Random Sampling and Population Calculations

BIOL 1014 Lab 10 Population Biology Name ________________________
Skills: Random Sampling, Population Calculations
Scientists cannot possibly count every organism in a population. One way to estimate the size of a population is to collect data by taking random samples. In this activity, you will look at how data obtained from random sampling compare with data obtained by an actual count.
Procedure
1. Cut out the Random Sampling Tool at the bottom of this lab sheet. Place numbers 1-10 into one cup. Place letters A-J into a different cup.
2. Draw one slip from each cup and record the letter-number combination drawn in column 1 – Grid Segment of the data table below.
3. Return the slips to the cups.
4. Repeat steps 2-3 until 10 Grid Locations have been chosen and recorded in the data table.
Random Sampling Data

Grid Segment(number-letter)

Number ofSunflowers



 


















Total Number ofSunflowers

Average per grid(divide total by 10)

Total number of plants in meadow(multiply average by 100)

5. Now refer to the population plot on the next page. Each dot on the plot represents a Sunflower plant. Use the letter number pairs you drew as “addresses”. In each case, locate the grid location where the letter row and number column intersect. Count the plants within each of the grid locations you selected and record the “Number of Sunflowers” in the data table.
6. To obtain the average per grid number, total the number of sunflowers in the table and since you counted sunflowers in 10 regions of the grid, divide that number by 10. Record the answer as the “Average per grid” in the data table.
BIOL 1014 Lab 10 Population Biology (Continued)
7. Because there are a total of 100 squares in the grid, multiply the average by 100 and record your answer as the “Total number of plants in meadow” in the data table. This is how the population of the entire area is extrapolated.
971550-9715500
Actual Data

Total number of Sunflowers ______ (count by hand)
Average number of Sunflowers (divide total by 100)Per grid _____

8. Since we purposely used a rather small grid for this activity to demonstrate the procedure it is possible to actually hand count this population as well. Hand count all the plants shown in the grid and record the number in the table above as the “total number of sunflowers”.
9. Divide the answer from #8 by 100 and record the “average number of sunflowers per grid box” in the table.
10. Complete the Analysis section on the next page.BIOL 1014 Lab 10 Population Biology (Continued)
Analysis Questions
1. Compare...