The NASA SCIence Files™
Plot Your Population
Purpose: To count the number of individual organisms living in the same area

Materials

Procedure
  1. Go to a large open area outside and randomly select a starting point.
  2. Place one of the dowels in the ground and tie one end of the 4.5-m string around the top of the dowel.
  3. Using the meter stick, measure one meter from the dowel and at that point, place a second dowel into the ground.
  4. Stretch the string from the first dowel to the second dowel and tie the string around the top of the second dowel. Diagrams 1 and 2, showing how to divide up the area with string
  5. Repeat steps 3-4 with the remaining two dowels to form a square. See diagram 1.
  6. Divide the square into two equal parts by laying a 1-m string from the middle of the square's left side to the middle of its right side.
  7. Divide the square again, this time by laying a 1-m string from the middle of the square's top to the middle of the bottom. You should now have four equal sections. See diagram 2.
  8. In your science journal or on graph paper, draw your plot of land.
  9. Carefully observe the plant and animal life in one section of your plot. Use a magnifying lens to see the really small ones!
  10. Count the number of each plant and animal and record in your science journal.
  11. Use a different symbol to represent each plant or animal and map the organisms in that section on the diagram of your plot.
  12. Repeat steps 9-11 with the remaining three sections.
  13. Total the number of each kind of plant or animal counted in the entire plot.
  14. Discuss and compare data with other students or groups.
  15. Using the data from all groups, determine an average number of organisms for each plant or animal found per 1-m square.
  16. Create a graph showing the class averages.
Conclusion
  1. Which plants and animals were more common than others? Explain why they were more common.
  2. How were the organisms distributed in the plot? Were the same plants and animals in each section?
  3. What are some factors that could affect the number of plants or animals over the next week, month, or year?
  4. Why is a class average a better estimate of the number of plants or animals in an area?