Ecology Lab Worksheet 2 - Field Sampling Techniques
This worksheet is designed to help you to:
i) Understand basic field sampling techniques.
ii) Present collected data in a manner suitable for analysis.
Note: The number of individuals per species included on the exercise was: species A- 10, species B - 25,
species C - 40, species D - 15. Compare these numbers with your results for questions 4c and 5c, and
reply question 8b.
Background questions
1. State in your own words why it is necessary to conduct random sampling within a habitat. (2)
2. What is accuracy? (2)
3. What is precision? (2)
Population density
Quadrat sampling:
4. Summarize your results:
a. Present a table summarizing the range, mean, and standard deviation of population density estimated
for each species (all groups’ data combined). (10)
b. Produce a bar graph showing the mean density of each species. Include error bars and remember to
label your graph. (8)
c. Estimate the total population size of each species for the entire island. (2)
5. Analyze your results
Determine if there is a significant difference in density among the four species.
a. State Ho and Ha. (2)
b. Perform appropriate statistical test (5)
c. Do you reject of fail to reject your null hypothesis and why? (5)
Transect Sampling:
6. Summarize your results
a. Present a table summarizing the range, mean, and standard deviation of population density estimated
for each species (all groups’ data combined). (10)
b. Produce a bar graph showing the mean density of each species. Include error bars and remember to
label your graph. (8)
c. Estimate the total population size of each species for the entire island. (2)
7. Analyze your results
Determine if there is a significant difference in density among the four species.
a. State Ho and Ha. (2)
b. Perform appropriate statistical test (5)
c. Do you reject of fail to reject your null hypothesis and why? (5)
Compare Methods
8. Present a table comparing the total population size of each species as estimated from each of the two
methods employed in this study. Include the estimates from just your group’s data and as all the groups’
data combined (5). Answer the following questions.
a. Are the estimates similar from the two sampling methods, and if not how do they differ. (5)
b. How does each estimate compare to the true population density? (5)
c. Does combining the entire class data set produce more accurate results than the results from just your
groups sampling effort? Why do you think accounts for the difference? (5)
d. What were some sources of error in our sampling? (5)
e. What could have been done to increase accuracy and precision? (5)