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### Teacher Notes

Objectives: Discover the skills necessary for desert field studies. Apply geometry, drawing on a grid and scouting skills.

Materials:

 *Graph paper *20p nails *Meter Sticks *Magnetic compass *Plastic Ziploc Bags for soil sample. (Leave it open to dry it out.) *String or twine (*50 Meter Reel Tapes would be ideal, but we will use-)

Following the spirit of constructivist teaching, we will first experience and observe a plot of land which we will use as a basis to ask several questions and create a need to know. Then we can help sculpt science concepts and vocabulary as well as bring in other disciplines like math or social studies. The activity begins with the skills of ecology. We will first look at a site in a measured, scientific way and then build up the concepts around what we see.

The tools of ecology are just a systematic way to "see" what is right in front of us much like a microscope helps us to see. This system gives us the "magnification" to see tiny differences that we might feel but cannot quantify.

Some of the ecology tools we could use are measuring, mapping, imaging, observing, comparing, keeping track of what we observed, and math. Many ecologists also use computer models to predict the interactions between groups of organisms. The computer toy "SimLife" is an ecological model.

A good overview of the research that has gone into the desert around the turn of the century is William McGinnies (1987) Discovering the Desert. It takes the history of Tumamoc Hill and intertwines many scientists' work into an overview of the ecology of the Sonoran Desert.

Using groups of two to four students, suggest the tasks of artist, measurer, navigator, keeper of the journals. Everyone needs to have eyes for the discerning of the plants.

Please refer to A-2 for assessment

Question: Are there plant invaders in the school yard? If so, what percentage of ground cover are they?

For our lesson, we will consider Bermuda grass as the "native" and all other plants as "invaders".

Set up a rectangle using diagonals (Pythagorean theorem and square roots).

 It doesn't matter what the lengths are of the rectangle, once both diagonals are equal, you have right angles.

NOW MAKE A MAP OF YOUR RECTANGLE.

 How easy it is to determine the diameter of each plant? It might be easier to plot the bare spots. Are there any plants overhanging each other? - Each plant must be considered, so overhanging plants will take up the same space. There might be over 100% coverage of a plot

How might you find the spot again to either check their work or come back and see if there are any changes? (No permanent spikes because of the lawn mowers.) Find the triangulation of landmarks:

 Use the three most prominent landmarks that form a rough equilateral triangle from your plot. With the magnetic compass, train the moveable circle on the Northward pointing arrow. Make sure that nothing metallic is underneath the compass or it will give a false reading. (Personal experience) Holding the inner circle still, move the outer flat piece until it points to one of the landmarks. This will give you a reading in degrees. Write down the land mark and how many degrees from North it is.

How do we tell what plants are which on the plot? On the drawing? A person needs to know a little bit about the species of plants in your plot. You can use different colored pencils on the drawing of the plot.