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How water, gases, and nutrients cycle throughout our ecosystems Cycles Many elements in our ecosystem are never lost, but simply recycled over and over again Water – makes up most of living things (we are about 60% water) Carbon – element that makes things organic (living) Oxygen – needed for cellular respiration Nitrogen – needed to make proteins and nucleic acids Water Cycle Vocabulary Hydrosphere – all the water on the Earth from oceans, creeks, streams, rivers, lakes, ponds, etc. Transpiration – The water that evaporates from the surface of leaves Condensation – when water cools from its gaseous state to form a liquid again Evaporation – when the surface of water vaporizes to become a gas Precipitation – water falling to the Earth over a certain period of time Water Cycle Water is never lost, it is just recycled through the atmosphere and organisms Animals and plants are composed mostly of water, but when these organisms are eaten or die this water is passed on to the organism that eats it. Much of the water we drink is recycled back into the environment as urine or sweat. The environment recycles water as well through a cycle of evaporation, condensation, and precipitation. Carbon Oxygen Cycle Carbon dioxide is taken in by plants During photosynthesis plants break down the carbon dioxide and add some more elements (carbon, oxygen, and hydrogen) to create glucose (C6H12O6) We then eat plants and break down that glucose for energy (ATP) in a process called cellular respiration. The carbon molecules we take from the glucose are then exhaled as carbon dioxide that plants can use. Plants also give off the oxygen we need to perform cellular respiration because it is a waste product of photosynthesis Carbon Oxygen Cycle It is not just plants and animals that contribute to this cycle though . . . Decomposers release carbon dioxide when they break down dead matter Anytime something is burned carbon dioxide is released and oxygen is consumed Volcanic activity also releases carbon dioxide into the atmosphere The oceans do absorb some of our atmospheric CO2 Nitrogen Cycle All living things need nitrogen because all living things contain nucleic acids (DNA) and amino acids (proteins) Nitrogen is extremely abundant on Earth because 72% of our atmosphere is made up of nitrogen, but most organisms are not able to use gaseous nitrogen (N2) Plants need nitrogen in the form of nitrate (No3-), ammonia (NH3), or urea (NH2)2CO2 to be able to make proteins and nucleic acids Nitrogen Cycle We get our nitrogen by consuming plants and other animals which feed on plants So, what is converting nitrogen to its different forms? Nitrogen fixation Decay Nitrification De-nitrification Nitrogen Fixation Nitrogen fixation is a process where N2 (atmospheric nitrogen) is broken apart and the individual nitrogen atoms are combined with other elements This can occur several ways Lightning Nitrogen Fixing Bacteria (these can be found in the soil, living in symbiotic relationships in the roots of plants, or in bodies of water) Industrially (in plants we heat up N2 and add a catalyst to create ammonia to be used in fertilizers) Decay Animals consume their nitrogen and any excess is excreted in the form of urine and feces Animals get their nitrogen by consuming others, so nitrogen is passed along in the food chain When an organism dies the decomposers break down the dead material and return nitrogen to the soil in the form of ammonia The decomposers also break down our wastes into usable forms Nitrification Some ammonia returned to the soil by decomposers can be taken up by plants roots, but plants prefer nitrogen in the form of nitrates. Nitrifying bacteria convert ammonia to nitrates that plants can use These bacteria live in the soil and in bodies of water De-nitrification De-nitrification is the process by which nitrates are converted back into N2 and returned to the atmosphere Once again bacteria called denitrifying bacteria are responsible for this process Agriculture is responsible for ½ of the nitrogen fixation on Earth, making it very difficult for these poor denitrifying bacteria to keep up!