Name _____________________________ Period___________________Date__________________
QUICK LAB
Quadrat Sampling
Teacher Notes
TIME 15 minutes
Purpose Estimate population sizes by quadrat sampling
LAB MANAGEMENT
 Conduct
the lab indoors using common objects, such as paperclips, pencils, and
erasers, placed randomly in a location whose area you have measured ahead of
time.
 Count and record the objects before distributing them.
 Have students count any object within or touched by the quadrat.
 If one of the species is low in density, students may not sample it.
Safety Avoid quadrats made from wire hangers.
Teacher Note "I used to make quadrats out of hangers and had a couple of
accidents with overzealous students. Surprisingly, a Hula-Hoop® ring is almost a
perfect square meter."
ANSWERS
Analyze and Conclude
1. Accept all reasonable answers. If the estimate is inaccurate, it could be due to
inaccurate counting, inaccurate calculation of averages, nonrandom sampling,
or nonrandom distribution of species in a population.
2. Increase the number of samples taken, be sure quadrat size is appropriate for
the size of the area sampled, obtain random samples, count accurately, and
calculate averages accurately.
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
QuickLab
1
Principles of Ecology
Section 1: Ecologists Study Relationships
Name _____________________________ Period___________________Date__________________
QUICK LAB
Quadrat Sampling
Ecologists often use quadrats—square or rectangular grids—to collect data about
population numbers in an ecosystem. In this lab, you will use a quadrat to collect
data on three "species."
PROBLEM
What is the population size of each species?
MATERIALS
 quadrat
 meter
stick
 calculator
 objects to count
PROCESS SKILLS
Sampling
PROCEDURE
1. Obtain a quadrat frame. Measure, calculate, and record the area of the quadrat.
2. Stand at the edge of the area you will sample and randomly throw your
quadrat.
3. Move your quadrat so that it does not overlap with any other quadrat. Each
different object represents a different species. Count how many individuals of
each species are in your quadrat and record your data in a data table. Repeat
this procedure three times.
4. Combine your data with that of your classmates. Find the average number of
each species for all of the samples. Obtain the area of the sampling plot from
your teacher. Calculate how many quadrats would fit in the area of the
sampling plot. Multiply this by the average number of each species found in
one quadrat to estimate the population of each species.
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
QuickLab
2
Principles of Ecology
Section 1: Ecologists Study Relationships
Name _____________________________ Period___________________Date__________________
Quadrat Sampling continued
ANALYZE AND CONCLUDE
1. Analyze Compare your population estimate for each species to the actual
number that your teacher provides. Is the estimate accurate? Why or why not?
_______________________________________________________________
_______________________________________________________________
2. Evaluate How can you ensure that your estimate of population size will be as
accurate as possible?
_______________________________________________________________
_______________________________________________________________
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
QuickLab
3
Principles of Ecology
Section 1: Ecologists Study Relationships