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Name __________________________________ Date _________________________ Period _______
Nitrogen Cycle Lab Make-up Assignment
PART 1: Ecosystem Recycling
Read the passage below, which covers topics from your textbook. Answer the questions that follow.
All organisms need nitrogen to make proteins
ammonia, NH3, which in soil becomes ammonium, NH41+,.
and nucleic acids. The complex pathway that nitrogen
This process is known as ammonification. Through
follows within an ecosystem is called the nitrogen cycle.
ammonification, nitrogen that would otherwise be lost is
However, most plants can use nitrogen only in the form of
reintroduced into the ecosystem. Bacteria in the soil take
nitrate. The process of converting nitrogen gas to nitrate is
up the ammonium and oxidize it into nitrites, NO21-, and
called nitrogen fixation. Organisms rely on the actions of
nitrates, NO31-, This process is called nitrification. The
nitrogen-fixing bacteria that are able to transform nitrogen
erosion of nitrate-rich rocks also releases nitrates into an
gas into a usable form. Nitrogen-fixing bacteria live in the
ecosystem. Plants use nitrates to form amino acids.
soil and in the roots of some kinds of plants, such as
beans, peas, clover, and alfalfa.
Decomposers break down the corpses and wastes of
organisms and release the nitrogen they contain as
bacteria break down nitrates and release nitrogen gas
Write your answers in the spaces provided.
1. Order the statements to show the steps by which nitrogen is recycled within an ecosystem. Write “1” on the line in
front of the statement that describes what happens first. Write “2” on the line in front of the statement that describes
what happens next, and so on.
_______ a. Bacteria in the soil oxidize the ammonia into nitrites and nitrates.
_______ b. Plants use nitrates to form amino acids.
_______ c. Decomposers break down corpses and wastes of organisms.
_______ d. Nitrogen is released into the ecosystem as ammonia.
Complete the sentence by logically finishing the thought.
2. The process by which bacteria in soil oxidize ammonium to form nitrates and nitrites is known as __________________.
3. Denitrification occurs when ________________________break down nitrates and release nitrogen gas back into the
4. Nitrogen fixation is the process of converting ________________________to nitrate.
5. The organisms that convert nitrogen gas to nitrate are known as ______________________________________________.
6. The nitrogen cycle is the pathway through which nitrogen flows within a(n) ____________________________.
Read the question and write your answer in the space provided.
7. The suffix -tion means “the act or state of.” How does knowledge of this word part aid in decoding the word
ammonification? ________________________________________________________________________________________
Choose the letter of the phrase that best completes the statement.
______ 8.
All organisms need nitrogen to
A. make proteins.
C. produce ammonia.
B. make nucleic acids.
D. both A and B
PART 2: Lab Simulation
1. Read the text box entitled “Things a Nitrogen Atom Experienced.”
2. Create a drawing in the “Nitrogen Cycle Drawing” box according to the SPECIFIC things that
the nitrogen atom experienced. Use drawings, arrows, process names (such as nitrogen
fixation, etc.), and organisms as necessary in the space below.
3. By each picture WRITE a SUMMARY of what the N atom experienced there.
4. Try to incorporate as many of the following terms as possible by writing them over the
arrows you draw: nitrogen fixation, denitrification, runoff, nitrification, excretion,
precipitation, decomposition, digestion, incorporation, evaporation, and percolation. Each
arrow should have a term over it.
Things a Nitrogen Atom Experienced
N atom is caught in a raindrop and falls to the ground.
N atom runs from the ground to a stream and travels down a stream into a pond.
N atom is converted into nitrates by algae and taken up in aquatic plants.
N atom is eaten by a fish in the pond.
fish dies during a drought and the N atom is returned to the soil by decomposers.
N atom is released by bacteria into the atmosphere through denitrification.