Math Graphing- Desert Saguaro Cactus Growth

Teacher of Lesson: Teresa Moore
Grade Level: 2/3

Objectives:

Materials:

Procedures:

  1. Ask the children how many strips each group would need if I wanted the class to make 100 loops, total, in a long paper chain. (there are 5 groups) Hand each group 20 strips and have them connect them in a chain. I'll connect the group chains together.
  2. Tell the children that each loop is one year on a time line. Lay it across the floor. Have them look at the Saguaro Cactus chart written on the board:
    Age Height If I want to make a strip of paper the height of the saguaro its first year, how long would I make the strip? (4 inches) What link would I link it to? (first)
  3. Assign each group a year. They are responsible for making the correct height length of strip, and attaching it to the correct loop (year). As groups finish and are waiting for others, they can start copying the chart on their own paper.
  4. I am almost 22 years old. Can you show me which loop I am at now? Look at the strips on either side of my age. By looking at their length can you make a guess at how tall I'd be now... If I were a saguaro? Talk about it with your group. Then we’ll share guesses and reasoning. Try making a math problem to figure it out or draw a picture.
  5. We are each going to chart this information on our regular, weekly bar graph paper. What would be a good title? What would I want to put for a title on the x-axis? On the y-axis? (these things have been used repeatedly in past graphing activities...previous knowledge) Pass out the graphing paper... on the back are photocopied questions: a) If you were a saguaro cactus, about how tall would you be now? b) Some saguaro cacti keep growing until they are 150 years old. About how tall do you think they are at that age?
  6. Take 5-10 minutes now to get started on this assignment while your neighbors can help you with any questions you come across. Work time.

Evaluation:

  1. Watch to see if everyone in the group is participating in making the loops and strips for the chain. Encourage more participation on an individual basis, if some are week participants.
  2. Students will fill out a bar graph chart to be collected and graded on accuracy.
  3. The questions on the back of the graph will be checked for well explained, logical reasoning leading to an estimate of heights.

Extensions/ Reteaching Strategies:

Read Cactus Hotel or Desert Giant: The World of the Saguaro Cactus before or after the math activity to continue discussion of the saguaro across the science and literature curriculums.
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