Name:  Pete Nelson

Subject: Biology (Ecology)

Period: 3rd

Approximate Time: 50 minutes

Objectives:

The students will identify the main concepts and ideas of the nitrogen cycle (Biology 7.a)

The students will review key concepts covered up to this point in ecology including food chains, food webs, energy pyramids, and biogeochemical cycles. (Biology 7.a.b.d)

Materials:

Writing utensil, blank paper, whiteboard and whiteboard markers, nitrogen cycle worksheet.

Set:

Yesterday we were able to follow the cyclic pathway of oxygen and carbon in our atmosphere. We also discovered how important these pathways are for our survival. Can anyone highlight the pathway of carbon? Oxygen? (have them start with atmospheric CO2 and O2) Today we will be looking at an equally important cycle, the nitrogen cycle. Nitrogen is especially important because it is used to make amino acids which as you might recall are the building blocks for proteins. Tell them that although 78% of the earth’s atmosphere is nitrogen gas, not many forms can use it in the gas form. So it must be changed to be used and made into amino acids. Today you will identify the main concepts of the nitrogen cycle after which we will review some of the concepts we have covered up to this point.  The nitrogen cycle can be a little more confusing than the other cycles so pay attention closely as we walk through its pathway.

Procedure:

1. For the bell ringer ask them to think of at least three questions about any of the topics covered so far in ecology. Write some of the main ideas on the board. As they are thinking of questions, you should write the vocabulary words for the day on the board as well. Vocabulary words: nodule, nitrogen fixation, nitrification, denitrification.

    Topics to write on board

       - Flow of energy and matter (Food Webs, Energy Pyramids, Biomass Pyramid)

       - Biogeochemical cycles (Water, Carbon, Oxygen, Nitrogen)

2. Begin the cycle with atmospheric nitrogen --> certain types of bacteria that live on nodules on the roots of some plants can take nitrogen gas (N2) and convert it to nitrate through the process of nitrogen fixation. Identify nodule and nitrogen fixation here. Nodule: a swelling on a root containing nitrogen fixing bacteria. Nitrogen fixation: process of converting nitrogen gas to nitrates. Check to see if everyone is with you.

3. Once the nitrogen has been fixed, other bacteria can change ammonia into nitrates and nitrites in a process called nitrification. Define nitrification. Plants can use nitrite and nitrate to make proteins. When consumers eat the plants, the nitrogen is reused to to make proteins for the consumers.  Stop here and ask for any questions. Retrace steps up to this point one more time and ask what would happen if nodules were unable to perform nitrogen fixation.

4. So now the nitrogen cycle has traveled all the way to consumers, how does it circle around?  Two ways: decomposers break down dead organisms and put nitrogen back into the soil in the form of either ammonia, nitrite, or nitrate. Some other types of bacteria in the soil can actually change nitrogen back into its gas form through a process called denitrification. Nitrogen found in in the ocean also goes through denitrification and is put back into the atmosphere. Ask for questions. Pass out worksheet.

5. Go over worksheet if time permits. Otherwise review using their bell ringer questions as a guideline.

Closure:

All right, good job today. We have now gone over the main biogeochemical cycles. And as you can see so far with the food webs and now the biogeochemical cycles, everything is connected and if one part of that process is not functioning right, everything is thrown off. So why is the nitrogen cycle so important? (proteins). We also were able to review the main points that we have covered so far. It is very important that you look over your notes for tomorrow because you will be getting a midway quiz for the ecology section. If you have anymore questions that didn’t get answered feel free to ask me between classes or during lunch.

Assessment/Evaluation:

Objective: The students will identify the main concepts and ideas of the nitrogen cycle (Biology 7.a)

Formal: The teacher will administer a worksheet that will be graded and recorded in the grade book.

Objective: The students will review key concepts covered up to this point in ecology (Biology 7.a.b.d)

Informal: The teacher will field questions pre-written by the students as well as pose additional review questions.