Biogeochemical Cycles: the exchange of matter through the biosphere Water Cycle Nitrogen Cycle Carbon Cycle

Water Cycle

Water Cycle All living organisms require fresh water Freshwater constitutes only about 3% all water on Earth

Water Cycle Evaporation: water molecules break free from oceans and lakes Purifies water Transpiration: a process in which water evaporates from the surface of plants

Condensation: H2O molecules rise in the atmosphere—cool—slow down Falls to Earth as precipitate (rain, snow, etc) Percolation: water is purified through filtration when in trickles through loose soil

H2O carried from lakes to oceans by streams, run-off (on ground) flows into lakes and oceans, ground water travels under ground to oceans H2O is also given off by living organisms—transpiration, perspiration, urination

Run off: water on the surface that usually occurs when the land is saturated or melting occurs Ground water: water under the ground that occurs when rain infiltrates the soil

Nitrogen Cycle

Nitrogen Cycle All living organisms need nitrogen to make proteins (for growth and repair) The atmosphere is 78% nitrogen gas (N2) but plants and animals cannot use N2 in this form

Nitrogen must be “fixed” to oxygen in order for plants to absorb it and to benefit an ecosystem . Nitrogen fixation: the capture and conversion of nitrogen into a form that is useable by plants

How is Nitrogen Fixed into a Usable Form? Nitrogen is “fixed” in the following ways: 5-10% of N2 is “fixed” by lightning Lightning splits bonds between N2 and N bonds with O2 90% of N2 is “fixed” by bacteria found in the roots of legumes (pea, soybean, peanut plants)

Man “fixes” nitrogen in fertilizer and introduces it to the ecosystem

Plants use these nitrogen compounds to make protein Animals eat plants and use the plants’ protein to make their own protein Animal passes waste or dies and releases nitrogen compounds into the soil

Nitrogen compounds go back into the soil where bacteria break it back into N2 gas Denitrification: the process of bacteria breaking down nitrogen compounds (such as ammonia) back into N2 gas (no longer useable for plants)

Carbon Cycle

Carbon Cycle Carbon Dioxide gas (CO2) is in the atmosphere Large reserves in oceans—dissolved in limestone deposits

Plants take in CO2 during photosynthesis 6 CO2 + 6 H2O + (light) → C6H12O6 + 6 O2 6 carbon dioxide + 6 molecules of water produce one molecule of sugar + 6 molecules of oxygen

Animals take in O2 and glucose and give off CO2 and H2O CO2 goes back into the atmosphere Cellular respiration

Plant dies and is buried for millions of years Fossil fuels form Man extracts and burns fossil fuels releasing CO2 into the atmosphere