Chapter 16 Section 3 Cycling of Materials in Ecosystems Biogeochemical Cycles

1. Chapter 16 Section 3 Cycling of Materials in Ecosystems • Biogeochemical Cycles • the physical parts of an ecosystem cycle continuously • producers → herbivores → carnivores → top carnivores → die and decay • both organic and inorganic elements are recycled • Biogeochemical cycle is a pathway where substances enter or pass through a living organism for a period of time and then is returned to the nonliving environment. - Water, Carbon, Nitrogen & Phosphorous are the most important substances that are important for the health of an ecosystem - In a biogeochemical cycle, there is more of a substance in the nonliving (abiotic) part of the ecosystem than in the living (biotic) part of the ecosystem

2. B. Water Cycle - water has the greatest influence on the ecosystem’s inhabitants -In the nonliving portion of the water cycle - water vapor in the atmosphere condenses forming clouds which can fall to the earth as rain or snow - rainwater gets into the soil and becomes part of the groundwater (water beneath the surface of the earth) - water on the surface of the earth can evaporate and re- enter the atmosphere. - in aquatic ecosystems, the nonliving aspect of the water cycle is the most important -In the living portion of the water cycle - water is taken up by plants which can move through the plant and then is released back into the atmosphere in a process known as transpiration - in land ecosystems, the living portion of the water cycle can be as important as the nonliving portion

4. C. Carbon Cycle - In the living portion of the cycle, carbon dioxide in the air is taken in by plants (photosynthetic organisms)→ then the carbon is converted into carbohydrates - Carbon can be returned to the nonliving portion of the cycle by: a. Cellular respiration- the use of carbohydrates by the cells of an organism to produce energy that they need to function → this releases carbon dioxide back into the atmosphere b. Combustion- or burning → the burning of wood can release carbon into the air (forest fires) - fossil fuels (oil, coal, natural gas) when burned releases carbon

5. c. Erosion- since the shells of many marine organisms are made of calcium carbonate (limestone) when the animal dies the shell is left behind and slowly erodes over time releasing the carbon products

6. D. Phosphorous & Nitrogen Cycles - nitrogen and phosphorous are needed to build proteins and nucleic acids (DNA & RNA) - phosphorous is important in ATP (energy source for cells) - phosphorous is found in the soil and rocks which can be dissolved in water and absorbed by plants which are then eaten by animals

7. - the atmosphere is 78 % nitrogen gas, N2 which is not usable by most living organisms → the nitrogen gas has to be converted by bacteria into a form that is usable - the ability of bacteria to convert nitrogen gas is called nitrogen fixation -There are 4 stages in the nitrogen cycle: 1) Assimilation- is the absorption and incorporation of nitrogen into organic compounds by plants 2) Ammonification- is the production of ammonia by bacteria during the decay of organic matter 3) Nitrification- is the production of nitrate from ammonia 4) Denitrification- is the conversion of nitrate to nitrogen gas by other bacteria - most farmers add ammonia and nitrates to the soil to enhance the grow of plants