Name: _________________________________________________ Period: _____________

Nitrogen Cycle Close Read

Earth’s atmosphere is approximately 70% nitrogen (N2). Unfortunately, consumers and producers cannot generally

make use of this gas directly. Some organisms have adapted to transforming nitrogen into more usable forms that

producers and consumers can use directly.

1. According to the diagram, which terrestrial organisms are able to obtain atmospheric nitrogen? ____________

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2. This atmospheric nitrogen must be converted to what molecule? ______________________________________

3. What other organism(s) add this molecule to the soil? _______________________________________________

4. What transformations must occur before plants can use the nitrogen? _________________________________

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5. What organism carries out the transformations addressed above? _____________________________________

6. How does nitrogen enter into plants? ____________________________________________________________

7. How does nitrogen enter into animals? ___________________________________________________________

8. How does nitrogen get back into the atmosphere?__________________________________________________

9. How must carnivores obtain their nitrogen? _______________________________________________________

Name: _________________________________________________ Period: _____________

Nitrogen Cycle Close Read

1. How do terrestrial and aquatic organisms obtain nitrogen? ________________________________________

2. What part of the plant/algae contains nitrogen? __________________

3. According to the diagram, which terrestrial organisms obtain and convert atmospheric nitrogen? ____________

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4. According to the diagram, which aquatic organisms obtain and convert atmospheric nitrogen? ______________

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5. In what two ways do animals return nitrogen to the soil? _____________________________________________

6. How do plants return nitrogen to the soil? _________________________________________________________

7. Refer to the previous figure if necessary. What organisms process dead organic matter? ___________________

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8. What type of bacteria puts nitrogen back into the atmosphere? _______________________________________

9. Use the internet to discover the role of lightning in this cycle: _________________________________________

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Name: _________________________________________________ Period: _____________

Nitrogen Cycle Close Read

Answer the following questions by applying what you have already learned about the nitrogen cycle from the previous 2

figures.

1. What is item 1 showing in relation to the fish? _____________________________________________________

2. What is item 2 showing in relation to the fish? _____________________________________________________

3. What organisms are represented in items 3, 4 and 7? ________________________________________________

4. A step is missing in the diagram above. Before NH3 can be processed it must be converted into which molecule?

(Carefully review figure 1 to find the answer). ______________________________________________________

5. What specific organism carries out this process? (Using Figure 1). ______________________________________

6. What happens to the NO3 once it has been formed? _________________________________________________

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7. What is the purpose of the organisms at number 7? How do they fit in to this cycle? ______________________

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8. What is item 6 representing and how is it tied to images 8 and 9? ______________________________________

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Name: _________________________________________________ Period: _____________

Nitrogen Cycle Close Read

Answer the following questions after reading the infographic above.

1. Provide 2 reasons that support a balance, or homeostatsis, of nitrogen compounds in an ecosystem.

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2. What two nitrogen sources are cited above? ______________________________________________________

3. What is the third nitrogen source that is missing from the infographic? _________________________________

4. What specific nitrogen source is toxic? __________________ What is it converted into? ___________________

What organism does this? ______________________________________________________________________

What is the process called? _____________________________________________________________________

5. What is this new chemical changed into? _________________ What organism does this? ___________________

Why is this a necessary step of the cycle? __________________________________________________________

6. What allows the cycle to continue? ______________________________________________________________

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Name: _________________________________ Nitrogen Cycle Close Read Period: _____________

Animals and Nutrient Cycling in Terrestrial Ecosystems

Burrowing animals, such as North American prairie dogs and pocket gophers as well as meerkats in Africa, affect local plant diversity and are often considered keystone species because of their ability to change the ecosystem. These burrowers also alter the distribution and abundance of nitrogen within their ecosystems.

Pocket gophers can significantly affect their ecosystems because their mounds may cover as much as 25% to 30% of the ground surface. This deposition represents a massive reorganization of soils and a substantial energy investment, since the cost of burrowing is 360 to 3,400 times that of above ground movements. Estimates of the amount of soil deposited in mounds by gophers range from 10,000 to 85,000 kg per hectare per year.

Nancy Huntley and Richard Inouye (1988) found that pocket gophers altered the nitrogen cycle at the Cedar Creek Natural History Area in Minnesota by bringing nitrogen-poor subsoil to the surface (Figure 1). The result was greater horizontal heterogeneity in nitrogen availability and greater heterogeneity in light penetration. These effects on the nitrogen cycle in prairie ecosystems help explain some of the positive influences that pocket gophers have on plant diversity.

April Whicker and James Detling (1988) found that the feeding activities of prairie dogs also influence the distribution of nutrients within prairie ecosystems. This should not be surprising since these researchers estimate that prairie dogs consume or waste 60% to 80% of the net annual production from the grass-dominated areas around their colonies. One result of this heavy

grazing is that aboveground biomass is reduced by 33% to 67% and the young grass tissue that remains is higher in nitrogen content (Figure 2). This higher nitrogen content may influence the behavior of bison, which spend a disproportionate amount of their time grazing near prairie dog colonies.

Bison and other large herbivorous mammals, such as

moose and African water buffalo, may also influence the

cycling of nutrients within terrestrial ecosystems. Sam

McNaughton and his colleagues (1988) report a positive

relationship between grazing intensity and the rate of

turnover of plant biomass in the Serengeti Plain of eastern

Africa. Studies suggest that increased grazing increases the

rate of nutrient cycling. How will nutrient cycling occur in the

absence of grazing by these large herbivores? Without grazing

and the kicking up of the soil by large herbivores, nutrient

cycling occurs more slowly through decomposition and

through the feeding on grasses by the small herbivores

discussed above.

Continue to the back to complete the C-E-R.

FIGURE 1. Pocket gophers and ecosystem structure (data from

Huntley and Inouye 1988).

FIGURE 2. Early season nitrogen content of grasses growing on uncolonized prairie and on a young prairie dog colony (data from

Whicker and Detling 1988).

CLAIM: State a claim that explains the role of burrowing animals in the nitrogen cycle: ___________________________

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EVIDENCE: Provide evidence from the information provided that supports your claim and explains how you know this:

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REASONING: Explain why your evidence supports your claim: _______________________________________________

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Name: _________________________________ Nitrogen Cycle Close Read Period: _____________

Termites Help Build Savanna Societies by Adam Mann

The great animals of the African savanna may owe a debt of gratitude to the humble termite. New research reveals that the dirt mounds the insects build sustain significantly more shrubs, fruit-bearing trees, bugs, and animals, such as elephants, cheetahs, and zebras, than do surrounding areas. It's a “very satisfying demonstration” of how the termites “support an entire ecosystem,” says physiologist Scott Turner of the State University of New York College of Environmental Science and Forestry in Syracuse who has studied termite mounds in Namibia.

Most of the African savanna is comprised of stiff, dry dirt, but every 50 meters or so you'll come across a foot-high mound covered in green grass. African termites (Odontotermes) can spend centuries creating the mounds. Like earthworms on farmland, the termites aerate the surrounding soil, allowing more water to penetrate. Scientists knew that this activity, along with termite droppings, creates highly fertile patches of earth with a higher percentage of nitrogen and phosphorous than ground farther away. Such conditions invite the growth of grasses, shrubs, and trees. But just how much of an impact do these termites have on their ecosystem?

To find out, researchers conducted field surveys and developed simulations of the savanna. They found that acacia trees, which dominate this landscape, grow 60% more new shoots near termite mounds and are more than twice as likely to bear fruit as those far away. The acacias and other plants attract insects: When the researchers set up sticky traps to collect beetles, flies, and other bugs, the side of each trap that faced the mound-collected 40% more insects than the side facing away. These insects, in turn, draw in larger animals, such as geckos. Geckos were more than twice as likely to be found on trees near mounds than on those far away, the researchers report.

The relatively high amount of grass on and near the mounds is also a magnet for large animals. Grazers such as zebra and buffalo congregate in these spots, fertilizing them further with their dung, says one of the paper’s co-authors, community ecologist Todd Palmer of the University of Florida, Gainesville. Even the way the termites organize their mounds likely affects the savanna ecosystem, the team found. The insects space their mounds 20 to 120 meters from one another in a regular “polka dot” pattern across the landscape. Such a pattern maximally utilizes the savanna’s resources and attracts far more plants, insects, and gecko communities than randomly spaced mounds, according to a computer simulation run by the team. Turner points out that African farmers often try to eradicate these termites, which they believe compete with cattle for grasses. He hopes the new work will help convince farmers that it's better to keep the termites around.

Continue to the back to complete the C-E-R.

CLAIM: State a claim that explains the role of insects like termites in the nitrogen cycle: __________________________

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EVIDENCE: Provide evidence from the information provided that supports your claim and explains how you know this:

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REASONING: Explain why your evidence supports your claim: _______________________________________________

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Name: _________________________________ Nitrogen Cycle Close Read Period: _____________

Sciencespeak: Whale Pump

Whales can poop almost anywhere they want. They have the entire ocean to relieve themselves in, so most of the planet can theoretically be their toilet. Yet, despite having a near-universal lavatory pass, cetaceans often relieve themselves near the surface. In the words of marine biologists Joe Roman and James McCarthy, many whales feed in the deeper tiers of the sea to then return to the surface and release “flocculent fecal plumes” – cetacean clouds that may create what Roman and McCarthy call a “whale pump“.

The researchers laid out their logic in a 2010 PLOS ONE paper. Our planet’s seas are constantly recycling themselves. Showers of marine snow send organic matter cascading down to the sea floor, and zooplankton excrete poop full of nitrogen, phosphorus, and iron in deep water as they go about their regular up-and-down migration through the water column. This is a downward “pump” of resources. But other organisms can also bring some of these elements back from the deep. Whales and other marine mammals, Roman and McCarthy hypothesized, replenish the surface waters with their excrement.

The researchers based their case on an array of cetacean observations. Whales must surface to breathe, the physiological consequences of diving and surfacing make it likely that marine mammals will let it all go near the surface, and observations of crappy clouds have shown that they dissipate through the water rather than sink. And even though whales sometimes feed in the upper portion of the sea, they often dive deeper to reach dense pockets of fish and invertebrates. These hard-to-reach resources are key to Roman and McCarthy’s proposal. Whales feed on deepwater prey that are taking up elements from far below. After a bit of digestion, the whales then jettison some of those elements in shallower waters and leave plankton to recycle the slightly-used nitrogen.

Seals and sea lions might do their share, too. If you’ve ever smelled a pinniped colony at the height of breeding season, you’ve probably cursed your sense of smell. What the blubbery mammals spill onto the shore can be washed back into the sea, emanating the ecological reek of seal-processed fish and squid returning nitrogen to the water.

It’s one thing to theorize from an armchair, though, and quite another to get out on a boat and collect some whale feces. That’s exactly what Roman and McCarthy did to further investigate their idea, taking 16 samples of billowy poops from the Gulf of Maine. All of the samples contained significantly more ammonium – a nitrogen-rich waste product – than the surrounding water. Based on these analyses, Roman and McCarthy suggested that whales could be responsible for dumping 23,000 metric tons of nitrogen into the Gulf of Maine every year. The amount was probably even higher before commercial whaling tried to sate its hunger for the massive mammals.

And seagoing beasts may only be continuing a trend that was in place long before they took to the water. At a recent PaleoFest at the Burpee Museum of Natural History, paleontologist Ryosuke Motani pointed out that marine reptiles were doing the dive-and-surface shuffle hundreds of millions of years before the hoofed ancestors of whales were even a glimmer in natural selection’s eye. Some of these marine reptiles – such as the fish-like ichthyosaurs – were some of the first deep-divers, Motani pointed out, and they could have played an ecological role similar to what Roman and McCarthy have suggested for whales. So perhaps it’s too narrow to talk about “whale pumps” or “marine reptile pumps” feeding the seas. Those are just more academically-acceptable ways of talking about “poop pumps”. Continue to the back to complete the C-E-R.

CLAIM: State a claim that explains the role of large animals like whales in the nitrogen cycle: ______________________

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EVIDENCE: Provide evidence from the information provided that supports your claim and explains how you know this:

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REASONING: Explain why your evidence supports your claim: _______________________________________________

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Name: _________________________________________________ Period: _____________

Nitrogen Cycle Close Read

What Is the Nitrogen Cycling Process in an Aquarium? The 3 Components and Phases of the Nitrogen Cycle Process

By Stan & Debbie Hauter

Keeping an aquarium serves as an efficient model of how nutrients cycle through an ecosystem as many of the components must occur the same way they would in nature. The nitrogen cycle of any aquarium is a chain reaction in nature resulting in the birth of various types of nitrifying bacteria, each with their own job to do. Each new bacteria born consumes the previous one, and in turn, gives birth to the next bacteria. The three components involved to make this happen are ammonia (NH³ or NH³+4), nitrite (NO²), and nitrate (NO³).

In general, the nitrogen cycling process usually takes about 30 days, but there is no exact time frame for this process to complete its task, as each aquarium is different. Factors such as how many fish, other livestock, and organic matter is present in the tank can vary the completion time, one way or the other. Testing your aquarium water during cycling is very important, as this will tell you what phase the aquarium is in at any given time throughout the process.

It should be noted here that there are methods to speed up the nitrogen cycling process, some of which can actually cycle the tank in as little as one day.

The 3 Components & Phases:

Phase 1 - Ammonia (NH³ or NH³+4)

The first component needed in the chain is ammonia, and it is only during the cycling process that elevated ammonia readings should be present in an aquarium. Once ammonia begins to accumulate in the aquarium, the cycling process begins. So where do you get the ammonia from? It is produced by such things as fish and other livestock waste, excess food, and decaying organic matter from both animals and plants. Now putting live animals into a tank for the purpose of cycling is not easy, because they are exposed to highly toxic levels of ammonia and nitrite during the process.

However, without ammonia present, the cycle cannot begin, and if ammonia is removed, or the supply is disrupted during cycling, the process stops. As you see the ammonia level rise during the cycling period, if you think by adding an ammonia destroyer or doing a water change to bring it down is helping, it isn't! You are only delaying the cycling process and preventing it from completing its mission. If you use fish to cycle an aquarium, it's a catch 22! You don't want to put the animals in harm's way by exposing them to toxic elements, but you need their waste as the ammonia source to get the job done. The good news is there are alternatives to cycling a new tank without having to use fish, as well as ways to help speed up the nitrogen cycling process.

Regardless of what method you use to cycle a new aquarium, the process is the same. Ammonia occurs in two states depending on the water pH. NH³, the unionized state, is more toxic than NH³+4, the ionized state because it can invade the body tissue of marine animals much easier. Almost all free ammonia in sea water with a normal pH is in the ionized state, thus less toxic. As pH rises, the less toxic ionized state decreases and the more toxic unionized state increases. For example, a toxic level of ammonia as NH³ may be present with a pH of 8.4 being lethal, but the same level of ammonia as NH³+4 with a pH of 7.8 may be tolerated. Higher tank temperatures can also affect the toxicity of ammonia.

Phase 2 - Nitrite (NO2)

At about ten days into the cycle, the nitrifying bacteria that convert ammonia into nitrite, Nitrosomonas, should begin to appear and build. Just like ammonia, nitrite can be toxic and harmful to marine animals even at lower levels, and without nitrite present, the cycling process cannot complete itself. Nitrite will continue to rise to a high level of about 15 ppm, the most critical stage, and at about day 25 the level should begin to fall off, although it's quite possible to run on for another 10 days. Most likely the nitrite reading will peak and fall off to less than 2 or 3 ppm by about day 30, and shortly thereafter to zero.

If it does not, don't worry, it should drop sometime within the next 10 days or so.

Phase 3 - Nitrate (NO3)

Now that the ammonia has given birth to nitrite, the nitrite, in turn, give birth to the third and final nitrifying bacteria, nitrobacters. These bacteria are living entities that require oxygen and food (an ammonia source) to survive, grow on the surfaces of everything in the tank, and the waste from nitrobacter are shown in the form of nitrate with a test kit. When nitrate readings begin to increase, you can tell that these beneficial nitrifying bacteria are starting to establish themselves, which is what you have painstakingly been going through the cycling process to achieve.

CLAIM: State a claim that explains the role of these specialized bacteria in the nitrogen cycle: _____________________

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EVIDENCE: Provide evidence from the information provided that supports your claim and explains how you know this:

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REASONING: Explain why your evidence supports your claim: _______________________________________________

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