Energy Flow through Organisms


Name: Lindsay Husta

Title of Lesson: Energy Flow through Organisms

Date of Lesson:

Length of Lesson: 55 minutes

Description of Class:

            Name of Course: Biology

            Grade Level: 9-12

            Honors or Regular: Both

Source of the Lesson:


TEKS Addressed:

(2) Scientific processes. The student uses scientific inquiry methods during field and laboratory investigations. The student is expected to:

(D) communicate valid conclusions; and

(E) construct graphs, tables, maps, and charts using tools including computers to organize, examine, and evaluate data.

(11)  Science concepts. The student knows that organisms maintain homeostasis. The student is expected to:

 (D)  summarize the role of microorganisms in maintaining and disrupting equilibrium including diseases in plants and animals and decay in an ecosystem.

(12)  Science concepts. The student knows that interdependence and interactions occur within an ecosystem. The student is expected to:

(A)  analyze the flow of energy through various cycles including the carbon, oxygen, nitrogen, and water cycles;

(D)  identify and illustrate that long-term survival of species is dependent on a resource base that may be limited; and

The Lesson:

I.                    Overview:

The students will construct the nitrogen cycle using clues about the pools and processes, read and illustrate a story about the nitrogen cycle, and discuss possible alterations to the cycle in the lakes they are studying.

II.                 Performance or Learner Objectives:

Students will be able to:

·           Draw the nitrogen cycle with pools and processes that change N from one form to another.

·           Classify pools as (a)biotic and (un)available.

·           Classify processes as energy releasing or requiring and oxic or anoxic.

·           Hypothesize affects of various changes in pool size on the nitrogen cycle.



III.               Resources, materials, and supplies needed:

Transparency or blackboard for Common/Unique



Colored pencils for illustrating

IV.              Safety considerations: Keep scissors pointing down while walking with them

V.                 Supplementary materials, handouts:

·        “The exciting cycle of nitrogen”

·        Clue cards

·        Board (may need to be enlarged)


Teacher Says/Does

Student Says/Does


Common/unique game with different forms of nitrogen.


Mantra of the lesson:  There are pools and processes.  Pools are forms nitrogen takes and can be described as (in)organic and (un)available.  Processes are chemical reactions that change one form to another.


Writes down a form of nitrogen that s/he doesn’t think any other group has.

Evaluate:  How many forms of nitrogen did they come up with?  Are they familiar with the common naturally occurring forms.


Mantra of the lesson:  There are pools and processes.  Pools are forms nitrogen takes and can be described as (in)organic and (un)available.  Processes are chemical reactions that change one form to another.


Make sure the students are aware of the following forms of nitrogen:

Nitrite (NO2), Nitrate (NO3), Nitrogen gases (NO, N2O, N2), Ammonia (NH3), organic forms (a.a., proteins, oil, coal)


Pass out the cards and game boards.

Have the students cut out the cards


Classify the types/forms of nitrogen into a cuadrat of organic and inorganic vs available and unavailable and have students write the information on each card.

How does the nitrogen get from one form to the other?

We can classify these reactions in two ways.  Some need oxygen and some need the absence of oxygen.  An environment with oxygen is called oxic.  An environment with no oxygen is called anoxic.

Please record the following information on your cards as you will need it.

Assimilatory nitrogen reduction, ammonification, and nitrification happen in the presence of oxygen, while nitrogen fixation and denitrification happen in anoxic regions. 

Some chemical reactions require energy while others release them.  Think of those that require energy as being big bowling balls that you have to lug up some stairs where as the chemical reactions that release energy are like bowling balls at the top of stairs that roll down with no work at all.  Assimilatory nitrogen reductionm, denitrification, and nitrogen fixations are all like carrying a huge weight uphill while nitrification is like rolling the ball down hill.  Ammonification doesn’t use or release energy.  Imagine yourself sitting at the top of a hill painting your bowling ball.  You have changed it, but haven’t pushed it uphill or rolled it downhill. 

Spot check students cards to make sure they have been filling them out. 















Student cuts out cards





Students write (in)organic and (un)available on each form of nitrogen.



Chemical reactions

Students listen









Students write (an)oxic or presence/ absence of oxygen on each chemical reaction card



Students write energy expended/released/

no change on each chemical reaction card



















Evaluate: Have students filled their cards.  Do they understand that reactions can be classified?  If they don’t compare processes to methods of travel: easy vs hard, with a machine or without.


Mantra of the lesson:  There are pools and processes.  Pools are forms nitrogen takes and can be described as (in)organic and (un)available.  Processes are chemical reactions that change one form to another.


Now we are going to use the clues on the cards to diagram the nitrogen cycle.  The pools or forms of nitrogen need to be placed in the correct environmental conditions (oxic vs an oxic)  and in the organic or inorganic column.  They also need to be placed correctly with respect to the y-axis which represents potential energy (where is the bowling ball).

Then you need to determine which process causes which form change.  Use the energy and environmental clues we wrote down.  Use arrows to indicate direction of reaction.









Students work in groups to determine the nitrogen cycle.  They place pools according to environment and use reaction reactants and products to figure out if a pool is high in potential energy or low.









Evaluate: Are students able to figure out the nitrogen cycle?


Mantra of the lesson:  There are pools and processes.  Pools are forms nitrogen takes and can be described as (in)organic and (un)available.  Processes are chemical reactions that change one form to another.


Have students read “The Exciting Cycle of Nitrogen” and create a comic book illustrating that story or another version which is based on the nitrogen cycle.  The panes should include important places (forms of nitrogen) and methods of travel (reactions)


-Day 2-

Have students switch comics with other 2-3 other students.  Have people who created original stories share their version.  Students should check each other for accuracy.


Let’s talk about our aquatic lake systems that we are studying.  What are the primary producers that are performing assimilatory nitrogen reduction (nitrogen uptake)?

Where does ammonification take place?


From your research, what is eutrophication?

What are some effects?





Where do these extra nutrients come from?

What form of nitrogen is it?


How would pool sizes and processes change in eutrophic vs oligotrophic lakes?






Using your knowledge of the nitrogen cycle, what would you do to reduce human impact on lakes?


Hypothesize about the nitrogen dynamics in the lakes they are studying from the internet data.  Give them time to write about it and create nitrogen cycle diagrams as they are required for their papers.










Students read story and create a comic book in groups of 3.  They are encouraged to create their own story.







Students share their books with others and check each other for accuracy of portrayal.  They are respectful of other artistic interpretations and ideas.




Phytoplankton, algae, aquatic plants.




All eukaryotes-plants, animals, decaying matter…


Addition of nutrients

increased N and P, algal blooms, decreased DO, death of animals and plants, bacterial bloom, further depletion of DO (anoxic environment), stagnation and swamp formation

Runoff from fertilizers, organic waste


NH3, NO2, NO3


Any number of logical scenarios could happen including: increased assimilation due to influx of nutrients.  Then after things start dying, increased ammonification due to decomposition.  When things go to anoxic conditions, most of the nitrogen cycling is through nitrification, denitrification, and N-fixing.

Reduce runoff and other nutrient input.




Students work on with their own lakes to decide what is going on in their system.  They may also think about what went on in their experiment.

Evaluate: A little N cycle quiz in which they take out a sheet of paper and tell me what they know.  By now they should be well versed in the mantra of the lesson.  Besides that any specific pool and process names or type of organism which catalyzes the reaction would be great.


The exciting cycle of nitrogen!!!


You awake with a tremendous headache and the unsettling feeling of having been here before.  With a Herculean strength you unglue eyelids, and when the world comes into focus, you realize that you have no idea where you are.  Gradually, the gang of tiny jackhammers in your skull quiet, and you realize that you are quite cold.  You get up, look around and espy a sign.  “Ammonia” it reads.  You stare in disbelief.  “Can it be true?  Am I really on this mountaintop again?  How did I get here this time?”  Suddenly you see a sled sitting in the snow.  You decide that a sled ride would be the quickest way down, so you hop on.  The sled picks up speed.  Niiiiiiiitriiiiifiiiicaaaaaaaaaaation,” you squeal delightedly on the ride.  You pass right through the tiny alpine hamlet(town) of Nitrite.  However, the terrain flattens out in the quaint village of Nitrate.  There is only a single street, but it forks.  Do you veer right towards the anoxic swamp or left towards oxygen rich lair of the primary producer monster?  If you choose the anoxic swamp read on, if you choose to brave the horrors of the primary producer monster skip to the last paragraph.


A brave soul! You chose the anoxic swamp and ocean sediments home to the ferocious cyanobacteria and nitrogen fixing bacteria.  I hope you can take the heat.  Everything is strange here.  At first it’s a land of carnival mirrors.  You pass through the quaint village of Nitrate and then up the hill to the alpine hamlet of Nitrite.  It’s hard work trudging uphill especially since there is no oxygen.  A rickshaw named Denitrification comes along.  Its hardworking driver, bacteria (Pseudomonas denitrificans) pulls you up a large hill.  Finally, you reach the thriving metropolis of Molecular Nitrogen.  Just as you are about to relax after your long arduous journey, you are recognized by the notorious thugs, Nitrogen fixing bacteria and cyanobacteria.  They have been up to no good since the time of the primordial soup, and today is no exception.  “We’ll FIX you!” they shout as they throw you into the Nitrogen Fixation Catapult-o-matic 3000.  You hear the snap of the machine, and then a hard thud as you hit the cold snow.  You pass out…Go to beginning.


            To scared of the swamp?  Think you can overpower the primary producer monster?  HA.  Good luck with that.  Almost as soon as you veer off into the seemingly pleasant and well oxygenated soils and sediments of the world, you are sucked up the giant vacuum tube of a plant monster roots or if you ended up in the water column, a ferocious phytoplankton.  You are incorporated into an amino acid where you spend your days as part of a busy protein.  And, when your trusty protein is worked to exhaustion, it is simply hydrolysed (broken apart).  Broken down by Ammonification you are unneeded, and in fact poisonous to the primary producer monster, so it excretes you, on the top of a tall, cold mountain.  It seem familiar, but then you lose consciousness.  Go to the beginning.


Assimilatory N reduction

(aka N uptake)


NO3-àa.a., proteins

By primary producers




Organic Nitrogen

Ex. Proteins





Nitrogen Gases

Ex. N2, NO2, NO



___________________ ___________________

N fixation



By bacteria











By bacteria



Nitrite (NO2-) and Nitrate (NO3-)





Ammonia (NH4)







NO2- & NO3-àNH3

By bacteria




Text Box: OrganicText Box: InorganicText Box: OxicText Box: AnoxicGame board