Matter Cycles How are nutrients recycled through ecosystems?

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1 9. In order to continually use the same area of land for agriculture, some farmers apply fertilizers to improve the level of nitrates in the soil. An alternative to this intensive use of fertilizer is to plow the roots of the leguminous plants back into the soil and leave the area unplanted for a season. Why would a farmer use this alternative method and what would be the benefit of turning over the soil and leaving the old plant roots? Leguminous plants have a symbiotic relationship with N-fixing bacteria held in nodules on their roots. They can capture nitrogen from the atmosphere and turn it into nitrates a form plants can use. By plowing these roots into the soil, the nitrogen content in the soil would increase. Make a chart or graphic organizer of the three types of matter we have discussed here. Where is each stored (sinks), where does each enter the food web? How do consumers get this matter? What happens to each type of matter once an organism dies? Why? Matter Cycles How are nutrients recycled through ecosystems? We have learned the importance of recycling our trash. It allows us to use something again for another purpose and prevents the loss of natural resources. But what happens to the waste in nature? Why aren t we up to our necks in natural refuse? Why is there always a supply of water? Why is there oxygen to breathe and carbon dioxide for photosynthesis? The biological molecules in nature are also recycled. This recycling process converts the complex organic compounds to simple, inorganic compounds, which then can be returned to nature to be used again and again. Activating Prior Knowledge (In the space below, brainstorm everything you know or think you know about matter cycles such as carbon, nitrogen and phosphorous). 12 1

2 cv Model 1 The Carbon Cycle 4. What happens when these organisms die? Decomposers that eat them use up even more oxygen from the water 5. Why is there less oxygen when water plants die? Plants make oxygen during photosynthesis Combustion of 6. What can ultimately happen to a lake, river or marine environment if the algae blooms happen repeatedly? The ecosysten collapses and most organisms including fish die 7. Why is it important to be careful about the detergents used in homes? Phosphorous in the detergent can make its way to water where it will cause an algae bloom. Fossil fuels (coal, oil, peat, gas) (Bacteria and fungi) (Diagram adapted from U.S. DOE, Biological and Environmental Research Information System. - May 6, 2012) 1. Model 1 shows the cycling of what type of matter? Carbon 2. Carbon is often in the form of carbon dioxide in certain stages of the matter cycle. What is the chemical formula for carbon dioxide? 8. Plants and animals are part of all of the nutrient cycles through the foods they eat and what eats them (food chains and food webs). Name the three classes of organic compounds (containing carbon) we have talked about so far and explain how the carbon cycle and nitrogen cycle contribute to the usable supplies of these macromolecules. Carbon in the atmosphere is incorporated into plants through photosynthesis. Consumers then eat the plants and so on. Carbon is the main atom in carbohydrates, lipids and proteins. Nitrogen is needed in proteins. Plants take it up from the soil due to decomposition of organisms, lightning or legumes all made possible by bacteria. Consumers eat plants or other animals to get their nitrogen. CO 2 3. Places where matter is stored are called sinks.where is the largest carbon sink? In the deep ocean 2 11

3 Model 4- Limiting Nutrients Nitrogen and Phosphorous 4. How much carbon is stored here (answer to #3)? 37,000 GT 5. Where in the cycle do you think carbon exists as carbon dioxide (in the soil? In the air?). In the air 6. Name two ways that carbon (usually in the form of CO 2 ) enters the atmosphere. Respiration, combustion, air-sea gas exchange 7. What process uses CO2 from the atmosphere? Photosynthesis 8. Describe the process (as much as you know) from #7. Extension Questions 1. What are the sources of extra nitrogen and phosphorous that make their way into waterways? Fertilizers, septic tanks and detergents 2. It seems like adding nutrients to water would be a good thing since it makes more producers. What organism blooms? algae 3. What problems does the bloom cause? Blocks sunlight, plant death which makes less oxygen in water, decomposers take more oxygen out of the water Producers take in carbon dioxide from the air and water through their roots and, using the sun s energy, make glucose. a. What organisms carry out the process in terrestrial (land) ecosystems? Plants b. What organisms carry out the process in marine ecosystems? Phytoplankton c. Do the organisms in 6a. and b. also undergo respiration? Yes! 9. Wastes and dead organisms must be broken down in order for their components to be used again. a. What organisms in the cycle carry out this process? Decomposers mainly bacteria and fungi b. Speculate which organism from 7.a does the most decomposition? Bacteria 10 3

4 c. Speculate: In what form is carbon returned to the atmosphere? Carbon dioxide or CO2 d. What would happen if decomposition did not occur? Dead organisms would pile up and no carbon would be available to new organisms. 10.Not all dead organisms are acted on by decomposers. Instead of being immediately recycled, the carbon from some organisms is kept in a type of long-term storage, or carbon sink. Using Model 2, answer the questions below about this long-term storage. a. What are the two biggest carbon sinks and how many gigatons does each store? Deep ocean (37,000 GT) and fossil fuels (10,000 GT) b. What is the collective term for the carbon sink materials in the earth? Fossil fuels c. How do humans use the materials in that part of the carbon sink? Burn it to heat, run factories, make electricity d. What is the scientific name for the process listed in question 8c? Combustion b. Model 4 indicates the main source of phosphates come from what geologic feature? Rocks c. How do plants get phosphorous? They absorb phosphate in the soil through their roots d. How do you think consumers get their phosphorous? Through their food e. Phosphorous makes up the backbone of DNA, a major part of cell membranes and lots of it is in ATP the energy molecule cells use. Speculate, is there life without phosphorous? No! Read This! Nitrogen and phosphorous are in very low supply in marine and freshwater ecosystems. These ecosystems have evolved around having a limited amount of these elements which limits producer growth. Too many producers cause problems. In addition to sources mentioned below, phosphorous is often found in high levels in laundry and dishwashing detergent. These household uses often make their way to water. Recently, Washington State lowered the allowable amount of phosphorous in detergents to help our water ecosystems List five examples of the process from 8.d in your everyday life. Cars, heating, cooking, lights, electronics 12. How is the majority of electricity generated in the area where you live? Does the process involve the combustion of coal? Check with your teacher if you are not sure.60% fossil fuels, 30% hydroelectric, 10% other mostly renewables. 13.Many of the carbon-based fuels are categorized as fossil fuels because they formed from decayed organisms over millions of 9

5 years. List as many examples of fossil fuels as you can. Model 3- The Phosphorus Cycle Coal, natural gas, oil and its products gas and diesel 14.Which process appears to mostly balance the process of photosynthesis? respiration 15.Does the ocean appear to mostly balance the uptake and release of CO2? Yes. 16.Which process appears mostly unbalanced? Combustion due to human use of fossil fuels 17.How many gigatons of CO2 enter the atmosphere due to human activity? 9 GT per year 18.What processes are taking up some of the CO2 human activity? Photosynthesis (3 GT) and air sea exchange (2 GT) 19. Is it enough to balance human CO2 output? No. Read This! Carbon dioxide (CO 2 ) is one of the greenhouse gases. These gases hold heat energy in the atmosphere, which raises the overall temperature of the Earth. This helps maintain the Earth s biosphere, but also has led to environmental concerns. The more CO 2 in the atmosphere, the higher the Earth s average temperature will be. 27. Model 3 illustrates how nature recycles what type of matter? Phosphorous 28. Phosphorus exists on earth in the form of phosphates (PO 4). a. Unlike the other forms of matter cycling shown in Models 1-3, in what part of the environment is phosphorus not found? The atmosphere (air) 20.How much excess carbon dioxide enters the atmosphere per year due to human activity? 4 GT 21.What are potential global effects of these changes in CO 2 levels? Warming, sea level rise, mass extinction, crop failure, extreme weather, drought, fires, desertification, disease 8 5

6 2 24.In what ways is N2 gas removed from the atmosphere? Lightning and N-fixing bacteria 25.By what process are animal wastes and dead organisms converted to other nitrogen-containing compounds? Decomposition and nitrification 26.What is the only form of nitrogen that nonlegume plants can take in and use? (NOTE: legumes are plants such as beans, peas, & clover) Nitrates 27.What do the denitrifying bacteria do during the denitrifying process? They convert nitrates in the soil back to nitrogen gas in the atmosphere. 28.How do plants get their nitrogen? They absorb it through roots from nitrates in soil or legumes have N- fixing bacteria in nodules on roots. 22.Model 2 illustrates how nature recycles what type of matter? Nitrogen 23.Name three types of bacteria involved in the nitrogen cycle. N-fixing bacteria, nitrifying bacteria, denitrifying bacteria Read This! Nitrification is a process by which specific bacteria convert different forms of Nitrogen-containing compounds (like ammonia, NH3) in the soil to nitrites (NO2) and nitrates (NO3). This process is important since the only forms of nitrogen that are usable by plants to build their proteins are the nitrates Why do plants need nitrogen? To build proteins mainly 30.Where do you think consumers get their nitrogen? From their food. 31. For emphasis: What organism turns nitrogen into a form plants can use? BACTERIA! 32.If the number of nitrifying bacteria decreased, what effect would this have on the nitrogen cycle and what type of compounds would accumulate as a result? No nitrates would form, leaving ammonia and other N-containing compounds in soil. Plants would die.