycle. Nitrogen Cycle Steps • Step 1- Nitrogen Fixation- Special bacteria convert nitrogen gas (N2) to ammonia (NH3) which the plants can use. • Step 2- Nitrification- Nitrification is the process which converts the ammonia into ions which the plants can take in as nutrients. Nitrogen Cycle Steps • Step 3- Ammonification- After all of the living organisms have used the nitrogen, decomposer bacteria convert the nitrogenrich waste compounds into simpler ones. • Step 4- Denitrification- This is the final step in which other bacteria convert the simple nitrogen compounds back into nitrogen gas (N2), which is then released back into the atmosphere to begin the cycle again. Nitrogen in the air nitrogen fixing plant eg pea, clover plant made animal protein protein root nodules (containing nitrogen fixing bacteria) nitrates absorbed dead plants & animals urine & faeces denitrifying bacteria decomposition by bacteria & fungi ammonia nitrates bacteria (nitrifying bacteria) nitrites bacteria How do humans affects the Nitrogen Cycle? • Nitric Oxide (NO) is released into the atmosphere when any type of fuel is burned. This includes byproducts of internal combustion engines. • Nitrous Oxide (N2O) is released into the atmosphere through bacteria in livestock waste and commercial fertilizers applied to the soil. How do humans affects the Nitrogen Cycle? (cont.) • Removing nitrogen from the Earth’s crust and soil when we mine nitrogenrich mineral deposits. • Discharge of municipal sewage adds nitrogen compounds to aquatic ecosystems which disrupts the ecosystem and kills fish. Phosphorus Cycle • Phosphorus is part of phospholipids, nucleic acids, and energy metabolism • It is the most prevalent limiting factor in ecosystems because it is slower moving than other cycles. • Main reservoir is Earth’s crust; no gaseous phase (it never enters the atmosphere – like carbon and nitrogen) • Plants absorb phosphate from soil and phosphatizing bacteria return it back to it’s abiotic reservoir when they decompose organic wastes. • Phosphates returns (moved) via weathering, volcanic activity, ect. Homeostasis Exists in Nutrient Cycles • In a stable ecosystem, biogeochemical cycles show homeostasis. • Meaning input = output • According to the Gaia theory by Lovelock, the Earth (biosphere) is a self-regulating system. The evolution of life and the planet are intimately connected as if the earth is a big “organism” itself. • Human impact from clear-cutting, slash/burn, and greenhouse gases can seriously affect the homeostasis of the cycles!