Nitrogen Cycle Worksheet



Nitrogen Cycle WorksheetIntroduction:All organisms need nitrogen to make DNA, RNA, and proteins, the building blocks of life. Although the Earth’s atmosphere is about 78% nitrogen, most of the nitrogen in the atmosphere occurs primarily in an inert form (N2) that few organisms can use; therefore, in order for plants and animals to be able to use nitrogen, N2 gas must first be converted into a more chemically available form. The movement of nitrogen between the atmosphere, biosphere, and geosphere in different forms is described by the nitrogen cycle. Five main processes cycle nitrogen through the biosphere, atmosphere, and geosphere: nitrogen fixation, assimilation, ammonification, nitrification, and denitrification. Microorganisms, particularly bacteria, play major roles in all of the principal nitrogen transformations. Animals are able to obtain nitrogen through eating plants and animals. Plants have much harder time obtaining nitrogen as they can only absorb nitrogen when it is mixed with oxygen or hydrogen. Nitrogen is mixed with oxygen or hydrogen through a process called nitrogen fixation.There are two ways nitrogen can be fixated:1. Lightening2. Bacteria in the soil or bacteria found in nodules of legumesNitrogen is a necessary component of life as plants need it to grow and animals need it to create DNA. The speed of decomposition is the key to keeping the nitrogen cycle moving as the majority of fixated nitrogen comes from bacteria breaking down dead matter and feces.The warmer an area is the faster decomposition will occur. 5 Main Processes in the Nitrogen Cycle Fixation - Fixation is the first step in the process of making nitrogen usable by plants. Here bacteria change nitrogen into ammonium. Nitrification - this is the process by which ammonium gets changed into nitrates by bacteria. Nitrates are what the plants can then absorb. 14278031972700Assimilation - This is how plants get nitrogen. They absorb nitrates from the soil into their roots. Then the nitrogen gets used in amino acids, nucleic acids, and chlorophyll. Ammonification - This is part of the decaying process. When a plant or animal dies, decomposers like fungi and bacteria turn the nitrogen back in ammonium so it can reenter the nitrogen cycle. Denitrification - Extra nitrogen in the soil gets put back out into the air. There are special bacteria that perform this task as well. Questions:Explain why bacteria are the most important part of the nitrogen cycle. If nearly 78% of the atmosphere is made of nitrogen, how could there be a shortage of nitrogen in soil?How do animals obtain usable nitrogen? Why is it important? Give the two ways nitrogen can be fixated so plants can use it to grow. Explain the problem if too much nitrogen enters an aquatic ecosystem.Explain the statement “Nutrients do not flow in one direction in the ecosystem, they recycle through the ecosystem.” Why is nitrogen important to organisms?What do nitrogen-fixing soil bacteria do to nitrogen in the atmosphere?What job are nitrifying bacteria of the genus Nitrosomonas doing?What is the name of the process by which nitrifying bacteria turn ammonia into nitrates?What is the name of the process by which plants get nitrates out of the soil?After assimilation, the nitrogen becomes part of the plant. When an animal eats the plant, what happens to the nitrogen?After an animal excretes or dies, what will decomposers do to the waste? ................
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