SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

 INTRODUCTION  The biotic factors of an environment include all organisms found within that environment. A                           group of organisms of the same species found within the same environment is called a                             population. Populations of different species sharing the same area and interacting with each                         other make up a community. One way of studying the interactions of organisms in a community                               is by taking an inventory of all the species in the area and comparing the sizes of their                                   populations.  In this investigation, you will observe the abiotic factors of two different sites (within GVC                             property, and next to Lake Minnewasta) and classify the species of plants and animals in those                               sites. You will measure randomly chosen quadrats within these sites and count the individuals of                             each poulation located within each quadrat. With this data, you will estimate the sizes of plant                               and animal populations within each community.  Before scientists can design an experiment, they must first make observations on which to base                             their hypotheses. Scientists have many different methods of collecting this data. The task of                           taking an inventory of the different kinds of organisms and their population sizes in an                             environmental site can be very difficult, especially if the area is teeming with life. Since it would                                 be impractical, if not impossible, to count each individual organism in a large area, ecologists                             randomly choose small portions of the whole area and classify and count the organisms in each                               small portion. They can then estimate the size of each population in the larger community. This                               process is called the quadrat method of sampling.  The goal of the quadrat method is to estimate the population density of each species in a given                                   community. Population density is the number of individuals of each species per unit area. Small                             square areas, called quadrats, are randomly selected to avoid choosing unrepresentative                     samples. Once the population densities for all quadrats are determined, the population size                         within the larger area can be estimated.  For example, if a 10 m x 10 m (100 m2) site is being surveyed, three quadrats of a smaller size,                                         perhaps 1 m x 1 m (1 m2), might be selected at random. If the population densities of a particular                                       species at the three quadrats are 10, 12, and 14 individuals per m2, an average is taken [(10 + 12                                       + 14)/3 = 12 individuals per m2]. That number is multiplied by the ratio of the larger area to the                                       area of each quadrat (100 m2/1 m2) to calculate the estimated population size within the site (12                                 x 100 = 1200 individuals). This process is repeated for all species in the community.  You should already be familiar with how to keep records of an experiment. When making entries,                               remember that this information is not just for you, but for anyone else who may need to use it. All                                       material should be presented in a clear and concise manner that can be understood even by                               those who are not in the class. PART 1: QUADRAT SAMPLING ON GVC PROPERTY 

Page 1 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

 PURPOSE: To estimate the population sizes of various species of organisms within a specific                           region of the school yard using the quadrat method.  HYPOTHESIS: Using the quadrat method, the population sizes of various species of organisms                         can be estimated.  MATERIALS: 1m x 1m quadrat, clipboard, record sheets, camera (for documenting species                       located).  PROCEDURE: 1) For this part, you will be located within the specific area shown here. Note the boundaries. 

On your record sheet, describe this site as completely as possible (enough so that another                             person can find it without your help). Use the sketch of the area above to assist. Observe the                                   abiotic factors of the site, such as whether the area is located in full sun or shade, or whether the                                       soil is moist or dry. Record your observations on your record sheet.  2) Select, at random, an area within the site to be your first quadrat. To do this, close your eyes                                       and toss a small object (rock, coin, etc.) somewhere within the site. Next, place the 1m x 1m                                   quadrat centered over the the location of the small object you tossed. This will be the quadrat                                 that you will study in more detail. Show, on your record sheet, the location of this quadrat.  3) Record on your record sheet the number of organisms of each plant or animal species within                                 the quadrat. To count grass or very small insects, select three smaller (10 cm x 10 cm) squares                                   at random, count the number of individual plants or insects in each smaller square, average the                               numbers, and multiply by 100 to get an estimate for the full quadrat. When surveying animals                               such as insects or worms, look under rocks, on branches, and in the soil, trying your best not to                                     disturb them.  

Page 2 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

4) Sketch out on your record sheet the approximate areas within your quadrat where organisms                             are located. Grass may be omitted, as it is assumed to cover the majority of the area. Rather,                                   identify areas where there is no grass or where non­grass organisms are found.  5) Repeat steps 3 and 4 twice more to obtain data for two other quadrats within the site. Record                                     this data on your record sheet.  6) Once each quadrat has been adequately sketched and recorded, proceed indoors to do all the                               following calculations: 

­ For each species, add the number of organisms found in all three quadrats and                           divide by three to calculate the average population density per square meter.                       Record the average population densities in your record sheet. 

­ For each species, multiply the population density by 100 to estimate the total                         number of organisms in the larger site. Record the estimated population sizes in                         your record sheet. 

 DATA:  See the attached record sheet for a convenient place to put your data.    CONCLUSION:  Answer the following questions. Place your answers on clearly labelled sheets of loose leaf. One                             set of answers per group is sufficient.  1) Why was it necessary to close your eyes before choosing the quadrat? 2) Which was the dominant plant species within the site? The dominant animal species? 3) How do your averages compare to the population densities of the individual quadrats? Were                             the populations spread out evenly over the site? 4) Did you observe any unusual features in one quadrat that were not found elsewhere on the                                 site, such as an ant hill? 5) Compare your results with those of other groups. Did any abiotic factors contribute to                             similarities or differences in your population sizes? Explain. 6) Using the quadrat method, how could you better estimate the actual population sizes of                             species within the site? 7) How is the sampling of animal populations more difficult than that of plant populations? 8) Predict how the removal of the dominant plant species from the site would affect the                               population sizes of the other organisms. Explain.     

Page 3 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

RECORD SHEET  LOCATION OF QUADRATS WITHIN THE SITE      ABIOTIC FACTORS IN THE SITE 

    

QUADRAT #1 

   

Page 4 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

QUADRAT #2 

 QUADRAT #3 

   

Page 5 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

  

SPECIES  NO. IN QUAD 1 

NO. IN QUAD 2 

NO. IN QUAD 3 

AVERAGE POPULATION DENSITY 

ESTIMATED POPULATION SIZE 

                 

                 

                 

                 

                 

                 

           

           

      

Page 6 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

PART 2: QUADRAT SAMPLING AT LAKE MINNEWASTA  PURPOSE: To estimate the population sizes of various species of organisms within a specific                           region of the Lake Minnewasta forest using the quadrat method.  HYPOTHESIS: Using the quadrat method, the population sizes of various species of organisms                         can be estimated.  MATERIALS: 1m x 1m quadrat, clipboard, record sheets, camera (for documenting species                       located).  PROCEDURE: 1) For this part, you will be located within the specific area shown here. Note the boundaries.  

 

 On your record sheet, describe this site as completely as possible (enough so that another                             person can find it without your help). Use the sketch of the area above to assist. Observe the                                   abiotic factors of the site, such as whether the area is located in full sun or shade, or whether the                                       soil is moist or dry. Record your observations on your record sheet.  2) Select, at random, an area within the site to be your first quadrat. To do this, close your eyes                                       and toss a small object (rock, coin, etc.) somewhere within the site. Next, place the 1m x 1m                                   quadrat centered over the the location of the small object you tossed. This will be the quadrat                                 that you will study in more detail. Show, on your record sheet, the location of this quadrat.  3) Record on your record sheet the number of organisms of each plant or animal species within                                 the quadrat. To count grass or very small insects, select three smaller (10 cm x 10 cm) squares                                   at random, count the number of individual plants or insects in each smaller square, average the                               numbers, and multiply by 100 to get an estimate for the full quadrat. When surveying animals                               such as insects or worms, look under rocks, on branches, and in the soil, trying your best not to                                     disturb them.  

Page 7 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

4) Sketch out on your record sheet the approximate areas within your quadrat where organisms                             are located. Grass may be omitted, as it is assumed to cover the majority of the area. Rather,                                   identify areas where there is no grass or where non­grass organisms are found.  5) Repeat steps 3 and 4 twice more to obtain data for two other quadrats within the site. Record                                     this data on your record sheet.  6) Once each quadrat has been adequately sketched and recorded, proceed indoors to do all the                               following calculations: 

­ For each species, add the number of organisms found in all three quadrats and                           divide by three to calculate the average population density per square meter.                       Record the average population densities in your record sheet. 

­ For each species, multiply the population density by 100 to estimate the total                         number of organisms in the larger site. Record the estimated population sizes in                         your record sheet. 

 DATA:  See the attached record sheet for a convenient place to put your data.    CONCLUSION:  Answer the following questions. Place your answers on clearly labelled sheets of loose leaf. One                             set of answers per group is sufficient.  1) Why was it necessary to close your eyes before choosing the quadrat? 2) Which was the dominant plant species within the site? The dominant animal species? 3) How do your averages compare to the population densities of the individual quadrats? Were                             the populations spread out evenly over the site? 4) Did you observe any unusual features in one quadrat that were not found elsewhere on the                                 site, such as an ant hill? 5) Compare your results with those of other groups. Did any abiotic factors contribute to                             similarities or differences in your population sizes? Explain. 6) Using the quadrat method, how could you better estimate the actual population sizes of                             species within the site? 7) How is the sampling of animal populations more difficult than that of plant populations? 8) Predict how the removal of the dominant plant species from the site would affect the                               population sizes of the other organisms. Explain.    

Page 8 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

Lake Minnewasta­ Location of Quadrat Site Record Sheet 

  

Abiotic Factors in the Site 

       

                 

Page 9 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

QUADRAT #1 

 QUADRAT #2 

  

Page 10 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

QUADRAT #3 

 QUADRAT #4 

 

Page 11 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

QUADRAT #5 

 QUADRAT #6 

 

Page 12 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995. 

SCIENCE 20F Name: ______________________ 

QUADRAT SAMPLING 

SPECIES  NO. IN QUAD 1 

NO. IN QUAD 2 

NO. IN QUAD 3 

AVERAGE POPULATION DENSITY 

ESTIMATED POPULATION SIZE 

                 

                 

                 

                 

                 

                 

           

           

  

SPECIES  NO. IN QUAD 4 

NO. IN QUAD 5 

NO. IN QUAD 6 

AVERAGE POPULATION DENSITY 

ESTIMATED POPULATION SIZE 

                 

                 

                 

                 

                 

                 

           

           

  

Page 13 *Adapted from Environmental Science Laboratory Manual, Addison­Wesley Pub. Co., 1995.